Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	IAMGOLD CORP
Entity Central Index Key	0001203464
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3

CONSOLIDATED BALANCE SHEETS - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 583,600,000	$ 652,000,000
Restricted cash	0	92,000,000
Short-term investments	227,000,000	0
Receivables and other current assets	56,800,000	61,000,000
Inventories	209,500,000	207,900,000
Current assets	1,076,900,000	1,012,900,000
Non-current assets
Investments in associates and incorporated joint ventures	64,700,000	52,600,000
Property, plant and equipment	1,948,000,000	1,868,200,000
Exploration and evaluation assets	446,900,000	169,200,000
Income taxes receivable	18,200,000	29,200,000
Restricted cash	24,700,000	18,700,000
Long-term receivable	93,500,000	0
Other assets	262,500,000	249,700,000
Non-current assets	2,858,500,000	2,387,600,000
Assets	3,935,400,000	3,400,500,000
Current liabilities
Accounts payable and accrued liabilities	188,100,000	162,900,000
Income taxes payable	16,000,000	14,700,000
Current portion of provisions	21,000,000	15,800,000
Other liabilities	100,000	2,100,000
Current liabilities	225,200,000	195,500,000
Non-current liabilities
Deferred income tax liabilities	184,100,000	159,000,000
Provisions	281,600,000	289,800,000
Long-term debt	388,700,000	485,100,000
Other liabilities	3,000,000	0
Non-current liabilities	857,400,000	933,900,000
Liabilities	1,082,600,000	1,129,400,000
Equity
Common shares	2,671,700,000	2,628,200,000
Contributed surplus	41,400,000	40,100,000
Retained earnings (deficit)	109,600,000	(409,700,000)
Accumulated other comprehensive loss	(24,300,000)	(36,900,000)
Equity attributable to owners of parent	2,798,400,000	2,221,700,000
Non-controlling interests	54,400,000	49,400,000
Equity	2,852,800,000	2,271,100,000
Contingencies and commitments
Equity and liabilities	$ 3,935,400,000	$ 3,400,500,000

CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Profit or loss [abstract]
Revenues	$ 268.8	$ 282.4	$ 803.8	$ 734.6
Cost of sales	227.9	230.2	692.0	651.5
Gross profit	40.9	52.2	111.8	83.1
General and administrative expenses	(8.9)	(10.0)	(27.8)	(28.8)
Exploration expenses	(6.6)	(6.5)	(29.6)	(20.6)
Reversal of impairment charges	0.0	0.0	524.1	0.0
Other income	1.5
Other (expenses)		(1.9)	(8.0)	(10.2)
Earnings from operations	26.9	33.8	570.5	23.5
Share of net earnings from investments in associates and incorporated joint ventures, net of income taxes	3.6	2.5	10.2	7.5
Finance costs	(2.1)	(6.3)	(9.6)	(21.7)
Foreign exchange gain	2.0	0.0	8.8	1.0
Interest income and derivatives and other investment gains	7.3	5.5	14.8	88.7
Earnings before income taxes	37.7	35.5	594.7	99.0
Income taxes	(5.1)	(14.4)	(67.3)	(34.4)
Net earnings	32.6	21.1	527.4	64.6
Net earnings attributable to
Equity holders of IAMGOLD Corporation	30.8	17.0	519.3	57.9
Non-controlling interests	1.8	4.1	8.1	6.7
Net earnings	$ 32.6	$ 21.1	$ 527.4	$ 64.6
Weighted average number of common shares outstanding
Basic (in shares)	464.7	428.3	462.3	410.3
Diluted (in shares)	469.3	432.2	466.7	413.2
Earnings per share
Basic (in dollars per share)	$ 0.07	$ 0.04	$ 1.12	$ 0.14
Diluted (in dollars per share)	$ 0.07	$ 0.04	$ 1.11	$ 0.14

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of comprehensive income [abstract]
Net earnings	$ 32.6	$ 21.1	$ 527.4	$ 64.6
Movement in marketable securities fair value reserve
Net unrealized change in fair value of marketable securities	(3.4)	0.1	0.9	11.9
Net realized change in fair value of marketable securities	5.1	0.0	5.3	(2.0)
Tax impact	0.1	(0.1)	(0.3)	(1.6)
Other comprehensive income, net of tax, marketable securities	1.8	0.0	5.9	8.3
Movement in cash flow hedge fair value reserve
Effective portion of changes in fair value of cash flow hedges	8.8	(4.7)	12.2	5.9
Time value of options contracts excluded from hedge relationship	(1.7)	(2.0)	(4.4)	(1.4)
Net change in fair value of cash flow hedges reclassified to the statements of earnings	(1.9)	0.9	(2.0)	5.2
Tax impact	(0.1)	0.5	0.1	(0.6)
Other comprehensive income, net of tax, cash flow hedges	5.1	(5.3)	5.9	9.1
Currency translation adjustment	0.5	0.3	1.4	(0.1)
Total other comprehensive income (loss)	7.4	(5.0)	13.2	17.3
Comprehensive income	40.0	16.1	540.6	81.9
Comprehensive income attributable to:
Equity holders of IAMGOLD Corporation	38.2	12.0	532.5	75.2
Non-controlling interests	1.8	4.1	8.1	6.7
Comprehensive income	$ 40.0	$ 16.1	$ 540.6	$ 81.9

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Equity attributable to equity holders of IAMGOLD Corporation	Common shares	Contributed surplus	Retained earnings (deficit)	Accumulated other comprehensive loss	Marketable securities fair value reserve	Cash flow hedge fair value reserve	Currency translation adjustment	Non-controlling interests
Equity at Dec. 31, 2015			$ 2,366.2	$ 38.2	$ (461.2)		$ (32.5)	$ (11.1)	$ (3.8)	$ 42.1
Issuance of common shares			220.1
Issuance of flow-through common shares			27.5
Issuance of common shares for share-based compensation			3.0	(3.0)
Share-based compensation				3.7
Other				(0.2)
Net earnings attributable to equity holders of IAMGOLD Corporation	$ 64.6				57.9					6.7
Net change in fair value of marketable securities, net of income taxes	17.3						8.3	9.1	(0.1)
Net change in fair value of cash flow hedges recognized in property, plant and equipment								0.1
Dividends to non-controlling interests										(1.5)
Equity at Sep. 30, 2016	2,269.5	$ 2,222.2	2,616.8	38.7	(403.3)	$ (30.0)	(24.2)	(1.9)	(3.9)	47.3
Equity at Dec. 31, 2016	2,271.1		2,628.2	40.1	(409.7)		(29.0)	(3.8)	(4.1)	49.4
Issuance of common shares			27.4
Issuance of flow-through common shares			13.4
Issuance of common shares for share-based compensation			2.7	(2.7)
Share-based compensation				4.4
Other				(0.4)
Net earnings attributable to equity holders of IAMGOLD Corporation	527.4				519.3					8.1
Net change in fair value of marketable securities, net of income taxes	13.2						5.9	5.9	1.4
Net change in fair value of cash flow hedges recognized in property, plant and equipment								(0.6)
Dividends to non-controlling interests										(3.1)
Equity at Sep. 30, 2017	$ 2,852.8	$ 2,798.4	$ 2,671.7	$ 41.4	$ 109.6	$ (24.3)	$ (23.1)	$ 1.5	$ (2.7)	$ 54.4

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net earnings	$ 32.6	$ 21.1	$ 527.4	$ 64.6
Adjustments for:
Finance costs	2.1	6.3	9.6	21.7
Depreciation expense	62.4	69.7	197.7	194.9
Income tax expense	5.1	14.4	67.3	34.4
Interest income	(2.5)	(0.8)	(6.4)	(1.9)
Reversal of impairment charges	0.0	0.0	(524.1)	0.0
Gain on sale of a 30% interest in the Côté Gold Project	0.0	0.0	(19.2)	0.0
Share of net earnings from investments in associates and incorporated joint ventures, net of income taxes	(3.6)	(2.5)	(10.2)	(7.5)
Write-down of inventories	1.9	0.0	11.9	0.1
(Gain on purchase) Loss on redemption of 6.75% Senior unsecured notes	0.0	(4.0)	20.2	(4.0)
Gain on sale of gold bullion	0.0	0.0	0.0	(72.9)
Effects of exchange rate fluctuation on restricted cash	(0.3)	0.6	(1.7)	(3.8)
Effects of exchange rate fluctuation on cash and cash equivalents	(6.0)	(0.4)	(11.3)	(1.7)
Other non-cash items	(6.2)	(4.2)	(5.1)	2.9
Adjustments for cash items:
Dividends from joint venture	2.1	11.3	2.1	11.3
Settlement of derivatives	(0.6)	(0.2)	(0.5)	(8.7)
Disbursements related to asset retirement obligations	(1.3)	(0.9)	(3.0)	(2.0)
Movements in non-cash working capital items and non-current ore stockpiles	3.5	14.5	4.3	22.4
Cash from operating activities, before income tax paid	89.2	128.9	259.0	253.8
Income tax paid	(12.2)	(3.1)	(28.9)	(6.5)
Net cash from operating activities	77.0	125.8	230.1	247.3
Investing activities
Capital expenditures	(41.0)	(71.9)	(134.0)	(218.3)
Capitalized borrowing costs	0.0	(9.9)	(11.2)	(17.3)
Net proceeds from sale of a 30% interest in the Côté Gold Project	0.0	0.0	96.5	0.0
Proceeds from sale of gold bullion	0.0	0.0	0.0	170.3
Decrease (increase) in restricted cash	0.0	(40.5)	88.2	(43.6)
Purchase of short-term investments	(227.0)	0.0	(227.0)	0.0
Capital expenditures for exploration and evaluation assets	(3.7)	(0.5)	(4.5)	(3.5)
Interest received	1.7	0.8	5.6	1.9
Purchase of additional common shares of associate	0.0	0.0	(7.4)	0.0
Other investing activities	(2.0)	1.3	(3.3)	(1.2)
Net cash used in investing activities	(272.0)	(120.7)	(197.1)	(111.7)
Financing activities
Net proceeds from issuance of Senior notes	0.0	0.0	393.6	0.0
Redemption of 6.75% Senior unsecured notes and purchase of 6.75% Senior unsecured notes	0.0	(141.5)	(505.6)	(141.5)
Proceeds from issuance of flow-through shares	0.0	0.0	15.1	30.3
Proceeds from issuance of shares	0.0	220.1	0.0	220.1
Interest paid	0.0	(10.4)	(5.3)	(24.6)
Repayment of credit facility	0.0	0.0	0.0	(70.0)
Long-term prepayment for finance lease	0.0	0.0	(4.9)	0.0
Other financing activities	(3.6)	(0.6)	(5.6)	(5.3)
Net cash from (used in) financing activities	(3.6)	67.6	(112.7)	9.0
Effects of exchange rate fluctuation on cash and cash equivalents	6.0	0.4	11.3	1.7
Increase (decrease) in cash and cash equivalents	(192.6)	73.1	(68.4)	146.3
Cash and cash equivalents, beginning of the period	776.2	554.2	652.0	481.0
Cash and cash equivalents, end of the period	$ 583.6	$ 627.3	$ 583.6	$ 627.3

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)		9 Months Ended
CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)	Jun. 20, 2017	Sep. 30, 2017	Mar. 16, 2017	Sep. 21, 2012
Fixed interest rate \| Senior Unsecured Notes at 6.75%
Investment [Line Items]
Interest rate		6.75%	6.75%	6.75%
Disposal Of Interest In Cote Gold Project
Investment [Line Items]
Proportion of ownership interest in joint venture	30.00%	30.00%

CORPORATE INFORMATION	9 Months Ended
CORPORATE INFORMATION	Sep. 30, 2017
Corporate Information And Statement Of IFRS Compliance [Abstract]
CORPORATE INFORMATION	CORPORATE INFORMATION IAMGOLD Corporation (“IAMGOLD” or “the Company”) is a corporation governed by the Canada Business Corporations Act and domiciled in Canada whose shares are publicly traded. The address of the Company’s registered office is 401 Bay Street, Suite 3200, Toronto, Ontario, Canada, M5H 2Y4. The principal activities of the Company are the exploration, development and operation of gold mining properties.

BASIS OF PREPARATION

9 Months Ended

Sep. 30, 2017

Corporate Information And Statement Of IFRS Compliance [Abstract]

BASIS OF PREPARATION

(a) Statement of compliance

The unaudited condensed consolidated interim financial statements ("consolidated interim financial statements") of IAMGOLD and all of its subsidiaries, joint ventures and associates as at and for the three and nine months ended September 30, 2017, have been prepared in accordance with IAS 34, Interim Financial Reporting, and do not include all of the information required for annual consolidated financial statements. Accordingly, certain information and disclosures normally included in annual financial statements prepared in accordance with International Financial Reporting Standards ("IFRS") have been omitted or condensed.

These consolidated interim financial statements should be read in conjunction with IAMGOLD's audited annual consolidated financial statements and related notes as at and for the year ended December 31, 2016.

These consolidated interim financial statements of IAMGOLD were authorized for issue in accordance with a resolution of the Board of Directors on November 7, 2017.


(b)	Basis of measurement

The consolidated interim financial statements have been prepared on a historical cost basis, except for items measured at fair value as discussed in note 19.


(c)	Basis of consolidation

Subsidiaries, divisions and investments in joint ventures related to significant properties of the Company are accounted for as outlined below.



Name	Property – Location	September 30, 2017	December 31, 2016	Type of Arrangement	Accounting Method
Essakane S.A.	Essakane mine (Burkina Faso)	90%	90%	Subsidiary	Consolidation
Rosebel Gold Mines N.V.	Rosebel mine (Suriname)	95%	95%	Subsidiary	Consolidation
Doyon division including the Westwood mine	Doyon division (Canada)	100%	100%	Division	Consolidation
Côté Gold division¹	Côté Gold Project (Canada)	70%	100%	Division	Proportionate share
Euro Ressources S.A.	France	90%	90%	Subsidiary	Consolidation
Société d'Exploitation des Mines d'Or de Sadiola S.A.	Sadiola mine (Mali)	41%	41%	Incorporated joint venture	Equity accounting
Merrex Gold Inc.²	Siribaya Project (Mali)	100%	23%	Subsidiary	Consolidation


1	Effective June 20, 2017, the Company holds an undivided interest in the assets, liabilities, revenues and expenses of the Côté Gold division through an unincorporated joint venture (note 5).


2	As of February 28, 2017 (note 4).


(d)	Significant accounting judgments, estimates and assumptions

The preparation of consolidated interim financial statements requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities and contingent liabilities as at the date of the consolidated interim financial statements and reported amounts of revenues and expenses during the three and nine months ended September 30, 2017. Estimates and assumptions are continuously evaluated and are based on management’s experience and other factors, including expectations of future events which are believed to be reasonable under the circumstances. Actual results may differ from these estimates.


(e)	Significant accounting policies

These consolidated interim financial statements, including comparatives, have been prepared following the same accounting policies and methods of computation as the audited annual consolidated financial statements for the year ended December 31, 2016.

NEW ACCOUNTING STANDARDS ISSUED BUT NOT YET EFFECTIVE	9 Months Ended
NEW ACCOUNTING STANDARDS ISSUED BUT NOT YET EFFECTIVE	Sep. 30, 2017
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
NEW ACCOUNTING STANDARDS ISSUED BUT NOT YET EFFECTIVE	NEW ACCOUNTING STANDARDS ISSUED BUT NOT YET EFFECTIVE The following new accounting standards were not yet effective for the nine months ended September 30, 2017, and have not been applied in preparing these consolidated financial statements. IFRS 15 - Revenue from Contracts with Customers In May 2014, the IASB issued IFRS 15 Revenue from Contracts with Customers, which will replace IAS 11 Construction Contracts and IAS 18 Revenue. The mandatory effective date of IFRS 15 is January 1, 2018. The objective of IFRS 15 is to establish a single, principles based model to be applied to all contracts with customers in determining how and when revenue is recognized. IFRS 15 also requires entities to provide users of financial statements with more informative and relevant disclosures. As at September 30, 2017, the Company has analyzed all revenue contracts to determine the impact that IFRS 15 is expected to have on the Company’s consolidated financial statements. The Company’s main revenue stream is the sale of gold bullion, with each sale occurring as a stand-alone transaction. The preliminary assessment using the five-step model in IFRS 15 focused on identifying potential multiple performance obligations as well as applying the concept of control transfer as opposed to transfer of risks and rewards of ownership, and revealed that there is no significant difference in the timing and nature of revenue recognition compared to IAS 18 Revenue. Furthermore, the Company’s revenue contracts do not contain significant variable consideration, financing components or non-cash consideration. The Company will adopt IFRS 15 for the annual period beginning January 1, 2018,and expects there will be no material impact on the Company's consolidated financial statements. IFRS 9 - Financial Instruments In July 2014, the IASB issued the final version IFRS 9 (2014) - Financial Instruments (“IFRS 9”) to replace IAS 39 Financial Instruments: Recognition and Measurement. IFRS 9 provides a revised model for recognition and measurement of financial instruments and a single, forward-looking ‘expected loss’ impairment model (the “ECL model”). IFRS 9 also includes a substantially reformed approach to hedge accounting. The standard is effective for annual periods beginning on or after January 1, 2018, with early adoption permitted. Effective April 1, 2014, the Company early adopted all of the requirements of IFRS 9 (2013), which was the previously issued version of IFRS 9. As a result of early adoption of IFRS 9 (2013), which is largely aligned with the requirements of IFRS 9, there will be no further impact on adoption of IFRS 9, with respect to the classification of financial assets and liabilities and hedge accounting. The Company has completed its assessment of the ECL model and does not expect the adoption of IFRS 9 to have any material impact on the Company's consolidated financial statements with respect to the amended impairment model for the annual period beginning January 1, 2018. IFRIC 22 - Foreign Currency Transactions and Advance Consideration In December 2016, the IASB issued IFRIC Interpretation 22 Foreign Currency Transactions and Advance Consideration. The interpretation clarifies which date should be used for translation of a foreign currency transaction when an entity recognizes a non-monetary asset or non-monetary liability arising from the payment or receipt of advance consideration before the entity recognizes the related asset, expense or income (or part of it). The interpretation is applicable for annual periods beginning on or after January 1, 2018. The Company has completed a preliminary assessment of the relevant transactions and identified that advances for the purchase of capital equipment are in scope of IFRIC 22. Further analysis is being completed and the Company will report the impact, if any, resulting from the adoption of IFRIC 22 on January 1, 2018, in its audited annual consolidated financial statements for the year ended December 31, 2017. IFRS 16 - Leases In January 2016, the IASB issued IFRS 16 Leases. The objective of IFRS 16 is to recognize all leases on balance sheet for lessees. IFRS 16 requires lessees to recognize a "right of use" asset and a lease liability calculated using a prescribed methodology. The mandatory effective date of IFRS 16 is for annual periods beginning on or after January 1, 2019. Early adoption is permitted provided that IFRS 15, Revenue from Contracts with Customers, is also adopted. The extent of the impact of adoption of this standard has not yet been determined. IFRIC 23 - Uncertainty over Income Tax Treatments On June 7, 2017, the IASB issued IFRIC Interpretation 23 Uncertainty over Income Tax Treatments. The Interpretation provides guidance on the accounting for current and deferred tax liabilities and assets in circumstances in which there is uncertainty over income tax treatments. The Interpretation is applicable for annual periods beginning on or after January 1, 2019. The extent of the impact of adoption of the Interpretation has not yet been determined.

ACQUISITION

9 Months Ended

Sep. 30, 2017

Acquisition [Abstract]

ACQUISITION

Merrex - Siribaya Project

On February 28, 2017, in an all-share transaction, the Company acquired all of the issued and outstanding common shares and all of the outstanding common share purchase warrants and options of Merrex Gold Inc. ("Merrex"), that it did not already own. Merrex owns a 50% interest in the Siribaya Project in Mali. Including the 50% interest held directly, the Company now has a 100% interest in the Siribaya Project. IAMGOLD issued an aggregate of approximately 6.9 million common shares. The total purchase price amounted to $27.5 million, which includes transaction costs of $0.2 million, and is net of cash and cash equivalents acquired of $0.1 million.

Based on management’s judgment, the acquisition does not meet the IFRS definition of a business combination as the primary asset (Siribaya Project) is an exploration stage property and has not identified economically recoverable ore reserves. Consequently, the transaction has been recorded as an asset acquisition.

The total purchase price was allocated to the assets acquired and the liabilities assumed based on the fair value of the total consideration transferred at the closing date of the acquisition.



Assets acquired and liabilities assumed	Notes
Exploration and evaluation assets	12	$	36.6
Current liabilities		(3.9		)
Other non-current liabilities		(0.4		)
		$	32.3
Consideration transferred
Share consideration		$	27.4
Less: Cash and cash equivalents acquired		(0.1		)
Transaction costs		0.2
		27.5
Initial investment¹	10	4.8
		$	32.3

1

Prior to completion of the above mentioned transaction, IAMGOLD owned approximately 45.8 million common shares of Merrex, which represented approximately 23% of Merrex's issued and outstanding common shares, and was accounted for as an investment in an associate, using the equity method (note 10). The carrying amount of the investment of $4.8 million on the date of the acquisition has been included in the total cost of the Merrex Exploration and evaluation assets (note 12).

DIVESTITURE

9 Months Ended

Sep. 30, 2017

Non-current Asset Held For Sale And Discontinued Operations [Abstract]

DIVESTITURE

Sale of a 30% interest in the Côté Gold Project

On May 8, 2017, the Company entered into a Memorandum of Understanding with Sumitomo Metal Mining Co., Ltd. (“SMM”) under which SMM would acquire a 30% interest in the Côté Gold Project (the "Project"), including certain assets and liabilities attributable thereto, for an aggregate consideration of $195 million. The Company undertook a reorganization of its interest in the Côté Gold Project so that the Company’s interest would be held directly. Prior to the reorganization, the Company held its interest through wholly-owned subsidiaries.

On June 5, 2017, the Company entered into a definitive Investment Agreement and a definitive Joint Venture Agreement with SMM with respect to the Côté Gold Project and the transaction closed on June 20, 2017. On closing, the Company received $100 million of the consideration and the remaining consideration of $95 million is receivable on the earlier of:


(a)	18 months following the closing date (December 20, 2018);


(b)	the date the Côté Gold Project feasibility study is made available to the public; and


(c)	should it elect to do so and only as permitted under the Joint Venture Agreement, the date SMM sells its participating interest.

The Company paid $3.5 million in transaction costs upon closing of the transaction and has committed to pay a further $2.9 million (note 15) on receipt of the remaining receivable of $95 million. The remaining $95 million long-term receivable from SMM has been discounted to its present value of $93.5 million as at September 30, 2017.

Upon entering into the Investment Agreement with SMM, the Company performed an impairment assessment of the Project, and as a result, reversed its previously recognized impairment charge of $400 million (note 27), resulting in a carrying amount of exploration and evaluation assets of the Côté Gold Project of $390.4 million as at June 20, 2017.

On closing, the Company recorded a net gain of $19.2 million, on the sale of a 30% interest in the Côté Gold Project to SMM, which has been included under Interest income and derivatives and other investment gains in the Consolidated statements of earnings and is net of transaction costs (note 25).

The Company continues to control the Côté Gold Project. Judgment was applied by the Company in determining the appropriate accounting treatment for its undivided interest in the Côté Gold Project's assets and liabilities beginning June 20, 2017, and based on interpretation of relevant guidance under IFRS 11 Joint Arrangements, the Company has accounted for the Côté Gold Project by recording its 70% share of assets, liabilities, revenues and expenses in these consolidated interim financial statements.

The following represents the Company's 30% interest in the Côté Gold Project which was sold to SMM on June 20, 2017:



Carrying amount	Notes	30% disposal
Current assets		$	0.1
Exploration and evaluation assets	12	167.3
Non-current assets		0.6
Current liabilities		(0.1		)
Other non-current liabilities		(0.3		)
		$	167.6

The following represents the Company's gain recorded on the sale of a 30% interest in the Côté Gold Project to SMM:



	Notes
Gross sale consideration		$	195.0
Less:
Sale of a 30% interest in the Côté Gold Project		(167.6		)
Transaction costs		(6.4		)
Time value discount on long-term receivable		(1.8		)
Gain on sale of a 30% interest in the Côté Gold Project	25	$	19.2

RESTRICTED CASH

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

RESTRICTED CASH


(a)	Short-term restricted cash

As at September 30, 2017, the Company had no short-term restricted cash. As at December 31, 2016, the Company had $92.0 million held by the Government of Quebec to guarantee the asset retirement obligation related to the Doyon mine. The Company replaced the cash collateral, pursuant to arrangements with international insurance companies, with uncollateralized surety bonds, as prescribed by Quebec Government regulations. As at September 30, 2017, C$123.6 million (September 30, 2017 - $98.8 million; December 31, 2016 - $nil) of uncollateralized surety bonds were outstanding to guarantee the asset retirement obligation related to the Doyon mine (note 17(c)).


(b)	Long-term restricted cash

The Company had long-term restricted cash of $19.7 million and $5.0 million as at September 30, 2017 (December 31, 2016 - $13.7 million and $5.0 million) for the guarantee of the asset retirement obligations related to Essakane and Rosebel, respectively.

SHORT-TERM INVESTMENTS

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

SHORT-TERM INVESTMENTS



	September 30, 2017		December 31, 2016
Money market funds¹	$	224.3	$	—
Other	2.7		—
	$	227.0	$	—


1	Money market funds are comprised of short-term fund investments with redemption notice periods of 95 or 185 days.

RECEIVABLES AND OTHER CURRENT ASSETS

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

RECEIVABLES AND OTHER CURRENT ASSETS



	Notes	September 30, 2017		December 31, 2016
Gold receivables		$	1.5	$	2.7
Receivables from governments¹		33.6		40.4
Receivables from related parties	29	0.1		1.2
Other receivables		4.9		4.9
Total receivables		40.1		49.2
Marketable securities and warrants		—		0.2
Prepaid expenses		6.0		7.2
Derivatives	19(a)	10.7		4.4
		$	56.8	$	61.0


1	Receivables from governments relate primarily to value added tax.

INVENTORIES

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

INVENTORIES



	Notes	September 30, 2017		December 31, 2016
Finished goods		$	59.4	$	49.1
Ore stockpiles		5.3		9.1
Mine supplies		144.8		149.7
		209.5		207.9
Ore stockpiles included in other non-current assets	13	167.6		156.0
		$	377.1	$	363.9

For the three and nine months ended September 30, 2017, the Company recognized a net realizable value write-down in non-current ore stockpiles amounting to $0.5 million and $3.9 million (three and nine months ended September 30, 2016 - $nil and $0.1 million), respectively.

For the three and nine months ended September 30, 2017, the Company recognized a write-down in mine supplies inventories amounting to $1.4 million and $8.0 million (three and nine months ended September 30, 2016 - $1.1 million and $4.0 million), respectively.

For the three and nine months ended September 30, 2017, $nil and $0.7 million were recognized in Cost of sales for costs related to operating below normal capacity at Westwood (three and nine months ended September 30, 2016 - $6.3 million and $17.0 million), respectively.

INVESTMENTS IN ASSOCIATES AND INCORPORATED JOINT VENTURES

9 Months Ended

Sep. 30, 2017

Interests In Other Entities [Abstract]

INVESTMENTS IN ASSOCIATES AND INCORPORATED JOINT VENTURES



	Associates¹			Sadiola²			Yatela²			Total
Balance, January 1, 2016	$	7.4		$	49.2		$	—		$	56.6
Currency translation adjustment	(0.3		)	—			—			(0.3		)
Share of net earnings (loss), net of income taxes	(0.8		)	9.0			(2.1		)	6.1
Share of net loss recorded as provision	—			—			2.1			2.1
Share of dividends received	—			(11.3		)	—			(11.3		)
Disposal³	(0.6		)	—			—			(0.6		)
Balance, December 31, 2016	5.7			46.9			—			52.6
Purchase of additional shares of associate⁴	7.4			—			—			7.4
Currency translation adjustment	1.4			—			—			1.4
Share of net earnings (loss), net of income taxes	(1.1		)	11.3			—			10.2
Share of dividends received	—			(2.1		)	—			(2.1		)
Acquisition of control over associate⁵	(4.8		)	—			—			(4.8		)
Balance, September 30, 2017	$	8.6		$	56.1		$	—		$	64.7


1	IAMGOLD includes results based on the latest publicly available information.


2	The Company's incorporated joint ventures are not publicly listed.


3	On March 16, 2016, the Company disposed of its 41% ownership interest in Galane Gold Ltd. ("Galane") which had a carrying amount of $0.6 million on the date of disposal for cash proceeds of $0.2 million. The resulting loss of $0.4 million, net of transaction costs, was recognized in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).

4

Associates include INV Metals Inc. ("INV Metals"), a publicly traded company incorporated in Canada, and Merrex prior to February 28, 2017 (note 4). The Company's ownership interest in INV Metals as at September 30, 2017 was 35.6% (December 31, 2016 - 35.6%). On March 2, 2017, the Company participated in INV Metals' common shares public equity offering and acquired an additional 9.8 million common shares of INV Metals at a price of C$1.00 per share for an aggregate amount of $7.4 million (C$9.8 million). This acquisition allowed the Company to maintain a 35.6% ownership in INV Metals.


5	On February 28, 2017, Merrex became a 100% subsidiary of the Company (note 4). As a result, the Company accounted for Merrex under the consolidation method as at February 28, 2017. The Company previously accounted for Merrex as an associate, using the equity method.

PROPERTY, PLANT AND EQUIPMENT

9 Months Ended

Sep. 30, 2017

Property, plant and equipment [abstract]

PROPERTY, PLANT AND EQUIPMENT



	Construction in progress			Mining properties			Plant and equipment			Total
Cost
Balance, January 1, 2016	$	7.9		$	2,133.6		$	1,821.3		$	3,962.8
Additions	34.9			172.1			87.3			294.3
Changes in asset retirement obligations	—			11.7			—			11.7
Disposals	—			—			(42.6		)	(42.6		)
Transfers within Property, plant and equipment	(40.0		)	19.1			20.9			—
Balance, December 31, 2016	2.8			2,336.5			1,886.9			4,226.2
Additions	15.3			99.5			57.3			172.1
Changes in asset retirement obligations	—			(1.0		)	—			(1.0		)
Disposals	—			(0.2		)	(25.1		)	(25.3		)
Transfers within Property, plant and equipment	(12.7		)	12.9			(0.2		)	—
Transfers to Exploration and evaluation assets	—			—			(0.5		)	(0.5		)
Balance, September 30, 2017	$	5.4		$	2,447.7		$	1,918.4		$	4,371.5



	Construction in progress			Mining properties			Plant and equipment			Total
Accumulated Depreciation and Impairment
Balance, January 1, 2016	$	3.5		$	1,383.0		$	722.5		$	2,109.0
Depreciation expense¹	—			98.5			187.5			286.0
Disposals	—			—			(37.0		)	(37.0		)
Transfers within Property, plant and equipment	(3.5		)	—			3.5			—
Balance, December 31, 2016	—			1,481.5			876.5			2,358.0
Depreciation expense¹	—			79.8			132.6			212.4
Disposals	—			—			(22.8		)	(22.8		)
Reversal of impairment charges²	—			(124.1		)	—			(124.1		)
Balance, September 30, 2017	$	—		$	1,437.2		$	986.3		$	2,423.5
Carrying amount, December 31, 2016	$	2.8		$	855.0		$	1,010.4		$	1,868.2
Carrying amount, September 30, 2017	$	5.4		$	1,010.5		$	932.1		$	1,948.0


1	Excludes depreciation expense related to Corporate assets, which is included in General and administrative expenses.


2	Note 27.

EXPLORATION AND EVALUATION ASSETS

9 Months Ended

Sep. 30, 2017

Exploration For And Evaluation Of Mineral Resources [Abstract]

EXPLORATION AND EVALUATION ASSETS



	Notes	September 30, 2017			December 31, 2016
Balance, beginning of the period		$	169.2		$	155.1
Exploration and evaluation expenditures		8.4			14.1
Acquired Merrex exploration and evaluation assets	4	36.6			—
Reversal of impairment charge	5, 27	400.0			—
Sale of a 30% interest in the Côté Gold Project	5	(167.3		)	—
Balance, end of the period		$	446.9		$	169.2

As at September 30, 2017, Exploration and evaluation assets primarily consist of the Côté Gold Project (carrying amount of $391.3 million), on which the Company recorded an impairment charge reversal of $400 million, as a result of the sale of a 30% interest to SMM (Note 5).

OTHER NON-CURRENT ASSETS

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

OTHER NON-CURRENT ASSETS



	Notes	September 30, 2017		December 31, 2016
Ore stockpiles	9	$	167.6	$	156.0
Loan receivable from related party	29	35.9		31.3
Marketable securities and warrants	19(a)	30.1		21.7
Advances for the purchase of capital equipment		7.5		19.9
Bond fund investments	19(a)	2.7		5.9
Royalty interests		5.6		5.6
Long-term prepayment¹		4.9		—
Derivatives		3.6		4.1
Other		4.6		5.2
		$	262.5	$	249.7

1

On March 6, 2017, the Company signed an agreement with a third-party for the construction of a solar power plant to deliver power to the Essakane mine for a period of 15 years, upon completion of construction expected in December 2017. During the second quarter 2017, the Company issued a prepayment of $4.9 million to the third-party, which will be applied as a credit towards the purchase of solar power from the third- party, over a period of 12 years. The agreement may be terminated by either party if certain conditions are not met. Upon completion of construction of the solar power plant, the Company will account for this arrangement as a finance lease.

As at September 30, 2017, the allowance for doubtful non-current non-trade receivables from related parties was $36.0 million, (December 31, 2016 - $36.0 million).

PROVISIONS

9 Months Ended

Sep. 30, 2017

Other Provisions, Contingent Liabilities And Contingent Assets [Abstract]

PROVISIONS



	September 30, 2017		December 31, 2016
Asset retirement obligations	$	280.6	$	285.1
Yatela loss provision	15.0		15.0
Other	7.0		5.5
	$	302.6	$	305.6

Current portion of provisions	$	21.0	$	15.8
Non-current provisions	281.6		289.8
	$	302.6	$	305.6

(a) Asset retirement obligations

The Company’s activities are subject to various laws and regulations regarding environmental restoration and closure provisions for which the Company estimates future costs. These provisions may be revised on the basis of amendments to such laws and regulations and the availability of new information, such as changes in reserves corresponding to a change in the mine life and discount rates, changes in estimated costs of reclamation activities and acquisition or construction of a new mine. The Company makes a provision based on the best estimate of the future cost of rehabilitating mine sites and related production facilities on a discounted basis.


(b)	Provisions for litigation claims and regulatory assessments

As at September 30, 2017, the Company did not have any material provisions for litigation claims or regulatory assessments. Further, the Company does not believe claims or regulatory assessments, for which no provision has been recorded, will have a material impact on the financial position of the Company.

OTHER LIABILITIES

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

OTHER LIABILITIES



	Notes	September 30, 2017		December 31, 2016
Finance lease liabilities	19(b)	$	0.1	$	0.1
Derivatives	19(a)	0.1		2.0
Other liabilities	5	2.9		—
		$	3.1	$	2.1
Current other liabilities		$	0.1	$	2.1
Non-current other liabilities		3.0		—
		$	3.1	$	2.1

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2017
Income Taxes [Abstract]
INCOME TAXES	INCOME TAXES The Company estimates the effective tax rate expected to be applied for the full fiscal year and uses this rate to determine income provisions in interim periods. The impact of changes in judgments and estimates concerning the probable realization of losses, changes in tax rates, and foreign exchange rates are recognized in the interim period in which they occur. The tax expense for the three and nine months ended September 30, 2017 was $5.1 million and $67.3 million, respectively (three and nine months ended September 30, 2016 - $14.4 million and $34.4 million, respectively) and varied from the tax expense calculated using the combined Canadian federal and provincial statutory income tax rate of 26.6%. The variance was mainly due to net foreign earnings taxed at different tax rates and fluctuations in the mix of income for the recognition of certain tax benefits and related deferred tax assets.

LONG-TERM DEBT AND CREDIT FACILITIES

9 Months Ended

Sep. 30, 2017

Financial Instruments [Abstract]

LONG-TERM DEBT AND CREDIT FACILITIES


(a)	Senior notes

i.7% Senior secured notes ("Notes")

On March 16, 2017, the Company issued at face value $400 million of Notes due in 2025 with an interest rate of 7% per annum. The Notes are denominated in U.S. dollars and mature on April 15, 2025. Interest is payable in arrears in equal semi-annual installments on April 15 and October 15 of each year, beginning on October 15, 2017. The Notes are guaranteed by some of the Company's subsidiaries.

The Company incurred transaction costs of $6.4 million which have been capitalized and offset against the carrying amount of the Notes within Long-term debt in the Consolidated balance sheets and are being amortized using the effective interest rate method.

Except for the prepayment options as noted below, the Notes are not redeemable, in whole or part, by the Company until April 15, 2020. On and after April 15, 2020, the Company may redeem the Notes, in whole or in part, at the relevant redemption price (expressed as a percentage of the principal amount of the Notes) and accrued and unpaid interest on the Notes up to the redemption date. The redemption price for the Notes during the 12-month period beginning on April 15 of each of the following years is: 2020 - 105.25%; 2021 - 103.50%; 2022 - 101.75%; 2023 and thereafter - 100%.

Prior to April 15, 2020, the Company may redeem some or all of the Notes at a price equal to 100% of the principal amount of the Notes plus a "make-whole" premium, plus accrued and unpaid interest.

Prior to April 15, 2020, using the cash proceeds from an equity offering, the Company may redeem up to 40% of the original aggregate principal amount of the Notes at a redemption price equal to 107% of the aggregate principal amount thereof, plus accrued and unpaid interest, if any, up to the redemption date.

The fair value of the prepayment option embedded derivative (note 19(a)), which is an option that represents a derivative asset to the Company, is presented as an offset to the Notes on the Consolidated balance sheets. The debt component was initially recognized at $400 million, which represents the difference between the fair value of the financial instrument as a whole and the fair value of the embedded derivative.

Subsequently, the debt component is recognized at amortized cost using the effective interest rate method. The embedded derivative represents the prepayment option and is classified as a financial asset at fair value through profit or loss ("FVTPL"). The embedded derivative is recognized at fair value with changes in the fair value recognized in the Company’s Consolidated statements of earnings. The fair value of the embedded derivative as at September 30, 2017 was $9.5 million (note 18(c)), (December 31, 2016 - $nil).

Under the indenture governing the Notes‎, if the Company makes certain asset sales it may use an amount equal to the net proceeds to repay certain debt obligations and/or reinvest, or commit to reinvest, in the Company’s business, within 365 days after the applicable asset sale. At the end of the 365-day period, if there remains $50 million or more of the net proceeds that the Company has not used in this manner, the Company would be required to use any such excess proceeds to offer to purchase the Notes at par in the manner described in the indenture.

The following are the contractual maturities related to the Notes, including interest payments:



	Payments due by period
Notes balance as at	Carrying amount¹		Contractual cash flows		<1 yr		1-2 yrs		3-5 yrs		>5 yrs
September 30, 2017	$	400.0	$	625.2	$	29.2	$	56.0	$	56.0	$	484.0
December 31, 2016	$	489.1	$	621.1	$	33.0	$	66.0	$	522.1	$	—


1	The carrying amount of the long-term debt excludes unamortized deferred transaction costs of the Notes of $6.0 million as at September 30, 2017 (December 31, 2016 – $4.0 million). The carrying amount of the long-term debt also excludes the embedded derivative classified as a financial asset at fair value through profit or loss (note 18(c)).

ii.6.75% Senior unsecured notes

On September 21, 2012, the Company issued at face value $650 million of Senior unsecured notes with an interest rate of 6.75% per annum. The 6.75% Senior unsecured notes are denominated in U.S. dollars and mature on October 1, 2020. Interest is payable in arrears in equal semi-annual installments on April 1 and October 1.

In April 2016, the Company canceled, at face value, $15.0 million of Notes it purchased in 2015.

In the third quarter of 2016, the Company purchased at face value, pursuant to a tender offer, an additional $145.9 million of the 6.75% Senior unsecured notes for cash consideration of $141.5 million. The resulting gain, net of transaction costs was $4.0 million and was recognized in the third quarter of 2016 in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).

On March 16, 2017, the Company issued a notice to redeem its 6.75% Senior unsecured notes for a total amount of $505.6 million and completed the redemption on April 3, 2017. As a result of the change in the estimated future cash flows, the amortized cost of $485.4 million of the 6.75% Senior unsecured notes was adjusted during the first quarter 2017 to reflect the actual future cash flows of $505.6 million. The resulting loss of $20.2 million was recognized in the first quarter 2017 in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).


(b)	Credit facilities

On February 1, 2016, the Company entered into a four-year $250 million credit facility consisting of a fully committed $100 million secured revolving credit facility and a $150 million accordion. During 2016, the Company amended the credit facility to increase the fully committed credit facility from $100 million to $170 million, resulting in $80 million remaining under the accordion. On February 7, 2017, the Company amended the credit facility, utilizing the remaining accordion and adding additional commitments of $80 million, bringing the total commitments under the facility to $250 million, with similar terms and conditions. The key terms of the facility include limitations on incremental debt, restrictions on distributions and financial covenants including Net Debt to EBITDA, Tangible Net Worth, Interest Coverage and Minimum Liquidity. The credit facility provides for an interest rate margin above London Interbank Offered Rate (“LIBOR”), banker’s acceptance (“BA”) prime rate and base rate advances which varies according to the total net debt ratio of the Company. Fees related to the credit facility vary according to the total net debt ratio of the Company. This credit facility is secured by some of the Company's real assets, guarantees by some of the Company’s subsidiaries and pledges of shares in some of the Company's subsidiaries. The maturity date of this credit facility is February 1, 2020. The Company was in compliance with its credit facility covenants as at September 30, 2017.

Upon entering into the $250 million credit facility described above, the Company terminated its four-year $500 million unsecured revolving credit facility. During the first quarter 2016 and prior to termination, the Company repaid the $70 million outstanding on the previous credit facility. Letters of credit worth $3.0 million were issued under the Company’s revolving credit facility and $0.4 million under a separate letter of credit. As of September 30, 2017, letters of credit worth $3.0 million were drawn against the credit facility for the guarantee of certain asset retirement obligations.


(c)	Uncollateralized surety bonds

As at September 30, 2017, C$123.6 million (September 30, 2017 - $98.8 million; December 31, 2016 ‐ $nil) of uncollateralized surety bonds were outstanding to guarantee the asset retirement obligation related to the Doyon mine. The uncollateralized surety bonds were issued pursuant to arrangements with international insurance companies (note 6(a)).

FINANCIAL INSTRUMENTS

9 Months Ended

Sep. 30, 2017

Financial Instruments [Abstract]

FINANCIAL INSTRUMENTS

(a)Financial assets measured at fair value through other comprehensive income

Marketable securities fair value reserve

Share market price exposure risk is related to the fluctuation in the market price of marketable securities. The Company’s portfolio of marketable securities is not part of its core operations, and accordingly, gains and losses from these marketable securities are not representative of the Company’s performance during the period. Consequently, the Company has designated all of its investments in marketable securities to be measured at fair value through Other comprehensive income ("OCI"). The Company’s portfolio of marketable securities is primarily focused on the mining sector and relates entirely to investments in equity securities.



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Proceeds from sale of marketable securities	$	7.4		$	—	$	7.7		$	0.1
Acquisition date fair value of marketable securities sold	(2.3		)	—		(2.4		)	(2.1		)
Gain (loss) on sale of marketable securities recorded in OCI	$	5.1		$	—	$	5.3		$	(2.0	)

(b)Cash flow hedge fair value reserve


(i)	Hedge gain/loss



	Gain (loss) recognized in cash flow hedge reserve						(Gain) loss reclassified or adjusted from cash flow hedge reserve
	Three months ended September 30, 2017			Nine months ended September 30, 2017			Three months ended September 30, 2017			Nine months ended September 30, 2017
Exchange rate risk
Canadian dollar option contracts	$	6.0		$	7.5		$	(1.4	)	$	(1.5	)
Euro option contracts	2.8			4.6			(1.1		)	(1.1		)
Crude oil option contracts	—			0.1			—			—
	8.8			12.2			(2.5		)	(2.6		)
Time value of option contracts excluded from hedge relationship	(1.7		)	(4.4		)	—			—
	$	7.1		$	7.8		$	(2.5	)	$	(2.6	)



	Gain (loss) recognized in cash flow hedge reserve						(Gain) loss reclassified or adjusted from cash flow hedge reserve
	Three months ended September 30, 2016			Nine months ended September 30, 2016			Three months ended September 30, 2016			Nine months ended September 30, 2016
Exchange rate risk
Canadian dollar option contracts	$	(2.3	)	$	0.5		$	1.2		$	4.8
Euro option contracts	—			1.8			(0.4		)	(1.2		)
Crude oil option contracts	(2.4		)	3.6			—			1.7
	(4.7		)	5.9			0.8			5.3
Time value of option contracts excluded from hedge relationship	(2.0		)	(1.4		)	—			—
	$	(6.7	)	$	4.5		$	0.8		$	5.3



	(Gain) loss reclassified from cash flow hedge reserve to:						(Gain) loss reclassified from cash flow hedge reserve to:
	Three months ended September 30, 2017			Three months ended September 30, 2016			Nine months ended September 30, 2017			Nine months ended September 30, 2016
Consolidated balance sheets
Property, plant and equipment	$	(0.6	)	$	(0.1	)	$	(0.6	)	$	0.1
Consolidated statements of earnings
Cost of sales	(1.6		)	0.6			(1.6		)	3.6
General and administrative expenses	(0.3		)	0.3			(0.4		)	1.6
Total	$	(2.5	)	$	0.8		$	(2.6	)	$	5.3

There was no hedge ineffectiveness for the three and nine months ended September 30, 2017 and 2016.


(ii)	Currency exchange rate risk

Movements in the Canadian dollar (C$) and the Euro (€) against the U.S. dollar ($) have a direct impact on the Company’s consolidated financial statements.

The Company manages its exposure to the Canadian dollar and the Euro by executing option contracts. The Company’s objective is to hedge its exposure to these currencies resulting from operating and capital expenditure requirements at some of its mine sites and corporate offices.

The Company has designated option contracts as cash flow hedges for its highly probable forecasted Canadian dollar and Euro expenditure requirements. The Company has elected to only designate the change in the intrinsic value of options in the hedging relationships. The change in fair value of the time value component of options is recorded in OCI as a cost of hedging.

An economic relationship exists between the hedged items and the hedging instruments as the fair values of both the hedged items and hedging instruments move in opposite directions in response to the same risk. The hedge ratio is determined by dividing the quantity of option contracts by the quantity of the forecasted Canadian dollar and Euro expenditure exposures.

As at September 30, 2017, the Company's outstanding derivative contracts which qualified for hedge accounting and the periods in which the cash flows are expected to occur and impact the Consolidated statements of earnings, are as follows:



	2017	2018	Total
Cash flow hedges
Exchange rate risk
Canadian dollar option contracts (millions of C$)	51	155	206
Contract rate range ($/C$)	1.30-1.40¹	1.30-1.45²
Euro option contracts (millions of €)	32	93	125
Contract rate range (€/$)	1.00-1.20³	1.08-1.19³

1

The Company purchased three types of Canadian dollar options in 2017, which consist of U.S. dollar put options at a strike price of $1.30, U.S. dollar put options at a strike price of $1.35, and collar options in the range of $1.30 and $1.40. The Company will benefit from the margin between the lower market price and the set U.S. dollar put strike price of $1.30 and $1.35. If U.S dollar to C$ market prices are above the $1.40 call strike prices in 2017, the Company will incur a loss from the margin between the higher market price and the $1.40 call strike price.

2

The Company purchased Canadian dollar collar options with strike prices within the given range in 2018. If U.S dollar to C$ market prices are below the low end of the range of the U.S. dollar put strike prices in 2018, the Company will benefit from the margin between the lower market price and the set put strike price. If U.S dollar to C$ market prices are above the high end of the range of the U.S. dollar call strike prices in 2018, the Company will incur a loss from the margin between the higher market price and the set call strike price.

3

The Company purchased Euro collar options with strike prices within the given range in 2017 and 2018. If EUR to U.S. dollar market prices are below the low end of the range in 2017 or 2018, the Company will incur a loss from the margin between the lower market price and the set put strike price. If EUR to U.S. dollar market prices are above the high end of the range of the call strike price in 2017 or 2018, the Company will benefit from the margin between the higher market price and the set call strike price.

Additional information on hedging instruments and hedged forecast transactions related to currency exchange rate risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Canadian option contracts	$	7.4	$	—	$	6.1	$	6.1	$	(6.1	)
Euro option contracts	4.6		—		3.2		3.2		(3.2		)
	$	12.0	$	—	$	9.3	$	9.3	$	(9.3	)



	Carrying amount								Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)			Hedging instruments			Hedged items
Canadian option contracts	$	2.1	$	—		$	0.2		$	0.2		$	(0.2	)
Euro option contracts	0.2		(2.0		)	(0.4		)	(0.4		)	0.4
	$	2.3	$	(2.0	)	$	(0.2	)	$	(0.2	)	$	0.2


(iii)	Oil and fuel market price risk

Low sulfur diesel and fuel oil are key inputs to extract tonnage and, in some cases, to wholly or partially power operations. Brent crude oil and West Texas Intermediate (WTI) are components of diesel and fuel oil, respectively, such that changes in the price of crude oil directly impacts diesel and fuel oil costs. The Company established a hedging strategy to limit the impact of fluctuations in crude oil prices and to economically hedge future consumption of diesel and fuel oil at the Rosebel and Essakane mines. The Company has designated option contracts as cash flow hedges for the crude oil component of its highly probable forecasted low sulfur diesel and fuel oil purchases.

As at September 30, 2017, the Company’s outstanding crude oil derivative contracts, which qualified for hedge accounting, and the periods in which the cash flows are expected to occur and impact the Consolidated statements of earnings, are as follows:



	2017	2018	2019	2020	Total
Brent crude oil option contracts (barrels)¹	130	488	366	243	1,227
Option contracts with strike prices at ($/barrel)	60²	42-60³	44-60³	50-62³
WTI crude oil option contracts (barrels)¹	99	390	306	207	1,002
Option contracts with strike prices at ($/barrel)	60²	36-60³	42-60³	45-55³


1	Quantities of barrels are in thousands.


2	The Company purchased call options with a strike price of $60. If crude oil prices are greater than the call strike price in 2017, the Company will benefit from the margin between the higher market price and the set call strike price.

3

The Company purchased Brent and WTI collar options with strike prices within the given range in 2018, 2019 and 2020. If Brent and WTI market prices are below the low end of the range in 2018, 2019 and 2020, the Company will incur a loss from the margin between the lower market price and the set put strike price. If Brent and WTI are above the high end of the range of the call strike price in 2018, 2019 and 2020, the Company will benefit from the margin between the higher market price and the set call strike price.

Additional information on hedging instruments and hedged forecast transactions related to oil and fuel market price risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount							Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	1.9	$	—		$	—	$	—	$	—
WTI crude oil option contracts	0.4		(0.1		)	—		—		—
	$	2.3	$	(0.1	)	$	—	$	—	$	—



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	4.0	$	—	$	—	$	—	$	—
WTI crude oil option contracts	2.2		—		—		—		—
	$	6.2	$	—	$	—	$	—	$	—

(c)Gain on embedded derivative and warrants

Gain on embedded derivative and warrants is included in Interest income and derivatives and other investment gains (note 25) in the Consolidated statements of earnings. These gains relate to warrants associated with the Company's investments in marketable securities and the fair value movement of the embedded derivative.



		Three months ended September 30,				Nine months ended September 30,
	Notes	2017		2016		2017		2016
Embedded derivative	17(a)	$	3.7	$	—	$	5.3	$	—
Warrants		0.5		1.3		0.1		5.3
	25	$	4.2	$	1.3	$	5.4	$	5.3

FAIR VALUE MEASUREMENTS

9 Months Ended

Sep. 30, 2017

Fair Value Measurement [Abstract]

FAIR VALUE MEASUREMENTS

The fair value hierarchy categorizes into three levels the inputs to valuation techniques used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices (unadjusted) in active markets for identical assets or liabilities (Level 1 inputs) and the lowest priority to unobservable inputs (Level 3 inputs).


▪	Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities which the entity can access at the measurement date.


▪	Level 2 inputs are inputs other than quoted prices included within Level 1 which are observable for the asset or liability, either directly or indirectly such as those derived from prices.


▪	Level 3 inputs are unobservable inputs for the asset or liability.

There have been no changes in the classification of the financial instruments in the fair value hierarchy since December 31, 2016.


(a)	Financial assets and liabilities measured at fair value on a recurring basis

As at September 30, 2017, the Company’s fair value of financial assets and liabilities were as follows:



	September 30, 2017														December 31, 2016
	Carrying Amount			Level 1			Level 2			Level 3		Total Fair Value			Total Fair Value
Assets
Cash and cash equivalents	$	583.6		$	583.6		$	—		$	—	$	583.6		$	652.0
Restricted cash	24.7			24.7			—			—		24.7			110.7
Short-term investments	227.0			227.0			—			—		227.0			—
Marketable securities and warrants	30.1			25.0			5.1			—		30.1			21.9
Bond fund investments	2.7			2.7			—			—		2.7			5.9
Derivatives
Currency contracts	12.0			—			12.0			—		12.0			2.3
Crude oil contracts	2.3			—			2.3			—		2.3			6.2
Embedded derivative	9.5			—			9.5			—		9.5			—
	$	891.9		$	863.0		$	28.9		$	—	$	891.9		$	799.0
Liabilities
Derivatives
Currency contracts	$	—		$	—		$	—		$	—	$	—		$	(2.0	)
Crude oil contracts	(0.1		)	—			(0.1		)	—		(0.1		)	—
6.75% Senior unsecured notes	—			—			—			—		—			(474.0		)
Long-term debt - 7% Senior notes	(400.0		)	(421.8		)	—			—		(421.8		)	—
	$	(400.1	)	$	(421.8	)	$	(0.1	)	$	—	$	(421.9	)	$	(476.0	)


(b)	Valuation techniques

Cash, cash equivalents and short-term investments

Cash, cash equivalents and short-term investments are included in Level 1 due to the short-term maturity of these financial instruments.

Marketable securities and warrants

The fair value of marketable securities included in Level 1 is determined based on a market approach. The closing price is a quoted market price from the exchange market which is the principal active market for the particular security. The fair value of warrants included in Level 2 is obtained through the use of Black-Scholes pricing model, which uses share price inputs and volatility measurements. The fair value of investments in equity instruments which are not actively traded is determined using valuation techniques which require inputs that are both unobservable and significant, and therefore were categorized as Level 3 in the fair value hierarchy. The Company used the latest transaction price for these securities, obtained from the entity, to value these marketable securities and warrants.

Bond fund investments

The fair value of bond fund investments included in Level 1 is measured using quoted prices (unadjusted) in active markets.

Derivatives

For derivative contracts, the Company obtains a valuation of the contracts from counterparties of those contracts. The Company assesses the reasonableness of these valuations through internal methods and third-party valuations. The Company then calculates a credit valuation adjustment to reflect the counterparty’s or the Company’s own default risk. Valuations are based on the present value of market valuations considering interest rate and volatility, taking into account the credit risk of the financial instrument. Valuations of derivative contracts are therefore classified within Level 2 of the fair value hierarchy (note 17(a)).

Embedded Derivative

The fair value of the embedded derivative as at September 30, 2017 was $9.5 million and is accounted for at FVTPL. The valuation is based on the discounted cash flows at the risk-free rate to determine the present value of the redemption option. Key inputs used in the valuation include the credit spread, volatility parameter and the risk-free rate curve. Valuation of the redemption option is therefore classified within Level 2 of the fair value hierarchy.

Senior Notes

The fair value of Senior Notes required to be disclosed is determined using quoted prices (unadjusted) in active markets, and is therefore classified within Level 1 of the fair value hierarchy. The fair value of the Notes as at September 30, 2017 was $421.8 million (December 31, 2016 - $474.0 million).

Investments in associates

Investments in associates are measured at fair value on a non-recurring basis when an impairment charge or reversal is to be recorded. After application of the equity method, the fair value of an investment in associate is determined for purposes of assessing whether an impairment charge or reversal of a previously recorded impairment charge is required. For publicly traded companies, the Company determines the fair value of its investments in associates based on a market approach reflecting the closing price of the investments in the associates' shares at the balance sheet date. Since there is a quoted market price, this is classified within Level 1 of the fair value hierarchy. As at September 30, 2017, no investments in associates were measured at fair value.

Finance lease liabilities

Finance lease liabilities are accounted for at amortized cost, using the effective interest rate method. The fair value required to be disclosed is determined using market interest rate inputs and is therefore classified within Level 2 of the fair value hierarchy (note 15). The fair value at September 30, 2017 of the Company's finance lease liabilities approximates their carrying amount of $0.1 million (December 31, 2016 - $0.1 million).

Other financial assets and liabilities

The fair value of all other financial assets and liabilities of the Company approximate their carrying amounts.

SHARE CAPITAL

9 Months Ended

Sep. 30, 2017

Share Capital, Reserves And Other Equity Interest [Abstract]

SHARE CAPITAL

The Company is authorized to issue an unlimited number of common shares, first preference shares issuable in series and second preference shares issuable in series.



		Nine months ended September 30,
Number of common shares (in millions)	Notes	2017	2016
Outstanding, beginning of the period		453.8	393.4
Equity issuance	4	6.9	44.7
Issuance of flow-through common shares		3.4	12.0
Issuance of shares for share-based compensation		0.8	0.6
Outstanding, end of period		464.9	450.7

Flow-through common shares

In March 2017, the Company issued 3.4 million flow-through common shares at C$5.91 per share for net proceeds of $15.1 million (C$20.0 million), which included a $1.7 million premium reported as a deferred gain on the balance sheet to be recognized in earnings as eligible expenditures are made. A total of $13.4 million was recognized in equity based on the quoted price of the shares on the date of the issue less issuance costs. The flow-through common shares were issued to fund prescribed development expenditures on the Westwood mine. Flow-through common shares require the Company to incur an amount equivalent to the proceeds of the issue on prescribed expenditures in accordance with the applicable tax legislation. As at September 30, 2017, there was no remaining unspent amount.

During the fourth quarter 2016, the Company issued 0.9 million flow-through common shares at prices ranging between C$6.56 and C$6.63 per share for net proceeds of $4.4 million (C$5.9 million), which included a $1.1 million premium reported as a deferred gain on the balance sheet to be recognized in earnings as eligible expenditures are made. A total of $3.3 million was recognized in equity based on the quoted price of the shares on the date of the issue less issuance costs. The flow-through common shares were issued to fund prescribed exploration expenditures on the Côté Gold Project. As at September 30, 2017, the remaining unspent amount was $0.5 million.

Additionally, during the fourth quarter 2016, the Company issued 2.2 million flow-through common shares at prices ranging between C$5.34 and C$5.60 per share for net proceeds of $8.9 million (C$11.9 million), which included a $0.8 million premium reported as a deferred gain on the balance sheet to be recognized in earnings as eligible expenditures are made. A total of $8.1 million was recognized in equity based on the quoted price of the shares on the date of the issue less issuance costs. The flow-through common shares were issued to fund prescribed development expenditures on the Westwood mine. As at September 30, 2017, there was no remaining unspent amount.

For the three and nine months ended September 30, 2017, $0.2 million and $3.5 million were recognized as amortization of the gains related to the issuances of flow-through common shares described above (three and nine months ended September 30, 2016 - $1.2 million and $3.3 million), respectively, and was included in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).

Contingently issuable shares

On December 12, 2016, the Company finalized the agreement with the Government of Suriname to acquire the rights to the Saramacca property. Under the terms of the agreement, the rights to the Saramacca property were transferred to Rosebel in exchange for an initial cash payment of $10.0 million which was accounted for as an Exploration and evaluation asset as at December 31, 2016. The purchase consideration also included 3.125 million contingently issuable IAMGOLD common shares to be delivered in three approximately equal tranches in 12 months intervals, from the date the rights to the Saramacca property were transferred to Rosebel. In addition, the agreement provides for a potential upward adjustment to the purchase price based on the contained gold ounces identified at the Saramacca property in National Instrument 43-101 indicated and measured resource categories, within a certain Whittle shell, over the first 24 months, to a maximum of $10.0 million. Under the terms of the agreement, the Company can at any time during the course of the agreement provide 60 days' notice to the Government of Suriname and terminate the agreement. In such an event, any contingently issuable IAMGOLD common shares not already issued will no longer be required to be delivered to the Government of Suriname.

Equity issuance

On August 8, 2016, the Company entered into a public equity offering of 38.9 million common shares at a price of $5.15 per common share for gross proceeds of $200 million. On August 16, 2016, the underwriters elected to exercise an option to purchase up to an additional 15% of the offering, and as a result, an additional 5.8 million common shares were issued at a price of $5.15 per common share. The issuance was completed on August 16, 2016 and increased the gross proceeds from the offering to $230.0 million, less transaction costs of $9.9 million for net proceeds of $220.1 million for a total of 44.7 million shares.

EARNINGS PER SHARE

9 Months Ended

Sep. 30, 2017

Earnings per share [abstract]

EARNINGS PER SHARE

Basic earnings per share computation



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Numerator
Net earnings attributable to equity holders of IAMGOLD	$	30.8	$	17.0	$	519.3	$	57.9
Denominator (in millions)
Weighted average number of common shares (basic)	464.7		428.3		462.3		410.3
Basic earnings attributable to equity holders of IAMGOLD ($/share)	$	0.07	$	0.04	$	1.12	$	0.14

Diluted earnings per share computation



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Denominator (in millions)
Weighted average number of common shares (basic)	464.7		428.3		462.3		410.3
Dilutive effect of share options	1.2		1.0		1.2		0.4
Dilutive effect of restricted share units	3.4		2.9		3.2		2.5
Weighted average number of common shares (diluted)	469.3		432.2		466.7		413.2
Diluted earnings attributable to equity holders of IAMGOLD ($/share)	$	0.07	$	0.04	$	1.11	$	0.14

Equity instruments excluded from the computation of diluted earnings per share, which could be dilutive in the future, were as follows:



		Three months ended September 30,		Nine months ended September 30,
(in millions)	Notes	2017	2016	2017	2016
Share options		2.6	3.0	2.6	4.1
Contingently issuable shares	20	3.1	3.1	3.1	3.1
		5.7	6.1	5.7	7.2

SHARE-BASED COMPENSATION

9 Months Ended

Sep. 30, 2017

Share-Based Payment Arrangements [Abstract]

SHARE-BASED COMPENSATION

(a)Share option award plan



Nine months ended September 30, 2017	Share options (in millions)		Weighted average exercise price (C$/share)¹
Outstanding, beginning of the period	6.0		$	7.79
Granted	1.6		5.24
Exercised	(0.2	)	5.26
Forfeited	(0.5	)	12.22
Outstanding, end of the period	6.9		$	7.03
Exercisable, end of the period	3.4		$	9.72


1	Exercise prices are denominated in Canadian dollars. The exchange rate at September 30, 2017 between the U.S. dollar and Canadian dollar was

$0.7992/C$.

The following were the weighted average inputs to the Black-Scholes model used in determining the fair value of the options granted. The estimated fair value of the options is expensed over their expected life.



Nine months ended September 30, 2017
Weighted average risk-free interest rate	1.1		%
Weighted average expected volatility¹	66		%
Weighted average dividend yield	0.00		%
Weighted average expected life of options issued (years)	5.0
Weighted average grant-date fair value (C$ per share)	$	2.89
Weighted average share price at grant date (C$ per share)	$	5.24
Weighted average exercise price (C$ per share)	$	5.24


1	Expected volatility is estimated by considering historic average share price volatility based on the average expected life of the options.

(b)Full value award plans

Full value awards consist of restricted share units.



Nine months ended September 30, 2017 (in millions)
Outstanding, beginning of the period	3.7
Granted	2.2
Issued	(0.6	)
Forfeited	(0.7	)
Outstanding, end of the period	4.6

The following were the weighted average inputs to the Black-Scholes model used in determining the fair value of the restricted share units granted. The estimated fair value of the awards is expensed over their vesting period.



Nine months ended September 30, 2017
Weighted average risk-free interest rate	0.8		%
Weighted average expected volatility¹	72		%
Weighted average dividend yield	0.00		%
Weighted average expected life of RSUs issued (years)	2.8
Weighted average grant-date fair value (C$ per share)	$	5.24
Weighted average share price at grant date (C$ per share)	$	5.24


1	Expected volatility is estimated by considering historic average share price volatility based on the average expected life of the restricted share units.

COST OF SALES

9 Months Ended

Sep. 30, 2017

Analysis of income and expense [abstract]

COST OF SALES



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Operating costs¹	$	154.5	$	147.4	$	461.9	$	425.9
Royalties	11.1		13.5		32.9		32.5
Depreciation expense²	62.3		69.3		197.2		193.1
	$	227.9	$	230.2	$	692.0	$	651.5


1	Operating costs include mine production, transport and smelter costs, and site administrative expenses.


2	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

FINANCE COSTS

9 Months Ended

Sep. 30, 2017

Borrowing costs [abstract]

FINANCE COSTS



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Interest expense	$	0.9	$	5.9	$	6.8	$	19.9
Credit facility fees	0.9		0.4		2.1		1.2
Accretion expense	0.3		—		0.7		0.6
	$	2.1	$	6.3	$	9.6	$	21.7

Total interest paid during the three and nine months ended September 30, 2017 was $nil and $16.5 million, respectively (three and nine months ended September 30, 2016 - $20.3 million and $41.9 million, respectively). Interest paid relates to interest charges on notes, credit facilities and finance leases.

INTEREST INCOME AND DERIVATIVES AND OTHER INVESTMENT GAINS

9 Months Ended

Sep. 30, 2017

Analysis of income and expense [abstract]

INTEREST INCOME AND DERIVATIVES AND OTHER INVESTMENT GAINS



		Three months ended September 30,					Nine months ended September 30,
	Notes	2017		2016			2017			2016
Interest income		$	2.5	$	0.8		$	6.4		$	1.9
Gain on embedded derivative and warrants	18(c)	4.2		1.3			5.4			5.3
Gain on sale of a 30% interest in the Côté Gold Project	5	—		—			19.2			—
Amortization of gains related to flow-through common shares	20	0.2		1.2			3.5			3.3
Loss on redemption of 6.75% Senior unsecured notes	17(a)	—		—			(20.2		)	—
Gain on purchase of 6.75% Senior unsecured notes	17(a)	—		4.0			—			4.0
Write-down of receivables		—		(1.5		)	—			—
Gain on sale of gold bullion		—		—			—			72.9
Other gains (losses)		0.4		(0.3		)	0.5			1.3
		$	7.3	$	5.5		$	14.8		$	88.7

CASH FLOW ITEMS

9 Months Ended

Sep. 30, 2017

Cash Flow Statement [Abstract]

CASH FLOW ITEMS

(a) Adjustments for other non-cash items within operating activities



		Three months ended September 30,						Nine months ended September 30,
	Notes	2017			2016			2017			2016
Share-based compensation		$	1.3		$	1.1		$	4.4		$	3.6
Amortization of gains related to flow-through common shares	25	(0.2		)	(1.2		)	(3.5		)	(3.3		)
Changes in estimates of asset retirement obligations at closed sites		(2.2		)	—			(0.9		)	3.3
Gain on derivatives		(6.1		)	(0.8		)	(7.3		)	(1.3		)
Gain on purchase of 6.75% senior unsecured notes	25	—			(4.0		)	—			(4.0		)
Write-down of assets		0.2			1.3			1.5			4.1
Other		0.8			(0.6		)	0.7			0.5
		$	(6.2	)	$	(4.2	)	$	(5.1	)	$	2.9


(b)	Movements in non-cash working capital items and non-current ore stockpiles



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Receivables and other current assets	$	7.8		$	6.6	$	10.1		$	(0.5	)
Inventories and non-current ore stockpiles	(19.8		)	1.9		(20.6		)	7.4
Accounts payable and accrued liabilities	15.5			6.0		14.8			15.5
	$	3.5		$	14.5	$	4.3		$	22.4


(c)	Other investing activities



		Three months ended September 30,						Nine months ended September 30,
	Notes	2017			2016			2017			2016
Disposal (acquisition) of investments		$	0.7		$	1.5		$	1.1		$	(2.0	)
Advances to related parties	29	(3.0		)	(0.6		)	(5.3		)	(2.4		)
Repayments from related parties	29	0.3			0.2			0.8			2.3
Other		—			0.2			0.1			0.9
		$	(2.0	)	$	1.3		$	(3.3	)	$	(1.2	)


(d)	Other financing activities



	Three months ended September 30,						Nine months ended September 30,
	2017			2016			2017			2016
Repayment of finance lease liabilities	$	—		$	(0.1	)	$	—		$	(1.0	)
Dividends paid to non-controlling interests	(2.0		)	—			(3.1		)	(1.5		)
Other finance costs	(1.6		)	(0.5		)	(2.5		)	(2.8		)
	$	(3.6	)	$	(0.6	)	$	(5.6	)	$	(5.3	)


(e)	Reconciliation of long-term debt arising from financing activities



	Notes
Balance, December 31, 2016		$	485.1
Net proceeds from issuance of senior notes	17(a)	393.6
Non-cash changes:
Amortization of deferred financing charges		0.7
Change in fair value of embedded derivative	18(c)	(5.3		)
Loss on redemption of 6.75% Senior unsecured notes	17(a)	20.2
Cash changes:
Repayment of 6.75% Senior unsecured notes	17(a)	(505.6		)
Balance, September 30, 2017		$	388.7

REVERSAL OF IMPAIRMENT CHARGES

9 Months Ended

Sep. 30, 2017

Impairment Of Assets [Abstract]

REVERSAL OF IMPAIRMENT CHARGES



		Three months ended September 30,				Nine months ended September 30,
	Notes	2017		2016		2017		2016
Suriname CGU¹
Property, plant and equipment	11	$	—	$	—	$	124.1	$	—
Côté Gold Project
Exploration and evaluation assets	12	—		—		400.0		—
		$	—	$	—	$	524.1	$	—

1 The Suriname CGU consists of Rosebel Gold Mines N.V. and Euro Ressources S.A.

Property, plant and equipment

The Company performs an assessment at each reporting date to determine whether there is an indication of potential reversal of previously recognized impairment losses. On July 26, 2017 (effective June 30, 2017), the Company identified a significant increase in reserves and resources and corresponding extension of the life of mine ("LOM") for the Rosebel mine, which were considered to be an indicator of reversal, as these represented a significant change in the key inputs used to determine the cash generating unit's ("CGU") recoverable amount. As a result, an assessment was performed for the Company’s Suriname CGU, and it was determined that the recoverable amount, representing the CGU’s fair value less costs of disposal ("FVLCD"), exceeded the carrying amount. This resulted in a reversal of the impairment charge recorded in 2013, which was limited to the carrying amount of the Suriname CGU that would have been determined had no impairment charge been recognized in prior years, net of depreciation charges. The pre-tax and after-tax amounts of impairment reversal recorded in the Company’s Consolidated statements of earnings in the second quarter of 2017 were $124.1 million and $79.9 million, respectively.

The significant estimates and assumptions used in determining the FVLCD for the CGU were LOM production profiles, future commodity prices, reserves and resources, discount rate, values of un-modeled mineralization and capital expenditures. The estimates of future cash flows were derived from the most recent LOM of approximately 11 years, which is based on Management’s current best estimates of optimized mine and processing plans, future operating costs and capital expenditures. For the assessment, the Company used an estimated gold price of $1,225 per ounce for the first 5 years starting 2018, decreasing to $1,200 per ounce for 2023 and beyond.

The future cash flows used to calculate the recoverable amount of the CGU were discounted using a real weighted average cost of capital of 6%, which reflects specific market risk factors for the mine. Un-modeled mineralization for the CGU was valued at $45 per ounce. Oil price is a significant component of cash costs of production and was estimated based on the current price, forward prices, forecasts of future prices from third-party sources and the Company’s hedging program.

Exploration and evaluation assets

On June 5, 2017, upon entering into a definitive Investment Agreement with SMM for the sale of a 30% interest in the Côté Gold Project (note 5), the Company performed an assessment of whether the previous impairment charge on the Project had reversed. The Company determined that the consideration agreed to by SMM indicated the recoverable amount exceeded the carrying amount, which resulted, in the second quarter of 2017, in the reversal of the previously recorded impairment charge of $400 million. The reversal is limited to the carrying amount that would have been determined had no impairment charge been recognized in prior years.

COMMITMENTS

9 Months Ended

Sep. 30, 2017

Commitments [Abstract]

COMMITMENTS



	September 30, 2017		December 31, 2016
Purchase obligations	$	78.2	$	53.2
Capital expenditure obligations	26.3		4.6
Operating leases	18.1		4.3
	$	122.6	$	62.1

Commitments – payments due by period



	Payments due by period
As at September 30, 2017	Total		<1 yr		1-2 yrs		3-5 yrs		>5 yrs
Purchase obligations	$	78.2	$	71.9	$	5.7	$	0.4	$	0.2
Capital expenditure obligations	26.3		22.5		3.8		—		—
Operating leases	18.1		1.5		10.1		6.5		—
	$	122.6	$	95.9	$	19.6	$	6.9	$	0.2

RELATED PARTY TRANSACTIONS

9 Months Ended

Sep. 30, 2017

Related Party [Abstract]

RELATED PARTY TRANSACTIONS

Receivables from related parties

The Company had the following related party transactions included in Receivables and other current assets and in Other non-current assets in the Consolidated balance sheets:



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Sadiola and Yatela (Non-interest bearing)
Balance, beginning of the period	$	0.2		$	—	$	0.2		$	0.2
Advances	0.2			—		0.7			—
Repayments	(0.3		)	—		(0.8		)	(0.2		)
Balance, end of the period¹	$	0.1		$	—	$	0.1		$	—
Sadiola Sulphide Project (LIBOR plus 2%)²
Balance, beginning of the period	$	33.1		$	30.2	$	31.3		$	29.3
Advances	2.8			0.3		4.6			1.2
Balance, end of the period¹	$	35.9		$	30.5	$	35.9		$	30.5


1	Balances as of December 31, 2016 for Sadiola and Yatela and for the Sadiola Sulphide Project were $0.2 million and $31.3 million, respectively.


2	These advances were part of an extended loan agreement, reached in the fourth quarter of 2016, for the Sadiola Sulphide Project, and are to be repaid on the earlier of December 31, 2020 or, at such time as Sadiola has sufficient free cash flow.

SEGMENTED INFORMATION

9 Months Ended

Sep. 30, 2017

Operating Segments [Abstract]

SEGMENTED INFORMATION

The Company’s gold mine segment is divided into the following geographic segments:

•Burkina Faso - Essakane mine;

•Suriname - Rosebel mine;

•Canada - Doyon division includes the Westwood mine and the Doyon mine, which is in closure; and

•Incorporated joint ventures (Mali) - Sadiola mine (41%) and Yatela mine, which is in closure (40%).

The Company’s non-gold segments are divided into the following:

•Exploration and evaluation; and

•Corporate - includes royalty interests located in Canada and investments in associates and incorporated joint ventures.



	September 30, 2017						December 31, 2016
	Total non- current assets		Total assets		Total liabilities		Total non- current assets		Total assets		Total liabilities
Gold mines
Burkina Faso	$	842.4	$	1,065.2	$	193.3	$	883.4	$	1,099.6	$	189.9
Suriname	615.3		799.0		247.6		512.8		667.3		198.1
Canada	691.1		713.8		188.5		675.0		783.7		195.8
Total gold mines	2,148.8		2,578.0		629.4		2,071.2		2,550.6		583.8
Exploration and evaluation	433.7		476.0		6.8		163.1		193.2		8.4
Corporate¹	276.0		881.4		446.4		153.3		656.7		537.2
Total per consolidated financial statements	$	2,858.5	$	3,935.4	$	1,082.6	$	2,387.6	$	3,400.5	$	1,129.4
Incorporated joint ventures (Mali)²	$	127.3	$	173.0	$	147.9	$	116.5	$	160.2	$	144.1


1	The carrying amount of the Investment in incorporated joint ventures is included in the corporate segment as non-current assets.


2	The breakdown of the financial information for the incorporated joint ventures has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess performance of the incorporated joint ventures and to make resource allocation decisions.

Three months ended September 30, 2017



	Consolidated statement of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other			Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	130.2	$	82.2	$	31.0	$	—	$	—	$	—	$	—		$	17.0		$	16.8
Suriname	97.1		57.5		20.0		—		0.1		—		0.4			19.1			13.2
Canada	41.4		25.9		10.5		—		—		—		(2.0		)	7.0			14.0
Total gold mines excluding incorporated joint ventures	268.7		165.6		61.5		—		0.1		—		(1.6		)	43.1			44.0
Exploration and evaluation⁴	—		—		—		—		6.5		—		0.1			(6.6		)	0.5
Corporate⁵	0.1		—		0.8		8.9		—		—		—			(9.6		)	0.2
Total per consolidated financial statements	268.8		165.6		62.3		8.9		6.6		—		(1.5		)	26.9			44.7
Incorporated joint ventures (Mali)⁶	19.6		13.9		0.4		—		0.5		—		—			4.8			2.4
	$	288.4	$	179.5	$	62.7	$	8.9	$	7.1	$	—	$	(1.5	)	$	31.7		$	47.1


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Three months ended September 30, 2016



	Consolidated statement of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other		Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	167.6	$	84.6	$	32.3	$	—	$	—	$	—	$	0.9	$	49.8		$	16.9
Suriname	92.2		53.4		21.7		—		1.2		—		0.2		15.7			34.2
Canada	22.4		21.6		14.2		—		—		—		0.3		(13.7		)	20.9
Total gold mines excluding incorporated joint ventures	282.2		159.6		68.2		—		1.2		—		1.4		51.8			72.0
Exploration and evaluation⁴	—		—		0.1		0.1		5.3				0.1		(5.6		)	0.4
Corporate⁵	0.2		1.3		1.0		9.9		—		—		0.4		(12.4		)	0.1
Total per consolidated financial statements	282.4		160.9		69.3		10.0		6.5		—		1.9		33.8			72.5
Incorporated Joint ventures (Mali)⁶	21.2		17.8		0.3		—		0.2		—		—		2.9			1.1
	$	303.6	$	178.7	$	69.6	$	10.0	$	6.7	$	—	$	1.9	$	36.7		$	73.6


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Nine months ended September 30, 2017



	Consolidated statements of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)			Other			Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	402.2	$	250.2	$	98.0	$	—	$	—	$	—		$	—		$	54.0		$	52.5
Suriname	286.3		171.4		63.4		—		4.9		(116.0		)	2.3			160.3			36.7
Canada	115.0		73.2		33.0		—		—		—			(1.0		)	9.8			47.6
Total gold mines excluding incorporated joint ventures	803.5		494.8		194.4		—		4.9		(116.0		)	1.3			224.1			136.8
Exploration and evaluation⁴	—		—		0.1		0.1		24.7		(400.0		)	0.3			374.8			1.3
Corporate⁵	0.3		—		2.7		27.7		—		(8.1		)	6.4			(28.4		)	0.4
Total per consolidated financial statements	803.8		494.8		197.2		27.8		29.6		(524.1		)	8.0			570.5			138.5
Incorporated joint ventures (Mali)⁶	58.7		41.1		1.1		—		1.1		—			—			15.4			5.8
	$	862.5	$	535.9	$	198.3	$	27.8	$	30.7	$	(524.1	)	$	8.0		$	585.9		$	144.3


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Nine months ended September 30, 2016



	Consolidated statements of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other		Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	399.2	$	223.8	$	78.8	$	—	$	—	$	—	$	0.8	$	95.8		$	82.4
Suriname	269.4		169.4		72.9		—		2.8		—		3.6		20.7			67.8
Canada	65.4		64.2		38.0		—		—		—		3.6		(40.4		)	69.1
Total gold mines excluding incorporated joint ventures	734.0		457.4		189.7		—		2.8		—		8.0		76.1			219.3
Exploration and evaluation⁴	—		—		0.2		0.3		17.8		—		0.3		(18.6		)	2.7
Corporate⁵	0.6		1.0		3.2		28.5		—		—		1.9		(34.0		)	0.8
Total per consolidated financial statements	734.6		458.4		193.1		28.8		20.6		—		10.2		23.5			222.8
Incorporated joint ventures (Mali)⁶	67.5		51.0		2.2		—		0.5		—		1.5		12.3			2.7
	$	802.1	$	509.4	$	195.3	$	28.8	$	21.1	$	—	$	11.7	$	35.8		$	225.5


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, finance lease payments and is net of proceeds from finance leases.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

BASIS OF PREPARATION (Policies)	9 Months Ended
BASIS OF PREPARATION (Policies)	Sep. 30, 2017
Corporate Information And Statement Of IFRS Compliance [Abstract]
Statement of compliance	The unaudited condensed consolidated interim financial statements ("consolidated interim financial statements") of IAMGOLD and all of its subsidiaries, joint ventures and associates as at and for the three and nine months ended September 30, 2017, have been prepared in accordance with IAS 34, Interim Financial Reporting, and do not include all of the information required for annual consolidated financial statements. Accordingly, certain information and disclosures normally included in annual financial statements prepared in accordance with International Financial Reporting Standards ("IFRS") have been omitted or condensed. These consolidated interim financial statements should be read in conjunction with IAMGOLD's audited annual consolidated financial statements and related notes as at and for the year ended December 31, 2016. These consolidated interim financial statements of IAMGOLD were authorized for issue in accordance with a resolution of the Board of Directors on November 7, 2017.
Basis of measurement	The consolidated interim financial statements have been prepared on a historical cost basis, except for items measured at fair value as discussed in note 19.
Significant accounting judgments, estimates and assumptions	The preparation of consolidated interim financial statements requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities and contingent liabilities as at the date of the consolidated interim financial statements and reported amounts of revenues and expenses during the three and nine months ended September 30, 2017. Estimates and assumptions are continuously evaluated and are based on management’s experience and other factors, including expectations of future events which are believed to be reasonable under the circumstances. Actual results may differ from these estimates.

BASIS OF PREPARATION (Tables)

9 Months Ended

Sep. 30, 2017

Corporate Information And Statement Of IFRS Compliance [Abstract]

Disclosure of subsidiaries

Subsidiaries, divisions and investments in joint ventures related to significant properties of the Company are accounted for as outlined below.



Name	Property – Location	September 30, 2017	December 31, 2016	Type of Arrangement	Accounting Method
Essakane S.A.	Essakane mine (Burkina Faso)	90%	90%	Subsidiary	Consolidation
Rosebel Gold Mines N.V.	Rosebel mine (Suriname)	95%	95%	Subsidiary	Consolidation
Doyon division including the Westwood mine	Doyon division (Canada)	100%	100%	Division	Consolidation
Côté Gold division¹	Côté Gold Project (Canada)	70%	100%	Division	Proportionate share
Euro Ressources S.A.	France	90%	90%	Subsidiary	Consolidation
Société d'Exploitation des Mines d'Or de Sadiola S.A.	Sadiola mine (Mali)	41%	41%	Incorporated joint venture	Equity accounting
Merrex Gold Inc.²	Siribaya Project (Mali)	100%	23%	Subsidiary	Consolidation


1	Effective June 20, 2017, the Company holds an undivided interest in the assets, liabilities, revenues and expenses of the Côté Gold division through an unincorporated joint venture (note 5).


2	As of February 28, 2017 (note 4).

Disclosure of joint ventures

Subsidiaries, divisions and investments in joint ventures related to significant properties of the Company are accounted for as outlined below.



Name	Property – Location	September 30, 2017	December 31, 2016	Type of Arrangement	Accounting Method
Essakane S.A.	Essakane mine (Burkina Faso)	90%	90%	Subsidiary	Consolidation
Rosebel Gold Mines N.V.	Rosebel mine (Suriname)	95%	95%	Subsidiary	Consolidation
Doyon division including the Westwood mine	Doyon division (Canada)	100%	100%	Division	Consolidation
Côté Gold division¹	Côté Gold Project (Canada)	70%	100%	Division	Proportionate share
Euro Ressources S.A.	France	90%	90%	Subsidiary	Consolidation
Société d'Exploitation des Mines d'Or de Sadiola S.A.	Sadiola mine (Mali)	41%	41%	Incorporated joint venture	Equity accounting
Merrex Gold Inc.²	Siribaya Project (Mali)	100%	23%	Subsidiary	Consolidation


1	Effective June 20, 2017, the Company holds an undivided interest in the assets, liabilities, revenues and expenses of the Côté Gold division through an unincorporated joint venture (note 5).


2	As of February 28, 2017 (note 4).

ACQUISITION (Tables)

9 Months Ended

Sep. 30, 2017

Acquisition [Abstract]

Disclosure of purchase price allocation



Assets acquired and liabilities assumed	Notes
Exploration and evaluation assets	12	$	36.6
Current liabilities		(3.9		)
Other non-current liabilities		(0.4		)
		$	32.3
Consideration transferred
Share consideration		$	27.4
Less: Cash and cash equivalents acquired		(0.1		)
Transaction costs		0.2
		27.5
Initial investment¹	10	4.8
		$	32.3

1

Prior to completion of the above mentioned transaction, IAMGOLD owned approximately 45.8 million common shares of Merrex, which represented approximately 23% of Merrex's issued and outstanding common shares, and was accounted for as an investment in an associate, using the equity method (note 10). The carrying amount of the investment of $4.8 million on the date of the acquisition has been included in the total cost of the Merrex Exploration and evaluation assets (note 12).

DIVESTITURE (Tables)

9 Months Ended

Sep. 30, 2017

Non-current Asset Held For Sale And Discontinued Operations [Abstract]

Sale Of Ownership Interest In Associates

The following represents the Company's 30% interest in the Côté Gold Project which was sold to SMM on June 20, 2017:



Carrying amount	Notes	30% disposal
Current assets		$	0.1
Exploration and evaluation assets	12	167.3
Non-current assets		0.6
Current liabilities		(0.1		)
Other non-current liabilities		(0.3		)
		$	167.6

The following represents the Company's gain recorded on the sale of a 30% interest in the Côté Gold Project to SMM:



	Notes
Gross sale consideration		$	195.0
Less:
Sale of a 30% interest in the Côté Gold Project		(167.6		)
Transaction costs		(6.4		)
Time value discount on long-term receivable		(1.8		)
Gain on sale of a 30% interest in the Côté Gold Project	25	$	19.2

SHORT-TERM INVESTMENTS (Tables)

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

Schedule Of Short-Term Investments



	September 30, 2017		December 31, 2016
Money market funds¹	$	224.3	$	—
Other	2.7		—
	$	227.0	$	—


1	Money market funds are comprised of short-term fund investments with redemption notice periods of 95 or 185 days.

RECEIVABLES AND OTHER CURRENT ASSETS (Tables)

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

Components of receivables and other current assets



	Notes	September 30, 2017		December 31, 2016
Gold receivables		$	1.5	$	2.7
Receivables from governments¹		33.6		40.4
Receivables from related parties	29	0.1		1.2
Other receivables		4.9		4.9
Total receivables		40.1		49.2
Marketable securities and warrants		—		0.2
Prepaid expenses		6.0		7.2
Derivatives	19(a)	10.7		4.4
		$	56.8	$	61.0


1	Receivables from governments relate primarily to value added tax.

INVENTORIES (Tables)

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

Disclosure of Current and Non-Current Inventories



	Notes	September 30, 2017		December 31, 2016
Finished goods		$	59.4	$	49.1
Ore stockpiles		5.3		9.1
Mine supplies		144.8		149.7
		209.5		207.9
Ore stockpiles included in other non-current assets	13	167.6		156.0
		$	377.1	$	363.9

INVESTMENTS IN ASSOCIATES AND INCORPORATED JOINT VENTURES (Tables)

9 Months Ended

Sep. 30, 2017

Interests In Other Entities [Abstract]

Disclosure of Associates



	Associates¹			Sadiola²			Yatela²			Total
Balance, January 1, 2016	$	7.4		$	49.2		$	—		$	56.6
Currency translation adjustment	(0.3		)	—			—			(0.3		)
Share of net earnings (loss), net of income taxes	(0.8		)	9.0			(2.1		)	6.1
Share of net loss recorded as provision	—			—			2.1			2.1
Share of dividends received	—			(11.3		)	—			(11.3		)
Disposal³	(0.6		)	—			—			(0.6		)
Balance, December 31, 2016	5.7			46.9			—			52.6
Purchase of additional shares of associate⁴	7.4			—			—			7.4
Currency translation adjustment	1.4			—			—			1.4
Share of net earnings (loss), net of income taxes	(1.1		)	11.3			—			10.2
Share of dividends received	—			(2.1		)	—			(2.1		)
Acquisition of control over associate⁵	(4.8		)	—			—			(4.8		)
Balance, September 30, 2017	$	8.6		$	56.1		$	—		$	64.7


1	IAMGOLD includes results based on the latest publicly available information.


2	The Company's incorporated joint ventures are not publicly listed.


3	On March 16, 2016, the Company disposed of its 41% ownership interest in Galane Gold Ltd. ("Galane") which had a carrying amount of $0.6 million on the date of disposal for cash proceeds of $0.2 million. The resulting loss of $0.4 million, net of transaction costs, was recognized in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).

4

Associates include INV Metals Inc. ("INV Metals"), a publicly traded company incorporated in Canada, and Merrex prior to February 28, 2017 (note 4). The Company's ownership interest in INV Metals as at September 30, 2017 was 35.6% (December 31, 2016 - 35.6%). On March 2, 2017, the Company participated in INV Metals' common shares public equity offering and acquired an additional 9.8 million common shares of INV Metals at a price of C$1.00 per share for an aggregate amount of $7.4 million (C$9.8 million). This acquisition allowed the Company to maintain a 35.6% ownership in INV Metals.


5	On February 28, 2017, Merrex became a 100% subsidiary of the Company (note 4). As a result, the Company accounted for Merrex under the consolidation method as at February 28, 2017. The Company previously accounted for Merrex as an associate, using the equity method.

Disclosure of joint ventures



	Associates¹			Sadiola²			Yatela²			Total
Balance, January 1, 2016	$	7.4		$	49.2		$	—		$	56.6
Currency translation adjustment	(0.3		)	—			—			(0.3		)
Share of net earnings (loss), net of income taxes	(0.8		)	9.0			(2.1		)	6.1
Share of net loss recorded as provision	—			—			2.1			2.1
Share of dividends received	—			(11.3		)	—			(11.3		)
Disposal³	(0.6		)	—			—			(0.6		)
Balance, December 31, 2016	5.7			46.9			—			52.6
Purchase of additional shares of associate⁴	7.4			—			—			7.4
Currency translation adjustment	1.4			—			—			1.4
Share of net earnings (loss), net of income taxes	(1.1		)	11.3			—			10.2
Share of dividends received	—			(2.1		)	—			(2.1		)
Acquisition of control over associate⁵	(4.8		)	—			—			(4.8		)
Balance, September 30, 2017	$	8.6		$	56.1		$	—		$	64.7


1	IAMGOLD includes results based on the latest publicly available information.


2	The Company's incorporated joint ventures are not publicly listed.


3	On March 16, 2016, the Company disposed of its 41% ownership interest in Galane Gold Ltd. ("Galane") which had a carrying amount of $0.6 million on the date of disposal for cash proceeds of $0.2 million. The resulting loss of $0.4 million, net of transaction costs, was recognized in Interest income and derivatives and other investment gains in the Consolidated statements of earnings (note 25).

4

Associates include INV Metals Inc. ("INV Metals"), a publicly traded company incorporated in Canada, and Merrex prior to February 28, 2017 (note 4). The Company's ownership interest in INV Metals as at September 30, 2017 was 35.6% (December 31, 2016 - 35.6%). On March 2, 2017, the Company participated in INV Metals' common shares public equity offering and acquired an additional 9.8 million common shares of INV Metals at a price of C$1.00 per share for an aggregate amount of $7.4 million (C$9.8 million). This acquisition allowed the Company to maintain a 35.6% ownership in INV Metals.


5	On February 28, 2017, Merrex became a 100% subsidiary of the Company (note 4). As a result, the Company accounted for Merrex under the consolidation method as at February 28, 2017. The Company previously accounted for Merrex as an associate, using the equity method.

PROPERTY, PLANT AND EQUIPMENT (Tables)

9 Months Ended

Sep. 30, 2017

Property, plant and equipment [abstract]

Disclosure of property, plant and equipment



	Construction in progress			Mining properties			Plant and equipment			Total
Cost
Balance, January 1, 2016	$	7.9		$	2,133.6		$	1,821.3		$	3,962.8
Additions	34.9			172.1			87.3			294.3
Changes in asset retirement obligations	—			11.7			—			11.7
Disposals	—			—			(42.6		)	(42.6		)
Transfers within Property, plant and equipment	(40.0		)	19.1			20.9			—
Balance, December 31, 2016	2.8			2,336.5			1,886.9			4,226.2
Additions	15.3			99.5			57.3			172.1
Changes in asset retirement obligations	—			(1.0		)	—			(1.0		)
Disposals	—			(0.2		)	(25.1		)	(25.3		)
Transfers within Property, plant and equipment	(12.7		)	12.9			(0.2		)	—
Transfers to Exploration and evaluation assets	—			—			(0.5		)	(0.5		)
Balance, September 30, 2017	$	5.4		$	2,447.7		$	1,918.4		$	4,371.5



	Construction in progress			Mining properties			Plant and equipment			Total
Accumulated Depreciation and Impairment
Balance, January 1, 2016	$	3.5		$	1,383.0		$	722.5		$	2,109.0
Depreciation expense¹	—			98.5			187.5			286.0
Disposals	—			—			(37.0		)	(37.0		)
Transfers within Property, plant and equipment	(3.5		)	—			3.5			—
Balance, December 31, 2016	—			1,481.5			876.5			2,358.0
Depreciation expense¹	—			79.8			132.6			212.4
Disposals	—			—			(22.8		)	(22.8		)
Reversal of impairment charges²	—			(124.1		)	—			(124.1		)
Balance, September 30, 2017	$	—		$	1,437.2		$	986.3		$	2,423.5
Carrying amount, December 31, 2016	$	2.8		$	855.0		$	1,010.4		$	1,868.2
Carrying amount, September 30, 2017	$	5.4		$	1,010.5		$	932.1		$	1,948.0


1	Excludes depreciation expense related to Corporate assets, which is included in General and administrative expenses.


2	Note 27.



	Notes	September 30, 2017			December 31, 2016
Balance, beginning of the period		$	169.2		$	155.1
Exploration and evaluation expenditures		8.4			14.1
Acquired Merrex exploration and evaluation assets	4	36.6			—
Reversal of impairment charge	5, 27	400.0			—
Sale of a 30% interest in the Côté Gold Project	5	(167.3		)	—
Balance, end of the period		$	446.9		$	169.2

EXPLORATION AND EVALUATION ASSETS (Tables)

9 Months Ended

Sep. 30, 2017

Exploration For And Evaluation Of Mineral Resources [Abstract]

Disclosure of exploration and evaluation assets



	Construction in progress			Mining properties			Plant and equipment			Total
Cost
Balance, January 1, 2016	$	7.9		$	2,133.6		$	1,821.3		$	3,962.8
Additions	34.9			172.1			87.3			294.3
Changes in asset retirement obligations	—			11.7			—			11.7
Disposals	—			—			(42.6		)	(42.6		)
Transfers within Property, plant and equipment	(40.0		)	19.1			20.9			—
Balance, December 31, 2016	2.8			2,336.5			1,886.9			4,226.2
Additions	15.3			99.5			57.3			172.1
Changes in asset retirement obligations	—			(1.0		)	—			(1.0		)
Disposals	—			(0.2		)	(25.1		)	(25.3		)
Transfers within Property, plant and equipment	(12.7		)	12.9			(0.2		)	—
Transfers to Exploration and evaluation assets	—			—			(0.5		)	(0.5		)
Balance, September 30, 2017	$	5.4		$	2,447.7		$	1,918.4		$	4,371.5



	Construction in progress			Mining properties			Plant and equipment			Total
Accumulated Depreciation and Impairment
Balance, January 1, 2016	$	3.5		$	1,383.0		$	722.5		$	2,109.0
Depreciation expense¹	—			98.5			187.5			286.0
Disposals	—			—			(37.0		)	(37.0		)
Transfers within Property, plant and equipment	(3.5		)	—			3.5			—
Balance, December 31, 2016	—			1,481.5			876.5			2,358.0
Depreciation expense¹	—			79.8			132.6			212.4
Disposals	—			—			(22.8		)	(22.8		)
Reversal of impairment charges²	—			(124.1		)	—			(124.1		)
Balance, September 30, 2017	$	—		$	1,437.2		$	986.3		$	2,423.5
Carrying amount, December 31, 2016	$	2.8		$	855.0		$	1,010.4		$	1,868.2
Carrying amount, September 30, 2017	$	5.4		$	1,010.5		$	932.1		$	1,948.0


1	Excludes depreciation expense related to Corporate assets, which is included in General and administrative expenses.


2	Note 27.



	Notes	September 30, 2017			December 31, 2016
Balance, beginning of the period		$	169.2		$	155.1
Exploration and evaluation expenditures		8.4			14.1
Acquired Merrex exploration and evaluation assets	4	36.6			—
Reversal of impairment charge	5, 27	400.0			—
Sale of a 30% interest in the Côté Gold Project	5	(167.3		)	—
Balance, end of the period		$	446.9		$	169.2

OTHER NON-CURRENT ASSETS (Tables)

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

Schedule of Other Non-Current Assets



	Notes	September 30, 2017		December 31, 2016
Ore stockpiles	9	$	167.6	$	156.0
Loan receivable from related party	29	35.9		31.3
Marketable securities and warrants	19(a)	30.1		21.7
Advances for the purchase of capital equipment		7.5		19.9
Bond fund investments	19(a)	2.7		5.9
Royalty interests		5.6		5.6
Long-term prepayment¹		4.9		—
Derivatives		3.6		4.1
Other		4.6		5.2
		$	262.5	$	249.7

1

On March 6, 2017, the Company signed an agreement with a third-party for the construction of a solar power plant to deliver power to the Essakane mine for a period of 15 years, upon completion of construction expected in December 2017. During the second quarter 2017, the Company issued a prepayment of $4.9 million to the third-party, which will be applied as a credit towards the purchase of solar power from the third- party, over a period of 12 years. The agreement may be terminated by either party if certain conditions are not met. Upon completion of construction of the solar power plant, the Company will account for this arrangement as a finance lease.

PROVISIONS (Tables)

9 Months Ended

Sep. 30, 2017

Other Provisions, Contingent Liabilities And Contingent Assets [Abstract]

Disclosure of Provisions



	September 30, 2017		December 31, 2016
Asset retirement obligations	$	280.6	$	285.1
Yatela loss provision	15.0		15.0
Other	7.0		5.5
	$	302.6	$	305.6

Current portion of provisions	$	21.0	$	15.8
Non-current provisions	281.6		289.8
	$	302.6	$	305.6

OTHER LIABILITIES (Tables)

9 Months Ended

Sep. 30, 2017

Subclassifications of assets, liabilities and equities [abstract]

Components of other liabilities



	Notes	September 30, 2017		December 31, 2016
Finance lease liabilities	19(b)	$	0.1	$	0.1
Derivatives	19(a)	0.1		2.0
Other liabilities	5	2.9		—
		$	3.1	$	2.1
Current other liabilities		$	0.1	$	2.1
Non-current other liabilities		3.0		—
		$	3.1	$	2.1

LONG-TERM DEBT AND CREDIT FACILITIES (Tables)

9 Months Ended

Sep. 30, 2017

Financial Instruments [Abstract]

Contractual maturities of notes

The following are the contractual maturities related to the Notes, including interest payments:



	Payments due by period
Notes balance as at	Carrying amount¹		Contractual cash flows		<1 yr		1-2 yrs		3-5 yrs		>5 yrs
September 30, 2017	$	400.0	$	625.2	$	29.2	$	56.0	$	56.0	$	484.0
December 31, 2016	$	489.1	$	621.1	$	33.0	$	66.0	$	522.1	$	—


1	The carrying amount of the long-term debt excludes unamortized deferred transaction costs of the Notes of $6.0 million as at September 30, 2017 (December 31, 2016 – $4.0 million). The carrying amount of the long-term debt also excludes the embedded derivative classified as a financial asset at fair value through profit or loss (note 18(c)).

FINANCIAL INSTRUMENTS (Tables)

9 Months Ended

Sep. 30, 2017

Financial Instruments [Abstract]

Financial assets measured at fair value



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Proceeds from sale of marketable securities	$	7.4		$	—	$	7.7		$	0.1
Acquisition date fair value of marketable securities sold	(2.3		)	—		(2.4		)	(2.1		)
Gain (loss) on sale of marketable securities recorded in OCI	$	5.1		$	—	$	5.3		$	(2.0	)

Disclosure of detailed information about hedging instruments

Additional information on hedging instruments and hedged forecast transactions related to currency exchange rate risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Canadian option contracts	$	7.4	$	—	$	6.1	$	6.1	$	(6.1	)
Euro option contracts	4.6		—		3.2		3.2		(3.2		)
	$	12.0	$	—	$	9.3	$	9.3	$	(9.3	)



	Carrying amount								Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)			Hedging instruments			Hedged items
Canadian option contracts	$	2.1	$	—		$	0.2		$	0.2		$	(0.2	)
Euro option contracts	0.2		(2.0		)	(0.4		)	(0.4		)	0.4
	$	2.3	$	(2.0	)	$	(0.2	)	$	(0.2	)	$	0.2



	Gain (loss) recognized in cash flow hedge reserve						(Gain) loss reclassified or adjusted from cash flow hedge reserve
	Three months ended September 30, 2017			Nine months ended September 30, 2017			Three months ended September 30, 2017			Nine months ended September 30, 2017
Exchange rate risk
Canadian dollar option contracts	$	6.0		$	7.5		$	(1.4	)	$	(1.5	)
Euro option contracts	2.8			4.6			(1.1		)	(1.1		)
Crude oil option contracts	—			0.1			—			—
	8.8			12.2			(2.5		)	(2.6		)
Time value of option contracts excluded from hedge relationship	(1.7		)	(4.4		)	—			—
	$	7.1		$	7.8		$	(2.5	)	$	(2.6	)



	Gain (loss) recognized in cash flow hedge reserve						(Gain) loss reclassified or adjusted from cash flow hedge reserve
	Three months ended September 30, 2016			Nine months ended September 30, 2016			Three months ended September 30, 2016			Nine months ended September 30, 2016
Exchange rate risk
Canadian dollar option contracts	$	(2.3	)	$	0.5		$	1.2		$	4.8
Euro option contracts	—			1.8			(0.4		)	(1.2		)
Crude oil option contracts	(2.4		)	3.6			—			1.7
	(4.7		)	5.9			0.8			5.3
Time value of option contracts excluded from hedge relationship	(2.0		)	(1.4		)	—			—
	$	(6.7	)	$	4.5		$	0.8		$	5.3



	(Gain) loss reclassified from cash flow hedge reserve to:						(Gain) loss reclassified from cash flow hedge reserve to:
	Three months ended September 30, 2017			Three months ended September 30, 2016			Nine months ended September 30, 2017			Nine months ended September 30, 2016
Consolidated balance sheets
Property, plant and equipment	$	(0.6	)	$	(0.1	)	$	(0.6	)	$	0.1
Consolidated statements of earnings
Cost of sales	(1.6		)	0.6			(1.6		)	3.6
General and administrative expenses	(0.3		)	0.3			(0.4		)	1.6
Total	$	(2.5	)	$	0.8		$	(2.6	)	$	5.3

Additional information on hedging instruments and hedged forecast transactions related to oil and fuel market price risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount							Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	1.9	$	—		$	—	$	—	$	—
WTI crude oil option contracts	0.4		(0.1		)	—		—		—
	$	2.3	$	(0.1	)	$	—	$	—	$	—



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	4.0	$	—	$	—	$	—	$	—
WTI crude oil option contracts	2.2		—		—		—		—
	$	6.2	$	—	$	—	$	—	$	—

Disclosure of terms and conditions of outstanding derivative contracts

As at September 30, 2017, the Company’s outstanding crude oil derivative contracts, which qualified for hedge accounting, and the periods in which the cash flows are expected to occur and impact the Consolidated statements of earnings, are as follows:



	2017	2018	2019	2020	Total
Brent crude oil option contracts (barrels)¹	130	488	366	243	1,227
Option contracts with strike prices at ($/barrel)	60²	42-60³	44-60³	50-62³
WTI crude oil option contracts (barrels)¹	99	390	306	207	1,002
Option contracts with strike prices at ($/barrel)	60²	36-60³	42-60³	45-55³


1	Quantities of barrels are in thousands.


2	The Company purchased call options with a strike price of $60. If crude oil prices are greater than the call strike price in 2017, the Company will benefit from the margin between the higher market price and the set call strike price.

3

The Company purchased Brent and WTI collar options with strike prices within the given range in 2018, 2019 and 2020. If Brent and WTI market prices are below the low end of the range in 2018, 2019 and 2020, the Company will incur a loss from the margin between the lower market price and the set put strike price. If Brent and WTI are above the high end of the range of the call strike price in 2018, 2019 and 2020, the Company will benefit from the margin between the higher market price and the set call strike price.

As at September 30, 2017, the Company's outstanding derivative contracts which qualified for hedge accounting and the periods in which the cash flows are expected to occur and impact the Consolidated statements of earnings, are as follows:



	2017	2018	Total
Cash flow hedges
Exchange rate risk
Canadian dollar option contracts (millions of C$)	51	155	206
Contract rate range ($/C$)	1.30-1.40¹	1.30-1.45²
Euro option contracts (millions of €)	32	93	125
Contract rate range (€/$)	1.00-1.20³	1.08-1.19³

1

The Company purchased three types of Canadian dollar options in 2017, which consist of U.S. dollar put options at a strike price of $1.30, U.S. dollar put options at a strike price of $1.35, and collar options in the range of $1.30 and $1.40. The Company will benefit from the margin between the lower market price and the set U.S. dollar put strike price of $1.30 and $1.35. If U.S dollar to C$ market prices are above the $1.40 call strike prices in 2017, the Company will incur a loss from the margin between the higher market price and the $1.40 call strike price.

2

The Company purchased Canadian dollar collar options with strike prices within the given range in 2018. If U.S dollar to C$ market prices are below the low end of the range of the U.S. dollar put strike prices in 2018, the Company will benefit from the margin between the lower market price and the set put strike price. If U.S dollar to C$ market prices are above the high end of the range of the U.S. dollar call strike prices in 2018, the Company will incur a loss from the margin between the higher market price and the set call strike price.

3

The Company purchased Euro collar options with strike prices within the given range in 2017 and 2018. If EUR to U.S. dollar market prices are below the low end of the range in 2017 or 2018, the Company will incur a loss from the margin between the lower market price and the set put strike price. If EUR to U.S. dollar market prices are above the high end of the range of the call strike price in 2017 or 2018, the Company will benefit from the margin between the higher market price and the set call strike price.

Disclosure of detailed information about hedged items

Additional information on hedging instruments and hedged forecast transactions related to currency exchange rate risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Canadian option contracts	$	7.4	$	—	$	6.1	$	6.1	$	(6.1	)
Euro option contracts	4.6		—		3.2		3.2		(3.2		)
	$	12.0	$	—	$	9.3	$	9.3	$	(9.3	)



	Carrying amount								Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)			Hedging instruments			Hedged items
Canadian option contracts	$	2.1	$	—		$	0.2		$	0.2		$	(0.2	)
Euro option contracts	0.2		(2.0		)	(0.4		)	(0.4		)	0.4
	$	2.3	$	(2.0	)	$	(0.2	)	$	(0.2	)	$	0.2

Additional information on hedging instruments and hedged forecast transactions related to oil and fuel market price risk as at September 30, 2017 and December 31, 2016 were as follows:



	Carrying amount							Fair value changes used for calculating hedge ineffectiveness
As at September 30, 2017	Assets		Liabilities			Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	1.9	$	—		$	—	$	—	$	—
WTI crude oil option contracts	0.4		(0.1		)	—		—		—
	$	2.3	$	(0.1	)	$	—	$	—	$	—



	Carrying amount						Fair value changes used for calculating hedge ineffectiveness
As at December 31, 2016	Assets		Liabilities		Accumulated cash flow hedge fair value reserve (before tax)		Hedging instruments		Hedged items
Brent crude oil option contracts	$	4.0	$	—	$	—	$	—	$	—
WTI crude oil option contracts	2.2		—		—		—		—
	$	6.2	$	—	$	—	$	—	$	—

Disclosure of detailed information about non-hedge derivatives



		Three months ended September 30,				Nine months ended September 30,
	Notes	2017		2016		2017		2016
Embedded derivative	17(a)	$	3.7	$	—	$	5.3	$	—
Warrants		0.5		1.3		0.1		5.3
	25	$	4.2	$	1.3	$	5.4	$	5.3

FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Measurement [Abstract]

Fair value measurement of assets

As at September 30, 2017, the Company’s fair value of financial assets and liabilities were as follows:



	September 30, 2017														December 31, 2016
	Carrying Amount			Level 1			Level 2			Level 3		Total Fair Value			Total Fair Value
Assets
Cash and cash equivalents	$	583.6		$	583.6		$	—		$	—	$	583.6		$	652.0
Restricted cash	24.7			24.7			—			—		24.7			110.7
Short-term investments	227.0			227.0			—			—		227.0			—
Marketable securities and warrants	30.1			25.0			5.1			—		30.1			21.9
Bond fund investments	2.7			2.7			—			—		2.7			5.9
Derivatives
Currency contracts	12.0			—			12.0			—		12.0			2.3
Crude oil contracts	2.3			—			2.3			—		2.3			6.2
Embedded derivative	9.5			—			9.5			—		9.5			—
	$	891.9		$	863.0		$	28.9		$	—	$	891.9		$	799.0
Liabilities
Derivatives
Currency contracts	$	—		$	—		$	—		$	—	$	—		$	(2.0	)
Crude oil contracts	(0.1		)	—			(0.1		)	—		(0.1		)	—
6.75% Senior unsecured notes	—			—			—			—		—			(474.0		)
Long-term debt - 7% Senior notes	(400.0		)	(421.8		)	—			—		(421.8		)	—
	$	(400.1	)	$	(421.8	)	$	(0.1	)	$	—	$	(421.9	)	$	(476.0	)

Fair value measurement of liabilities

As at September 30, 2017, the Company’s fair value of financial assets and liabilities were as follows:



	September 30, 2017														December 31, 2016
	Carrying Amount			Level 1			Level 2			Level 3		Total Fair Value			Total Fair Value
Assets
Cash and cash equivalents	$	583.6		$	583.6		$	—		$	—	$	583.6		$	652.0
Restricted cash	24.7			24.7			—			—		24.7			110.7
Short-term investments	227.0			227.0			—			—		227.0			—
Marketable securities and warrants	30.1			25.0			5.1			—		30.1			21.9
Bond fund investments	2.7			2.7			—			—		2.7			5.9
Derivatives
Currency contracts	12.0			—			12.0			—		12.0			2.3
Crude oil contracts	2.3			—			2.3			—		2.3			6.2
Embedded derivative	9.5			—			9.5			—		9.5			—
	$	891.9		$	863.0		$	28.9		$	—	$	891.9		$	799.0
Liabilities
Derivatives
Currency contracts	$	—		$	—		$	—		$	—	$	—		$	(2.0	)
Crude oil contracts	(0.1		)	—			(0.1		)	—		(0.1		)	—
6.75% Senior unsecured notes	—			—			—			—		—			(474.0		)
Long-term debt - 7% Senior notes	(400.0		)	(421.8		)	—			—		(421.8		)	—
	$	(400.1	)	$	(421.8	)	$	(0.1	)	$	—	$	(421.9	)	$	(476.0	)

SHARE CAPITAL (Tables)

9 Months Ended

Sep. 30, 2017

Share Capital, Reserves And Other Equity Interest [Abstract]

Outstanding common stock rollforward



		Nine months ended September 30,
Number of common shares (in millions)	Notes	2017	2016
Outstanding, beginning of the period		453.8	393.4
Equity issuance	4	6.9	44.7
Issuance of flow-through common shares		3.4	12.0
Issuance of shares for share-based compensation		0.8	0.6
Outstanding, end of period		464.9	450.7

EARNINGS PER SHARE (Tables)

9 Months Ended

Sep. 30, 2017

Earnings per share [abstract]

Earnings (loss) per share computations

Basic earnings per share computation



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Numerator
Net earnings attributable to equity holders of IAMGOLD	$	30.8	$	17.0	$	519.3	$	57.9
Denominator (in millions)
Weighted average number of common shares (basic)	464.7		428.3		462.3		410.3
Basic earnings attributable to equity holders of IAMGOLD ($/share)	$	0.07	$	0.04	$	1.12	$	0.14

Diluted earnings per share computation



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Denominator (in millions)
Weighted average number of common shares (basic)	464.7		428.3		462.3		410.3
Dilutive effect of share options	1.2		1.0		1.2		0.4
Dilutive effect of restricted share units	3.4		2.9		3.2		2.5
Weighted average number of common shares (diluted)	469.3		432.2		466.7		413.2
Diluted earnings attributable to equity holders of IAMGOLD ($/share)	$	0.07	$	0.04	$	1.11	$	0.14

Equity instruments excluded from the computation of diluted earnings per share, which could be dilutive in the future, were as follows:



		Three months ended September 30,		Nine months ended September 30,
(in millions)	Notes	2017	2016	2017	2016
Share options		2.6	3.0	2.6	4.1
Contingently issuable shares	20	3.1	3.1	3.1	3.1
		5.7	6.1	5.7	7.2

SHARE-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2017

Share-Based Payment Arrangements [Abstract]

Share option award plan



Nine months ended September 30, 2017	Share options (in millions)		Weighted average exercise price (C$/share)¹
Outstanding, beginning of the period	6.0		$	7.79
Granted	1.6		5.24
Exercised	(0.2	)	5.26
Forfeited	(0.5	)	12.22
Outstanding, end of the period	6.9		$	7.03
Exercisable, end of the period	3.4		$	9.72


1	Exercise prices are denominated in Canadian dollars. The exchange rate at September 30, 2017 between the U.S. dollar and Canadian dollar was

$0.7992/C$.

Weighted average inputs used in determining the fair value of the options granted

The following were the weighted average inputs to the Black-Scholes model used in determining the fair value of the options granted. The estimated fair value of the options is expensed over their expected life.



Nine months ended September 30, 2017
Weighted average risk-free interest rate	1.1		%
Weighted average expected volatility¹	66		%
Weighted average dividend yield	0.00		%
Weighted average expected life of options issued (years)	5.0
Weighted average grant-date fair value (C$ per share)	$	2.89
Weighted average share price at grant date (C$ per share)	$	5.24
Weighted average exercise price (C$ per share)	$	5.24


1	Expected volatility is estimated by considering historic average share price volatility based on the average expected life of the options.

Full value awards consisting of restricted share units

Full value awards consist of restricted share units.



Nine months ended September 30, 2017 (in millions)
Outstanding, beginning of the period	3.7
Granted	2.2
Issued	(0.6	)
Forfeited	(0.7	)
Outstanding, end of the period	4.6

Weighted average inputs used in determining fair value of restricted share units

The following were the weighted average inputs to the Black-Scholes model used in determining the fair value of the restricted share units granted. The estimated fair value of the awards is expensed over their vesting period.



Nine months ended September 30, 2017
Weighted average risk-free interest rate	0.8		%
Weighted average expected volatility¹	72		%
Weighted average dividend yield	0.00		%
Weighted average expected life of RSUs issued (years)	2.8
Weighted average grant-date fair value (C$ per share)	$	5.24
Weighted average share price at grant date (C$ per share)	$	5.24


1	Expected volatility is estimated by considering historic average share price volatility based on the average expected life of the restricted share units.

COST OF SALES (Tables)

9 Months Ended

Sep. 30, 2017

Analysis of income and expense [abstract]

Components of cost of sales



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Operating costs¹	$	154.5	$	147.4	$	461.9	$	425.9
Royalties	11.1		13.5		32.9		32.5
Depreciation expense²	62.3		69.3		197.2		193.1
	$	227.9	$	230.2	$	692.0	$	651.5


1	Operating costs include mine production, transport and smelter costs, and site administrative expenses.


2	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

FINANCE COSTS (Tables)

9 Months Ended

Sep. 30, 2017

Borrowing costs [abstract]

Components of financing costs



	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Interest expense	$	0.9	$	5.9	$	6.8	$	19.9
Credit facility fees	0.9		0.4		2.1		1.2
Accretion expense	0.3		—		0.7		0.6
	$	2.1	$	6.3	$	9.6	$	21.7

INTEREST INCOME AND DERIVATIVES AND OTHER INVESTMENT GAINS (Tables)

9 Months Ended

Sep. 30, 2017

Analysis of income and expense [abstract]

Schedule of Interest Income and Derivatives and Other Investment Gains



		Three months ended September 30,					Nine months ended September 30,
	Notes	2017		2016			2017			2016
Interest income		$	2.5	$	0.8		$	6.4		$	1.9
Gain on embedded derivative and warrants	18(c)	4.2		1.3			5.4			5.3
Gain on sale of a 30% interest in the Côté Gold Project	5	—		—			19.2			—
Amortization of gains related to flow-through common shares	20	0.2		1.2			3.5			3.3
Loss on redemption of 6.75% Senior unsecured notes	17(a)	—		—			(20.2		)	—
Gain on purchase of 6.75% Senior unsecured notes	17(a)	—		4.0			—			4.0
Write-down of receivables		—		(1.5		)	—			—
Gain on sale of gold bullion		—		—			—			72.9
Other gains (losses)		0.4		(0.3		)	0.5			1.3
		$	7.3	$	5.5		$	14.8		$	88.7

CASH FLOW ITEMS (Tables)

9 Months Ended

Sep. 30, 2017

Cash Flow Statement [Abstract]

Schedule of Other Non-cash Items, Operating Activities

Adjustments for other non-cash items within operating activities



		Three months ended September 30,						Nine months ended September 30,
	Notes	2017			2016			2017			2016
Share-based compensation		$	1.3		$	1.1		$	4.4		$	3.6
Amortization of gains related to flow-through common shares	25	(0.2		)	(1.2		)	(3.5		)	(3.3		)
Changes in estimates of asset retirement obligations at closed sites		(2.2		)	—			(0.9		)	3.3
Gain on derivatives		(6.1		)	(0.8		)	(7.3		)	(1.3		)
Gain on purchase of 6.75% senior unsecured notes	25	—			(4.0		)	—			(4.0		)
Write-down of assets		0.2			1.3			1.5			4.1
Other		0.8			(0.6		)	0.7			0.5
		$	(6.2	)	$	(4.2	)	$	(5.1	)	$	2.9

Schedule of Changes in Non-cash Working Capital Items and Non-current Ore Stockpiles

Movements in non-cash working capital items and non-current ore stockpiles



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Receivables and other current assets	$	7.8		$	6.6	$	10.1		$	(0.5	)
Inventories and non-current ore stockpiles	(19.8		)	1.9		(20.6		)	7.4
Accounts payable and accrued liabilities	15.5			6.0		14.8			15.5
	$	3.5		$	14.5	$	4.3		$	22.4

Schedule of Other Investing Activities

Other investing activities



		Three months ended September 30,						Nine months ended September 30,
	Notes	2017			2016			2017			2016
Disposal (acquisition) of investments		$	0.7		$	1.5		$	1.1		$	(2.0	)
Advances to related parties	29	(3.0		)	(0.6		)	(5.3		)	(2.4		)
Repayments from related parties	29	0.3			0.2			0.8			2.3
Other		—			0.2			0.1			0.9
		$	(2.0	)	$	1.3		$	(3.3	)	$	(1.2	)

Schedule of Other Financing Activities

Other financing activities



	Three months ended September 30,						Nine months ended September 30,
	2017			2016			2017			2016
Repayment of finance lease liabilities	$	—		$	(0.1	)	$	—		$	(1.0	)
Dividends paid to non-controlling interests	(2.0		)	—			(3.1		)	(1.5		)
Other finance costs	(1.6		)	(0.5		)	(2.5		)	(2.8		)
	$	(3.6	)	$	(0.6	)	$	(5.6	)	$	(5.3	)

Schedule of Reconciliation of Long-term Debt Arising from Financing Activities

Reconciliation of long-term debt arising from financing activities



	Notes
Balance, December 31, 2016		$	485.1
Net proceeds from issuance of senior notes	17(a)	393.6
Non-cash changes:
Amortization of deferred financing charges		0.7
Change in fair value of embedded derivative	18(c)	(5.3		)
Loss on redemption of 6.75% Senior unsecured notes	17(a)	20.2
Cash changes:
Repayment of 6.75% Senior unsecured notes	17(a)	(505.6		)
Balance, September 30, 2017		$	388.7

REVERSAL OF IMPAIRMENT CHARGES (Tables)

9 Months Ended

Sep. 30, 2017

Impairment Of Assets [Abstract]

Disclosure of reversal of impairment loss



		Three months ended September 30,				Nine months ended September 30,
	Notes	2017		2016		2017		2016
Suriname CGU¹
Property, plant and equipment	11	$	—	$	—	$	124.1	$	—
Côté Gold Project
Exploration and evaluation assets	12	—		—		400.0		—
		$	—	$	—	$	524.1	$	—

1 The Suriname CGU consists of Rosebel Gold Mines N.V. and Euro Ressources S.A.

COMMITMENTS (Tables)

9 Months Ended

Sep. 30, 2017

Commitments [Abstract]

Disclosure of commitments and payments due by period



	September 30, 2017		December 31, 2016
Purchase obligations	$	78.2	$	53.2
Capital expenditure obligations	26.3		4.6
Operating leases	18.1		4.3
	$	122.6	$	62.1

Commitments – payments due by period



	Payments due by period
As at September 30, 2017	Total		<1 yr		1-2 yrs		3-5 yrs		>5 yrs
Purchase obligations	$	78.2	$	71.9	$	5.7	$	0.4	$	0.2
Capital expenditure obligations	26.3		22.5		3.8		—		—
Operating leases	18.1		1.5		10.1		6.5		—
	$	122.6	$	95.9	$	19.6	$	6.9	$	0.2

RELATED PARTY TRANSACTIONS (Tables)

9 Months Ended

Sep. 30, 2017

Related Party [Abstract]

Disclosure of transactions between related parties

The Company had the following related party transactions included in Receivables and other current assets and in Other non-current assets in the Consolidated balance sheets:



	Three months ended September 30,					Nine months ended September 30,
	2017			2016		2017			2016
Sadiola and Yatela (Non-interest bearing)
Balance, beginning of the period	$	0.2		$	—	$	0.2		$	0.2
Advances	0.2			—		0.7			—
Repayments	(0.3		)	—		(0.8		)	(0.2		)
Balance, end of the period¹	$	0.1		$	—	$	0.1		$	—
Sadiola Sulphide Project (LIBOR plus 2%)²
Balance, beginning of the period	$	33.1		$	30.2	$	31.3		$	29.3
Advances	2.8			0.3		4.6			1.2
Balance, end of the period¹	$	35.9		$	30.5	$	35.9		$	30.5


1	Balances as of December 31, 2016 for Sadiola and Yatela and for the Sadiola Sulphide Project were $0.2 million and $31.3 million, respectively.


2	These advances were part of an extended loan agreement, reached in the fourth quarter of 2016, for the Sadiola Sulphide Project, and are to be repaid on the earlier of December 31, 2020 or, at such time as Sadiola has sufficient free cash flow.

SEGMENTED INFORMATION (Tables)

9 Months Ended

Sep. 30, 2017

Operating Segments [Abstract]

Disclosure of operating segments



	September 30, 2017						December 31, 2016
	Total non- current assets		Total assets		Total liabilities		Total non- current assets		Total assets		Total liabilities
Gold mines
Burkina Faso	$	842.4	$	1,065.2	$	193.3	$	883.4	$	1,099.6	$	189.9
Suriname	615.3		799.0		247.6		512.8		667.3		198.1
Canada	691.1		713.8		188.5		675.0		783.7		195.8
Total gold mines	2,148.8		2,578.0		629.4		2,071.2		2,550.6		583.8
Exploration and evaluation	433.7		476.0		6.8		163.1		193.2		8.4
Corporate¹	276.0		881.4		446.4		153.3		656.7		537.2
Total per consolidated financial statements	$	2,858.5	$	3,935.4	$	1,082.6	$	2,387.6	$	3,400.5	$	1,129.4
Incorporated joint ventures (Mali)²	$	127.3	$	173.0	$	147.9	$	116.5	$	160.2	$	144.1


1	The carrying amount of the Investment in incorporated joint ventures is included in the corporate segment as non-current assets.


2	The breakdown of the financial information for the incorporated joint ventures has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess performance of the incorporated joint ventures and to make resource allocation decisions.

Three months ended September 30, 2017



	Consolidated statement of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other			Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	130.2	$	82.2	$	31.0	$	—	$	—	$	—	$	—		$	17.0		$	16.8
Suriname	97.1		57.5		20.0		—		0.1		—		0.4			19.1			13.2
Canada	41.4		25.9		10.5		—		—		—		(2.0		)	7.0			14.0
Total gold mines excluding incorporated joint ventures	268.7		165.6		61.5		—		0.1		—		(1.6		)	43.1			44.0
Exploration and evaluation⁴	—		—		—		—		6.5		—		0.1			(6.6		)	0.5
Corporate⁵	0.1		—		0.8		8.9		—		—		—			(9.6		)	0.2
Total per consolidated financial statements	268.8		165.6		62.3		8.9		6.6		—		(1.5		)	26.9			44.7
Incorporated joint ventures (Mali)⁶	19.6		13.9		0.4		—		0.5		—		—			4.8			2.4
	$	288.4	$	179.5	$	62.7	$	8.9	$	7.1	$	—	$	(1.5	)	$	31.7		$	47.1


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Three months ended September 30, 2016



	Consolidated statement of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other		Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	167.6	$	84.6	$	32.3	$	—	$	—	$	—	$	0.9	$	49.8		$	16.9
Suriname	92.2		53.4		21.7		—		1.2		—		0.2		15.7			34.2
Canada	22.4		21.6		14.2		—		—		—		0.3		(13.7		)	20.9
Total gold mines excluding incorporated joint ventures	282.2		159.6		68.2		—		1.2		—		1.4		51.8			72.0
Exploration and evaluation⁴	—		—		0.1		0.1		5.3				0.1		(5.6		)	0.4
Corporate⁵	0.2		1.3		1.0		9.9		—		—		0.4		(12.4		)	0.1
Total per consolidated financial statements	282.4		160.9		69.3		10.0		6.5		—		1.9		33.8			72.5
Incorporated Joint ventures (Mali)⁶	21.2		17.8		0.3		—		0.2		—		—		2.9			1.1
	$	303.6	$	178.7	$	69.6	$	10.0	$	6.7	$	—	$	1.9	$	36.7		$	73.6


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Nine months ended September 30, 2017



	Consolidated statements of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)			Other			Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	402.2	$	250.2	$	98.0	$	—	$	—	$	—		$	—		$	54.0		$	52.5
Suriname	286.3		171.4		63.4		—		4.9		(116.0		)	2.3			160.3			36.7
Canada	115.0		73.2		33.0		—		—		—			(1.0		)	9.8			47.6
Total gold mines excluding incorporated joint ventures	803.5		494.8		194.4		—		4.9		(116.0		)	1.3			224.1			136.8
Exploration and evaluation⁴	—		—		0.1		0.1		24.7		(400.0		)	0.3			374.8			1.3
Corporate⁵	0.3		—		2.7		27.7		—		(8.1		)	6.4			(28.4		)	0.4
Total per consolidated financial statements	803.8		494.8		197.2		27.8		29.6		(524.1		)	8.0			570.5			138.5
Incorporated joint ventures (Mali)⁶	58.7		41.1		1.1		—		1.1		—			—			15.4			5.8
	$	862.5	$	535.9	$	198.3	$	27.8	$	30.7	$	(524.1	)	$	8.0		$	585.9		$	144.3


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, and finance lease payments.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

Nine months ended September 30, 2016



	Consolidated statements of earnings information
	Revenues		Cost of sales¹		Depreciation expense⁷		General and administrative²		Exploration		Impairments (reversals)		Other		Earnings (loss) from operations			Net capital expenditures³
Gold mines
Burkina Faso	$	399.2	$	223.8	$	78.8	$	—	$	—	$	—	$	0.8	$	95.8		$	82.4
Suriname	269.4		169.4		72.9		—		2.8		—		3.6		20.7			67.8
Canada	65.4		64.2		38.0		—		—		—		3.6		(40.4		)	69.1
Total gold mines excluding incorporated joint ventures	734.0		457.4		189.7		—		2.8		—		8.0		76.1			219.3
Exploration and evaluation⁴	—		—		0.2		0.3		17.8		—		0.3		(18.6		)	2.7
Corporate⁵	0.6		1.0		3.2		28.5		—		—		1.9		(34.0		)	0.8
Total per consolidated financial statements	734.6		458.4		193.1		28.8		20.6		—		10.2		23.5			222.8
Incorporated joint ventures (Mali)⁶	67.5		51.0		2.2		—		0.5		—		1.5		12.3			2.7
	$	802.1	$	509.4	$	195.3	$	28.8	$	21.1	$	—	$	11.7	$	35.8		$	225.5


1	Excludes depreciation expense.


2	Includes depreciation expense relating to Corporate and Exploration and evaluation assets.


3	Includes cash expenditures for Property, plant and equipment, Exploration and evaluation assets, finance lease payments and is net of proceeds from finance leases.


4	Closed site costs on Exploration and evaluation properties included in other operating costs.


5	Includes earnings from royalty interests.


6	Net earnings from incorporated joint ventures are included in a separate line in the Consolidated statements of earnings. The breakdown of the financial information has been disclosed above as it is reviewed regularly by the Company’s chief operating decision maker to assess its performance and to make resource allocation decisions.


7	Depreciation expense excludes depreciation related to Corporate assets, which is included in General and administrative expenses.

BASIS OF PREPARATION (Details)	9 Months Ended	12 Months Ended
BASIS OF PREPARATION (Details)	Sep. 30, 2017	Dec. 31, 2016
Essakane S.A.
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	90.00%	90.00%
Rosebel Gold Mines N.V.
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	95.00%	95.00%
Doyon division including the Westwood mine
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	100.00%	100.00%
Côté Gold
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	70.00%	100.00%
Euro Ressources S.A.
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	90.00%	90.00%
Merrex Gold Inc.
Disclosure of subsidiaries [line items]
Ownership interest in subsidiary	100.00%	23.00%
Société d'Exploitation des Mines d'Or de Sadiola S.A.
Disclosure of joint ventures [line items]
Ownership interest in joint venture	41.00%	41.00%

ACQUISITION (Details) - USD ($) shares in Millions, $ in Millions	Feb. 28, 2017	Feb. 27, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Assets acquired and liabilities assumed
Exploration and evaluation assets			$ 446.9		$ 169.2
Current liabilities			(225.2)		(195.5)
Other non-current liabilities			(3.0)		0.0
Consideration transferred
Less: Cash and cash equivalents acquired			$ (583.6)	$ (776.2)	$ (652.0)	$ (627.3)	$ (554.2)	$ (481.0)
Merrex Gold Inc.
Assets acquired and liabilities assumed
Exploration and evaluation assets	$ 36.6
Current liabilities	(3.9)
Other non-current liabilities	(0.4)
Assets acquired (liabilities assumed)	32.3
Consideration transferred
Share consideration	27.4
Less: Cash and cash equivalents acquired	(0.1)
Transaction costs	0.2
Consideration transferred	27.5
Assets acquired	$ 32.3
Merrex Gold Inc.
Disclosure of detailed information about business combination [line items]
Merrex Siribaya Project ownership percentage		50.00%
Siribaya Project ownership percentage	100.00%	50.00%
Number of shares issued as consideration	6.9
Consideration transferred
Less: Cash and cash equivalents acquired	$ (0.1)
Transaction costs	0.2
Consideration transferred	$ 27.5
Initial investment		$ 4.8
Number of shares held in entity		45.8
Proportion of ownership interest in associate		23.00%

DIVESTITURE (Details) - USD ($) $ in Millions			3 Months Ended			9 Months Ended
DIVESTITURE (Details) - USD ($) $ in Millions	Jun. 20, 2017	Jun. 05, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Disclosure of joint ventures [line items]
Net proceeds from sale of a 30% interest in the Côté Gold Project			$ 0.0		$ 0.0	$ 96.5	$ 0.0
Long-term receivable			93.5			93.5		$ 0.0
Reversal of impairment charges			0.0		0.0	524.1	0.0
Assets			3,935.4			3,935.4		$ 3,400.5
Gain on sale of a 30% interest in the Côté Gold Project			0.0		0.0	19.2	0.0
Côté Gold
Disclosure of joint ventures [line items]
Proportion of ownership interest in joint venture		30.00%
Ownership interest in joint venture	70.00%
Exploration and evaluation assets
Disclosure of joint ventures [line items]
Reversal of impairment charges			0.0	$ 400.0	$ 0.0	$ 400.0	$ 0.0
Disposal Of Interest In Cote Gold Project
Disclosure of joint ventures [line items]
Proportion of ownership interest in joint venture	30.00%					30.00%
Sale of ownership interest in joint venture, aggregate consideration	$ 195.0
Net proceeds from sale of a 30% interest in the Côté Gold Project	100.0
Sale of ownership interest in joint venture, consideration receivable	$ 95.0
Sale of ownership interest in joint venture, consideration receivable terms, period following close date	18 months
Payments of transaction costs	$ 3.5
Sale of ownership interest in joint venture, consideration receivable, additional transactions costs	2.9
Long-term receivable			93.5			$ 93.5
Assets	390.4		$ 391.3			$ 391.3
Gain on sale of a 30% interest in the Côté Gold Project	$ 19.2

DIVESTITURE - Carrying Amount of Cote Gold Disposal (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 20, 2017	Dec. 31, 2016
Disclosure of subsidiaries [line items]
Current assets	$ 1,076.9		$ 1,012.9
Exploration and evaluation assets	446.9		169.2
Other assets	262.5		249.7
Current liabilities	(225.2)		(195.5)
Other non-current liabilities	$ (3.0)		$ 0.0
Disposal Of Interest In Cote Gold Project
Disclosure of subsidiaries [line items]
Current assets		$ 0.1
Exploration and evaluation assets		167.3
Other assets		0.6
Current liabilities		(0.1)
Other non-current liabilities		(0.3)
Net carrying amount of assets disposed		$ 167.6

DIVESTITURE - Calculation Of Net Gain On Sale Of Ownership Interest In Joint Venture (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jun. 20, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure of subsidiaries [line items]
Gain on sale of a 30% interest in the Côté Gold Project		$ 0.0	$ 0.0	$ 19.2	$ 0.0
Disposal Of Interest In Cote Gold Project
Disclosure of subsidiaries [line items]
Gross sale consideration	$ 195.0
Sale of a 30% interest in the Côté Gold Project	(167.6)
Transaction costs	(6.4)
Time value discount on long-term receivable	(1.8)
Gain on sale of a 30% interest in the Côté Gold Project	$ 19.2

RESTRICTED CASH (Details) CAD in Millions	Sep. 30, 2017 USD ($)	Sep. 30, 2017 CAD	Dec. 31, 2016 USD ($)
Subclassifications of assets, liabilities and equities [abstract]
Current restricted cash	$ 0		$ 92,000,000
Schedule Of Fair Value, Off-balance Sheet Risks1 [Line Items]
Non-current restricted cash	24,700,000		18,700,000
Essakane S.A.
Schedule Of Fair Value, Off-balance Sheet Risks1 [Line Items]
Non-current restricted cash	19,700,000		13,700,000
Rosebel Gold Mines N.V.
Schedule Of Fair Value, Off-balance Sheet Risks1 [Line Items]
Non-current restricted cash	5,000,000		5,000,000
Surety Bond
Schedule Of Fair Value, Off-balance Sheet Risks1 [Line Items]
Uncollateralized surety bonds outstanding to guarantee asset retirement obligations related to the Doyon mine	$ 98,800,000	CAD 123.6	$ 0

SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Millions	9 Months Ended
SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [line items]
Short-term investments	$ 227.0	$ 0.0
Money market funds
Disclosure of detailed information about financial instruments [line items]
Short-term investments	224.3	0.0
Other
Disclosure of detailed information about financial instruments [line items]
Short-term investments	$ 2.7	$ 0.0
Top of range
Disclosure of detailed information about financial instruments [line items]
Redemption notice period	185 days
Bottom of range
Disclosure of detailed information about financial instruments [line items]
Redemption notice period	95 days

RECEIVABLES AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Subclassifications of assets, liabilities and equities [abstract]
Gold receivables	$ 1.5	$ 2.7
Receivables from governments	33.6	40.4
Receivables from related parties	0.1	1.2
Other receivables	4.9	4.9
Total receivables	40.1	49.2
Marketable securities and warrants	0.0	0.2
Prepaid expenses	6.0	7.2
Derivatives	10.7	4.4
Receivables and other current assets	$ 56.8	$ 61.0

INVENTORIES (Details) - USD ($)	3 Months Ended		9 Months Ended
INVENTORIES (Details) - USD ($)	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Subclassifications of assets, liabilities and equities [abstract]
Finished goods	$ 59,400,000		$ 59,400,000		$ 49,100,000
Ore stockpiles	5,300,000		5,300,000		9,100,000
Mine supplies	144,800,000		144,800,000		149,700,000
Current inventories	209,500,000		209,500,000		207,900,000
Ore stockpiles included in other non-current assets	167,600,000		167,600,000		156,000,000
Inventories	377,100,000		377,100,000		$ 363,900,000
Disclosure of Inventories [Line Items]
Cost of inventories recognised as expense during period	0	$ 6,300,000	700,000	$ 17,000,000
Ore Stockpiles
Disclosure of Inventories [Line Items]
Inventory write-down	500,000	0	3,900,000	100,000
Mine Supplies
Disclosure of Inventories [Line Items]
Inventory write-down	$ 1,400,000	$ 1,100,000	$ 8,000,000	$ 4,000,000

INVESTMENTS IN ASSOCIATES AND INCORPORATED JOINT VENTURES (Details) CAD / shares in Units, shares in Millions, CAD in Millions, $ in Millions				3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 02, 2017 USD ($) shares	Mar. 02, 2017 CAD CAD / shares shares	Mar. 16, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Investments in associates and joint ventures, beginning balance						$ 52.6	$ 56.6	$ 56.6
Purchase of additional shares of associate						7.4
Currency translation adjustment						1.4		(0.3)
Share of net earnings (loss), net of income taxes				$ 3.6	$ 2.5	10.2	7.5	6.1
Share of net loss recorded as provision								2.1
Share of dividends received						(2.1)		(11.3)
Disposal								(0.6)
Acquisition of control over associate						(4.8)
Investments in associates and joint ventures, ending balance				64.7		64.7		$ 52.6
Net proceeds from sale of a 30% interest in the Côté Gold Project				0.0	$ 0.0	$ 96.5	0.0
Merrex Gold Inc.
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Ownership interest in subsidiary						100.00%		23.00%
Sadiola
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Investments in associates and joint ventures, beginning balance						$ 46.9	49.2	$ 49.2
Purchase of additional shares of associate						0.0
Currency translation adjustment						0.0		0.0
Share of net earnings (loss), net of income taxes						11.3		9.0
Share of net loss recorded as provision								0.0
Share of dividends received						(2.1)		(11.3)
Disposal								0.0
Acquisition of control over associate						0.0
Investments in associates and joint ventures, ending balance				56.1		56.1		46.9
Yatela
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Investments in associates and joint ventures, beginning balance						0.0	0.0	0.0
Purchase of additional shares of associate						0.0
Currency translation adjustment						0.0		0.0
Share of net earnings (loss), net of income taxes						0.0		(2.1)
Share of net loss recorded as provision								2.1
Share of dividends received						0.0		0.0
Disposal								0.0
Acquisition of control over associate						0.0
Investments in associates and joint ventures, ending balance				0.0		0.0		0.0
Associates
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Investments in associates and joint ventures, beginning balance						5.7	$ 7.4	7.4
Purchase of additional shares of associate						7.4
Currency translation adjustment						1.4		(0.3)
Share of net earnings (loss), net of income taxes						(1.1)		(0.8)
Share of net loss recorded as provision								0.0
Share of dividends received						0.0		0.0
Disposal								(0.6)
Acquisition of control over associate						(4.8)
Investments in associates and joint ventures, ending balance				$ 8.6		$ 8.6		$ 5.7
Galance Gold Ltd.
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Investments in associates and joint ventures, ending balance			$ 0.6
Proportion of ownership interest in associate			41.00%
Net proceeds from sale of a 30% interest in the Côté Gold Project			$ 0.2
Loss on sale of interests in associates			$ 0.4
INV Metals Inc.
Disclosure Of Joint Ventures, Associates And Subsidiaries [Line Items]
Purchase of additional shares of associate	$ 7.4	CAD 9.8
Proportion of ownership interest in associate						35.60%		35.60%
Additional associate shares acquired \| shares	9.8	9.8
Additional associate shares purchased (in cad per share) \| CAD / shares		CAD 1.00

PROPERTY, PLANT AND EQUIPMENT - Property, Plant and Equipment Rollforward (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	$ 1,868.2
Balance, end of the period	1,948.0	$ 1,868.2
Construction in progress
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	2.8
Balance, end of the period	5.4	2.8
Mining properties
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	855.0
Balance, end of the period	1,010.5	855.0
Plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	1,010.4
Balance, end of the period	932.1	1,010.4
Gross carrying amount
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	4,226.2	3,962.8
Additions	172.1	294.3
Changes in asset retirement obligations	(1.0)	11.7
Disposals	(25.3)	(42.6)
Transfers within Property, plant and equipment	0.0	0.0
Transfers to Exploration and evaluation assets	(0.5)
Balance, end of the period	4,371.5	4,226.2
Gross carrying amount \| Construction in progress
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	2.8	7.9
Additions	15.3	34.9
Changes in asset retirement obligations	0.0	0.0
Disposals	0.0	0.0
Transfers within Property, plant and equipment	(12.7)	(40.0)
Transfers to Exploration and evaluation assets	0.0
Balance, end of the period	5.4	2.8
Gross carrying amount \| Mining properties
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	2,336.5	2,133.6
Additions	99.5	172.1
Changes in asset retirement obligations	(1.0)	11.7
Disposals	(0.2)	0.0
Transfers within Property, plant and equipment	12.9	19.1
Transfers to Exploration and evaluation assets	0.0
Balance, end of the period	2,447.7	2,336.5
Gross carrying amount \| Plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period	1,886.9	1,821.3
Additions	57.3	87.3
Changes in asset retirement obligations	0.0	0.0
Disposals	(25.1)	(42.6)
Transfers within Property, plant and equipment	(0.2)	20.9
Transfers to Exploration and evaluation assets	(0.5)
Balance, end of the period	$ 1,918.4	$ 1,886.9

PROPERTY, PLANT AND EQUIPMENT - Accumulated Depreciation and Impairment Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			$ 1,868.2
Impairments (reversals)	$ 0.0	$ 0.0	(524.1)	$ 0.0
Balance, end of the period	1,948.0		1,948.0		$ 1,868.2
Construction in progress
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			2.8
Balance, end of the period	5.4		5.4		2.8
Mining properties
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			855.0
Balance, end of the period	1,010.5		1,010.5		855.0
Plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			1,010.4
Balance, end of the period	932.1		932.1		1,010.4
Accumulated depreciation, amortisation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			2,358.0	2,109.0	2,109.0
Depreciation expense			212.4		286.0
Disposals			(22.8)		(37.0)
Transfers within Property, plant and equipment					0.0
Impairments (reversals)			(124.1)
Balance, end of the period	2,423.5		2,423.5		2,358.0
Accumulated depreciation, amortisation and impairment \| Construction in progress
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			0.0	3.5	3.5
Depreciation expense			0.0		0.0
Disposals			0.0		0.0
Transfers within Property, plant and equipment					(3.5)
Impairments (reversals)			0.0
Balance, end of the period	0.0		0.0		0.0
Accumulated depreciation, amortisation and impairment \| Mining properties
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			1,481.5	1,383.0	1,383.0
Depreciation expense			79.8		98.5
Disposals			0.0		0.0
Transfers within Property, plant and equipment					0.0
Impairments (reversals)			(124.1)
Balance, end of the period	1,437.2		1,437.2		1,481.5
Accumulated depreciation, amortisation and impairment \| Plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period			876.5	$ 722.5	722.5
Depreciation expense			132.6		187.5
Disposals			(22.8)		(37.0)
Transfers within Property, plant and equipment					3.5
Impairments (reversals)			0.0
Balance, end of the period	$ 986.3		$ 986.3		$ 876.5

EXPLORATION AND EVALUATION ASSETS (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 20, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period					$ 1,868.2
Exploration and evaluation expenditures		$ 6.6		$ 6.5	29.6	$ 20.6
Reversal of impairment charge		0.0		0.0	524.1	0.0
Balance, end of the period		1,948.0			1,948.0		$ 1,868.2
Assets		3,935.4			3,935.4		3,400.5
Reversal of impairment charges		0.0		0.0	524.1	0.0
Exploration and evaluation assets
Reconciliation of changes in property, plant and equipment [abstract]
Reversal of impairment charges		0.0	$ 400.0	$ 0.0	400.0	0.0
Disposal Of Interest In Cote Gold Project
Reconciliation of changes in property, plant and equipment [abstract]
Assets	$ 390.4	391.3			$ 391.3
Proportion of ownership interest in joint venture	30.00%				30.00%
Tangible exploration and evaluation assets
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of the period					$ 169.2	$ 155.1	155.1
Exploration and evaluation expenditures					8.4		14.1
Acquired Merrex exploration and evaluation assets					36.6		0.0
Reversal of impairment charge					400.0		0.0
Sale of a 30% interest in the Côté Gold Project					(167.3)		0.0
Balance, end of the period		$ 446.9			$ 446.9		$ 169.2

OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Millions		3 Months Ended
OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Millions	Mar. 06, 2017	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Ore stockpiles			$ 167.6	$ 156.0
Loan receivable from related party			35.9	31.3
Advances for the purchase of capital equipment			7.5	19.9
Royalty interests			5.6	5.6
Long-term prepayments			4.9	0.0
Derivatives			3.6	4.1
Other			4.6	5.2
Other assets			262.5	249.7
Contract term (in years)	15 years
Prepayment issued during period		$ 4.9
Prepayment amortization period (in years)		12 years
Allowance for doubtful non-current non-trade receivables from related parties			36.0	36.0
Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Marketable securities and warrants and bond fund investments			30.1	21.7
Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Marketable securities and warrants and bond fund investments			$ 2.7	$ 5.9

PROVISIONS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Disclosure of other provisions [line items]
Other provisions	$ 302.6	$ 305.6
Current portion of provisions	21.0	15.8
Non-current provisions	281.6	289.8
Asset retirement obligations
Disclosure of other provisions [line items]
Other provisions	280.6	285.1
Yatela loss provision
Disclosure of other provisions [line items]
Other provisions	15.0	15.0
Other
Disclosure of other provisions [line items]
Other provisions	$ 7.0	$ 5.5

OTHER LIABILITIES (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Subclassifications of assets, liabilities and equities [abstract]
Finance lease liabilities	$ 0.1	$ 0.1
Derivatives	0.1	2.0
Other liabilities	2.9	0.0
Total other liabilities	3.1	2.1
Current other liabilities	0.1	2.1
Non-current other liabilities	$ 3.0	$ 0.0

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
INCOME TAXES (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Abstract]
Current tax expense (income)	$ 5.1	$ 14.4	$ 67.3	$ 34.4
Applicable tax rate			26.60%

- Definition

The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax that relate to continuing operations. [Refer: Continuing operations [member]; Current tax expense (income); Deferred tax expense (income)]

+ References + Details

LONG-TERM DEBT AND CREDIT FACILITIES - Senior Notes (Details) - USD ($)		3 Months Ended		9 Months Ended
	Mar. 16, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Disclosure of detailed information about borrowings [line items]
Transaction costs		$ 0	$ 9,900,000	$ 11,200,000	$ 17,300,000
Assets		3,935,400,000		3,935,400,000		$ 3,400,500,000
7.0% Senior Secured Notes
Disclosure of detailed information about borrowings [line items]
Face amount	$ 400,000,000
Transaction costs	$ 6,400,000
Percentage of principal amount redeemed utilizing equity offering proceeds	40.00%
Redemption price percentage utilizing equity offering proceeds	107.00%
Fair value of embedded derivative	$ 400,000,000
Period to reinvest asset sale proceeds	365 days
Threshold amount required to utilize proceeds to repurchase borrowings	$ 50,000,000
7.0% Senior Secured Notes \| 2020
Disclosure of detailed information about borrowings [line items]
Redemption price percentage	105.25%
7.0% Senior Secured Notes \| 2021
Disclosure of detailed information about borrowings [line items]
Redemption price percentage	103.50%
7.0% Senior Secured Notes \| 2022
Disclosure of detailed information about borrowings [line items]
Redemption price percentage	101.75%
7.0% Senior Secured Notes \| 2023 and thereafter
Disclosure of detailed information about borrowings [line items]
Redemption price percentage	100.00%
7.0% Senior Secured Notes \| Prior to April 15, 2020
Disclosure of detailed information about borrowings [line items]
Redemption price percentage	100.00%
7.0% Senior Secured Notes \| Fixed interest rate
Disclosure of detailed information about borrowings [line items]
Interest rate	7.00%					7.00%
Carrying Amount
Disclosure of detailed information about borrowings [line items]
Assets		891,900,000		891,900,000
Carrying Amount \| Embedded derivative
Disclosure of detailed information about borrowings [line items]
Assets		$ 9,500,000		$ 9,500,000		$ 0

LONG-TERM DEBT AND CREDIT FACILITIES - Schedule of Contractual Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
7.0% Senior Secured Notes
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Contractual cash flows	$ 625.2	$ 621.1
7.0% Senior Secured Notes \| Less than 1 yr
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Contractual cash flows	29.2	33.0
7.0% Senior Secured Notes \| 1-2 yrs
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Contractual cash flows	56.0	66.0
7.0% Senior Secured Notes \| 3-5 yrs
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Contractual cash flows	56.0	522.1
7.0% Senior Secured Notes \| Greater than 5 yrs
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Contractual cash flows	484.0	0.0
Gross carrying amount \| 7.0% Senior Secured Notes
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Carrying amount	400.0	489.1
Unamortized Deferred Transactions Costs
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Carrying amount	$ 6.0	$ 4.0

LONG-TERM DEBT AND CREDIT FACILITIES - 6.75% Senior Unsecured Notes (Details) - USD ($)		3 Months Ended			9 Months Ended
	Mar. 16, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Apr. 30, 2016	Sep. 21, 2012
Disclosure of detailed information about borrowings [line items]
Repayments of borrowings		$ 0		$ 141,500,000	$ 505,600,000	$ 141,500,000
Gain (loss) on purchase and redemption of Senior unsecured notes		$ 0		4,000,000	$ (20,200,000)	4,000,000
Senior Unsecured Notes at 6.75%
Disclosure of detailed information about borrowings [line items]
Face amount								$ 650,000,000
Repurchase of face value of borrowings				145,900,000		$ 145,900,000	$ 15,000,000
Repayments of borrowings	$ 505,600,000			141,500,000
Gain (loss) on purchase and redemption of Senior unsecured notes			$ (20,200,000)	$ 4,000,000
Carrying amount			485,400,000
Contractual cash flows			$ 505,600,000
Senior Unsecured Notes at 6.75% \| Fixed interest rate
Disclosure of detailed information about borrowings [line items]
Interest rate	6.75%	6.75%			6.75%			6.75%

LONG-TERM DEBT AND CREDIT FACILITIES - Credit Facilities (Details) - USD ($)		3 Months Ended			9 Months Ended
	Feb. 01, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Feb. 07, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [line items]
Repayment of credit facility		$ 0	$ 0		$ 0	$ 70,000,000
February 2016 Four Year Credit Facility
Disclosure of detailed information about borrowings [line items]
Line of credit term	4 years
Maximum borrowing capacity	$ 100,000,000						$ 250,000,000	$ 170,000,000
Accordion feature	150,000,000							$ 80,000,000
February 2016 Four Year Credit Facility, Letters of Credit
Disclosure of detailed information about borrowings [line items]
Maximum borrowing capacity	$ 3,000,000	$ 3,000,000			$ 3,000,000
Four Year Unsecured Revolving Credit Facility
Disclosure of detailed information about borrowings [line items]
Line of credit term	4 years
Maximum borrowing capacity	$ 500,000,000
Repayment of credit facility				$ 70,000,000
Other Letters of Credit
Disclosure of detailed information about borrowings [line items]
Maximum borrowing capacity	$ 400,000

LONG-TERM DEBT AND CREDIT FACILITIES - Uncollateralized Surety Bonds (Details) CAD in Millions	Sep. 30, 2017 USD ($)	Sep. 30, 2017 CAD	Dec. 31, 2016 USD ($)
Surety Bond
Disclosure of detailed information about borrowings [line items]
Uncollateralized surety bonds outstanding to guarantee asset retirement obligations related to the Doyon mine	$ 98,800,000	CAD 123.6	$ 0

FINANCIAL INSTRUMENTS - Marketable Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financial Instruments [Abstract]
Proceeds from sale of marketable securities	$ 7.4	$ 0.0	$ 7.7	$ 0.1
Acquisition date fair value of marketable securities sold	(2.3)	0.0	(2.4)	(2.1)
Gain (loss) on sale of marketable securities recorded in OCI	$ 5.1	$ 0.0	$ 5.3	$ (2.0)

FINANCIAL INSTRUMENTS - Cash Flow Hedge Fair Value Reserve (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Gain (loss) recognized in cash flow hedge reserve
Gain (loss) recognized in cash flow hedge reserve, hedging items	$ 8.8	$ (4.7)	$ 12.2	$ 5.9
Gain (loss) recognized in cash flow hedge reserve, time value of options contracts excluded from hedge relationship	(1.7)	(2.0)	(4.4)	(1.4)
Total gain (loss) recognized in cash flow hedge reserve	7.1	(6.7)	7.8	4.5
(Gain) loss reclassified or adjusted from cash flow hedge reserve
(Gain) loss reclassified or adjusted from cash flow hedge reserve	(2.5)	0.8	(2.6)	5.3
(Gain) loss reclassified or adjusted from cash flow hedge reserve, time value of option contracts excluded from hedge relationship	0.0	0.0	0.0	0.0
Total gain (loss) reclassified or adjusted from cash flow hedge reserve	(2.5)	0.8	(2.6)	5.3
Exchange rate risk \| Canadian dollar option contracts
Gain (loss) recognized in cash flow hedge reserve
Gain (loss) recognized in cash flow hedge reserve, hedging items	6.0	(2.3)	7.5	0.5
(Gain) loss reclassified or adjusted from cash flow hedge reserve
(Gain) loss reclassified or adjusted from cash flow hedge reserve	(1.4)	1.2	(1.5)	4.8
Exchange rate risk \| Euro option contracts
Gain (loss) recognized in cash flow hedge reserve
Gain (loss) recognized in cash flow hedge reserve, hedging items	2.8	0.0	4.6	1.8
(Gain) loss reclassified or adjusted from cash flow hedge reserve
(Gain) loss reclassified or adjusted from cash flow hedge reserve	(1.1)	(0.4)	(1.1)	(1.2)
Crude oil option contracts
Gain (loss) recognized in cash flow hedge reserve
Gain (loss) recognized in cash flow hedge reserve, hedging items	0.0	(2.4)	0.1	3.6
(Gain) loss reclassified or adjusted from cash flow hedge reserve
(Gain) loss reclassified or adjusted from cash flow hedge reserve	$ 0.0	$ 0.0	$ 0.0	$ 1.7

FINANCIAL INSTRUMENTS - Cash Flow Reclassification of Gain (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure of detailed information about hedging instruments [line items]
Amounts removed from equity and included in carrying amount of non-financial asset (liability) whose acquisition or incurrence was hedged highly probable forecast transaction, before tax	$ (0.6)	$ (0.1)	$ (0.6)	$ 0.1
Net change in fair value of cash flow hedges reclassified to the statements of earnings	(1.9)	0.9	(2.0)	5.2
(Gain) loss reclassified or adjusted from cash flow hedge reserve	(2.5)	0.8	(2.6)	5.3
Cost of sales
Disclosure of detailed information about hedging instruments [line items]
Net change in fair value of cash flow hedges reclassified to the statements of earnings	(1.6)	0.6	(1.6)	3.6
General and administrative expenses
Disclosure of detailed information about hedging instruments [line items]
Net change in fair value of cash flow hedges reclassified to the statements of earnings	$ (0.3)	$ 0.3	$ (0.4)	$ 1.6

FINANCIAL INSTRUMENTS - Currency Exchange Rate Derivative Contracts (Details) - Sep. 30, 2017 - Exchange rate risk € in Millions, CAD in Millions	CAD $ / CAD € / $	EUR (€) $ / CAD € / $
Canadian option contracts
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| CAD	CAD 206
Canadian option contracts \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| CAD	CAD 51
Canadian option contracts \| 2017 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.30	1.30
Canadian option contracts \| 2017 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.40	1.40
Canadian option contracts \| 2018
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| CAD	CAD 155
Canadian option contracts \| 2018 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.30	1.30
Canadian option contracts \| 2018 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.45	1.45
Canadian dollar option contracts, Put option one \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.30	1.30
Canadian dollar option contracts, Put option two \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.35	1.35
Canadian dollar option contracts, collar option \| 2017 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.30	1.30
Canadian dollar option contracts, collar option \| 2017 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD)	1.40	1.40
Euro option contracts
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| €		€ 125
Euro option contracts \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| €		€ 32
Euro option contracts \| 2017 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD) \| € / $	1.00	1.00
Euro option contracts \| 2017 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD) \| € / $	1.20	1.20
Euro option contracts \| 2018
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts \| €		€ 93
Euro option contracts \| 2018 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD) \| € / $	1.08	1.08
Euro option contracts \| 2018 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Contract rate range (in USD per CAD and EUR per USD) \| € / $	1.19	1.19

FINANCIAL INSTRUMENTS - Currency Exchange Risk (Details) - Exchange rate risk - Cash flow hedges - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	$ 12.0	$ 2.3
Carrying amount, Liabilities	0.0	(2.0)
Accumulated cash flow hedge fair value reserve (before tax)	9.3	(0.2)
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	9.3	(0.2)
Fair value changes used for calculating hedge ineffectiveness, Hedged items	(9.3)	0.2
Canadian option contracts
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	7.4	2.1
Carrying amount, Liabilities	0.0	0.0
Accumulated cash flow hedge fair value reserve (before tax)	6.1	0.2
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	6.1	0.2
Fair value changes used for calculating hedge ineffectiveness, Hedged items	(6.1)	(0.2)
Euro option contracts
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	4.6	0.2
Carrying amount, Liabilities	0.0	(2.0)
Accumulated cash flow hedge fair value reserve (before tax)	3.2	(0.4)
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	3.2	(0.4)
Fair value changes used for calculating hedge ineffectiveness, Hedged items	$ (3.2)	$ 0.4

FINANCIAL INSTRUMENTS - Crude Oil Derivative Contracts (Details) - Oil and Fuel Market Price Risk bbl in Thousands	Sep. 30, 2017 bbl $ / bbl
2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	60
Brent crude oil option contracts
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	1,227
Brent crude oil option contracts \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	130
Option contracts with strike prices at (USD/barrel)	60
Brent crude oil option contracts \| 2018
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	488
Brent crude oil option contracts \| 2018 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	42
Brent crude oil option contracts \| 2018 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	60
Brent crude oil option contracts \| 2019
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	366
Brent crude oil option contracts \| 2019 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	44
Brent crude oil option contracts \| 2019 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	60
Brent crude oil option contracts \| 2020
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	243
Brent crude oil option contracts \| 2020 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	50
Brent crude oil option contracts \| 2020 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	62
WTI crude oil option contracts
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	1,002
WTI crude oil option contracts \| 2017
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	99
Option contracts with strike prices at (USD/barrel)	60
WTI crude oil option contracts \| 2018
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	390
WTI crude oil option contracts \| 2018 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	36
WTI crude oil option contracts \| 2018 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	60
WTI crude oil option contracts \| 2019
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	306
WTI crude oil option contracts \| 2019 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	42
WTI crude oil option contracts \| 2019 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	60
WTI crude oil option contracts \| 2020
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Outstanding derivative contracts (in barrels) \| bbl	207
WTI crude oil option contracts \| 2020 \| Bottom of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	45
WTI crude oil option contracts \| 2020 \| Top of range
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]
Option contracts with strike prices at (USD/barrel)	55

FINANCIAL INSTRUMENTS - Oil and Fuel Market Price Risk (Details) - Oil and Fuel Market Price Risk - Cash flow hedges - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	$ 2.3	$ 6.2
Carrying amount, Liabilities	(0.1)	0.0
Accumulated cash flow hedge fair value reserve (before tax)	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedged items	0.0	0.0
Brent crude oil option contracts
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	1.9	4.0
Carrying amount, Liabilities	0.0	0.0
Accumulated cash flow hedge fair value reserve (before tax)	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedged items	0.0	0.0
WTI crude oil option contracts
Disclosure of detailed information about hedging instruments [line items]
Carrying amount, Assets	0.4	2.2
Carrying amount, Liabilities	(0.1)	0.0
Accumulated cash flow hedge fair value reserve (before tax)	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedging instruments	0.0	0.0
Fair value changes used for calculating hedge ineffectiveness, Hedged items	$ 0.0	$ 0.0

FINANCIAL INSTRUMENTS - Gain (Loss) on Non-Hedge Derivatives and Warrants (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financial Instruments [Abstract]
Change in fair value of embedded derivative	$ 3.7	$ 0.0	$ 5.3	$ 0.0
Warrants	0.5	1.3	0.1	5.3
Gain (loss) on non-hedge derivatives and warrants	$ 4.2	$ 1.3	$ 5.4	$ 5.3

FAIR VALUE MEASUREMENTS - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($)	Sep. 30, 2017	Mar. 16, 2017	Dec. 31, 2016	Sep. 21, 2012
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	$ 3,935,400,000		$ 3,400,500,000
Liabilities	$ (1,082,600,000)		$ (1,129,400,000)
Fixed interest rate \| Senior Unsecured Notes at 6.75%
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Interest rate	6.75%	6.75%		6.75%
Fixed interest rate \| 7.0% Senior Secured Notes
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Interest rate		7.00%	7.00%
Carrying Amount
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	$ 891,900,000
Liabilities	(400,100,000)
Carrying Amount \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Carrying Amount \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(100,000)
Carrying Amount \| Long-term debt
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(400,000,000)
Carrying Amount \| Cash and cash equivalents
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	583,600,000
Carrying Amount \| Restricted cash
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	24,700,000
Carrying Amount \| Short-term investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	227,000,000
Carrying Amount \| Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	30,100,000
Carrying Amount \| Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,700,000
Carrying Amount \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	12,000,000
Carrying Amount \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,300,000
Carrying Amount \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	9,500,000		$ 0
Recurring fair value measurement
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	891,900,000		799,000,000
Liabilities	(421,900,000)		(476,000,000)
Recurring fair value measurement \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0		(2,000,000)
Recurring fair value measurement \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(100,000)		0
Recurring fair value measurement \| Long-term debt
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(421,800,000)		(474,000,000)
Recurring fair value measurement \| Cash and cash equivalents
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	583,600,000		652,000,000
Recurring fair value measurement \| Restricted cash
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	24,700,000		110,700,000
Recurring fair value measurement \| Short-term investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	227,000,000		0
Recurring fair value measurement \| Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	30,100,000		21,900,000
Recurring fair value measurement \| Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,700,000		5,900,000
Recurring fair value measurement \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	12,000,000		2,300,000
Recurring fair value measurement \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,300,000		6,200,000
Recurring fair value measurement \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	9,500,000		$ 0
Recurring fair value measurement \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	863,000,000
Liabilities	(421,800,000)
Recurring fair value measurement \| Level 1 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 1 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 1 \| Long-term debt
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(421,800,000)
Recurring fair value measurement \| Level 1 \| Cash and cash equivalents
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	583,600,000
Recurring fair value measurement \| Level 1 \| Restricted cash
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	24,700,000
Recurring fair value measurement \| Level 1 \| Short-term investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	227,000,000
Recurring fair value measurement \| Level 1 \| Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	25,000,000
Recurring fair value measurement \| Level 1 \| Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,700,000
Recurring fair value measurement \| Level 1 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 1 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 1 \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	28,900,000
Liabilities	(100,000)
Recurring fair value measurement \| Level 2 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 2 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	(100,000)
Recurring fair value measurement \| Level 2 \| Long-term debt
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 2 \| Cash and cash equivalents
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 2 \| Restricted cash
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 2 \| Short-term investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 2 \| Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	5,100,000
Recurring fair value measurement \| Level 2 \| Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 2 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	12,000,000
Recurring fair value measurement \| Level 2 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	2,300,000
Recurring fair value measurement \| Level 2 \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	9,500,000
Recurring fair value measurement \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Liabilities	0
Recurring fair value measurement \| Level 3 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 3 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 3 \| Long-term debt
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	0
Recurring fair value measurement \| Level 3 \| Cash and cash equivalents
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Restricted cash
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Short-term investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Marketable securities and warrants
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Bond fund investments
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Currency contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Crude oil contracts
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	0
Recurring fair value measurement \| Level 3 \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	$ 0

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	$ 3,935,400,000	$ 3,400,500,000
Liabilities	1,082,600,000	1,129,400,000
Recurring fair value measurement
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	891,900,000	799,000,000
Liabilities	421,900,000	476,000,000
Recurring fair value measurement \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	9,500,000	0
Carrying Amount
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	891,900,000
Liabilities	400,100,000
Carrying Amount \| Embedded derivative
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Assets	9,500,000	0
Long-term debt \| Recurring fair value measurement
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	421,800,000	474,000,000
Long-term debt \| Carrying Amount
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	400,000,000
Finance Lease Liability \| Carrying Amount
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Liabilities	$ 100,000	$ 100,000

SHARE CAPITAL - ROLLFORWARD OF COMMON SHARES (Details) - Common shares - shares shares in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of number of shares outstanding [abstract]
Outstanding, beginning of the period	450.7	453.8	393.4
Equity issuance		6.9	44.7
Issuance of flow-through common shares		3.4	12.0
Issuance of shares for share-based compensation		0.8	0.6
Outstanding, end of period	453.8	464.9	450.7

SHARE CAPITAL (Details) CAD / shares in Units, $ / shares in Units, shares in Thousands, CAD in Millions					1 Months Ended		3 Months Ended				9 Months Ended
	Dec. 12, 2016 USD ($) tranche shares	Aug. 16, 2016 shares	Aug. 16, 2016 USD ($) $ / shares shares	Aug. 08, 2016 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) shares	Mar. 31, 2017 CAD CAD / shares shares	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) shares	Dec. 31, 2016 CAD CAD / shares shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($) shares
Disclosure of classes of share capital [line items]
Proceeds from issuance of shares							$ 0			$ 220,100,000	$ 0	$ 220,100,000
Other liabilities							3,000,000	$ 0			3,000,000
Common shares							2,671,700,000	2,628,200,000			2,671,700,000
Amortization of gains related to flow-through common shares							200,000			1,200,000	3,500,000	3,300,000
Payments for exploration and evaluation expenses							3,700,000			$ 500,000	4,500,000	$ 3,500,000
Number of shares issued \| shares		44,700	44,700
Proceeds from issuing shares			$ 220,100,000
Gross proceeds from the offering before transaction costs			230,000,000
Transaction costs			$ 9,900,000
Tangible exploration and evaluation assets
Disclosure of classes of share capital [line items]
Payments for exploration and evaluation expenses	$ 10,000,000
Contingently issuable consideration for purchase of exploration and evaluation rights (in shares) \| shares	3,125
Number of tranches for delivery of contingently issuable consideration \| tranche	3
Contingently issuable consideration, tranche intervals	12 months
Measurement period for upward adjustment of purchase price	24 months
Maximum upward adjustment to purchase price	$ 10,000,000
Agreement termination notification period	60 days
Flow-through shares issued to fund expenditures on Westwood Mine, March 2017
Disclosure of classes of share capital [line items]
Common shares					$ 13,400,000
Unspent portion							0				0
Flow-through shares issued to fund expenditures on Cote Gold Project
Disclosure of classes of share capital [line items]
Common shares								3,300,000
Unspent portion							500,000				500,000
Flow-through shares issued to fund expenditures on Westwood Mine, fourth quarter of 2016
Disclosure of classes of share capital [line items]
Common shares								$ 8,100,000
Unspent portion							$ 0				$ 0
Public Offering
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| $ / shares				$ 5.15
Number of shares issued \| shares				38,900
Proceeds from issuing shares				$ 200,000,000
Underwriters' option
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| $ / shares			$ 5.15
Number of shares issued \| shares		5,800	5,800
Percent of shares offered, underwriter additional purchase option		15.00%
Common shares
Disclosure of classes of share capital [line items]
Issuance of flow-through common shares (in shares) \| shares											3,400	12,000
Common shares \| Flow-through shares issued to fund expenditures on Westwood Mine, March 2017
Disclosure of classes of share capital [line items]
Issuance of flow-through common shares (in shares) \| shares					3,400	3,400
Shares issued during period, price per share (in CAD and dollars per share) \| CAD / shares						CAD 5.91
Proceeds from issuance of shares					$ 15,100,000	CAD 20.0
Other liabilities					$ 1,700,000
Common shares \| Flow-through shares issued to fund expenditures on Cote Gold Project
Disclosure of classes of share capital [line items]
Issuance of flow-through common shares (in shares) \| shares								900	900
Proceeds from issuance of shares								$ 4,400,000	CAD 5.9
Other liabilities								$ 1,100,000
Common shares \| Flow-through shares issued to fund expenditures on Cote Gold Project \| Bottom of range
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| CAD / shares									CAD 6.56
Common shares \| Flow-through shares issued to fund expenditures on Cote Gold Project \| Top of range
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| CAD / shares									CAD 6.63
Common shares \| Flow-through shares issued to fund expenditures on Westwood Mine, fourth quarter of 2016
Disclosure of classes of share capital [line items]
Issuance of flow-through common shares (in shares) \| shares								2,200	2,200
Proceeds from issuance of shares								$ 8,900,000	CAD 11.9
Other liabilities								$ 800,000
Common shares \| Flow-through shares issued to fund expenditures on Westwood Mine, fourth quarter of 2016 \| Bottom of range
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| CAD / shares									CAD 5.34
Common shares \| Flow-through shares issued to fund expenditures on Westwood Mine, fourth quarter of 2016 \| Top of range
Disclosure of classes of share capital [line items]
Shares issued during period, price per share (in CAD and dollars per share) \| CAD / shares									CAD 5.60

EARNINGS PER SHARE - Earnings (loss) per share computations (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator
Net earnings attributable to equity holders of IAMGOLD	$ 30.8	$ 17.0	$ 519.3	$ 57.9
Denominator
Weighted average number of common shares (basic)	464.7	428.3	462.3	410.3
Basic earnings attributable to equity holders of IAMGOLD (in dollars share)	$ 0.07	$ 0.04	$ 1.12	$ 0.14
Dilutive effect of share options	1.2	1.0	1.2	0.4
Dilutive effect of restricted share units	3.4	2.9	3.2	2.5
Weighted average number of common shares (diluted)	469.3	432.2	466.7	413.2
Diluted earnings attributable to equity holders of IAMGOLD (in dollars per share)	$ 0.07	$ 0.04	$ 1.11	$ 0.14

EARNINGS PER SHARE - Antidilutive Securities (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings per share [line items]
Antidilutive securities	5.7	6.1	5.7	7.2
Share options
Earnings per share [line items]
Antidilutive securities	2.6	3.0	2.6	4.1
Contingently issuable shares
Earnings per share [line items]
Antidilutive securities	3.1	3.1	3.1	3.1

SHARE-BASED COMPENSATION - Share Option Award Plan (Details) shares in Millions	9 Months Ended
	Sep. 30, 2017 CAD shares $ / CAD
Share-Based Payment Arrangements [Abstract]
Outstanding, beginning of the period (in shares) \| shares	6.0
Granted (in shares) \| shares	1.6
Exercised (in shares) \| shares	(0.2)
Forfeited (in shares) \| shares	(0.5)
Outstanding, end of the period (in shares) \| shares	6.9
Exercisable, end of the period (in shares) \| shares	3.4
Outstanding, beginning of the period (C$ per share) \| CAD	CAD 7.79
Granted (C$ per share) \| CAD	5.24
Exercised (C$ per share) \| CAD	5.26
Forfeited (C$ per share) \| CAD	12.22
Outstanding, end of the period (C$ per share) \| CAD	7.03
Exercisable, end of the period (C$ per share) \| CAD	CAD 9.72
Closing foreign exchange rate \| $ / CAD	0.7992

SHARE-BASED COMPENSATION - Stock Options Fair Value Inputs (Details)	9 Months Ended
	Sep. 30, 2017 CAD year
Share-Based Payment Arrangements [Abstract]
Weighted average risk-free interest rate	1.10%
Weighted average expected volatility	66.00%
Weighted average dividend yield	0.00%
Weighted average expected life of options issued (years) \| year	5.0
Weighted average grant-date fair value (C$ per share)	CAD 2.89
Weighted average share price at grant date (C$ per share)	5.24
Weighted average exercise price (C$ per share)	CAD 5.24

SHARE-BASED COMPENSATION - Full Value Award Plans (Details) shares in Millions	9 Months Ended
	Sep. 30, 2017 shares
Share-Based Payment Arrangements [Abstract]
Outstanding, beginning of the period (in shares)	3.7
Granted (in shares)	2.2
Issued (in shares)	(0.6)
Forfeited (in shares)	(0.7)
Outstanding, end of the period (in shares)	4.6

SHARE-BASED COMPENSATION - Restricted Stock Units Fair Value Inputs (Details)	9 Months Ended
	Sep. 30, 2017 CAD year
Share-Based Payment Arrangements [Abstract]
Weighted average risk-free interest rate	0.80%
Weighted average expected volatility	72.00%
Weighted average dividend yield	0.00%
Weighted average expected life of RSUs issued (years) \| year	2.8
Weighted average grant-date fair value (C$ per share)	CAD 5.24
Weighted average share price at grant date (C$ per share)	CAD 5.24

COST OF SALES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
COST OF SALES (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Analysis of income and expense [abstract]
Operating costs	$ 154.5	$ 147.4	$ 461.9	$ 425.9
Royalties	11.1	13.5	32.9	32.5
Depreciation expense	62.3	69.3	197.2	193.1
Cost of sales	$ 227.9	$ 230.2	$ 692.0	$ 651.5

FINANCE COSTS (Details) - USD ($)	3 Months Ended		9 Months Ended
FINANCE COSTS (Details) - USD ($)	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Borrowing costs [abstract]
Interest expense	$ 900,000	$ 5,900,000	$ 6,800,000	$ 19,900,000
Credit facility fees	900,000	400,000	2,100,000	1,200,000
Accretion expense	300,000	0	700,000	600,000
Finance costs	2,100,000	6,300,000	9,600,000	21,700,000
Interest paid	$ 0	$ 20,300,000	$ 16,500,000	$ 41,900,000

INTEREST INCOME AND DERIVATIVES AND OTHER INVESTMENT GAINS (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Jun. 20, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 16, 2017	Sep. 21, 2012
Analysis of income and expense [abstract]
Interest income		$ 2.5		$ 0.8	$ 6.4	$ 1.9
Gain on embedded derivative and warrants		4.2		1.3	5.4	5.3
Gain on sale of a 30% interest in the Côté Gold Project		0.0		0.0	19.2	0.0
Amortization of gains related to flow-through common shares		0.2		1.2	3.5	3.3
Gain (loss) on purchase and redemption of Senior unsecured notes		0.0		4.0	(20.2)	4.0
Write-down of receivables		0.0		(1.5)	0.0	0.0
Gain on sale of gold bullion		0.0		0.0	0.0	72.9
Other gains (losses)		0.4		(0.3)	0.5	1.3
Interest income and derivatives and other investment gains		$ 7.3		5.5	$ 14.8	$ 88.7
Senior Unsecured Notes at 6.75%
Analysis of income and expense [abstract]
Gain (loss) on purchase and redemption of Senior unsecured notes			$ (20.2)	$ 4.0
Senior Unsecured Notes at 6.75% \| Fixed interest rate
Investment [Line Items]
Interest rate		6.75%			6.75%		6.75%	6.75%
Disposal Of Interest In Cote Gold Project
Analysis of income and expense [abstract]
Gain on sale of a 30% interest in the Côté Gold Project	$ 19.2
Investment [Line Items]
Proportion of ownership interest in joint venture	30.00%				30.00%

CASH FLOW ITEMS - Other Non-Cash Items, Operating Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Statement [Abstract]
Share-based compensation	$ 1.3	$ 1.1	$ 4.4	$ 3.6
Amortization of gains related to flow-through common shares	(0.2)	(1.2)	(3.5)	(3.3)
Changes in estimates of asset retirement obligations at closed sites	(2.2)	0.0	(0.9)	3.3
Gain on derivatives	(6.1)	(0.8)	(7.3)	(1.3)
(Gain on purchase) Loss on redemption of 6.75% Senior unsecured notes	0.0	(4.0)	20.2	(4.0)
Write-down of assets	0.2	1.3	1.5	4.1
Other	0.8	(0.6)	0.7	0.5
Total adjustments for other non-cash items within operating activities	$ (6.2)	$ (4.2)	$ (5.1)	$ 2.9

CASH FLOW ITEMS - Changes in Non-Cash Working Capital Items and Non-Current Ore Stockpiles (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Statement [Abstract]
Receivables and other current assets	$ 7.8	$ 6.6	$ 10.1	$ (0.5)
Inventories and non-current ore stockpiles	(19.8)	1.9	(20.6)	7.4
Accounts payable and accrued liabilities	15.5	6.0	14.8	15.5
Movements in non-cash working capital items and non-current ore stockpiles	$ 3.5	$ 14.5	$ 4.3	$ 22.4

CASH FLOW ITEMS - Changes in Other Investing Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Statement [Abstract]
Disposal of investments	$ 0.7	$ 1.5	$ 1.1
Acquisition of investments				$ (2.0)
Advances to related parties	(3.0)	(0.6)	(5.3)	(2.4)
Repayments from related parties	0.3	0.2	0.8	2.3
Other	0.0	0.2	0.1	0.9
Other investing activities	$ (2.0)	$ 1.3	$ (3.3)	$ (1.2)

CASH FLOW ITEMS - Other Financing Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Statement [Abstract]
Repayment of finance lease liabilities	$ 0.0	$ (0.1)	$ 0.0	$ (1.0)
Dividends paid to non-controlling interests	(2.0)	0.0	(3.1)	(1.5)
Other finance costs	(1.6)	(0.5)	(2.5)	(2.8)
Other financing activities	$ (3.6)	$ (0.6)	$ (5.6)	$ (5.3)

CASH FLOW ITEMS - Reconciliation of Long-Term Debt Arising from Financing Activities (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Mar. 16, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 21, 2012
Reconciliation Of Long-Term Debt Arising From Financing Activities [Roll Forward]
Net proceeds from issuance of Senior notes		$ 0.0		$ 0.0	$ 393.6	$ 0.0
Non-cash changes:
Change in fair value of embedded derivative		3.7		0.0	5.3	0.0
Loss on redemption of 6.75% Senior unsecured notes		0.0		(4.0)	20.2	(4.0)
Cash changes:
Redemption of 6.75% Senior unsecured notes		$ 0.0		(141.5)	$ (505.6)	$ (141.5)
Senior Unsecured Notes at 6.75%
Non-cash changes:
Loss on redemption of 6.75% Senior unsecured notes			$ 20.2	(4.0)
Cash changes:
Redemption of 6.75% Senior unsecured notes	$ (505.6)			$ (141.5)
Senior Unsecured Notes at 6.75% \| Fixed interest rate
Cash changes:
Interest rate	6.75%	6.75%			6.75%		6.75%
Long-term debt - 7% Senior notes
Reconciliation Of Long-Term Debt Arising From Financing Activities [Roll Forward]
Balance, December 31, 2016			$ 485.1		$ 485.1
Net proceeds from issuance of Senior notes					393.6
Non-cash changes:
Amortization of deferred financing charges					0.7
Change in fair value of embedded derivative					(5.3)
Loss on redemption of 6.75% Senior unsecured notes					20.2
Cash changes:
Redemption of 6.75% Senior unsecured notes					(505.6)
Balance, September 30, 2017		$ 388.7			$ 388.7

REVERSAL OF IMPAIRMENT CHARGES (Details) $ in Millions		3 Months Ended				9 Months Ended
REVERSAL OF IMPAIRMENT CHARGES (Details) $ in Millions	Jun. 05, 2017	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 $ / oz	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) $ / oz	Sep. 30, 2016 USD ($)
Disclosure of impairment loss and reversal of impairment loss [line items]
Reversal of impairment charges		$ 0.0			$ 0.0	$ 524.1	$ 0.0
Côté Gold
Disclosure of impairment loss and reversal of impairment loss [line items]
Proportion of ownership interest in joint venture	30.00%
Euro Ressources S. A. and Rosebel Gold Mines N. V.
Disclosure of impairment loss and reversal of impairment loss [line items]
Valuation assumption, life of mine						11 years
Valuation assumption, estimated price for first 5 years (in dollars per ounce) \| $ / oz						1,225
Valuation assumption, estimated price after first 5 years (in dollars per ounce) \| $ / oz				1,200
Real weighted average cost of capital discount rate		6.00%				6.00%
Fair value assumptions, mineralization of cash generating units (in dollars per ounce) \| $ / oz						45
Property, plant and equipment [member]
Disclosure of impairment loss and reversal of impairment loss [line items]
Reversal of impairment charges		$ 0.0	$ 124.1		0.0	$ 124.1	0.0
Reversal of impairment charges, net of tax			79.9
Exploration and evaluation assets
Disclosure of impairment loss and reversal of impairment loss [line items]
Reversal of impairment charges		$ 0.0	$ 400.0		$ 0.0	$ 400.0	$ 0.0

COMMITMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Disclosure Of Commitments [Line Items]
Purchase obligations	$ 78.2	$ 53.2
Capital expenditure obligations	26.3	4.6
Operating leases	18.1	4.3
Total commitments	122.6	$ 62.1
Less than 1 yr
Disclosure Of Commitments [Line Items]
Purchase obligations	71.9
Capital expenditure obligations	22.5
Operating leases	1.5
Total commitments	95.9
1-2 yrs
Disclosure Of Commitments [Line Items]
Purchase obligations	5.7
Capital expenditure obligations	3.8
Operating leases	10.1
Total commitments	19.6
3-5 yrs
Disclosure Of Commitments [Line Items]
Purchase obligations	0.4
Capital expenditure obligations	0.0
Operating leases	6.5
Total commitments	6.9
Greater than 5 yrs
Disclosure Of Commitments [Line Items]
Purchase obligations	0.2
Capital expenditure obligations	0.0
Operating leases	0.0
Total commitments	$ 0.2

RELATED PARTY TRANSACTIONS (Details) - Joint ventures where entity is venturer - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Non-Interest Bearing Receivable
Disclosure of transactions between related parties [line items]
Amounts receivable, related party transactions beginning balance	$ 0.2	$ 0.0	$ 0.2	$ 0.2
Advances	0.2	0.0	0.7	0.0
Repayments	(0.3)	0.0	(0.8)	(0.2)
Amounts receivable, related party transactions ending balance	0.1	0.0	0.1	0.0
Interest Bearing Receivable
Disclosure of transactions between related parties [line items]
Amounts receivable, related party transactions beginning balance	33.1	30.2	31.3	29.3
Advances	2.8	0.3	4.6	1.2
Amounts receivable, related party transactions ending balance	$ 35.9	$ 30.5	$ 35.9	$ 30.5
Interest Bearing Receivable \| Floating interest rate
Disclosure of transactions between related parties [line items]
Borrowings, adjustment to interest rate basis			2.00%

SEGMENTED INFORMATION - BALANCE SHEETS (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Disclosure of operating segments [line items]
Total non- current assets	$ 2,858.5	$ 2,387.6
Total assets	3,935.4	3,400.5
Total liabilities	1,082.6	1,129.4
Gold mines
Disclosure of operating segments [line items]
Total non- current assets	2,148.8	2,071.2
Total assets	2,578.0	2,550.6
Total liabilities	629.4	583.8
Gold mines \| BURKINA FASO
Disclosure of operating segments [line items]
Total non- current assets	842.4	883.4
Total assets	1,065.2	1,099.6
Total liabilities	193.3	189.9
Gold mines \| SURINAME
Disclosure of operating segments [line items]
Total non- current assets	615.3	512.8
Total assets	799.0	667.3
Total liabilities	247.6	198.1
Gold mines \| CANADA
Disclosure of operating segments [line items]
Total non- current assets	691.1	675.0
Total assets	713.8	783.7
Total liabilities	188.5	195.8
Exploration and evaluation
Disclosure of operating segments [line items]
Total non- current assets	433.7	163.1
Total assets	476.0	193.2
Total liabilities	6.8	8.4
Corporate
Disclosure of operating segments [line items]
Total non- current assets	276.0	153.3
Total assets	881.4	656.7
Total liabilities	$ 446.4	$ 537.2
Société d'Exploitation des Mines d'Or de Sadiola S.A.
Disclosure of operating segments [line items]
Ownership interest in joint venture	41.00%	41.00%
Total non- current assets	$ 127.3	$ 116.5
Total assets	173.0	160.2
Total liabilities	$ 147.9	$ 144.1
Yatela
Disclosure of operating segments [line items]
Ownership interest in joint venture	40.00%

SEGMENTED INFORMATION - STATEMENT OF EARNINGS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure of operating segments [line items]
Revenues	$ 268.8	$ 282.4	$ 803.8	$ 734.6
Cost of sales	165.6	160.9	494.8	458.4
Depreciation expense	62.3	69.3	197.2	193.1
General and administrative	8.9	10.0	27.8	28.8
Exploration	6.6	6.5	29.6	20.6
Impairments (reversals)	0.0	0.0	(524.1)	0.0
Other income	(1.5)
Other expenses		1.9	8.0	10.2
Earnings from operations	26.9	33.8	570.5	23.5
Net capital expenditures	44.7	72.5	138.5	222.8
Operating Segments Including Incorporated Joint Ventures
Disclosure of operating segments [line items]
Revenues	288.4	303.6	862.5	802.1
Cost of sales	179.5	178.7	535.9	509.4
Depreciation expense	62.7	69.6	198.3	195.3
General and administrative	8.9	10.0	27.8	28.8
Exploration	7.1	6.7	30.7	21.1
Impairments (reversals)	0.0	0.0	(524.1)	0.0
Other income	(1.5)
Other expenses		1.9	8.0	11.7
Earnings from operations	31.7	36.7	585.9	35.8
Net capital expenditures	47.1	73.6	144.3	225.5
Société d'Exploitation des Mines d'Or de Sadiola S.A.
Disclosure of operating segments [line items]
Revenues	19.6	21.2	58.7	67.5
Cost of sales	13.9	17.8	41.1	51.0
Depreciation expense	0.4	0.3	1.1	2.2
General and administrative	0.0	0.0	0.0	0.0
Exploration	0.5	0.2	1.1	0.5
Impairments (reversals)	0.0	0.0	0.0	0.0
Other expenses	0.0	0.0	0.0	1.5
Earnings from operations	4.8	2.9	15.4	12.3
Net capital expenditures	2.4	1.1	5.8	2.7
Gold mines
Disclosure of operating segments [line items]
Revenues	268.7	282.2	803.5	734.0
Cost of sales	165.6	159.6	494.8	457.4
Depreciation expense	61.5	68.2	194.4	189.7
General and administrative	0.0	0.0	0.0	0.0
Exploration	0.1	1.2	4.9	2.8
Impairments (reversals)	0.0	0.0	(116.0)	0.0
Other income	(1.6)
Other expenses		1.4	1.3	8.0
Earnings from operations	43.1	51.8	224.1	76.1
Net capital expenditures	44.0	72.0	136.8	219.3
Gold mines \| BURKINA FASO
Disclosure of operating segments [line items]
Revenues	130.2	167.6	402.2	399.2
Cost of sales	82.2	84.6	250.2	223.8
Depreciation expense	31.0	32.3	98.0	78.8
General and administrative	0.0	0.0	0.0	0.0
Exploration	0.0	0.0	0.0	0.0
Impairments (reversals)	0.0	0.0	0.0	0.0
Other expenses	0.0	0.9	0.0	0.8
Earnings from operations	17.0	49.8	54.0	95.8
Net capital expenditures	16.8	16.9	52.5	82.4
Gold mines \| SURINAME
Disclosure of operating segments [line items]
Revenues	97.1	92.2	286.3	269.4
Cost of sales	57.5	53.4	171.4	169.4
Depreciation expense	20.0	21.7	63.4	72.9
General and administrative	0.0	0.0	0.0	0.0
Exploration	0.1	1.2	4.9	2.8
Impairments (reversals)	0.0	0.0	(116.0)	0.0
Other expenses	0.4	0.2	2.3	3.6
Earnings from operations	19.1	15.7	160.3	20.7
Net capital expenditures	13.2	34.2	36.7	67.8
Gold mines \| CANADA
Disclosure of operating segments [line items]
Revenues	41.4	22.4	115.0	65.4
Cost of sales	25.9	21.6	73.2	64.2
Depreciation expense	10.5	14.2	33.0	38.0
General and administrative	0.0	0.0	0.0	0.0
Exploration	0.0	0.0	0.0	0.0
Impairments (reversals)	0.0	0.0	0.0	0.0
Other income	(2.0)
Other expenses		0.3	(1.0)	3.6
Earnings from operations	7.0	(13.7)	9.8	(40.4)
Net capital expenditures	14.0	20.9	47.6	69.1
Exploration and evaluation
Disclosure of operating segments [line items]
Revenues	0.0	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0	0.0
Depreciation expense	0.0	0.1	0.1	0.2
General and administrative	0.0	0.1	0.1	0.3
Exploration	6.5	5.3	24.7	17.8
Impairments (reversals)	0.0		(400.0)	0.0
Other expenses	0.1	0.1	0.3	0.3
Earnings from operations	(6.6)	(5.6)	374.8	(18.6)
Net capital expenditures	0.5	0.4	1.3	2.7
Corporate
Disclosure of operating segments [line items]
Revenues	0.1	0.2	0.3	0.6
Cost of sales	0.0	1.3	0.0	1.0
Depreciation expense	0.8	1.0	2.7	3.2
General and administrative	8.9	9.9	27.7	28.5
Exploration	0.0	0.0	0.0	0.0
Impairments (reversals)	0.0	0.0	(8.1)	0.0
Other expenses	0.0	0.4	6.4	1.9
Earnings from operations	(9.6)	(12.4)	(28.4)	(34.0)
Net capital expenditures	$ 0.2	$ 0.1	$ 0.4	$ 0.8