Document and Entity Information - shares shares in Millions	9 Months Ended
Document and Entity Information - shares shares in Millions	Oct. 01, 2017	Oct. 20, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Illumina Inc
Entity Central Index Key	0001110803
Current Fiscal Year End Date	--01-01
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Oct. 01, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		146

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Current assets:
Cash and cash equivalents	$ 1,354	$ 735
Short-term investments	687	824
Accounts receivable, net	383	381
Inventory	327	300
Prepaid expenses and other current assets	54	78
Total current assets	2,805	2,318
Property and equipment, net	862	713
Goodwill	771	776
Intangible assets, net	185	243
Deferred tax assets	117	123
Other assets	306	108
Total assets	5,046	4,281
Current liabilities:
Accounts payable	158	138
Accrued liabilities	381	342
Build-to-suit lease liability	124	223
Long-term debt, current portion	2	2
Total current liabilities	665	705
Long-term debt	1,180	1,056
Other long-term liabilities	222	206
Redeemable noncontrolling interests	124	44
Stockholders’ equity:
Common stock	2	2
Additional paid-in capital	2,891	2,733
Accumulated other comprehensive loss		(1)
Retained earnings	2,188	1,485
Treasury stock, at cost	(2,226)	(2,022)
Total Illumina stockholders' equity	2,855	2,197
Noncontrolling interests		73
Total stockholders’ equity	2,855	2,270
Total liabilities and stockholders’ equity	$ 5,046	$ 4,281

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Revenue:
Product revenue	$ 596	$ 514	$ 1,631	$ 1,506
Service and other revenue	118	93	344	273
Total revenue	714	607	1,975	1,779
Cost of revenue:
Cost of product revenue	173	132	508	383
Cost of service and other revenue	50	38	153	117
Amortization of acquired intangible assets	9	11	30	32
Total cost of revenue	232	181	691	532
Gross profit	482	426	1,284	1,247
Operating expense:
Research and development	134	126	409	374
Selling, general and administrative	167	139	499	438
Legal contingencies				(9)
Total operating expense	301	265	908	803
Income from operations	181	161	376	444
Other income (expense):
Interest income	4	2	13	7
Interest expense	(10)	(9)	(26)	(25)
Other income, net			457	1
Total other (expense) income, net	(6)	(7)	444	(17)
Income before income taxes	175	154	820	427
Provision for income taxes	23	37	199	106
Consolidated net income	152	117	621	321
Add: Net loss attributable to noncontrolling interests	11	12	37	18
Net income attributable to Illumina stockholders	163	129	658	339
Net income attributable to Illumina stockholders for earnings per share	$ 163	$ 129	$ 657	$ 336
Earnings per share attributable to Illumina stockholders:
Basic (in dollars per share)	$ 1.12	$ 0.88	$ 4.49	$ 2.29
Diluted (in dollars per share)	$ 1.11	$ 0.87	$ 4.45	$ 2.27
Shares used in computing earnings per common share:
Basic (in shares)	146	147	146	147
Diluted (in shares)	148	148	148	148

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Statement of Comprehensive Income [Abstract]
Consolidated net income	$ 152	$ 117	$ 621	$ 321
Unrealized gain (loss) on available-for-sale securities, net of deferred tax	1	(1)	1	1
Total consolidated comprehensive income	153	116	622	322
Add: Comprehensive loss attributable to noncontrolling interests	11	12	37	18
Comprehensive income attributable to Illumina stockholders	$ 164	$ 128	$ 659	$ 340

Condensed Consolidated Statement of Stockholders' Equity Statement - 9 months ended Oct. 01, 2017 - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interests [Member]
Beginning balance at Jan. 01, 2017	$ 2,270	$ 2	$ 2,733	$ (1)	$ 1,485	$ (2,022)	$ 73
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	651				658		(7)
Unrealized gain on available-for-sale securities, net of deferred tax	1			1
Issuance of common stock, net of repurchases	(141)		63			(204)
Share-based compensation	123		123
Adjustment to the carrying value of redeemable noncontrolling interests	(30)		(30)
Vesting of redeemable equity awards	(12)		(12)
Cumulative-effect adjustment from adoption of ASU 2016-09	48		3		45
Deconsolidation of GRAIL	(55)		11				(66)
Ending balance at Oct. 01, 2017	$ 2,855	$ 2	$ 2,891	$ 0	$ 2,188	$ (2,226)	$ 0

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016
Cash flows from operating activities:
Consolidated net income	$ 621	$ 321
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on deconsolidation of GRAIL	(453)
Depreciation expense	81	65
Amortization of intangible assets	36	38
Share-based compensation expense	123	102
Accretion of debt discount	23	22
Deferred income taxes	53	58
Impairment of intangible assets	23
Other	(2)	5
Changes in operating assets and liabilities:
Accounts receivable	1	5
Inventory	(27)	(42)
Prepaid expenses and other current assets	14	3
Other assets	(3)	(6)
Accounts payable	12	(7)
Accrued liabilities	56	(57)
Other long-term liabilities	23	10
Net cash provided by operating activities	581	517
Cash flows from investing activities:
Purchases of available-for-sale securities	(359)	(679)
Sales of available-for-sale securities	314	406
Maturities of available-for-sale securities	181	148
Net cash paid for acquisitions		(18)
Proceeds from sale of GRAIL securities	278
Deconsolidation of GRAIL cash	(52)
Net purchases of strategic investments	(25)	(9)
Purchases of property and equipment	(234)	(178)
Cash paid for intangible assets	2	11
Net cash provided by (used in) investing activities	101	(341)
Cash flows from financing activities:
Payments on financing obligations	(7)	(71)
Payments on acquisition related contingent consideration liability	(3)	(29)
Proceeds from issuance of debt	5	5
Common stock repurchases	(176)	(113)
Taxes paid related to net share settlement of equity awards	(28)	(76)
Proceeds from issuance of common stock	63	47
Proceeds from early exercise of equity awards from a subsidiary		6
Contributions from noncontrolling interest owners	79	80
Net cash used in financing activities	(67)	(151)
Effect of exchange rate changes on cash and cash equivalents	4	1
Net increase in cash and cash equivalents	619	26
Cash and cash equivalents at beginning of period	735	769
Cash and cash equivalents at end of period	$ 1,354	$ 795

Basis of Presentation and Summary of Significant Accounting Policies

9 Months Ended

Oct. 01, 2017

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. Interim financial results are not necessarily indicative of results anticipated for the full year. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the fiscal year ended January 1, 2017, from which the balance sheet information herein was derived. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, and expense, and related disclosure of contingent assets and liabilities. Actual results could differ from those estimates.

The unaudited condensed consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, majority-owned or controlled companies, and variable interest entities (VIEs) for which the Company is the primary beneficiary. All intercompany transactions and balances have been eliminated in consolidation. Effective February 28, 2017, Illumina deconsolidated GRAIL, Inc.’s financial statements. In management’s opinion, the accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented.

The Company evaluates its ownership, contractual, and other interests in entities that are not wholly-owned by the Company to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and is therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company continuously assesses whether it is the primary beneficiary of a VIE as changes to existing relationships or future transactions may result in the consolidation or deconsolidation, as the case may be, of such VIE. The Company has not provided financial or other support during the periods presented to its VIEs that it was not previously contractually required to provide.

The equity method is used to account for investments in which the Company has the ability to exercise significant influence, but not control, over the investee. Such investments are recorded within other assets, and the share of net income or losses of equity investments is recognized on a one quarter lag in other income, net.

Redeemable Noncontrolling Interests

Noncontrolling interests represent the portion of equity (net assets) in a consolidated entity that is not wholly-owned by the Company that is not attributable, directly or indirectly, to the Company. Noncontrolling interests with embedded contingent redemption features, such as put rights, that are not solely within the Company’s control are considered redeemable noncontrolling interests. Redeemable noncontrolling interests are presented outside of stockholders’ equity on the condensed consolidated balance sheets.

Fiscal Year

The Company’s fiscal year consists of 52 or 53 weeks ending the Sunday closest to December 31, with quarters of 13 or 14 weeks ending the Sunday closest to March 31, June 30, September 30, and December 31. The three and nine months ended October 1, 2017 and October 2, 2016 were both 13 and 39 weeks, respectively.

Reclassifications

Certain prior period amounts have been reclassified to conform to the current period presentation.

Significant Accounting Policies

During the three and nine months ended October 1, 2017, there have been no changes to the Company’s significant accounting policies as described in the Annual Report on Form 10-K for the fiscal year ended January 1, 2017.

Recently Adopted Accounting Pronouncements

In March 2016, the Financial Accounting Standards Board issued Accounting Standard Update (ASU) 2016-09, Compensation - Stock Compensation (Topic 718), which aims to simplify the accounting for share-based payment transactions, including accounting for income taxes, classification on the statement of cash flows, accounting for forfeitures, and classification of awards as either liabilities or equity. This ASU was effective for the Company beginning in the first quarter of 2017.

Under the ASU, excess tax benefits from share-based payment arrangements are classified as discrete items within the provision for income taxes, rather than recognizing excess tax benefits in additional paid-in capital. Upon adoption in Q1 2017, the Company recorded $45 million, net, to retained earnings, primarily related to unrealized tax benefits associated with share-based compensation. During the three and nine months ended October 1, 2017, excess tax benefits of $12 million and $31 million, respectively, were reflected as a component of the provision for income taxes.

In addition, under the ASU, excess income tax benefits from share-based compensation arrangements are classified as cash flow from operations, rather than cash flow from financing activities. The Company has elected to apply the cash flow classification guidance retrospectively and reclassified $110 million from financing activity to operating activity for the nine months ended October 2, 2016.

Recently Issued Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). The new standard is based on the principle that revenue should be recognized in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the transfer of promised goods or services. Since its initial release, the FASB has issued several amendments to the standard, which include clarification of accounting guidance related to identification of performance obligations, intellectual property licenses, and principal vs. agent considerations.

ASU 2014-09 and all subsequent amendments (collectively, the “new standards”) will be effective for the Company beginning in the first quarter of 2018 and may be applied using either the full retrospective method, in which case the standard would be applied to each prior reporting period presented, or the modified retrospective method, in which case the cumulative effect of applying the standard would be recognized at the date of initial application.

The Company continues to work through steps in the implementation project plan, which include: finalizing new disclosures required by the new standards and implementing changes to business processes and reporting in support of the adoption of the new standards. The Company will adopt the new standards using the modified retrospective method with an adjustment to beginning retained earnings for the cumulative effect of the change, which is not expected to be material.

In January 2016, the Financial Accounting Standards Board issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10), which requires equity investments (other than those accounted for under the equity method or those that result in consolidation) to be measured at fair value, with changes in fair value recognized in net income. ASU 2016-01 will be effective for the Company beginning in the first quarter of 2018. The Company anticipates that the adoption of ASU 2016-01 may increase the volatility of other income and expense, net, as a result of the remeasurement of the Company’s cost-method investments.

In February 2016, the Financial Accounting Standards Board issued ASU 2016-02, Leases (Topic 842). The new standard requires lessees to recognize most leases on their balance sheets as lease liabilities with corresponding right-of-use assets and eliminates certain real estate-specific provisions. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. ASU 2016-02 will be adopted on a modified retrospective transition basis for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently evaluating the impact of ASU 2016-02 on its consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments, which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available for sale debt securities. The ASU is effective for the Company beginning in the first quarter of 2020, with early adoption permitted. The Company is currently evaluating the impact of ASU 2016-13 on its consolidated financial statements.

Earnings per Share

Basic earnings per share attributable to Illumina stockholders is computed based on the weighted average number of common shares outstanding during the period. Diluted earnings per share attributable to Illumina stockholders is computed based on the sum of the weighted average number of common shares and potentially dilutive common shares outstanding during the period. Per-share earnings of our VIEs are included in the Company’s consolidated basic and diluted earnings per share computations based on the Company’s share of the VIEs’ securities.

Potentially dilutive common shares consist of shares issuable under convertible senior notes and equity awards. Convertible senior notes have a dilutive impact when the average market price of the Company’s common stock exceeds the applicable conversion price of the respective notes. Potentially dilutive common shares from equity awards are determined using the average share price for each period under the treasury stock method. In addition, proceeds from exercise of equity awards and the average amount of unrecognized compensation expense for equity awards are assumed to be used to repurchase shares. In loss periods, basic net loss per share and diluted net loss per share are identical because the otherwise dilutive potential common shares become anti-dilutive and are therefore excluded.

The following table presents the calculation of weighted average shares used to calculate basic and diluted earnings per share (in millions):



	Three Months Ended		Nine Months Ended
	October 1, 2017	October 2, 2016	October 1, 2017	October 2, 2016
Weighted average shares outstanding	146	147	146	147
Effect of potentially dilutive common shares from:
Equity awards	2	1	2	1
Weighted average shares used in calculating diluted earnings per share	148	148	148	148
Potentially dilutive shares excluded from calculation due to anti-dilutive effect	—	—	—	1

Balance Sheet Account Details

9 Months Ended

Oct. 01, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Account Details

Short-Term Investments

The following is a summary of short-term investments (in millions):



	October 1, 2017							January 1, 2017
	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Debt securities in government sponsored entities	$	74	$	—		$	74	$	34	$	—		$	34
Corporate debt securities	343		(1		)	342		478		(2		)	476
U.S. Treasury securities	272		(1		)	271		316		(2		)	314
Total available-for-sale securities	$	689	$	(2	)	$	687	$	828	$	(4	)	$	824

Realized gains and losses are determined based on the specific identification method and are reported in interest income.

Contractual maturities of available-for-sale debt securities as of October 1, 2017 were as follows (in millions):



	Estimated Fair Value
Due within one year	$	421
After one but within five years	266
Total	$	687

The Company has the ability, if necessary, to liquidate any of its cash equivalents and short-term investments in order to meet its liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase nonetheless are classified as short-term on the accompanying condensed consolidated balance sheets.

Strategic Investments

As of October 1, 2017 and January 1, 2017, the aggregate carrying amounts of the Company’s cost-method investments in non-publicly traded companies included in other assets were $250 million and $57 million, respectively. Revenue recognized from transactions with such companies was $38 million and $96 million, respectively, for the three and nine months ended October 1, 2017 and $12 million and $42 million, respectively, for the three and nine months ended October 2, 2016.

The Company’s cost-method investments are assessed for impairment quarterly. The Company determines that it is not practicable to estimate the fair value of its cost-method investments on a regular basis and does not reassess the fair value of cost-method investments unless there are identified events or changes in circumstances that may have a significant adverse effect on the fair value of the investments. No material impairment losses were recorded during the three and nine months ended October 1, 2017 or October 2, 2016.

The Company invests in a venture capital investment fund (the Fund) with a capital commitment of $100 million that is callable over ten years. The Company’s investment in the Fund is accounted for as an equity method investment. The carrying amounts included in other assets were $14 million and $10 million as of October 1, 2017 and January 1, 2017, respectively.

Inventory

Inventory consists of the following (in millions):



	October 1, 2017		January 1, 2017
Raw materials	$	90	$	102
Work in process	192		161
Finished goods	45		37
Total inventory	$	327	$	300

Property and Equipment

Property and equipment, net consists of the following (in millions):



	October 1, 2017			January 1, 2017
Leasehold improvements	$	320		$	270
Machinery and equipment	301			274
Computer hardware and software	178			156
Furniture and fixtures	34			24
Building	147			9
Construction in progress	273			307
Total property and equipment, gross	1,253			1,040
Accumulated depreciation	(391		)	(327		)
Total property and equipment, net	$	862		$	713

Property and equipment, net included non-cash expenditures of $94 million and $194 million for the nine months ended October 1, 2017 and October 2, 2016, respectively, which were excluded from the condensed consolidated statements of cash flows. Such non-cash expenditures included $60 million and $169 million recorded under build-to-suit lease accounting for the nine months ended October 1, 2017 and October 2, 2016, respectively.

Intangible Assets and Goodwill

The Company tests the carrying value of goodwill in accordance with accounting rules on impairment of goodwill, which require the Company to estimate the fair value of the reporting unit annually, or when impairment indicators exist, and compare such amounts to their respective carrying values to determine if an impairment is required. The Company performed its annual assessment for goodwill impairment in the second quarter of 2017, noting no impairment.

Changes to the Company’s goodwill balance during the nine months ended October 1, 2017 are as follows (in millions):



	Goodwill
Balance as of January 1, 2017	$	776
GRAIL deconsolidation	(5		)
Balance as of October 1, 2017	$	771

The Company regularly performs reviews to determine if any event has occurred that may indicate its identifiable intangible assets are potentially impaired. During the nine months ended October 1, 2017, the Company performed a recoverability test when the planned use of a finite-lived acquired intangible asset changed, resulting in an impairment charge of $18 million recorded in cost of product revenue. Also during the nine months ended October 1, 2017, the Company recorded a $5 million impairment charge of in-process research and development as it was determined the project had no future alternative use.

Derivatives

The Company is exposed to foreign exchange rate risks in the normal course of business. The Company enters into foreign exchange contracts to manage foreign currency risks related to monetary assets and liabilities that are denominated in currencies other than the U.S. dollar. These foreign exchange contracts are carried at fair value in other assets or other liabilities and are not designated as hedging instruments. Changes in the value of derivatives are recognized in other income, net, along with the remeasurement gain or loss on the foreign currency denominated assets or liabilities.

As of October 1, 2017, the Company had foreign exchange forward contracts in place to hedge exposures in the euro, Japanese yen, Australian dollar, and Canadian dollar. As of October 1, 2017 and January 1, 2017, the total notional amounts of outstanding forward contracts in place for foreign currency purchases were $79 million and $69 million, respectively.

Accrued Liabilities

Accrued liabilities consist of the following (in millions):



	October 1, 2017		January 1, 2017
Accrued compensation expenses	$	138	$	112
Deferred revenue, current portion	131		121
Accrued taxes payable	41		32
Customer deposits	18		20
Other	53		57
Total accrued liabilities	$	381	$	342

Warranties

The Company generally provides a one-year warranty on instruments. Additionally, the Company provides a warranty on consumables through the expiration date, which generally ranges from six to twelve months after the manufacture date. At the time revenue is recognized, the Company establishes an accrual for estimated warranty expenses based on historical experience as well as anticipated product performance. The Company periodically reviews its warranty reserve for adequacy and adjusts the warranty accrual, if necessary, based on actual experience and estimated costs to be incurred. Warranty expense is recorded as a component of cost of product revenue.

Changes in the Company’s reserve for product warranties during the three and nine months ended October 1, 2017 and October 2, 2016 are as follows (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Balance at beginning of period	$	14		$	16		$	13		$	17
Additions charged to cost of product revenue	7			4			18			17
Repairs and replacements	(5		)	(6		)	(15		)	(20		)
Balance at end of period	$	16		$	14		$	16		$	14

Leases

Changes in the Company’s facility exit obligation related to its former headquarters lease during the three and nine months ended October 1, 2017 and October 2, 2016 are as follows (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Balance at beginning of period	$	18		$	21		$	19		$	22
Accretion of interest expense	—			—			—			1
Cash payments	(1		)	(1		)	(2		)	(3		)
Balance at end of period	$	17		$	20		$	17		$	20

On February 22, 2017, the Company entered into a lease agreement for a building under construction in Madison, Wisconsin. Minimum lease payments during the initial 15-year term are estimated to be $46 million.

Investments in Consolidated Variable Interest Entities

GRAIL, Inc.

In January 2016, the Company obtained a majority equity ownership interest in GRAIL, a company formed with unrelated third party investors to develop a blood test for early-stage cancer detection. The Company determined that GRAIL was a variable interest entity as the entity lacked sufficient equity to finance its activities without additional support. Additionally, the Company determined that it had (a) control of GRAIL’s board of directors, which had unilateral power over the activities that most significantly impacted the economic performance of GRAIL and (b) the obligation to absorb losses of and the right to receive benefits from GRAIL that were potentially significant to GRAIL. As a result, the Company was deemed to be the primary beneficiary of GRAIL and was required to consolidate GRAIL.

In January 2016, GRAIL completed its Series A convertible preferred stock financing, raising $120 million, of which the Company invested $40 million. Additionally, the Company and GRAIL executed a long-term supply agreement in which the Company contributed certain perpetual licenses, employees, and discounted supply terms in exchange for 113 million shares of GRAIL’s Class B common stock. Such contributions were recorded at their historical basis as they remained within the control of the Company. The $80 million received by GRAIL from unrelated third party investors upon issuance of its Series A convertible preferred stock was classified as noncontrolling interests in stockholders’ equity on the Company’s condensed consolidated balance sheet.

In June 2016, GRAIL authorized for issuance 98 million shares of Series A-1 convertible preferred stock, all of which were issued to Illumina in exchange for Illumina’s 98 million shares of GRAIL Class B common stock. As a result of the exchange, Illumina recorded a $10 million deemed dividend, net of tax of $10 million, through equity, which was eliminated in consolidation.

Deconsolidation of GRAIL, Inc.

On February 28, 2017, GRAIL completed the initial close of its Series B preferred stock financing, raising over $900 million, in which the Company did not participate. Concurrent with the financing, GRAIL repurchased from the Company 35 million shares of its Series A preferred stock and approximately 34 million shares of its Series A-1 preferred stock for an aggregate purchase price of $278 million. At this time, the Company ceased to have a controlling financial interest in GRAIL and the Company’s equity ownership was reduced from 52% to 19%. Additionally, the Company’s voting interest was reduced to 13%, and the Company no longer has representation on GRAIL’s board of directors. As a result, the Company deconsolidated GRAIL’s financial statements effective February 28, 2017 and accounts for the remaining retained investment as a cost method investment. During the three months ended July 2, 2017, the Company purchased approximately 3 million Series B preferred shares for $14 million resulting in an ownership of approximately 17% of GRAIL’s outstanding stock and a 12% voting interest. As of October 1, 2017, the Company holds $185 million in other assets related to this investment, which consists of 5 million Series A preferred shares, and approximately 3 million Series B preferred shares and 78 million Class A common shares of GRAIL.

The operations of GRAIL from January 2, 2017 up to the date of deconsolidation are included in the accompanying condensed consolidated statements of income for the nine months ended October 1, 2017. During this period, the Company absorbed approximately 50% of GRAIL’s losses based upon its proportional ownership of GRAIL’s common stock.

On February 28, 2017, the Company recorded a pretax gain of $453 million included in other income, net, of which $159 million relates to the remeasurement of the Company’s retained equity interest to its fair value. The pretax gain on deconsolidation includes (i) the consideration received from GRAIL for its repurchase of a portion of the Company’s ownership interest, (ii) the derecognition of the carrying amounts of GRAIL’s assets and liabilities, (iii) the derecognition of the noncontrolling interest related to GRAIL, and (iv) the recording of the Company’s remaining interest in GRAIL at fair value. This fair value measurement of the Company’s remaining interest was derived using the market approach. Significant estimates and assumptions required for this valuation included, but were not limited to, various Black-Scholes option-pricing model assumptions as of the date of deconsolidation and estimated discounts for lack of marketability related to the equity securities. These unobservable inputs, which represent a Level 3 measurement, are supported by little or no market activity and reflect the Company’s own assumptions in measuring fair value.

In connection with the deconsolidation of GRAIL, the parties amended their long-term supply agreement, including the discounted supply terms. The repurchase and supply arrangements, which were entered into concurrently, contain various elements and, as such, are deemed to be an arrangement with multiple deliverables as defined under the respective authoritative accounting guidance. The Company determined that each of the elements, which include the purchase obligation, the purchase right, and services to be provided in accordance with the long-term supply agreement, were at, or approximated, fair value on a standalone basis, and therefore, there was no discount to allocate among the deliverables. As such, none of the deconsolidation gain was allocated to these elements.

Helix Holdings I, LLC

In July 2015, the Company obtained a 50% voting equity ownership interest in Helix Holdings I, LLC (Helix), a limited liability company formed with unrelated third party investors to pursue the development and commercialization of a marketplace for consumer genomics. The Company determined that Helix is a variable interest entity as the holders of the at-risk equity investments as a group lack the power to direct the activities of Helix that most significantly impact Helix’s economic performance. Additionally, the Company determined that it has (a) unilateral power over one of the activities that most significantly impacts the economic performance of Helix through its contractual arrangements and no one individual party has unilateral power over the remaining significant activities of Helix and (b) the obligation to absorb losses of and the right to receive benefits from Helix that are potentially significant to Helix. As a result, the Company is deemed to be the primary beneficiary of Helix and is required to consolidate Helix.

As contractually committed, the Company contributed certain perpetual licenses, instruments, intangibles, initial laboratory setup, and discounted supply terms in exchange for voting equity interests in Helix. Such contributions are recorded at their historical basis as they remain within the control of the Company. Helix is financed through cash contributions made by the third party investors in exchange for voting equity interests in Helix.

Certain noncontrolling Helix investors may require the Company to redeem all noncontrolling interests in cash at the then approximate fair market value. Such redemption right is exercisable at the option of certain noncontrolling interest holders after January 1, 2021, provided that a bona fide pursuit of the sale of Helix has occurred and an initial public offering of Helix has not been completed. The fair value of the redeemable noncontrolling interests is considered a Level 3 instrument.

As the contingent redemption is outside of the control of Illumina, the redeemable noncontrolling interests in Helix are classified outside of stockholders’ equity on the accompanying condensed consolidated balance sheets. The balance of the redeemable noncontrolling interests is reported at the greater of its carrying value after receiving its allocation of Helix’s profits and losses or its estimated redemption value at each reporting date. As of October 1, 2017, the noncontrolling shareholders and Illumina each held 50% of Helix’s outstanding voting equity interests.

The assets and liabilities of Helix are not significant to the Company’s financial position as of October 1, 2017. Helix has an immaterial impact on the Company’s condensed consolidated statements of income and cash flows for the three and nine months ended October 1, 2017.

As of October 1, 2017, the accompanying condensed consolidated balance sheet includes $32 million of cash and cash equivalents attributable to Helix that will be used to settle their respective obligations and will not be available to settle obligations of the Company.

Redeemable Noncontrolling Interests

The activity of the redeemable noncontrolling interests during the nine months ended October 1, 2017 is as follows (in millions):



	Redeemable Noncontrolling Interests
Balance as of January 1, 2017	$	44
Amount released from escrow	79
Vesting of redeemable equity awards	12
Net loss attributable to noncontrolling interests	(30		)
Adjustment up to the redemption value	30
Deconsolidation of GRAIL	(11		)
Balance as of October 1, 2017	$	124

Fair Value Measurements

9 Months Ended

Oct. 01, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following table presents the Company’s hierarchy for assets and liabilities measured at fair value on a recurring basis as of October 1, 2017 and January 1, 2017 (in millions):



	October 1, 2017								January 1, 2017
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets:
Money market funds (cash equivalents)	$	1,051	$	—	$	—	$	1,051	$	386	$	—	$	—	$	386
Debt securities in government-sponsored entities	—		74		—		74		—		34		—		34
Corporate debt securities	—		342		—		342		—		476		—		476
U.S. Treasury securities	271		—		—		271		314		—		—		314
Deferred compensation plan assets	—		34		—		34		—		31		—		31
Total assets measured at fair value	$	1,322	$	450	$	—	$	1,772	$	700	$	541	$	—	$	1,241
Liabilities:
Acquisition related contingent consideration liabilities	$	—	$	—	$	—	$	—	$	—	$	—	$	4	$	4
Deferred compensation liability	—		31		—		31		—		29		—		29
Total liabilities measured at fair value	$	—	$	31	$	—	$	31	$	—	$	29	$	4	$	33

The Company holds available-for-sale securities that consist of highly liquid, investment grade debt securities. The Company considers information provided by the Company’s investment accounting and reporting service provider in the measurement of fair value of its debt securities. The investment service provider provides valuation information from an industry-recognized valuation service. Such valuations may be based on trade prices in active markets for identical assets or liabilities (Level 1 inputs) or valuation models using inputs that are observable either directly or indirectly (Level 2 inputs), such as quoted prices for similar assets or liabilities, yield curve, volatility factors, credit spreads, default rates, loss severity, current market and contractual prices for the underlying instruments or debt, broker and dealer quotes, as well as other relevant economic measures. The Company’s deferred compensation plan assets consist primarily of investments in life insurance contracts carried at cash surrender value, which reflects the net asset value of the underlying publicly traded mutual funds. The Company performs control procedures to corroborate the fair value of its holdings, including comparing valuations obtained from its investment service provider to valuations reported by the Company’s asset custodians, validation of pricing sources and models, and review of key model inputs if necessary.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Debt

9 Months Ended

Oct. 01, 2017

Debt Disclosure [Abstract]

Debt

Summary of debt obligations

The Company’s debt obligations consist of the following (dollars in millions):



	October 1, 2017			January 1, 2017
Principal amount of 2019 Notes outstanding	$	633		$	633
Principal amount of 2021 Notes outstanding	517			517
Unamortized discount of liability component of convertible senior notes	(83		)	(105		)
Net carrying amount of liability component of convertible senior notes	1,067			1,045
Obligations under financing leases	111			9
Other	4			4
Less: current portion	(2		)	(2		)
Long-term debt	$	1,180		$	1,056
Carrying value of equity component of convertible senior notes, net of debt issuance cost	$	161		$	161
Fair value of convertible senior notes outstanding (Level 2)	$	1,262		$	1,108
Weighted-average remaining amortization period of discount on the liability component of convertible senior notes	3.0 years			3.6 years

Convertible Senior Notes

0% Convertible Senior Notes due 2019 (2019 Notes) and 0.5% Convertible Senior Notes due 2021 (2021 Notes)

In June 2014, the Company issued $633 million aggregate principal amount of 2019 Notes and $517 million aggregate principal amount of 2021 Notes. The Company used the net proceeds plus cash on hand to repurchase outstanding debt. The 2019 and 2021 Notes mature on June 15, 2019 and June 15, 2021, respectively, and the implied estimated effective rates of the liability components of the Notes were 2.9% and 3.5%, respectively, assuming no conversion.

Both the 2019 and 2021 Notes will be convertible into cash, shares of common stock, or a combination of cash and shares of common stock, at the Company's election, based on an initial conversion rate, subject to adjustment, of 3.9318 shares per $1,000 principal amount of the notes (which represents an initial conversion price of approximately $254.34 per share), only in the following circumstances and to the following extent: (1) during the five business-day period after any 10 consecutive trading day period (the measurement period) in which the trading price per 2019 and 2021 Note for each day of such measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such day; (2) during any calendar quarter (and only during that quarter) after the calendar quarter ending September 30, 2014, if the last reported sale price of the Company’s common stock for 20 or more trading days in the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter exceeds 130% of the applicable conversion price in effect on the last trading day of the immediately preceding calendar quarter; (3) upon the occurrence of specified events described in the indenture for the 2019 and 2021 Notes; and (4) at any time on or after March 15, 2019 for the 2019 Notes, or March 15, 2021 for the 2021 Notes, through the second scheduled trading day immediately preceding the maturity date.

Neither the 2019 nor the 2021 Notes were convertible as of October 1, 2017, and had no dilutive impact during the three and nine months ended October 1, 2017. If the 2019 and 2021 Notes were converted as of October 1, 2017, the if-converted value would not exceed the principal amount.

0.25% Convertible Senior Notes due 2016

In 2011, the Company issued $920 million aggregate principal amount of 0.25% convertible senior notes due 2016 (2016 Notes) with a maturity date of March 15, 2016. The effective rate of the liability component was estimated to be 4.5%. Based upon meeting the stock trading price conversion requirement during the three months ended March 30, 2014, the 2016 Notes became convertible on April 1, 2014 through, and including, March 11, 2016. All notes were converted by March 11, 2016.

Build-to-suit leases

The Company evaluates whether it is the accounting owner of leased assets during the construction period when the Company is involved in the construction of leased assets. Including the Madison lease agreement entered on February 28, 2017, the Company is considered the owner of two construction projects for accounting purposes only under build-to-suit lease accounting due to certain indemnification obligations related to the construction. As of October 1, 2017 and January 1, 2017, the Company has recorded $124 million and $223 million, respectively, in project construction costs paid or reimbursed by the landlord as construction in progress and a corresponding build-to-suit lease liability.

During the nine months ended October 1, 2017, construction of a build-to-suit property was completed. The Company concluded it did not qualify for “sale-leaseback” treatment and the lease is accounted for as a financing obligation. Accordingly, the Company reclassified $102 million of construction in progress and build-to-suit lease liability to building asset and obligations under financing leases, respectively.

On February 28, 2017, the Company deconsolidated GRAIL, as further described in note “2. Balance Sheet Account Details”, and removed $58 million of construction in progress and the corresponding build-to-suit lease liability.

Share-based Compensation Expense

9 Months Ended

Oct. 01, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-based Compensation Expense

Share-based compensation expense for all stock awards consists of the following (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Cost of product revenue	$	3		$	2		$	9		$	6
Cost of service and other revenue	1			1			2			2
Research and development	12			12			38			33
Selling, general and administrative	18			20			74			61
Share-based compensation expense before taxes	34			35			123			102
Related income tax benefits	(11		)	(8		)	(34		)	(23		)
Share-based compensation expense, net of taxes	$	23		$	27		$	89		$	79

The assumptions used for the specified reporting periods and the resulting estimates of weighted-average fair value per share for stock purchased under the Employee Stock Purchase Plan (ESPP) during the nine months ended October 1, 2017 are as follows:



	Employee Stock Purchase Rights
Risk-free interest rate	0.50% - 1.22%
Expected volatility	29% - 44%
Expected term	0.5 - 1.0 year
Expected dividends	0		%
Weighted-average fair value per share	$	46.85

As of October 1, 2017, approximately $242 million of unrecognized compensation cost related to restricted stock and ESPP shares granted to date is expected to be recognized over a weighted-average period of approximately 2.2 years.

Stockholders' Equity

9 Months Ended

Oct. 01, 2017

Equity [Abstract]

Stockholders' Equity

Stockholders’ Equity

As of October 1, 2017, approximately 6.3 million shares remained available for future grants under the 2015 Stock Plan.

Restricted Stock

The Company’s restricted stock activity and related information for the nine months ended October 1, 2017 is as follows (units in thousands):



	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		Weighted-Average Grant-Date Fair Value per Share
	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		RSA		RSU		PSU
Outstanding at January 1, 2017	32		2,293		460		$	136.30	$	141.80	$	158.66
Awarded	—		141		38		—		$	173.08	$	154.93
Vested	(11	)	(257	)	—		$	179.00	$	110.56	—
Cancelled	—		(184	)	(60	)	—		$	149.22	$	176.15
Outstanding at October 1, 2017	21		1,993		438		$	114.59	$	147.41	$	155.95

______________________________________


(1)	The number of units reflect the estimated number of shares to be issued at the end of the performance period.

Stock Options

The Company’s stock option activity under all stock option plans during the nine months ended October 1, 2017 is as follows:



	Options (in thousands)		Weighted-Average Exercise Price
Outstanding at January 1, 2017	1,045		$	48.56
Exercised	(604	)	$	46.43
Outstanding and exercisable at October 1, 2017	441		$	51.51

Employee Stock Purchase Plan

The price at which common stock is purchased under the ESPP is equal to 85% of the fair market value of the common stock on the first day of the offering period or purchase date, whichever is lower. During the nine months ended October 1, 2017, approximately 0.3 million shares were issued under the ESPP. As of October 1, 2017, there were approximately 14.0 million shares available for issuance under the ESPP.

Share Repurchases

On July 28, 2016, the Company’s Board of Directors authorized a share repurchase program, which superseded all prior and available repurchase authorizations, to repurchase $250 million of outstanding common stock. During the three months ended April 2, 2017, the Company repurchased 0.6 million shares for $101 million, completing the share repurchase program.

On May 4, 2017, the Company’s Board of Directors authorized an additional share repurchase program to repurchase $250 million of outstanding common stock. The repurchases may be completed under a 10b5-1 plan or at management’s discretion. During the three months ended October 1, 2017, the Company repurchased 0.4 million shares for $75 million under a 10b5-1 plan. Authorizations to repurchase $175 million of the Company’s common stock remained available as of October 1, 2017.

Income Taxes	9 Months Ended
Income Taxes	Oct. 01, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s effective tax rate may vary from the U.S. federal statutory tax rate due to the change in the mix of earnings in tax jurisdictions with different statutory rates, benefits related to tax credits, and the tax impact of non-deductible expenses and other permanent differences between income before income taxes and taxable income. The effective tax rates for the three and nine months ended October 1, 2017 were 12.9% and 24.3%, respectively. For the three and nine months ended October 1, 2017, the variance from the U.S. federal statutory tax rate of 35% was primarily attributable to the mix of earnings in jurisdictions with lower statutory tax rates than the U.S. federal statutory tax rate, such as in Singapore and the United Kingdom, and excess tax benefits related to share-based compensation. In addition, for the nine months ended October 1, 2017, the decrease from the federal statutory tax rate was partially offset by the discrete tax impact of $150 million from the gain on the deconsolidation of GRAIL.

Legal Proceedings	9 Months Ended
Legal Proceedings	Oct. 01, 2017
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	Legal Proceedings The Company is involved in various lawsuits and claims arising in the ordinary course of business, including actions with respect to intellectual property, employment, and contractual matters. In connection with these matters, the Company assesses, on a regular basis, the probability and range of possible loss based on the developments in these matters. A liability is recorded in the financial statements if it is believed to be probable that a loss has been incurred and the amount of the loss can be reasonably estimated. Because litigation is inherently unpredictable and unfavorable results could occur, assessing contingencies is highly subjective and requires judgments about future events. The Company regularly reviews outstanding legal matters to determine the adequacy of the liabilities accrued and related disclosures. The amount of ultimate loss may differ from these estimates. Each matter presents its own unique circumstances, and prior litigation does not necessarily provide a reliable basis on which to predict the outcome, or range of outcomes, in any individual proceeding. Because of the uncertainties related to the occurrence, amount, and range of loss on any pending litigation or claim, the Company is currently unable to predict their ultimate outcome, and, with respect to any pending litigation or claim where no liability has been accrued, to make a meaningful estimate of the reasonably possible loss or range of loss that could result from an unfavorable outcome. In the event that opposing litigants in outstanding litigations or claims ultimately succeed at trial and any subsequent appeals on their claims, any potential loss or charges in excess of any established accruals, individually or in the aggregate, could have a material adverse effect on the Company’s business, financial condition, results of operations, and/or cash flows in the period in which the unfavorable outcome occurs or becomes probable, and potentially in future periods.

Segment Information (Notes)

9 Months Ended

Oct. 01, 2017

Segment Reporting [Abstract]

Segment Reporting Disclosure [Text Block]

Segment Information

The Company has two reportable segments: Core Illumina and one segment related to the combined activities of the Company’s consolidated VIEs, GRAIL and Helix (Consolidated VIEs). Following the GRAIL deconsolidation on February 28, 2017, the Company’s Consolidated VIEs no longer include GRAIL. The Company reports segment information based on the management approach. This approach designates the internal reporting used by the Chief Operating Decision Maker (“CODM”) for making decisions and assessing performance as the source of the Company’s reportable segments. The CODM allocates resources and assesses the performance of each operating segment using information about its revenues and income (losses) from operations. Based on the information used by the CODM, the Company has determined its reportable segments as follows:

Core Illumina:

Core Illumina’s products and services serve customers in the research, clinical and applied markets, and enable the adoption of a variety of genomic solutions. Core Illumina includes all operations of the Company, excluding the results of its consolidated VIEs.

Consolidated VIEs:

GRAIL: GRAIL was created to develop a blood test for early-stage cancer detection. GRAIL is currently in the early stages of developing this test and as such, had no revenues through the date of deconsolidation.

Helix: Helix was established to enable individuals to explore their genetic information by providing affordable sequencing and database services for consumers through third party partners, driving the creation of an ecosystem of consumer applications.

Management evaluates the performance of the Company’s operating segments based upon income (loss) from operations. The Company does not allocate expenses between segments. Core Illumina sells products and provides services to GRAIL and Helix in accordance with contractual agreements between the entities.

The following table presents the operating performance of each reportable segment (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Revenues:
Core Illumina	$	715		$	615		$	1,978		$	1,792
Consolidated VIEs	1			—			4			—
Elimination of intersegment revenues	(2		)	(8		)	(7		)	(13		)
Consolidated revenues	$	714		$	607		$	1,975		$	1,779

Operating income (loss):
Core Illumina	$	203		$	191		$	447		$	502
Consolidated VIEs	(22		)	(25		)	(72		)	(50		)
Elimination of intersegment earnings	—			(5		)	1			(8		)
Consolidated operating income	$	181		$	161		$	376		$	444

The following table presents the total assets of each reportable segment (in millions):



	October 1, 2017			January 1, 2017
Total assets:
Core Illumina	$	4,999		$	4,167
Consolidated VIEs	59			180
Elimination of intersegment assets	(12		)	(66		)
Consolidated total assets	$	5,046		$	4,281

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Oct. 01, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements.
Consolidation	The unaudited condensed consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, majority-owned or controlled companies, and variable interest entities (VIEs) for which the Company is the primary beneficiary. All intercompany transactions and balances have been eliminated in consolidation. Effective February 28, 2017, Illumina deconsolidated GRAIL, Inc.’s financial statements. In management’s opinion, the accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented.
Variable Interest Entities	The Company evaluates its ownership, contractual, and other interests in entities that are not wholly-owned by the Company to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and is therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company continuously assesses whether it is the primary beneficiary of a VIE as changes to existing relationships or future transactions may result in the consolidation or deconsolidation, as the case may be, of such VIE. The Company has not provided financial or other support during the periods presented to its VIEs that it was not previously contractually required to provide.
Equity Method Investments	The equity method is used to account for investments in which the Company has the ability to exercise significant influence, but not control, over the investee. Such investments are recorded within other assets, and the share of net income or losses of equity investments is recognized on a one quarter lag in other income, net.
Redeemable Noncontrolling Interests	Noncontrolling interests represent the portion of equity (net assets) in a consolidated entity that is not wholly-owned by the Company that is not attributable, directly or indirectly, to the Company. Noncontrolling interests with embedded contingent redemption features, such as put rights, that are not solely within the Company’s control are considered redeemable noncontrolling interests. Redeemable noncontrolling interests are presented outside of stockholders’ equity on the condensed consolidated balance sheets.
Fiscal Year	The Company’s fiscal year consists of 52 or 53 weeks ending the Sunday closest to December 31, with quarters of 13 or 14 weeks ending the Sunday closest to March 31, June 30, September 30, and December 31. The three and nine months ended October 1, 2017 and October 2, 2016 were both 13 and 39 weeks, respectively.
Reclassifications	Certain prior period amounts have been reclassified to conform to the current period presentation.
Recently Adopted Accounting Pronouncements	In March 2016, the Financial Accounting Standards Board issued Accounting Standard Update (ASU) 2016-09, Compensation - Stock Compensation (Topic 718), which aims to simplify the accounting for share-based payment transactions, including accounting for income taxes, classification on the statement of cash flows, accounting for forfeitures, and classification of awards as either liabilities or equity. This ASU was effective for the Company beginning in the first quarter of 2017. Under the ASU, excess tax benefits from share-based payment arrangements are classified as discrete items within the provision for income taxes, rather than recognizing excess tax benefits in additional paid-in capital. Upon adoption in Q1 2017, the Company recorded $45 million, net, to retained earnings, primarily related to unrealized tax benefits associated with share-based compensation. During the three and nine months ended October 1, 2017, excess tax benefits of $12 million and $31 million, respectively, were reflected as a component of the provision for income taxes. In addition, under the ASU, excess income tax benefits from share-based compensation arrangements are classified as cash flow from operations, rather than cash flow from financing activities. The Company has elected to apply the cash flow classification guidance retrospectively and reclassified $110 million from financing activity to operating activity for the nine months ended October 2, 2016.
Recently Issued Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). The new standard is based on the principle that revenue should be recognized in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the transfer of promised goods or services. Since its initial release, the FASB has issued several amendments to the standard, which include clarification of accounting guidance related to identification of performance obligations, intellectual property licenses, and principal vs. agent considerations. ASU 2014-09 and all subsequent amendments (collectively, the “new standards”) will be effective for the Company beginning in the first quarter of 2018 and may be applied using either the full retrospective method, in which case the standard would be applied to each prior reporting period presented, or the modified retrospective method, in which case the cumulative effect of applying the standard would be recognized at the date of initial application. The Company continues to work through steps in the implementation project plan, which include: finalizing new disclosures required by the new standards and implementing changes to business processes and reporting in support of the adoption of the new standards. The Company will adopt the new standards using the modified retrospective method with an adjustment to beginning retained earnings for the cumulative effect of the change, which is not expected to be material. In January 2016, the Financial Accounting Standards Board issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10), which requires equity investments (other than those accounted for under the equity method or those that result in consolidation) to be measured at fair value, with changes in fair value recognized in net income. ASU 2016-01 will be effective for the Company beginning in the first quarter of 2018. The Company anticipates that the adoption of ASU 2016-01 may increase the volatility of other income and expense, net, as a result of the remeasurement of the Company’s cost-method investments. In February 2016, the Financial Accounting Standards Board issued ASU 2016-02, Leases (Topic 842). The new standard requires lessees to recognize most leases on their balance sheets as lease liabilities with corresponding right-of-use assets and eliminates certain real estate-specific provisions. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. ASU 2016-02 will be adopted on a modified retrospective transition basis for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently evaluating the impact of ASU 2016-02 on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments, which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available for sale debt securities. The ASU is effective for the Company beginning in the first quarter of 2020, with early adoption permitted. The Company is currently evaluating the impact of ASU 2016-13 on its consolidated financial statements.
Earnings per Share	Basic earnings per share attributable to Illumina stockholders is computed based on the weighted average number of common shares outstanding during the period. Diluted earnings per share attributable to Illumina stockholders is computed based on the sum of the weighted average number of common shares and potentially dilutive common shares outstanding during the period. Per-share earnings of our VIEs are included in the Company’s consolidated basic and diluted earnings per share computations based on the Company’s share of the VIEs’ securities. Potentially dilutive common shares consist of shares issuable under convertible senior notes and equity awards. Convertible senior notes have a dilutive impact when the average market price of the Company’s common stock exceeds the applicable conversion price of the respective notes. Potentially dilutive common shares from equity awards are determined using the average share price for each period under the treasury stock method. In addition, proceeds from exercise of equity awards and the average amount of unrecognized compensation expense for equity awards are assumed to be used to repurchase shares. In loss periods, basic net loss per share and diluted net loss per share are identical because the otherwise dilutive potential common shares become anti-dilutive and are therefore excluded.
Derivatives	The Company is exposed to foreign exchange rate risks in the normal course of business. The Company enters into foreign exchange contracts to manage foreign currency risks related to monetary assets and liabilities that are denominated in currencies other than the U.S. dollar. These foreign exchange contracts are carried at fair value in other assets or other liabilities and are not designated as hedging instruments. Changes in the value of derivatives are recognized in other income, net, along with the remeasurement gain or loss on the foreign currency denominated assets or liabilities.
Warranties	The Company generally provides a one-year warranty on instruments. Additionally, the Company provides a warranty on consumables through the expiration date, which generally ranges from six to twelve months after the manufacture date. At the time revenue is recognized, the Company establishes an accrual for estimated warranty expenses based on historical experience as well as anticipated product performance. The Company periodically reviews its warranty reserve for adequacy and adjusts the warranty accrual, if necessary, based on actual experience and estimated costs to be incurred. Warranty expense is recorded as a component of cost of product revenue.

Basis of Presentation and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Oct. 01, 2017

Accounting Policies [Abstract]

Summary of Calculation of Weighted Average Shares used to Calculate Basic and Diluted Earnings Per Share, Earnings Per Share

The following table presents the calculation of weighted average shares used to calculate basic and diluted earnings per share (in millions):



	Three Months Ended		Nine Months Ended
	October 1, 2017	October 2, 2016	October 1, 2017	October 2, 2016
Weighted average shares outstanding	146	147	146	147
Effect of potentially dilutive common shares from:
Equity awards	2	1	2	1
Weighted average shares used in calculating diluted earnings per share	148	148	148	148
Potentially dilutive shares excluded from calculation due to anti-dilutive effect	—	—	—	1

Summary of Calculation of Weighted Average Shares used to Calculate Basic and Diluted Earnings Per Share, Antidilutive Securities

The following table presents the calculation of weighted average shares used to calculate basic and diluted earnings per share (in millions):



	Three Months Ended		Nine Months Ended
	October 1, 2017	October 2, 2016	October 1, 2017	October 2, 2016
Weighted average shares outstanding	146	147	146	147
Effect of potentially dilutive common shares from:
Equity awards	2	1	2	1
Weighted average shares used in calculating diluted earnings per share	148	148	148	148
Potentially dilutive shares excluded from calculation due to anti-dilutive effect	—	—	—	1

Balance Sheet Account Details (Tables)

9 Months Ended

Oct. 01, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Short-term Investments

The following is a summary of short-term investments (in millions):



	October 1, 2017							January 1, 2017
	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Debt securities in government sponsored entities	$	74	$	—		$	74	$	34	$	—		$	34
Corporate debt securities	343		(1		)	342		478		(2		)	476
U.S. Treasury securities	272		(1		)	271		316		(2		)	314
Total available-for-sale securities	$	689	$	(2	)	$	687	$	828	$	(4	)	$	824

Summary of Contractual Maturities of Available-for-sale Debt Securities

Contractual maturities of available-for-sale debt securities as of October 1, 2017 were as follows (in millions):



	Estimated Fair Value
Due within one year	$	421
After one but within five years	266
Total	$	687

Summary of Inventory

Inventory consists of the following (in millions):



	October 1, 2017		January 1, 2017
Raw materials	$	90	$	102
Work in process	192		161
Finished goods	45		37
Total inventory	$	327	$	300

Summary of Property and Equipment

Property and equipment, net consists of the following (in millions):



	October 1, 2017			January 1, 2017
Leasehold improvements	$	320		$	270
Machinery and equipment	301			274
Computer hardware and software	178			156
Furniture and fixtures	34			24
Building	147			9
Construction in progress	273			307
Total property and equipment, gross	1,253			1,040
Accumulated depreciation	(391		)	(327		)
Total property and equipment, net	$	862		$	713

Summary of Changes in Goodwill

Changes to the Company’s goodwill balance during the nine months ended October 1, 2017 are as follows (in millions):



	Goodwill
Balance as of January 1, 2017	$	776
GRAIL deconsolidation	(5		)
Balance as of October 1, 2017	$	771

Summary of Accrued Liabilities

Accrued liabilities consist of the following (in millions):



	October 1, 2017		January 1, 2017
Accrued compensation expenses	$	138	$	112
Deferred revenue, current portion	131		121
Accrued taxes payable	41		32
Customer deposits	18		20
Other	53		57
Total accrued liabilities	$	381	$	342

Summary of Changes in Reserve for Product Warranties

Changes in the Company’s reserve for product warranties during the three and nine months ended October 1, 2017 and October 2, 2016 are as follows (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Balance at beginning of period	$	14		$	16		$	13		$	17
Additions charged to cost of product revenue	7			4			18			17
Repairs and replacements	(5		)	(6		)	(15		)	(20		)
Balance at end of period	$	16		$	14		$	16		$	14

Summary of Changes in Facility Exit Obligation Related to the Former Headquarters Lease

Changes in the Company’s facility exit obligation related to its former headquarters lease during the three and nine months ended October 1, 2017 and October 2, 2016 are as follows (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Balance at beginning of period	$	18		$	21		$	19		$	22
Accretion of interest expense	—			—			—			1
Cash payments	(1		)	(1		)	(2		)	(3		)
Balance at end of period	$	17		$	20		$	17		$	20

Summary of Activity of Redeemable Noncontrolling Interests

The activity of the redeemable noncontrolling interests during the nine months ended October 1, 2017 is as follows (in millions):



	Redeemable Noncontrolling Interests
Balance as of January 1, 2017	$	44
Amount released from escrow	79
Vesting of redeemable equity awards	12
Net loss attributable to noncontrolling interests	(30		)
Adjustment up to the redemption value	30
Deconsolidation of GRAIL	(11		)
Balance as of October 1, 2017	$	124

Fair Value Measurements (Tables)

9 Months Ended

Oct. 01, 2017

Fair Value Disclosures [Abstract]

Summary of Hierarchy for Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table presents the Company’s hierarchy for assets and liabilities measured at fair value on a recurring basis as of October 1, 2017 and January 1, 2017 (in millions):



	October 1, 2017								January 1, 2017
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets:
Money market funds (cash equivalents)	$	1,051	$	—	$	—	$	1,051	$	386	$	—	$	—	$	386
Debt securities in government-sponsored entities	—		74		—		74		—		34		—		34
Corporate debt securities	—		342		—		342		—		476		—		476
U.S. Treasury securities	271		—		—		271		314		—		—		314
Deferred compensation plan assets	—		34		—		34		—		31		—		31
Total assets measured at fair value	$	1,322	$	450	$	—	$	1,772	$	700	$	541	$	—	$	1,241
Liabilities:
Acquisition related contingent consideration liabilities	$	—	$	—	$	—	$	—	$	—	$	—	$	4	$	4
Deferred compensation liability	—		31		—		31		—		29		—		29
Total liabilities measured at fair value	$	—	$	31	$	—	$	31	$	—	$	29	$	4	$	33

Debt (Tables)

9 Months Ended

Oct. 01, 2017

Debt Disclosure [Abstract]

Convertible Debt [Table Text Block]

Summary of debt obligations

The Company’s debt obligations consist of the following (dollars in millions):



	October 1, 2017			January 1, 2017
Principal amount of 2019 Notes outstanding	$	633		$	633
Principal amount of 2021 Notes outstanding	517			517
Unamortized discount of liability component of convertible senior notes	(83		)	(105		)
Net carrying amount of liability component of convertible senior notes	1,067			1,045
Obligations under financing leases	111			9
Other	4			4
Less: current portion	(2		)	(2		)
Long-term debt	$	1,180		$	1,056
Carrying value of equity component of convertible senior notes, net of debt issuance cost	$	161		$	161
Fair value of convertible senior notes outstanding (Level 2)	$	1,262		$	1,108
Weighted-average remaining amortization period of discount on the liability component of convertible senior notes	3.0 years			3.6 years

Share-based Compensation Expense (Tables)

9 Months Ended

Oct. 01, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Share-based Compensation Expense for all Stock Awards

Share-based compensation expense for all stock awards consists of the following (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Cost of product revenue	$	3		$	2		$	9		$	6
Cost of service and other revenue	1			1			2			2
Research and development	12			12			38			33
Selling, general and administrative	18			20			74			61
Share-based compensation expense before taxes	34			35			123			102
Related income tax benefits	(11		)	(8		)	(34		)	(23		)
Share-based compensation expense, net of taxes	$	23		$	27		$	89		$	79

Summary of Assumptions used to Estimate the Weighted-Average Fair Value Per Share for Stock Purchase under the Employee Stock Purchase Plan

The assumptions used for the specified reporting periods and the resulting estimates of weighted-average fair value per share for stock purchased under the Employee Stock Purchase Plan (ESPP) during the nine months ended October 1, 2017 are as follows:



	Employee Stock Purchase Rights
Risk-free interest rate	0.50% - 1.22%
Expected volatility	29% - 44%
Expected term	0.5 - 1.0 year
Expected dividends	0		%
Weighted-average fair value per share	$	46.85

Stockholders' Equity (Tables)

9 Months Ended

Oct. 01, 2017

Equity [Abstract]

Summary of Restricted Stock Activity and Related Information, Restricted Stock

The Company’s restricted stock activity and related information for the nine months ended October 1, 2017 is as follows (units in thousands):



	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		Weighted-Average Grant-Date Fair Value per Share
	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		RSA		RSU		PSU
Outstanding at January 1, 2017	32		2,293		460		$	136.30	$	141.80	$	158.66
Awarded	—		141		38		—		$	173.08	$	154.93
Vested	(11	)	(257	)	—		$	179.00	$	110.56	—
Cancelled	—		(184	)	(60	)	—		$	149.22	$	176.15
Outstanding at October 1, 2017	21		1,993		438		$	114.59	$	147.41	$	155.95

______________________________________


(1)	The number of units reflect the estimated number of shares to be issued at the end of the performance period.

Summary of Restricted Stock Activity and Related Information, Performance Units

The Company’s restricted stock activity and related information for the nine months ended October 1, 2017 is as follows (units in thousands):



	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		Weighted-Average Grant-Date Fair Value per Share
	Restricted Stock Awards (RSA)		Restricted Stock Units (RSU)		Performance Stock Units (PSU)(1)		RSA		RSU		PSU
Outstanding at January 1, 2017	32		2,293		460		$	136.30	$	141.80	$	158.66
Awarded	—		141		38		—		$	173.08	$	154.93
Vested	(11	)	(257	)	—		$	179.00	$	110.56	—
Cancelled	—		(184	)	(60	)	—		$	149.22	$	176.15
Outstanding at October 1, 2017	21		1,993		438		$	114.59	$	147.41	$	155.95

______________________________________


(1)	The number of units reflect the estimated number of shares to be issued at the end of the performance period.

Summary of Stock Option Activity Under all Stock Option Plans

The Company’s stock option activity under all stock option plans during the nine months ended October 1, 2017 is as follows:



	Options (in thousands)		Weighted-Average Exercise Price
Outstanding at January 1, 2017	1,045		$	48.56
Exercised	(604	)	$	46.43
Outstanding and exercisable at October 1, 2017	441		$	51.51

Segment Information (Tables)

9 Months Ended

Oct. 01, 2017

Segment Reporting [Abstract]

Summary of Operating Performance and Assets by Segment

The following table presents the operating performance of each reportable segment (in millions):



	Three Months Ended						Nine Months Ended
	October 1, 2017			October 2, 2016			October 1, 2017			October 2, 2016
Revenues:
Core Illumina	$	715		$	615		$	1,978		$	1,792
Consolidated VIEs	1			—			4			—
Elimination of intersegment revenues	(2		)	(8		)	(7		)	(13		)
Consolidated revenues	$	714		$	607		$	1,975		$	1,779

Operating income (loss):
Core Illumina	$	203		$	191		$	447		$	502
Consolidated VIEs	(22		)	(25		)	(72		)	(50		)
Elimination of intersegment earnings	—			(5		)	1			(8		)
Consolidated operating income	$	181		$	161		$	376		$	444

The following table presents the total assets of each reportable segment (in millions):



	October 1, 2017			January 1, 2017
Total assets:
Core Illumina	$	4,999		$	4,167
Consolidated VIEs	59			180
Elimination of intersegment assets	(12		)	(66		)
Consolidated total assets	$	5,046		$	4,281

Basis of Presentation and Summary of Significant Accounting Policies - Narrative - Recently Adopted Accounting Principles (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Oct. 01, 2017	Oct. 01, 2017	Oct. 02, 2016	Apr. 02, 2017
Accounting Policies [Abstract]
Excess tax benefits from share-based compensation not yet recognized recorded in retained earnings				$ 45
Excess tax benefits from share-based compensation recorded in provision for income taxes	$ 12	$ 31
Excess tax benefits from share-based compensation recorded in operating activities			$ 110

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Calculation of Weighted Average Shares used to Calculate Basic and Diluted Earnings Per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Weighted average shares used to calculate basic and diluted earnings per share
Weighted average shares outstanding	146	147	146	147
Effect of potentially dilutive common shares from:
Equity awards	2	1	2	1
Weighted average shares used in calculating diluted earnings per share	148	148	148	148
Potentially dilutive shares excluded from calculation due to anti-dilutive effect				1

Balance Sheet Account Details - Summary of Short-term Investments (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Available-for-sale securities:
Amortized Cost	$ 689	$ 828
Gross Unrealized Losses	(2)	(4)
Estimated Fair Value	687	824
Debt securities in government sponsored entities [Member]
Available-for-sale securities:
Amortized Cost	74	34
Estimated Fair Value	74	34
Corporate debt securities [Member]
Available-for-sale securities:
Amortized Cost	343	478
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	342	476
U.S. Treasury securities [Member]
Available-for-sale securities:
Amortized Cost	272	316
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	$ 271	$ 314

Balance Sheet Account Details - Summary of Contractual Maturities of Available-for-sale Debt Securities (Details) $ in Millions	Oct. 01, 2017 USD ($)
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Due within one year	$ 421
After one but within five years	266
Total	$ 687

Balance Sheet Account Details - Narrative - Strategic Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016	Jan. 01, 2017
Schedule of Investments [Line Items]
Commitment in new venture capital investment fund	$ 100		$ 100
Callable period			10 years
Equity method investments	14		$ 14		$ 10
Cost-Method Investee [Member]
Schedule of Investments [Line Items]
Revenue from transactions with Company's cost-method investments in non-publicly traded companies	38	$ 12	96	$ 42
Other Assets [Member]
Schedule of Investments [Line Items]
Company's cost-method investments in non-publicly traded companies	$ 250		$ 250		$ 57

Balance Sheet Account Details - Summary of Inventory (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Inventory [Abstract]
Raw materials	$ 90	$ 102
Work in process	192	161
Finished goods	45	37
Total inventory	$ 327	$ 300

Balance Sheet Account Details - Summary of Property and Equipment (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,253	$ 1,040
Accumulated depreciation	(391)	(327)
Total property and equipment, net	862	713
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	320	270
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	301	274
Computer hardware and software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	178	156
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	34	24
Building
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	147	9
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 273	$ 307

Balance Sheet Account Details - Narrative - Property and Equipment (Details) - USD ($) $ in Millions	9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016
Property, Plant and Equipment [Line Items]
Non-cash expenditures included in capital expenditures	$ 94	$ 194
Construction in progress
Property, Plant and Equipment [Line Items]
Non-cash expenditures included in capital expenditures	$ 60	$ 169

Balance Sheet Account Details - Summary of Changes in Goodwill (Details) $ in Millions	9 Months Ended
	Oct. 01, 2017 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 776
GRAIL deconsolidation	(5)
Ending balance	$ 771

Balance Sheet Account Details - Narrative - Intangible Assets and Goodwill (Details) $ in Millions	9 Months Ended
	Oct. 01, 2017 USD ($)
Finite-Lived Intangible Assets [Line Items]
Impairment of in-process research and development	$ 5
Cost of Sales [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment of finite-lived intangible assets	$ 18

Balance Sheet Account Details - Narrative - Derivatives (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative, notional amount	$ 79	$ 69

Balance Sheet Account Details - Summary of Accrued Liabilities (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Accrued Liabilities, Current [Abstract]
Accrued compensation expenses	$ 138	$ 112
Deferred revenue, current portion	131	121
Accrued taxes payable	41	32
Customer deposits	18	20
Other	53	57
Total accrued liabilities	$ 381	$ 342

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References + Details

Balance Sheet Account Details - Narrative - Warranties (Details)	9 Months Ended
	Oct. 01, 2017
Instruments [Member]
Product Warranty Liability [Line Items]
Warranty period	1 year
Consumables [Member] \| Minimum [Member]
Product Warranty Liability [Line Items]
Warranty period	6 months
Consumables [Member] \| Maximum [Member]
Product Warranty Liability [Line Items]
Warranty period	12 months

Balance Sheet Account Details - Summary of Changes in Reserve for Product Warranties (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Reserve for product warranties [Roll Forward]
Balance at beginning of period	$ 14	$ 16	$ 13	$ 17
Additions charged to cost of product revenue	7	4	18	17
Repairs and replacements	(5)	(6)	(15)	(20)
Balance at end of period	$ 16	$ 14	$ 16	$ 14

Balance Sheet Account Details - Summary of Changes in Facility Exit Obligation Related to the Former Headquarters Lease (Details) - Facility Exit Obligation [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Headquarter Facility Exit Obligation [Roll Forward]
Balance at beginning of period	$ 18	$ 21	$ 19	$ 22
Accretion of interest expense	0	0	0	1
Cash payments	(1)	(1)	(2)	(3)
Balance at end of period	$ 17	$ 20	$ 17	$ 20

Balance Sheet Account Details - Narrative - Leases (Details) - February2017 Lease Agreements [Member] $ in Millions	Feb. 22, 2017 USD ($)
Lessee, Lease, Description [Line Items]
Finance lease term	15 years
Future minimum payment due for lease addition in period	$ 46

Balance Sheet Account Details - Narrative - Investment in Consolidated Variable Interest Entities (Details) - USD ($) shares in Millions, $ in Millions		1 Months Ended		9 Months Ended
	Feb. 28, 2017	Jul. 03, 2016	Jan. 31, 2016	Oct. 01, 2017	Oct. 02, 2016	Feb. 27, 2017	Jan. 01, 2017	Jan. 03, 2016	Jul. 31, 2015
Variable Interest Entity [Line Items]
Contributions from noncontrolling interest owners				$ 79	$ 80
Noncontrolling shareholders interest percentage				50.00%
Cash and cash equivalents attributable to variable interest entities				$ 1,354	$ 795		$ 735	$ 769
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents attributable to variable interest entities				$ 32
GRAIL, Inc. [Member]
Variable Interest Entity [Line Items]
Deemed dividend		$ 10
Deemed dividend, tax effect		$ 10
GRAIL, Inc. [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Series A financing			$ 120
Amount contributed			40
Contributions from noncontrolling interest owners			$ 80
Equity ownership interest percentage						52.00%
Helix Holdings I, LLC [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Equity ownership interest percentage				50.00%					50.00%
GRAIL Class B [Member] \| GRAIL, Inc. [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Series A financing	$ 900
Stock exchanged (in shares)			113
GRAIL Class A-1 Convertible [Member] \| GRAIL, Inc. [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Shares authorized by GRAIL issued to Illumina		98
Illumina Class B [Member] \| GRAIL, Inc. [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Shares authorized by Illumina issued to GRAIL		98

Balance Sheet Account Details - Narrative - Deconsolidation of GRAIL, Inc. (Details) - USD ($) shares in Millions, $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended	9 Months Ended
	Feb. 28, 2017	Jan. 31, 2016	Feb. 28, 2017	Jul. 02, 2017	Oct. 01, 2017	Oct. 02, 2016	Feb. 27, 2017	Jan. 01, 2017
Variable Interest Entity [Line Items]
Proceeds from sale of GRAIL preferred stock					$ 278
Payments for additional GRAIL shares purchased by Illumina					25	$ 9
Gain on deconsolidation of GRAIL	$ 453				453
Portion of gain on deconsolidation related to remeasurement of Company's retained equity interest	$ 159
Other Assets [Member]
Variable Interest Entity [Line Items]
Cost-method investments					250			$ 57
GRAIL, Inc. [Member]
Variable Interest Entity [Line Items]
Cost-method investment ownership percentage	19.00%		19.00%	17.00%
Cost-method investment voting interest percentage	13.00%		13.00%	12.00%
GRAIL, Inc. [Member] \| Other Assets [Member]
Variable Interest Entity [Line Items]
Cost-method investments					$ 185
GRAIL, Inc. [Member] \| GRAIL Class B [Member]
Variable Interest Entity [Line Items]
Payments for additional GRAIL shares purchased by Illumina				$ 14
Additional GRAIL shares purchased by Illumina				3
Remaining shares of GRAIL owned by Illumina				3
GRAIL, Inc. [Member] \| GRAIL Class A Preferred [Member]
Variable Interest Entity [Line Items]
Remaining shares of GRAIL owned by Illumina				5
GRAIL, Inc. [Member] \| GRAIL Class A Common [Member]
Variable Interest Entity [Line Items]
Remaining shares of GRAIL owned by Illumina				78
Variable Interest Entity, Primary Beneficiary [Member] \| GRAIL, Inc. [Member]
Variable Interest Entity [Line Items]
GRAIL Series B preferred financing		$ 120
Proceeds from sale of GRAIL preferred stock	$ 278
Equity ownership interest percentage							52.00%
Percentage of entity's losses absorbed			50.00%
Variable Interest Entity, Primary Beneficiary [Member] \| GRAIL, Inc. [Member] \| GRAIL Class B [Member]
Variable Interest Entity [Line Items]
GRAIL Series B preferred financing	$ 900
Variable Interest Entity, Primary Beneficiary [Member] \| GRAIL, Inc. [Member] \| GRAIL Class A Preferred [Member]
Variable Interest Entity [Line Items]
Shares repurchased by GRAIL from Illumina	35
Variable Interest Entity, Primary Beneficiary [Member] \| GRAIL, Inc. [Member] \| GRAIL Class A-1 Convertible [Member]
Variable Interest Entity [Line Items]
Shares repurchased by GRAIL from Illumina	34

Balance Sheet Account Details - Summary of Activity of Redeemable Noncontrolling Interests (Details) $ in Millions	9 Months Ended
	Oct. 01, 2017 USD ($)
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Balance as of January 1, 2017	$ 44
Amount released from escrow	79
Vesting of redeemable equity awards	12
Net loss attributable to noncontrolling interests	(30)
Adjustment up to the redemption value	30
Deconsolidation of GRAIL	(11)
Balance as of October 1, 2017	$ 124

Fair Value Measurements - Summary of Hierarchy for Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Assets:
Available-for-sale securities	$ 687	$ 824
Debt securities in government sponsored entities [Member]
Assets:
Available-for-sale securities	74	34
Corporate debt securities [Member]
Assets:
Available-for-sale securities	342	476
U.S. Treasury securities [Member]
Assets:
Available-for-sale securities	271	314
Fair Value, Measurements, Recurring [Member]
Assets:
Deferred compensation plan assets	34	31
Total assets measured at fair value	1,772	1,241
Liabilities:
Acquisition related contingent consideration liabilities		4
Deferred compensation liability	31	29
Total liabilities measured at fair value	31	33
Fair Value, Measurements, Recurring [Member] \| Debt securities in government sponsored entities [Member]
Assets:
Available-for-sale securities	74	34
Fair Value, Measurements, Recurring [Member] \| Corporate debt securities [Member]
Assets:
Available-for-sale securities	342	476
Fair Value, Measurements, Recurring [Member] \| U.S. Treasury securities [Member]
Assets:
Available-for-sale securities	271	314
Fair Value, Measurements, Recurring [Member] \| Money market funds (cash equivalents) [Member]
Assets:
Money market funds (cash equivalents)	1,051	386
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Assets:
Total assets measured at fair value	1,322	700
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| U.S. Treasury securities [Member]
Assets:
Available-for-sale securities	271	314
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Money market funds (cash equivalents) [Member]
Assets:
Money market funds (cash equivalents)	1,051	386
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Assets:
Deferred compensation plan assets	34	31
Total assets measured at fair value	450	541
Liabilities:
Deferred compensation liability	31	29
Total liabilities measured at fair value	31	29
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Debt securities in government sponsored entities [Member]
Assets:
Available-for-sale securities	74	34
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Corporate debt securities [Member]
Assets:
Available-for-sale securities	$ 342	476
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Liabilities:
Acquisition related contingent consideration liabilities		4
Total liabilities measured at fair value		$ 4

Debt - Summary of Information about Equity and Liability Components of Convertible Senior Notes Outstanding (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 01, 2017	Jan. 01, 2017	Jun. 29, 2014
Summarized information about equity and liability components of convertible senior notes
Obligations under financing leases	$ 111	$ 9
Other	4
Less: current portion	(2)	(2)
Long-term debt	1,180	1,056
Convertible Senior Notes [Member]
Summarized information about equity and liability components of convertible senior notes
Unamortized discount of liability component	(83)	(105)
Net carrying amount of liability component in long-term debt	1,067	1,045
Long-term debt	1,180	1,056
Carrying value of equity component, net of debt issuance cost	$ 161	$ 161
Weighted-average remaining amortization period of discount on the liability component	3 years	3 years 7 months
Fair Value, Inputs, Level 2 [Member] \| Convertible Senior Notes [Member]
Summarized information about equity and liability components of convertible senior notes
Fair value of convertible senior notes outstanding (Level 2)	$ 1,262	$ 1,108
2019 Notes [Member] \| Convertible Senior Notes [Member]
Summarized information about equity and liability components of convertible senior notes
Principal amount of notes outstanding	633	633	$ 633
2021 Notes [Member] \| Convertible Senior Notes [Member]
Summarized information about equity and liability components of convertible senior notes
Principal amount of notes outstanding	$ 517	517	$ 517
Helix Holdings I, LLC [Member] \| Line of Credit [Member]
Summarized information about equity and liability components of convertible senior notes
Other		$ 4

Debt - Narrative (Details) - Convertible Senior Notes [Member] $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Jun. 29, 2014 USD ($) $ / shares	Oct. 01, 2017 USD ($)	Jan. 01, 2017 USD ($)	Dec. 31, 2011 USD ($)
2019 Notes [Member]
Debt Instrument [Line Items]
Principal amount of notes outstanding	$ 633	$ 633	$ 633
Effective interest rate used to measure fair value of converted notes upon conversion	2.90%
Conversion rate	0.0039318
Conversion price (in dollars per share) \| $ / shares	$ 254.34
Threshold note trading days		5
Threshold consecutive note trading days		10
Threshold percentage of note price trigger		98.00%
Threshold common stock trading days		20
Threshold consecutive common stock trading days		30
Threshold percentage of common stock price trigger		130.00%
2021 Notes [Member]
Debt Instrument [Line Items]
Principal amount of notes outstanding	$ 517	$ 517	$ 517
Effective interest rate used to measure fair value of converted notes upon conversion	3.50%
Conversion rate	0.0039318
Conversion price (in dollars per share) \| $ / shares	$ 254.34
Threshold note trading days		5
Threshold consecutive note trading days		10
Threshold percentage of note price trigger		98.00%
Threshold common stock trading days		20
Threshold consecutive common stock trading days		30
Threshold percentage of common stock price trigger		130.00%
2016 Notes [Member]
Debt Instrument [Line Items]
Principal amount of notes outstanding				$ 920
Interest rate on convertible senior notes				0.25%
Effective interest rate used to measure fair value of converted notes upon conversion				4.50%

Debt - Build-to-suit leases Narrative (Details) $ in Millions	Oct. 01, 2017 USD ($) Leases	Feb. 28, 2017 USD ($)	Jan. 01, 2017 USD ($)
Debt Instrument [Line Items]
Number of projects accounted for under build-to-suit lease accounting \| Leases	2
Build-to-suit lease liability	$ 124		$ 223
Build-to-suit lease asset under construction	124		223
Obligations under financing leases	111		$ 9
Construction In Progress And Build to Suit Lease Liability [Member]
Debt Instrument [Line Items]
Obligations under financing leases	$ 102
GRAIL, Inc. [Member]
Debt Instrument [Line Items]
Build-to-suit lease liability		$ 58
Build-to-suit lease asset under construction		$ 58

Share-based Compensation Expense - Summary of Share-based Compensation Expense for all Stock Awards (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Share-based Compensation
Share-based compensation expense before taxes	$ 34	$ 35	$ 123	$ 102
Related income tax benefits	(11)	(8)	(34)	(23)
Share-based compensation expense, net of taxes	23	27	89	79
Cost of product revenue [Member]
Share-based Compensation
Share-based compensation expense before taxes	3	2	9	6
Cost of service and other revenue [Member]
Share-based Compensation
Share-based compensation expense before taxes	1	1	2	2
Research and development [Member]
Share-based Compensation
Share-based compensation expense before taxes	12	12	38	33
Selling, general and administrative [Member]
Share-based Compensation
Share-based compensation expense before taxes	$ 18	$ 20	$ 74	$ 61

Share-based Compensation Expense - Summary of Assumptions used to Estimate the Weighted-Average Fair Value Per Share for Stock Purchase under the Employee Stock Purchase Plan (Details) - Employee Stock [Member]	9 Months Ended
	Oct. 01, 2017 $ / shares
Assumptions used to estimate the fair value per share of employee stock purchase rights granted
Expected volatility, minimum	29.00%
Expected volatility, maximum	44.00%
Expected dividends	0.00%
Weighted-average fair value per share (in dollars per share)	$ 46.85
Minimum [Member]
Assumptions used to estimate the fair value per share of employee stock purchase rights granted
Risk-free interest rate	0.50%
Expected term	6 months
Maximum [Member]
Assumptions used to estimate the fair value per share of employee stock purchase rights granted
Risk-free interest rate	1.22%
Expected term	1 year

Share-based Compensation Expense - Narrative (Details) $ in Millions	9 Months Ended
	Oct. 01, 2017 USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Unrecognized compensation cost related to stock options, restricted stock, and ESPP shares granted to date	$ 242
Weighted-average period of unrecognized compensation cost related to stock options, restricted stock, and ESPP shares granted to date	2 years 2 months

Stockholders' Equity - Narrative (Details) shares in Millions	Oct. 01, 2017 shares
2015 Illumina and 2005 Solexa Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance (in shares)	6.3

Stockholders' Equity - Summary of Restricted Stock Activity and Related Information (Details) shares in Thousands	9 Months Ended
	Oct. 01, 2017 $ / shares shares
Restricted Stock Awards (RSA) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at period start (in shares) \| shares	32
Vested (in shares) \| shares	(11)
Outstanding at period end (in shares) \| shares	21
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-Average Grant Date Fair Value per Share, Outstanding at period start (in dollars per share) \| $ / shares	$ 136.30
Weighted-Average Grant Date Fair Value per Share, Vested (in dollars per share) \| $ / shares	179.00
Weighted-Average Grant Date Fair Value per Share, Outstanding at period end (in dollars per share) \| $ / shares	$ 114.59
Restricted Stock Units (RSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at period start (in shares) \| shares	2,293
Awarded (in shares) \| shares	141
Vested (in shares) \| shares	(257)
Cancelled (in shares) \| shares	(184)
Outstanding at period end (in shares) \| shares	1,993
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-Average Grant Date Fair Value per Share, Outstanding at period start (in dollars per share) \| $ / shares	$ 141.80
Weighted-Average Grant Date Fair Value per Share, Awarded (in dollars per share) \| $ / shares	173.08
Weighted-Average Grant Date Fair Value per Share, Vested (in dollars per share) \| $ / shares	110.56
Weighted-Average Grant Date Fair Value per Share, Cancelled (in dollars per share) \| $ / shares	149.22
Weighted-Average Grant Date Fair Value per Share, Outstanding at period end (in dollars per share) \| $ / shares	$ 147.41
Performance Stock Units (PSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at period start (in shares) \| shares	460
Awarded (in shares) \| shares	38
Cancelled (in shares) \| shares	(60)
Outstanding at period end (in shares) \| shares	438
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-Average Grant Date Fair Value per Share, Outstanding at period start (in dollars per share) \| $ / shares	$ 158.66
Weighted-Average Grant Date Fair Value per Share, Awarded (in dollars per share) \| $ / shares	154.93
Weighted-Average Grant Date Fair Value per Share, Cancelled (in dollars per share) \| $ / shares	176.15
Weighted-Average Grant Date Fair Value per Share, Outstanding at period end (in dollars per share) \| $ / shares	$ 155.95

Stockholders' Equity - Summary of Stock Option Activity Under all Stock Option Plans (Details) shares in Thousands	9 Months Ended
	Oct. 01, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding at period start (in shares) \| shares	1,045
Options, Exercised (in shares) \| shares	(604)
Options, Outstanding at period end (in shares) \| shares	441
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price, Options, Outstanding at period start (in dollars per share) \| $ / shares	$ 48.56
Weighted-Average Exercise Price, Options, Exercised (in dollars per share) \| $ / shares	46.43
Weighted-Average Exercise Price, Options, Outstanding at period end (in dollars per share) \| $ / shares	$ 51.51
Stock options exercisable (in shares) \| shares	441
Stock options exercisable outstanding weighted-average exercise price per share (in dollars per share) \| $ / shares	$ 51.51

Stockholders' Equity - Narrative - Employee Stock Purchase Plan (Details) - ESPP [Member] - Employee Stock [Member] shares in Millions	9 Months Ended
	Oct. 01, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Specified percentage of the fair market value of the common stock on the first or last day of the offering period whichever is lower at which stock is purchased	85.00%
Total shares issued under the ESPP (in shares)	0.3
Shares available for issuance (in shares)	14.0

Stockholders' Equity - Narrative - Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Apr. 02, 2017	Oct. 01, 2017	Oct. 02, 2016	May 04, 2017	Jul. 28, 2016
Class of Stock [Line Items]
Common stock repurchases			$ 176	$ 113
Common Stock [Member]
Class of Stock [Line Items]
Dollar amount remaining in authorized stock repurchase program	$ 175		$ 175
Common Stock [Member] \| July 2016 Share Repurchase Plan [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 250
Repurchase of common shares (in shares)		0.6
Common stock repurchases		$ 101
Common Stock [Member] \| May 2017 Share Repurchase Plan [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 250
Repurchase of common shares (in shares)	0.4
Common stock repurchases	$ 75

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Oct. 01, 2017	Oct. 01, 2017
Income Tax Disclosure [Abstract]
Effective tax rate	12.90%	24.30%
U.S. federal statutory tax rate	35.00%	35.00%
Tax impact from the gain on the deconsolidation of GRAIL		$ 150

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016	Jan. 01, 2017
Segment Reporting Information [Line Items]
Segment revenues	$ 714	$ 607	$ 1,975	$ 1,779
Segment operating income (loss)	181	161	376	444
Segment assets	5,046		5,046		$ 4,281
Intersegment Eliminations
Segment Reporting Information [Line Items]
Segment revenues	(2)	(8)	(7)	(13)
Segment operating income (loss)		(5)	1	(8)
Segment assets	(12)		(12)		(66)
Operating Segments [Member] \| Core Illumina
Segment Reporting Information [Line Items]
Segment revenues	715	615	1,978	1,792
Segment operating income (loss)	203	191	447	502
Segment assets	4,999		4,999		4,167
Operating Segments [Member] \| Consolidated VIEs
Segment Reporting Information [Line Items]
Segment revenues	1		4
Segment operating income (loss)	(22)	$ (25)	(72)	$ (50)
Segment assets	$ 59		$ 59		$ 180