Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	Apr. 26, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	Square, Inc.
Entity Central Index Key	0001512673
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		336,267,871
Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		86,698,955

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 521,676	$ 583,173
Short-term investments	566,539	540,991
Restricted cash	33,220	33,838
Settlements receivable	1,391,078	364,946
Customer funds	445,417	334,017
Loans held for sale	123,471	89,974
Other current assets	185,121	164,966
Total current assets	3,266,522	2,111,905
Property and equipment, net	133,706	142,402
Goodwill	267,012	261,705
Acquired intangible assets, net	79,697	77,102
Long-term investments	481,063	464,680
Restricted cash	14,433	15,836
Built-to-suit lease asset	0	149,000
Operating lease right-of-use assets	111,956
Other non-current assets	48,202	58,393
Total assets	4,402,591	3,281,023
Current liabilities:
Customers payable	1,661,894	749,215
Settlements payable	266,121	54,137
Accrued transaction losses	36,047	33,682
Accrued expenses	87,812	82,354
Operating lease liabilities, current	23,041	0
Other current liabilities	108,644	99,153
Total current liabilities	2,183,559	1,018,541
Long-term debt, net of current portion (Note 12)	909,302	899,695
Built-to-suit lease liability	0	149,000
Operating lease liabilities, non-current	112,556
Other non-current liabilities	75,585	93,286
Total liabilities	3,281,002	2,160,522
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock, $0.0000001 par value: 100,000,000 shares authorized at March 31, 2019 and December 31, 2018. None issued and outstanding at March 31, 2019 and December 31, 2018.	0	0
Additional paid-in capital	2,048,938	2,012,328
Accumulated other comprehensive loss	(3,424)	(6,053)
Accumulated deficit	(923,925)	(885,774)
Total stockholders’ equity	1,121,589	1,120,501
Total liabilities and stockholders’ equity	4,402,591	3,281,023
Class A
Stockholders’ equity:
Common stock	0	0
Class B
Stockholders’ equity:
Common stock	$ 0	$ 0

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, par value (in USD per share)	$ 0.0000001	$ 0.0000001
Preferred stock, shares authorized (in shares)	100,000,000	100,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class A
Class of Stock [Line Items]
Common stock, par value (in USD per share)	$ 0.0000001	$ 0.0000001
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	334,650,231	323,546,864
Common stock, shares outstanding (in shares)	334,650,231	323,546,864
Class B
Class of Stock [Line Items]
Common stock, par value (in USD per share)	$ 0.0000001	$ 0.0000001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	86,973,715	93,501,142
Common stock, shares outstanding (in shares)	86,973,715	93,501,142

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Revenue	$ 959,359	$ 668,603
Cost of revenue:
Total cost of revenue	562,605	413,433
Gross profit	396,754	255,170
Operating expenses:
Product development	153,559	105,095
Sales and marketing	133,713	77,266
General and administrative	101,598	75,501
Transaction, loan and advance losses	27,841	18,031
Amortization of acquired customer assets	2,085	269
Total operating expenses	418,796	276,162
Operating loss	(22,042)	(20,992)
Interest expense, net	4,681	2,112
Other expense, net	11,299	707
Loss before income tax	(38,022)	(23,811)
Provision for income taxes	129	175
Net loss	$ (38,151)	$ (23,986)
Net loss per share:
Basic (in USD per share)	$ (0.09)	$ (0.06)
Diluted (in USD per share)	$ (0.09)	$ (0.06)
Weighted-average shares used to compute net loss per share
Basic (in shares)	419,289	395,948
Diluted (in shares)	419,289	395,948
Technology assets
Cost of revenue:
Amortization of acquired technology	$ 1,376	$ 1,580
Transaction-based revenue
Revenue:
Revenue	656,762	523,037
Cost of revenue:
Cost of revenue	409,069	327,911
Subscription and services-based revenue
Revenue:
Revenue	190,307	77,215
Revenue	218,857	97,054
Cost of revenue:
Cost of revenue	60,523	30,368
Hardware revenue
Revenue:
Revenue	18,212	14,417
Cost of revenue:
Cost of revenue	26,941	19,702
Bitcoin revenue
Revenue:
Revenue	65,528	34,095
Cost of revenue:
Cost of revenue	$ 64,696	$ 33,872

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (38,151)	$ (23,986)
Net foreign currency translation adjustments	266	549
Net unrealized gain on revaluation of intercompany loans	75	665
Net unrealized gain (loss) on marketable debt securities, net of tax	2,288	(1,190)
Total comprehensive loss	$ (35,522)	$ (23,962)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (38,151)	$ (23,986)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	18,971	10,160
Non-cash interest and other expense	8,224	4,847
Share-based compensation	61,088	46,824
Loss on revaluation of equity investment	14,087	0
Amortization of operating lease right-of-use assets and accretion of operating lease liabilities	6,690
Recovery of common stock in connection with indemnification settlement agreement	(789)	0
Transaction, loan and advance losses	27,841	18,031
Change in deferred income taxes	(754)	(654)
Changes in operating assets and liabilities:
Settlements receivable	(1,027,472)	(81,452)
Customer funds	(109,439)	(49,619)
Purchase of loans held for sale	(507,755)	(344,976)
Sales and principal payments of loans held for sale	467,518	337,092
Other current assets	(19,327)	(13,444)
Other non-current assets	(2,527)	(1,256)
Customers payable	912,749	147,977
Settlements payable	211,984	2,114
Charge-offs to accrued transaction losses	(17,443)	(12,842)
Accrued expenses	15,721	2,703
Other current liabilities	16,991	5,155
Payments for operating lease liabilities	(9,293)
Other non-current liabilities	3,530	5,379
Net cash provided by operating activities	32,444	52,053
Cash flows from investing activities:
Purchase of marketable debt securities	(193,673)	(50,221)
Proceeds from maturities of marketable debt securities	111,505	45,450
Proceeds from sale of marketable debt securities	44,810	0
Purchase of marketable debt securities from customer funds	(34,613)	0
Proceeds from maturities of marketable debt securities from customer funds	33,000	0
Purchase of property and equipment	(18,168)	(8,083)
Payments for other investments	(2,000)	0
Purchase of intangible assets	0	(1,584)
Business combinations, net of cash acquired	(11,248)	(1,055)
Net cash used in investing activities	(70,387)	(15,493)
Cash flows from financing activities:
Payment of deferred purchase consideration	(95)	0
Principal payments on finance lease obligation	(1,284)	(665)
Proceeds from the exercise of stock options, net	25,328	31,354
Payments for tax withholding related to vesting of restricted stock units	(50,801)	(27,651)
Net cash provided by (used in) financing activities	(26,852)	3,038
Effect of foreign exchange rate on cash and cash equivalents	1,277	1,397
Net increase (decrease) in cash, cash equivalents and restricted cash	(63,518)	40,995
Cash, cash equivalents and restricted cash, beginning of period	632,847	735,081
Cash, cash equivalents and restricted cash, end of period	$ 569,329	$ 776,076

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Class A and B common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2017		395,194,075
Beginning balance at Dec. 31, 2017	$ 786,333	$ 0	$ 1,630,386	$ (1,318)	$ (842,735)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(23,986)				(23,986)
Shares issued in connection with:
Exercise of stock options (in shares)		4,213,775
Exercise of stock options	31,354		31,354
Vesting of early exercised stock options and other	136		136
Vesting of restricted stock units (in shares)		1,625,534
Change in other comprehensive loss	24			24
Share-based compensation	48,356		48,356
Tax withholding related to vesting of restricted stock units (in shares)		(649,305)
Tax withholding related to vesting of restricted stock units	(27,651)		(27,651)
Ending balance (in shares) at Mar. 31, 2018		400,384,079
Ending balance at Mar. 31, 2018	809,980	$ 0	1,682,581	(1,294)	(871,307)
Beginning balance (in shares) at Dec. 31, 2018		417,048,006
Beginning balance at Dec. 31, 2018	1,120,501	$ 0	2,012,328	(6,053)	(885,774)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (38,151)				(38,151)
Shares issued in connection with:
Exercise of stock options (in shares)	3,588,052	3,588,052
Exercise of stock options	$ 25,328		25,328
Vesting of early exercised stock options and other (in shares)	425
Vesting of early exercised stock options and other	$ 36		36
Vesting of restricted stock units (in shares)		1,994,156
Change in other comprehensive loss	2,629			2,629
Share-based compensation	62,835		62,835
Tax withholding related to vesting of restricted stock units (in shares)		(741,324)
Tax withholding related to vesting of restricted stock units	(50,801)		(50,801)
Issuance of common stock in conjunction with the conversion of senior notes, due 2022 (in shares)		43
Issuance of common stock in conjunction with the conversion of senior notes, due 2022	1		1
Exercise of bond hedges in conjunction with the conversion of senior notes, due 2022 (in shares)		(250,614)
Recovery of common stock in connection with indemnification settlement agreement (in shares)		(14,798)
Recovery of common stock in connection with indemnification settlement agreement	(789)		(789)
Ending balance (in shares) at Mar. 31, 2019		421,623,946
Ending balance at Mar. 31, 2019	$ 1,121,589	$ 0	$ 2,048,938	$ (3,424)	$ (923,925)

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Business Square, Inc. (together with its subsidiaries, Square or the Company) creates tools that help sellers start, run, and grow their businesses. Square enables sellers to accept card payments and also provides reporting and analytics, and next-day settlement. Square’s point-of-sale software and other business services help sellers manage inventory, locations, and employees; access financing; engage buyers; build a website or online store; and grow sales. The Cash App is an easy way to send, spend, and store money, and Caviar is a food-ordering service. Square was founded in 2009 and is headquartered in San Francisco, with offices in the United States, Canada, Japan, Australia, Ireland, and the UK. Basis of Presentation The accompanying interim condensed consolidated financial statements of the Company are unaudited. These interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP) and the applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The December 31, 2018 condensed consolidated balance sheet was derived from the audited financial statements as of that date, but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The accompanying unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company's consolidated financial position, results of operations, comprehensive income (loss), and cash flows for the interim periods. All intercompany transactions and balances have been eliminated in consolidation. The interim results for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019, or for any other future annual or interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and notes thereto included in Items 7, 7A, and 8, respectively, in the Company's Annual Report on Form 10-K for the year ended December 31, 2018. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, as well as related disclosure of contingent assets and liabilities. Actual results could differ from the Company’s estimates. To the extent that there are material differences between these estimates and actual results, the Company’s financial condition or operating results will be materially affected. The Company bases its estimates on past experience and other assumptions that the Company believes are reasonable under the circumstances, and the Company evaluates these estimates on an ongoing basis. Estimates, judgments, and assumptions in these consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued transaction losses, valuation of the debt component of convertible senior notes, valuation of loans held for sale, goodwill, acquired intangible assets and deferred revenue, income and other taxes, operating and financing lease right-of-use assets and related liabilities, and share-based compensation. Concentration of Credit Risk For the three months ended March 31, 2019 and 2018, the Company had no customer that accounted for greater than 10% of total net revenue. The Company had three third-party payment processors that represented approximately 55%, 35%, and 6% of settlements receivable as of March 31, 2019. The same three parties represented approximately 45%, 33%, and 9% of settlements receivable as of December 31, 2018. All other third-party processors were insignificant. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, marketable debt securities, settlements receivables, customer funds, and loans held for sale. The associated risk of concentration for cash and cash equivalents and restricted cash is mitigated by banking with creditworthy institutions. At certain times, amounts on deposit exceed federal deposit insurance limits. The associated risk of concentration for marketable debt securities is mitigated by holding a diversified portfolio of highly rated investments. Settlements receivable are amounts due from well-established payment processing companies and normally take one or two business days to settle which mitigates the associated risk of concentration. The associated risk of concentration for loans held for sale is partially mitigated by credit evaluations that are performed prior to facilitating the offering of loans and ongoing performance monitoring of the Company’s loan customers. New Accounting Policies The Company adopted Accounting Standards Codification (ASC) 842, Leases on January 1, 2019, and elected the optional transition method to apply the transition provisions from the effective date of adoption, which requires the Company to report the cumulative effect of the adoption of the standard on the date of adoption with no changes to the prior period balances. Pursuant to the practical expedients, the Company has elected not to reassess: (i) whether expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases, or, (iii) initial direct costs for any existing leases. Additionally, the Company has lease agreements with lease and non-lease components, which are accounted for separately. The Company recognized $112.0 million of operating right-of-use lease assets and $135.6 million of operating lease liabilities on its consolidated balance sheet as of March 31, 2019. Additionally, the Company derecognized $149 million related to the build-to-suit asset and liability upon adoption of this standard because the Company is no longer deemed to be the owner of the related asset under construction under the new standard. Refer to Note 17 for further detail. Except for the adoption of ASC 842, there have been no material changes to the Company’s accounting policies during the three months ended March 31, 2019, as compared to the accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018. Recent Accounting Pronouncements Recently issued accounting pronouncements not yet adopted In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses, which requires measurement and recognition of expected credit losses for financial assets held. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The Company intends to adopt this guidance effective January 1, 2020. The Company is currently evaluating the impact this guidance may have on the consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The new guidance eliminates the requirement to calculate the implied fair value of goodwill assuming a hypothetical purchase price allocation (i.e., Step 2 of the goodwill impairment test) to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value, not to exceed the carrying amount of goodwill. This standard should be adopted when the Company performs its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019, with early adoption permitted. The amendments should be applied on a prospective basis. The Company intends to adopt this guidance effective with its 2019 annual goodwill impairment test which it performs as of December 31. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. In July 2018, the FASB issued ASU 2018-13, Changes to the Disclosure Requirements for Fair Value Measurement, which will remove, modify, and add disclosure requirements for fair value measurements to improve the overall usefulness of such disclosures. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any removed or modified disclosure requirements. Transition is on a prospective basis for the new and modified disclosures, and on a retrospective basis for disclosures that have been eliminated. The Company currently does not intend to early adopt any portion of this disclosure guidance. The Company is currently evaluating the impact this guidance may have on the consolidated financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which is intended to align the requirements for capitalization of implementation costs incurred in a cloud computing arrangement that is a service contract with the existing guidance for internal-use software. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. The guidance provides flexibility in adoption, allowing for either retrospective adjustment or prospective adjustment for all implementation costs incurred after the date of adoption. The Company is currently evaluating whether to early adopt this guidance as well as the impact it may have on the consolidated financial statements and related disclosures.

REVENUE

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

REVENUE

The following table presents the Company's revenue disaggregated by revenue source (in thousands):



	Three Months Ended March 31,
	2019		2018
Revenue from Contracts with Customers:
Transaction-based revenue	$	656,762	$	523,037
Subscription and services-based revenue	190,307		77,215
Hardware revenue	18,212		14,417
Bitcoin revenue	$	65,528	$	34,095
Revenue from other sources:
Subscription and services-based revenue	$	28,550	$	19,839

The deferred revenue balances were as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Deferred revenue, beginning of the period	$	36,451	$	5,893
Less: cumulative impact of the adoption of ASC 606	—		(4,303		)
Deferred revenue, beginning of the period, as adjusted	36,451		1,590
Deferred revenue, end of the period	42,160		3,353
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	$	12,306	$	298

INVESTMENTS

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

INVESTMENTS

The Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	113,508	$	142	$	(15	)	$	113,635
Corporate bonds	84,832		289		(25		)	85,096
Municipal securities	20,237		54		(18		)	20,273
U.S. government securities	317,787		394		(71		)	318,110
Non-U.S. government securities	29,355		70		—			29,425
Total	$	565,719	$	949	$	(129	)	$	566,539

Long-term debt securities:
U.S. agency securities	$	85,993	$	299	$	(28	)	$	86,264
Corporate bonds	186,674		1,233		(11		)	187,896
Municipal securities	23,267		128		(2		)	23,393
U.S. government securities	174,515		541		(8		)	175,048
Non-U.S. government securities	8,417		45		—			8,462
Total	$	478,866	$	2,246	$	(49	)	$	481,063

The Company's short-term and long-term investments as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	80,160	$	32	$	(70	)	$	80,122
Corporate bonds	109,807		80		(368		)	109,519
Municipal securities	27,839		52		(59		)	27,832
U.S. government securities	292,615		161		(509		)	292,267
Non-U.S. government securities	31,263		4		(16		)	31,251
Total	$	541,684	$	329	$	(1,022	)	$	540,991

Long-term debt securities:
U.S. agency securities	$	114,444	$	194	$	(78	)	$	114,560
Corporate bonds	159,783		419		(950		)	159,252
Municipal securities	28,453		167		(26		)	28,594
U.S. government securities	153,743		553		(172		)	154,124
Non-U.S. government securities	8,122		28		—			8,150
Total	$	464,545	$	1,361	$	(1,226	)	$	464,680

For the periods presented, gains or losses realized on the sale of investments were not material. Investments are reviewed periodically to identify possible other-than-temporary impairments. As the Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of fair value, which may be maturity, the Company does not consider these investments to be other-than-temporarily impaired for any of the periods presented.

The amortized cost of investments classified as cash equivalents approximated the fair value due to the short term nature of the investments.

The contractual maturities of the Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	565,719	$	566,539
Due in one to five years	478,866		481,063
Total	$	1,044,585	$	1,047,602

CUSTOMER FUNDS

The following table presents the assets underlying customer funds (in thousands):



	March 31, 2019		December 31, 2018
Cash	$	278,967	$	158,697
Cash Equivalents:
Money market funds	862		18
U.S. agency securities	14,539		39,991
U.S. government securities	49,125		35,349
Short-term debt securities:
U.S. agency securities	22,286		27,291
U.S. government securities	79,638		72,671
Total	$	445,417	$	334,017

The Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	22,281	$	7	$	(2	)	$	22,286
U.S. government securities	79,607		33		(2		)	79,638
Total	$	101,888	$	40	$	(4	)	$	101,924

The Company's investments within customer funds as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	27,293		2		(4		)	27,291
U.S. government securities	72,662		12		(3		)	72,671
Total	$	99,955	$	14	$	(7	)	$	99,962

For the periods presented, gains or losses realized on the sale of investments were not material. Investments are reviewed periodically to identify possible other-than-temporary impairments. As the Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of fair value, which may be maturity, the Company does not consider these investments to be other-than-temporarily impaired for any of the periods presented.

The amortized cost of investments classified as cash equivalents approximated the fair value due to the short term nature of the investments.

The contractual maturities of the Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	101,888	$	101,924
Due in one to five years	—		—
Total	$	101,888	$	101,924

CUSTOMER FUNDS

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

CUSTOMER FUNDS

INVESTMENTS

The Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	113,508	$	142	$	(15	)	$	113,635
Corporate bonds	84,832		289		(25		)	85,096
Municipal securities	20,237		54		(18		)	20,273
U.S. government securities	317,787		394		(71		)	318,110
Non-U.S. government securities	29,355		70		—			29,425
Total	$	565,719	$	949	$	(129	)	$	566,539

Long-term debt securities:
U.S. agency securities	$	85,993	$	299	$	(28	)	$	86,264
Corporate bonds	186,674		1,233		(11		)	187,896
Municipal securities	23,267		128		(2		)	23,393
U.S. government securities	174,515		541		(8		)	175,048
Non-U.S. government securities	8,417		45		—			8,462
Total	$	478,866	$	2,246	$	(49	)	$	481,063

The Company's short-term and long-term investments as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	80,160	$	32	$	(70	)	$	80,122
Corporate bonds	109,807		80		(368		)	109,519
Municipal securities	27,839		52		(59		)	27,832
U.S. government securities	292,615		161		(509		)	292,267
Non-U.S. government securities	31,263		4		(16		)	31,251
Total	$	541,684	$	329	$	(1,022	)	$	540,991

Long-term debt securities:
U.S. agency securities	$	114,444	$	194	$	(78	)	$	114,560
Corporate bonds	159,783		419		(950		)	159,252
Municipal securities	28,453		167		(26		)	28,594
U.S. government securities	153,743		553		(172		)	154,124
Non-U.S. government securities	8,122		28		—			8,150
Total	$	464,545	$	1,361	$	(1,226	)	$	464,680

For the periods presented, gains or losses realized on the sale of investments were not material. Investments are reviewed periodically to identify possible other-than-temporary impairments. As the Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of fair value, which may be maturity, the Company does not consider these investments to be other-than-temporarily impaired for any of the periods presented.

The amortized cost of investments classified as cash equivalents approximated the fair value due to the short term nature of the investments.

The contractual maturities of the Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	565,719	$	566,539
Due in one to five years	478,866		481,063
Total	$	1,044,585	$	1,047,602

CUSTOMER FUNDS

The following table presents the assets underlying customer funds (in thousands):



	March 31, 2019		December 31, 2018
Cash	$	278,967	$	158,697
Cash Equivalents:
Money market funds	862		18
U.S. agency securities	14,539		39,991
U.S. government securities	49,125		35,349
Short-term debt securities:
U.S. agency securities	22,286		27,291
U.S. government securities	79,638		72,671
Total	$	445,417	$	334,017

The Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	22,281	$	7	$	(2	)	$	22,286
U.S. government securities	79,607		33		(2		)	79,638
Total	$	101,888	$	40	$	(4	)	$	101,924

The Company's investments within customer funds as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	27,293		2		(4		)	27,291
U.S. government securities	72,662		12		(3		)	72,671
Total	$	99,955	$	14	$	(7	)	$	99,962

For the periods presented, gains or losses realized on the sale of investments were not material. Investments are reviewed periodically to identify possible other-than-temporary impairments. As the Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of fair value, which may be maturity, the Company does not consider these investments to be other-than-temporarily impaired for any of the periods presented.

The amortized cost of investments classified as cash equivalents approximated the fair value due to the short term nature of the investments.

The contractual maturities of the Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	101,888	$	101,924
Due in one to five years	—		—
Total	$	101,888	$	101,924

FAIR VALUE OF FINANCIAL INSTRUMENTS

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE OF FINANCIAL INSTRUMENTS

The Company measures its cash equivalents, customer funds, short-term and long-term marketable debt securities, and marketable equity investments at fair value. The Company classifies these investments within Level 1 or Level 2 of the fair value hierarchy because the Company values these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs.

The Company’s financial assets and liabilities that are measured at fair value on a recurring basis are classified as follows (in thousands):



	March 31, 2019						December 31, 2018
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Cash Equivalents:
Money market funds	$	164,457	$	—	$	—	$	218,109	$	—	$	—
U.S. agency securities	—		19,712		—		—		46,423		—
Commercial paper	—		2,997		—		—		—		—
U.S. government securities	102,199		—		—		—		—		—
Municipal securities	—		—		—		86,239		—		—
Non-U.S. government securities	—		—		—		—		23,981		—
Customer funds:
Money market funds	862		—		—		18		—		—
U.S. agency securities	—		36,825		—		—		67,282		—
U.S. government securities	128,763		—		—		108,020		—		—
Short-term debt securities:
U.S. agency securities	—		113,635		—		—		80,122		—
Corporate bonds	—		85,096		—		—		109,519		—
Municipal securities	—		20,273		—		—		27,832		—
U.S. government securities	318,110		—		—		292,267		—		—
Non-U.S. government securities	—		29,425		—		—		31,251		—
Long-term debt securities:
U.S. agency securities	—		86,264		—		—		114,560		—
Corporate bonds	—		187,896		—		—		159,252		—
Municipal securities	—		23,393		—		—		28,594		—
U.S. government securities	175,048		—		—		154,124		—		—
Non-U.S. government securities	—		8,462		—		—		8,150		—
Other:
Equity investment	31,255		—		—		45,342		—		—
Total	$	920,694	$	613,978	$	—	$	904,119	$	696,966	$	—

The carrying amounts of certain financial instruments, including settlements receivable, accounts payable, customers payable, accrued expenses and settlements payable, approximate their fair values due to their short-term nature.

The Company estimates the fair value of its convertible senior notes based on their last actively traded prices (Level 1) or market observable inputs (Level 2). The estimated fair value and carrying value of the convertible senior notes were as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Value		Fair Value (Level 2)		Carrying Value		Fair Value (Level 2)
2023 Notes	$	725,900	$	1,042,987	$	718,522	$	901,468
2022 Notes	183,402		690,691		181,173		515,693
Total	$	909,302	$	1,733,678	$	899,695	$	1,417,161

The estimated fair value and carrying value of loans held for sale is as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Value		Fair Value (Level 3)		Carrying Value		Fair Value (Level 3)
Loans held for sale	$	123,471	$	128,358	$	89,974	$	93,064
Total	$	123,471	$	128,358	$	89,974	$	93,064

For the three months ended March 31, 2019, the Company recorded a charge for the excess of amortized cost over fair value of the loans of $6.7 million. For the three months ended March 31, 2018, the Company recorded a charge for the excess of amortized cost over fair value of the loans of $2.5 million.

If applicable, the Company will recognize transfers into and out of levels within the fair value hierarchy at the end of the reporting period in which the actual event or change in circumstance occurs. During the three months ended March 31, 2019 and 2018, the Company did not have any transfers in or out of Level 1, Level 2, or Level 3 assets or liabilities.

- 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

PROPERTY AND EQUIPMENT, NET

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

The following is a summary of property and equipment, less accumulated depreciation and amortization (in thousands):



	March 31, 2019			December 31, 2018
Leasehold improvements	$	105,244		$	107,611
Computer equipment	82,056			80,093
Capitalized software	64,233			58,908
Office furniture and equipment	20,713			20,699
	272,246			267,311
Less: Accumulated depreciation and amortization	(138,540		)	(124,909		)
Property and equipment, net	$	133,706		$	142,402

Depreciation and amortization expense on property and equipment was $15.5 million for the three months ended March 31, 2019. Depreciation and amortization expense on property and equipment was $8.3 million for the three months ended March 31, 2018.

ACQUISITIONS

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

ACQUISITIONS

Weebly, Inc.

On May 31, 2018, the Company acquired 100% of the outstanding shares of Weebly, a technology company that offers customers website hosting and domain name registration solutions. The acquisition of Weebly enables the Company to combine Weebly’s web presence tools with the Company's in-person and online offerings to create a cohesive solution for sellers to start or grow an omnichannel business. The acquisition expanded the Company’s customer base globally and added a new recurring revenue stream.

The purchase consideration was comprised of $132.4 million in cash and 2,418,271 shares of the Company’s Class A common stock with an aggregate fair value of $140.1 million based on the closing price of the Company’s Class A common stock on the acquisition date. As part of the acquisition, the Company paid an aggregate of $17.7 million in cash and shares to settle outstanding vested and unvested employee options, of which $2.6 million was accounted for as post-combination compensation expense and is excluded from the purchase consideration. Third-party acquisition-related costs were insignificant. The results of Weebly's operations have been included in the consolidated financial statements since the closing date.

The acquisition was accounted for as a business combination. This method requires, among other things, that assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date and that the difference between the fair value of the consideration paid for the acquired entity and the fair value of the net assets acquired be recorded as goodwill, which is not amortized but is tested at least annually for impairment.

The table below summarizes the consideration paid for Weebly and the preliminary assessment of the fair value of the assets acquired and liabilities assumed at the closing date (in thousands, except share data).



Consideration:
Cash	$	132,432
Stock (2,418,271 shares of Class A common stock)	140,107
	$	272,539
Recognized amounts of identifiable assets acquired and liabilities assumed:
Current assets (inclusive of cash acquired of $25,758)	$	46,814
Intangible customer assets	42,700
Intangible technology assets	14,900
Intangible trade name	11,300
Intangible other assets	961
Total liabilities assumed (including deferred revenue of $22,800)	(37,592		)
Total identifiable net assets acquired	79,083
Goodwill	193,456
Total	$	272,539

The Company prepared an initial determination of the fair value of the assets acquired and liabilities assumed as of the acquisition date using preliminary information. Subsequently, the Company recognized measurement period adjustments to the purchase consideration and the fair value of certain liabilities assumed as a result of further refinements in the Company’s estimates. These adjustments were prospectively applied. The effect of these adjustments on the preliminary purchase price allocation was an increase in goodwill and tax liabilities assumed of $3.9 million and $4.8 million, respectively. There was no impact to the consolidated statements of operations as result of these adjustments. The Company continues the process of completing the evaluation of contingencies and potential tax exposures related to the acquisition. Accordingly, the preliminary values reflected in the table above are subject to change.

As of March 31, 2019, $19.1 million of cash and 357,780 shares of the total consideration were withheld as security for indemnification obligations related to general representations and warranties, in addition to certain potential tax exposures.

Goodwill from the Weebly acquisition is primarily attributable to the value of expected synergies created by incorporating Weebly solutions into the Company's technology platform and the value of the assembled workforce. None of the goodwill generated from the Weebly acquisition or the acquired intangible assets are expected to be deductible for tax purposes. Additionally the acquisition would have resulted in recognition of deferred tax assets arising mainly from the net of deferred tax assets from acquired net operating losses (NOLs) and research and development credits, and deferred tax liabilities associated with intangible assets and deferred revenue. However, the realization of such deferred tax assets depends primarily on the Company's post-acquisition ability to generate taxable income in future periods. Accordingly, a valuation allowance was recorded against the net acquired deferred tax asset in accounting for the acquisition.

The acquisition of Weebly did not have a material impact on the Company's reported revenue or net loss amounts for any period presented. Accordingly, pro forma financial information has not been presented.

GOODWILL

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL

Goodwill is recorded when the consideration paid for an acquisition of a business exceeds the fair value of identifiable net tangible and intangible assets acquired.

The change in carrying value of goodwill in the period was as follows (in thousands):



Balance at December 31, 2018	$	261,705
Acquisitions	7,437
Other adjustments	(2,130		)
Balance at March 31, 2019	$	267,012

The Company performs a goodwill impairment test annually on December 31 and more frequently if events and circumstances indicate that the asset might be impaired. For the periods presented, the Company had recorded no impairment charges.

ACQUIRED INTANGIBLE ASSETS

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

ACQUIRED INTANGIBLE ASSETS

During the three months ended March 31, 2019, the Company did not make any material acquisitions.

The following table presents the detail of acquired intangible assets as of the periods presented (in thousands):



	Balance at March 31, 2019
	Cost		Accumulated Amortization			Net
Technology assets	49,007		(29,796		)	19,211
Customer assets	57,109		(9,361		)	47,748
Trade name	11,300		(2,354		)	8,946
Other	5,299		(1,507		)	3,792
Total	$	122,715	$	(43,018	)	$	79,697



	Balance at December 31, 2018
	Cost		Accumulated Amortization			Net
Technology assets	45,978		(28,420		)	17,558
Customer assets	57,109		(8,068		)	49,041
Trade name	11,300		(1,648		)	9,652
Other	2,246		(1,395		)	851
Total	$	116,633	$	(39,531	)	$	77,102

All intangible assets are amortized over their estimated useful lives. The weighted average amortization periods for acquired technology, customer intangible assets, and acquired trade name are approximately 5 years, 11 years and 4 years, respectively.

The changes to the carrying value of intangible assets were as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Acquired intangible assets, net, beginning of the period	$	77,102	$	14,334
Acquisitions	6,082		1,679
Amortization expense	3,487		1,875
Acquired intangible assets, net, end of the period	$	79,697	$	14,138

The total estimated future amortization expense of these intangible assets as of March 31, 2019 is as follows (in thousands):



2019 (remaining 9 months)	$	11,185
2020	12,611
2021	11,413
2022	9,484
2023	7,953
Thereafter	27,051
Total	$	79,697

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)

Other Current Assets

The following table presents the detail of other current assets (in thousands):



	March 31, 2019		December 31, 2018
Inventory, net	$	26,679	$	28,627
Processing costs receivable	59,470		46,102
Prepaid expenses	23,526		21,782
Accounts receivable, net	28,665		22,393
Other	46,781		46,062
Total	$	185,121	$	164,966

Accrued Expenses

The following table presents the detail of accrued expenses (in thousands):



	March 31, 2019		December 31, 2018
Accrued facilities expenses	$	5,853	$	13,040
Accrued payroll	18,282		9,612
Accrued professional fees	6,173		5,232
Accrued advertising and other marketing	15,940		12,201
Processing costs payable	13,190		12,683
Accrued non income tax liabilities	6,568		9,503
Accrued hardware costs	5,413		5,125
Other accrued liabilities	16,393		14,958
Total	$	87,812	$	82,354

Other Current Liabilities

The following table presents the detail of other current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Accounts payable	$	24,635	$	36,416
Deferred revenue, current	36,343		31,474
Square Capital payable (i)	18,459		6,092
Square Payroll payable (ii)	12,338		7,534
Other	16,869		17,637
Total	$	108,644	$	99,153

⁽ⁱ⁾Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties.

⁽ⁱⁱ⁾Square Payroll payable represents amounts received from Square Payroll product customers that will be utilized to settle the customers' employee payroll and related obligations.

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)

Other Non-Current Assets

The following table presents the detail of other non-current assets (in thousands):



	March 31, 2019		December 31, 2018
Equity investment (i)	$	31,255	$	45,342
Other	16,947		13,051
Total	$	48,202	$	58,393

⁽ⁱ⁾ This balance represents the Company's investment in Class B common shares of Eventbrite, Inc. (Eventbrite). The investment is carried at fair value with changes in fair value being recorded on the consolidated statement of operations. During the three months ended March 31, 2019, the Company recorded a loss of $14.1 million to other expense (income), net on the consolidated statements of operations arising from revaluation of this investment.

Other Non-Current Liabilities

The following table presents the detail of other non-current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Statutory liabilities (ii)	$	57,839	$	54,748
Deferred rent, non-current (iii)	—		23,003
Deferred revenue, non-current	5,817		4,977
Other	11,929		10,558
Total	$	75,585	$	93,286

⁽ⁱⁱ⁾Statutory liabilities represent loss contingencies that may arise from the Company's interpretation and application of certain guidelines and rules issued by various federal, state, local, and foreign regulatory authorities.

⁽ⁱⁱⁱ⁾The adoption of ASC 842 on January 1, 2019, resulted in the reclassification of deferred rent as an offset to right-of-use lease assets.

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)

Other Current Assets

The following table presents the detail of other current assets (in thousands):



	March 31, 2019		December 31, 2018
Inventory, net	$	26,679	$	28,627
Processing costs receivable	59,470		46,102
Prepaid expenses	23,526		21,782
Accounts receivable, net	28,665		22,393
Other	46,781		46,062
Total	$	185,121	$	164,966

Accrued Expenses

The following table presents the detail of accrued expenses (in thousands):



	March 31, 2019		December 31, 2018
Accrued facilities expenses	$	5,853	$	13,040
Accrued payroll	18,282		9,612
Accrued professional fees	6,173		5,232
Accrued advertising and other marketing	15,940		12,201
Processing costs payable	13,190		12,683
Accrued non income tax liabilities	6,568		9,503
Accrued hardware costs	5,413		5,125
Other accrued liabilities	16,393		14,958
Total	$	87,812	$	82,354

Other Current Liabilities

The following table presents the detail of other current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Accounts payable	$	24,635	$	36,416
Deferred revenue, current	36,343		31,474
Square Capital payable (i)	18,459		6,092
Square Payroll payable (ii)	12,338		7,534
Other	16,869		17,637
Total	$	108,644	$	99,153

⁽ⁱ⁾Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties.

⁽ⁱⁱ⁾Square Payroll payable represents amounts received from Square Payroll product customers that will be utilized to settle the customers' employee payroll and related obligations.

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)

Other Non-Current Assets

The following table presents the detail of other non-current assets (in thousands):



	March 31, 2019		December 31, 2018
Equity investment (i)	$	31,255	$	45,342
Other	16,947		13,051
Total	$	48,202	$	58,393

⁽ⁱ⁾ This balance represents the Company's investment in Class B common shares of Eventbrite, Inc. (Eventbrite). The investment is carried at fair value with changes in fair value being recorded on the consolidated statement of operations. During the three months ended March 31, 2019, the Company recorded a loss of $14.1 million to other expense (income), net on the consolidated statements of operations arising from revaluation of this investment.

Other Non-Current Liabilities

The following table presents the detail of other non-current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Statutory liabilities (ii)	$	57,839	$	54,748
Deferred rent, non-current (iii)	—		23,003
Deferred revenue, non-current	5,817		4,977
Other	11,929		10,558
Total	$	75,585	$	93,286

⁽ⁱⁱ⁾Statutory liabilities represent loss contingencies that may arise from the Company's interpretation and application of certain guidelines and rules issued by various federal, state, local, and foreign regulatory authorities.

⁽ⁱⁱⁱ⁾The adoption of ASC 842 on January 1, 2019, resulted in the reclassification of deferred rent as an offset to right-of-use lease assets.

INDEBTEDNESS

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

INDEBTEDNESS

Revolving Credit Facility

In November 2015, the Company entered into a revolving credit agreement with certain lenders, which extinguished the prior revolving credit agreement and provided for a $375.0 million revolving secured credit facility maturing in November 2020. This revolving credit agreement is secured by certain tangible and intangible assets.

Loans under the credit facility bear interest at the Company’s option of (i) a base rate based on the highest of the prime rate, the federal funds rate plus 0.50%, and an adjusted LIBOR rate for a one-month interest period, in each case plus a margin ranging from 0.00% to 1.00%, or (ii) an adjusted LIBOR rate plus a margin ranging from 1.00% to 2.00%. This margin is determined based on the Company’s total leverage ratio for the preceding four fiscal quarters. The Company is obligated to pay other customary fees for a credit facility of this size and type including an annual administrative agent fee of $0.1 million and an unused commitment fee of 0.15%. To date no funds have been drawn under the credit facility, with $375.0 million remaining available. The Company paid $0.1 million and $0.1 million in unused commitment fees during both the three months ended March 31, 2019 and 2018, respectively. As of March 31, 2019, the Company was in compliance with all financial covenants associated with this credit facility.

Convertible Senior Notes due in 2023

On May 25, 2018, the Company issued an aggregate principal amount of $862.5 million of convertible senior notes (2023 Notes). The 2023 Notes mature on May 15, 2023, unless earlier converted or repurchased, and bear interest at a rate of 0.50% payable semi-annually on May 15 and November 15 of each year. The 2023 Notes are convertible at an initial conversion rate of 12.8456 shares of the Company's Class A common stock per $1,000 principal amount of 2023 Notes, which is equivalent to an initial conversion price of approximately $77.85 per share of Class A common stock. Holders may convert their 2023 Notes at any time prior to the close of business on the business day immediately preceding February 15, 2023 only under the following circumstances: (1) during any calendar quarter commencing after September 30, 2018 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the measurement period) in which the trading price (as defined in the indenture governing the 2023 Notes) per $1,000 principal amount of 2023 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s Class A common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events, including certain distributions, the occurrence of a fundamental change (as defined in the indenture governing the 2023 Notes) or a transaction resulting in the Company’s Class A common stock converting into other securities or property or assets. On or after February 15, 2023, up until the close of business on the second scheduled trading day immediately preceding the maturity date, a holder may convert all or any portion of its 2023 Notes regardless of the foregoing circumstances. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of its Class A common stock, or a combination of cash and shares of its Class A common stock, at the Company’s election. The Company's current policy is to settle conversions entirely in shares of the Company's Class A common stock. The Company will reevaluate this policy from time to time as conversion notices are received from holders of the 2023 Notes. The circumstances required to allow the holders to convert their 2023 Notes were not met during the three months ended March 31, 2019.

In accounting for the issuance of the 2023 Notes, the Company separated the 2023 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was $155.3 million and was determined by deducting the fair value of the liability component from the par value of the 2023 Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The excess of the principal amount of the liability component over its carrying amount ("debt discount") is amortized to interest expense over the term of the 2023 Notes at an effective interest rate of 4.69% over the contractual terms of the 2023 Notes.

Debt issuance costs related to the 2023 Notes comprised of discounts and commissions payable to the initial purchasers of $6.0 million and third party offering costs of $0.8 million. The Company allocated the total amount incurred to the liability and equity components of the 2023 Notes based on their relative values. Issuance costs attributable to the liability component were $5.6 million and will be amortized to interest expense using the effective interest method over the contractual term. Issuance costs attributable to the equity component were netted with the equity component in stockholders’ equity.

Convertible Senior Notes due in 2022

On March 6, 2017, the Company issued an aggregate principal amount of $440.0 million of convertible senior notes (2022 Notes). The 2022 Notes mature on March 1, 2022, unless earlier converted or repurchased, and bear interest at a rate of 0.375% payable semi-annually on March 1 and September 1 of each year. The 2022 Notes are convertible at an initial conversion rate of 43.5749 shares of the Company's Class A common stock per $1,000 principal amount of 2022 Notes, which is equivalent to an initial conversion price of approximately $22.95 per share of Class A common stock. Holders may convert their 2022 Notes at any time prior to the close of business on the business day immediately preceding December 1, 2021 only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s Class A common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the measurement period) in which the trading price (as defined in the indenture governing the 2022 Notes) per $1,000 principal amount of 2022 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s Class A common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events, including certain distributions, the occurrence of a fundamental change (as defined in the indenture governing the 2022 Notes) or a transaction resulting in the Company’s Class A common stock converting into other securities or property or assets. On or after December 1, 2021, up until the close of business on the second scheduled trading day immediately preceding the maturity date, a holder may convert all or any portion of its 2022 Notes regardless of the foregoing circumstances. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of its Class A common stock, or a combination of cash and shares of its Class A common stock, at the Company’s election. The circumstances required to allow the holders to convert their 2022 Notes were met starting January 1, 2018 and continued to be met through March 31, 2019. In 2018, certain holders of the 2022 Notes converted an aggregate principal amount of $228.3 million of their Notes. The Company settled the conversions through a combination of $219.4 million in cash and issuance of 7.3 million shares of the Company's Class A common stock. Conversions in the three months ended March 31, 2019 were not material. The Company currently expects to settle future conversions entirely in shares of the Company's Class A common stock. The Company will reevaluate this policy from time to time as conversion notices are received from holders of the 2022 Notes.

In accounting for the issuance of the 2022 Notes, the Company separated the 2022 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was $86.2 million and was determined by deducting the fair value of the liability component from the par value of the 2022 Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The debt discount is amortized to interest expense over the term of the 2022 Notes at an effective interest rate of 5.34% over the contractual terms of the 2022 Notes.

Debt issuance costs related to the 2022 Notes comprised of discounts and commissions payable to the initial purchasers of $11.0 million and third party offering costs of $0.8 million. The Company allocated the total amount incurred to the liability and equity components of the 2022 Notes based on their relative values. Issuance costs attributable to the liability component were $9.4 million and will be amortized to interest expense using the effective interest method over the contractual term. Issuance costs attributable to the equity component were netted with the equity component in stockholders’ equity.

The debt component associated with the 2022 Notes that were converted as of December 31, 2018, was accounted for as an extinguishment of debt, with the Company recording loss on extinguishment of $5.0 million, as the difference between the estimated fair value and the carrying value of such 2022 Notes. The equity component associated with the 2022 Notes that were converted was accounted for as a reacquisition of equity upon the conversion of such 2022 Notes. Accordingly, the excess of the fair value of the consideration issued to settle the conversion over the fair value of the debt component of $21.0 million was accounted for as a reduction to the additional paid in capital.

The net carrying amount of the Notes were as follows (in thousands):



	Principal outstanding		Unamortized debt discount			Unamortized debt issuance costs			Net carrying value
March 31, 2019
2023 Notes	$	862,500	$	(131,767	)	$	(4,833	)	$	725,900
2022 Notes	211,728		(25,563		)	(2,763		)	183,402
Total	$	1,074,228	$	(157,330	)	$	(7,596	)	$	909,302

December 31, 2018
2023 Notes	$	862,500	$	(138,924	)	$	(5,054	)	$	718,522
2022 Notes	211,728		(27,569		)	(2,986		)	181,173
	$	1,074,228	$	(166,493	)	$	(8,040	)	$	899,695

The net carrying amount of the equity component of the 2023 Notes and 2022 Notes were as follows (in thousands):



	Amount allocated to conversion option		Less: allocated issuance costs			Equity component, net
March 31, 2019 and December 31, 2018
2023 Notes	$	155,250	$	(1,231	)	$	154,019
2022 Notes	41,481		(1,108		)	40,373
Total	196,731		(2,339		)	194,392

The Company recognized interest expense on the Notes as follows (in thousands, except for percentages):



	Three Months Ended March 31,
	2019		2018
Contractual interest expense	$	1,277	$	413
Amortization of debt discount and issuance costs	9,608		4,393
Total	$	10,885	$	4,806

The effective interest rate of the liability component is 4.69% and 5.34% for the 2023 Notes and 2022 Notes, respectively.

Convertible Note Hedge and Warrant Transactions

In connection with the offering of the 2023 Notes, the Company entered into convertible note hedge transactions (2023 convertible note hedges) with certain financial institution counterparties (2018 Counterparties) whereby the Company has the option to purchase a total of approximately 11.1 million shares of its Class A common stock at a price of approximately $77.85 per share. The total cost of the 2023 convertible note hedge transactions was $172.6 million. In addition, the Company sold warrants (2023 warrants) to the 2018 Counterparties whereby the 2018 Counterparties have the option to purchase a total of 11.1 million shares of the Company’s Class A common stock at a price of approximately $109.26 per share. The Company received $112.1 million in cash proceeds from the sale of the 2023 warrants. Taken together, the purchase of the 2023 convertible note hedges and sale of the 2023 warrants are intended to reduce dilution from the conversion of the 2023 Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of the converted 2023 Notes, as the case may be, and to effectively increase the overall conversion price from approximately $77.85 per share to approximately $109.26 per share. As these instruments are considered indexed to the Company's own stock and are considered equity classified, the 2023 convertible note hedges and 2023 warrants are recorded in stockholders’ equity, are not accounted for as derivatives and are not remeasured each reporting period. The net costs incurred in connection with the 2023 convertible note hedge and 2023 warrant transactions were recorded as a reduction to additional paid-in capital on the condensed consolidated balance sheets.

In connection with the offering of the 2022 Notes, the Company entered into convertible note hedge transactions (2022 convertible note hedges) with certain financial institution counterparties (2017 Counterparties) whereby the Company has the option to purchase a total of approximately 19.2 million shares of its Class A common stock at a price of approximately $22.95 per share. The total cost of the 2022 convertible note hedge transactions was $92.1 million. In addition, the Company sold warrants (2022 warrants) to the 2017 Counterparties whereby the 2017 Counterparties have the option to purchase a total of 19.2 million shares of the Company’s Class A common stock at a price of approximately $31.18 per share. The Company received $57.2 million in cash proceeds from the sale of the 2022 warrants. Taken together, the purchase of the 2022 convertible note hedges and sale of the 2022 warrants are intended to reduce dilution from the conversion of the 2022 Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of the converted 2022 Notes, as the case may be, and to effectively increase the overall conversion price from approximately $22.95 per share to approximately $31.18 per share. As these instruments are considered indexed to the Company's own stock and are considered equity classified, the 2022 convertible note hedges and 2022 warrants are recorded in stockholders’ equity, are not accounted for as derivatives and are not remeasured each reporting period. The net costs incurred in connection with the 2022 convertible note hedge and 2022 warrant transactions were recorded as a reduction to additional paid-in capital on the condensed consolidated balance sheets. In 2018, the Company exercised a pro-rata portion of the 2022 convertible note hedges to offset the shares of the Company's Class A common stock issued to settle the conversion of the 2022 Notes discussed above. The 2022 convertible note hedges were net share settled, and the Company received 6.9 million shares of the Company's Class A common stock from the 2017 Counterparties in 2018. During the three months ended March 31, 2019, the Company received an additional 0.3 million shares of the Company's Class A common stock.

ACCRUED TRANSACTION LOSSES

3 Months Ended

Mar. 31, 2019

Product Warranties Disclosures [Abstract]

ACCRUED TRANSACTION LOSSES

The Company is exposed to transaction losses due to chargebacks as a result of fraud or uncollectibility.

The following table summarizes the activities of the Company’s reserve for transaction losses (in thousands):



	Three Months Ended March 31,
	2019			2018
Accrued transaction losses, beginning of the period	$	33,682		$	26,893
Provision for transaction losses	19,808			14,258
Charge-offs to accrued transaction losses	(17,443		)	(12,842		)
Accrued transaction losses, end of the period	$	36,047		$	28,309

INCOME TAXES	3 Months Ended
INCOME TAXES	Mar. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company recorded an income tax expense of $0.1 million for the three months ended March 31, 2019, compared to income tax expense of $0.2 million for the three months ended March 31, 2018. The income tax expense recorded for the three months ended March 31, 2019 was primarily due to state and foreign income tax expense as well as a change in the valuation allowance on the Company's deferred tax assets. The Company’s effective tax rate was (0.3)% for the three months ended March 31, 2019, compared to an effective tax rate of (0.7)% for the three months ended March 31, 2018. The difference between the effective tax rate and the federal statutory tax rate for the three months ended March 31, 2019 and March 31, 2018 primarily relates to fluctuations in the Company's pre-tax book income. The Company’s effective tax rate may be subject to fluctuation during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as the mix of forecasted pre-tax earnings in the various jurisdictions in which the Company operates, valuation allowances against deferred tax assets, the recognition and de-recognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where the Company conducts business. As of March 31, 2019, the Company retains a full valuation allowance on its deferred tax assets in the U.S. and certain foreign jurisdictions. The realization of the Company’s deferred tax assets depends primarily on its ability to generate taxable income in future periods. The amount of deferred tax assets considered realizable in future periods may change as management continues to reassess the underlying factors it uses in estimating future taxable income. The tax provision for the three months ended March 31, 2019 and March 31, 2018, was calculated on a jurisdictional basis. The Company estimated the foreign income tax provision using the effective income tax rate expected to be applicable for the full year.

STOCKHOLDERS' EQUITY

3 Months Ended

Mar. 31, 2019

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

STOCKHOLDERS' EQUITY

STOCKHOLDERS’ EQUITY

Common Stock

The Company has authorized the issuance of Class A common stock and Class B common stock. Class A common stock and Class B common stock are referred to as "common stock" throughout these Notes to the Condensed Consolidated Financial Statements, unless otherwise noted. As of March 31, 2019, the Company was authorized to issue 1,000,000,000 shares of Class A common stock and 500,000,000 shares of Class B common stock, each with a par value of $0.0000001 per share. As of March 31, 2019, there were 334,650,231 shares of Class A common stock and 86,973,715 shares of Class B common stock outstanding. Options and awards granted following the Company's initial public offering are related to underlying Class A common stock. Additionally, holders of Class B common stock are able to convert such shares into Class A common stock.

Warrants

In conjunction with the 2023 Notes offering, the Company sold the 2023 warrants whereby the 2018 Counterparties have the option to purchase a total of approximately 11.1 million shares of the Company’s Class A common stock at a price of $109.26 per share. The Company received $112.1 million in cash proceeds from the sale of the 2023 warrants. See Note 12, Indebtedness, for more details on this transaction.

In conjunction with the 2022 Notes offering, the Company sold warrants whereby the 2017 Counterparties have the option to purchase a total of approximately 19.2 million shares of the Company’s Class A common stock at a price of $31.18 per share. None of the warrants associated with the 2022 and 2023 Notes offering were exercised as of March 31, 2019.

Stock Plans

The Company maintains two share-based employee compensation plans: the 2009 Stock Plan (2009 Plan) and the 2015 Equity Incentive Plan (2015 Plan). The 2015 Plan serves as the successor to the 2009 Plan. The 2015 Plan became effective as of November 17, 2015. Outstanding awards under the 2009 Plan continue to be subject to the terms and conditions of the 2009 Plan. Since November 17, 2015, no additional awards have been nor will be in the future granted under the 2009 Plan.

Under the 2015 Plan, shares of the Company's Class A common stock are reserved for the issuance of incentive and nonstatutory stock options, restricted stock awards (RSAs), restricted stock units (RSUs), performance shares, and stock bonuses to qualified employees, directors, and consultants. The awards must be granted at a price per share not less than the fair market value at the date of grant. Initially, 30,000,000 shares were reserved under the 2015 Plan, and any shares subject to options or other similar awards granted under the 2009 Plan that expire, are forfeited, are repurchased by the Company, or otherwise terminate unexercised, will become available under the 2015 Plan. The number of shares available for issuance under the 2015 Plan will be increased on the first day of each fiscal year, in an amount equal to the least of (i) 40,000,000 shares, (ii) 5% of the outstanding shares on the last day of the immediately preceding fiscal year, or (iii) such number of shares determined by the Company’s board of directors or a committee thereof. As of March 31, 2019, the total number of shares subject to stock options, RSAs and RSUs outstanding under the 2015 Plan was 20,822,979, and 86,449,187 shares were available for future issuance. As of March 31, 2019, the total number of shares subject to stock options, RSAs and RSUs outstanding under the 2009 Plan was 24,792,142.

A summary of stock option activity for the three months ended March 31, 2019 is as follows (in thousands, except share and per share data):



	Number of Stock Options Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance at December 31, 2018	33,152,881		$	9.52	5.45	$	1,543,793
Granted	97,701		73.94
Exercised	(3,588,052	)	7.06
Forfeited	(95,141	)	11.78
Balance at March 31, 2019	29,567,389		$	10.03	5.41	$	1,918,661
Options exercisable as of
March 31, 2019	27,693,334		$	8.88	5.23	$	1,828,856

Restricted Stock Activity

Activity related to RSAs and RSUs during the three months ended March 31, 2019 is set forth below:



	Number of shares		Weighted Average Grant Date Fair Value
Unvested as of December 31, 2018	17,934,728		$	31.34
Granted	552,596		69.20
Vested	(1,880,545	)	24.12
Forfeited	(559,047	)	29.35
Unvested as of March 31, 2019	16,047,732		$	33.56

Share-Based Compensation

The fair value of stock options and employee stock purchase plan rights are estimated on the date of grant using the Black-Scholes-Merton option valuation model. The fair value of RSAs and RSUs is determined by the closing price of the Company’s common stock on each grant date.

The fair value of stock options granted was estimated using the following weighted-average assumptions:



	Three Months Ended March 31,
	2019
Dividend yield	—	%
Risk-free interest rate	2.59	%
Expected volatility	38.55	%
Expected term (years)	6.08

There were no stock options granted during the three months ended March 31, 2018.

The following table summarizes the effects of share-based compensation on the Company's condensed consolidated statements of operations (in thousands):



	Three Months Ended March 31,
	2019		2018
Cost of revenue	$	21	$	31
Product development	42,649		30,482
Sales and marketing	6,202		4,961
General and administrative	12,216		11,350
Total	$	61,088	$	46,824

The Company recorded $4.3 million of share-based compensation expense related to the Company's 2015 Employee Stock Purchase Plan during the three months ended March 31, 2019, compared to $2.3 million for the three months ended March 31, 2018, which are included in the table above.

The Company capitalized $1.7 million of share-based compensation expense related to capitalized software costs during the three months ended March 31, 2019, compared to $1.5 million for the three months ended March 31, 2018.

As of March 31, 2019, there was $527.0 million of total unrecognized compensation cost related to outstanding awards that are expected to be recognized over a weighted-average period of 2.7 years.

NET LOSS PER SHARE

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

NET LOSS PER SHARE

LOSS PER SHARE

Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is the same as basic net loss per share because the effects of potentially dilutive items were anti-dilutive given the Company’s net loss.

The following table presents the calculation of basic and diluted net loss per share (in thousands, except per share data):



	Three Months Ended March 31,
	2019			2018
Net loss	$	(38,151	)	$	(23,986	)
Basic shares:
Weighted-average common shares outstanding	419,860			397,246
Weighted-average unvested shares	(571		)	(1,298		)
Weighted-average shares used to compute basic net loss per share	419,289			395,948
Diluted shares:
Weighted-average shares used to compute diluted net loss per share	419,289			395,948
Net loss per share:
Basic	$	(0.09	)	$	(0.06	)
Diluted	$	(0.09	)	$	(0.06	)

Additionally, since the Company intends to settle future conversions of its outstanding 2022 Notes and 2023 Notes entirely in shares of its Class A common stock, the Company will consider the number of shares expected to be issued in calculating any potential dilutive effect of the conversions, if applicable. In the periods that the Company has reported a net loss the diluted loss per share is the same as basic loss per share for those periods.

The following potential common shares were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):



	Three Months Ended March 31,
	2019	2018
Stock options and restricted stock units	47,833	66,382
Common stock warrants	30,252	19,173
Convertible senior notes	20,305	—
Unvested shares	571	1,298
Employee stock purchase plan	212	264
Total anti-dilutive securities	99,173	87,117

COMMITMENTS AND CONTINGENCIES

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Operating and Finance Leases

The Company’s operating leases are primarily comprised of office facilities, with the most significant leases relating to corporate headquarters in San Francisco and an office in New York. The Company's leases have remaining lease terms of 1 year to 12 years, some of which include options to extend for 5 year terms, or include options to terminate the leases within 1 year. None of the options to extend the leases have been included in the measurement of the right of use asset or the associated lease liability. The Company elects to apply the short-term lease measurement and recognition exemption to its leases where applicable. In December 2018, the Company entered into a lease arrangement for 355,762 square feet of office space in Oakland, California for a term of 12 years with options to extend the lease term for two five year terms. The lease commencement date is expected to be in November 2019 with total lease payments over the term of approximately $276 million. Under the terms of this lease, the Company is required to make certain payments during the construction stage of the office space, which the Company will record as a prepaid lease asset. Additionally, the Company has finance leases for data center equipment, with remaining lease terms of approximately 2 years.

The components of lease expense were as follows (in thousands):



	Three Months Ended March 31,
	2019
Operating lease costs	$	6,690

Finance lease costs
Amortization of right-of-use assets	1,293
Interest on lease liabilities	—
Total finance lease costs	$	1,293

For the periods presented, costs associated with short-term leases were not material.

Other information related to leases was as follows:



	Three Months Ended March 31,
	2019
Weighted Average Remaining Lease Term:
Operating leases	4.80 years
Finance leases	1.75 years
Weighted Average Discount Rate:
Operating leases	4	%
Finance leases	—	%

Future minimum lease payments under non-cancelable operating leases (with initial lease terms in excess of one year) and future minimum finance lease payments as of March 31, 2019 are as follows (in thousands):



	Finance		Operating
Year:
2019 (remaining 9 months)	$	3,745	$	20,112
2020	2,446		39,182
2021	—		53,426
2022	—		54,229
2023	—		47,952
Thereafter	—		211,056
Total	$	6,191	$	425,957
Less amount representing interest	—		14,323
Less leases executed but not yet commenced	—		276,037
Total	$	6,191	$	135,597

The current portion of the finance lease liability is included within other current liabilities while the non-current portion is included within other non-current liabilities on the condensed consolidated balance sheets. The associated finance lease assets are included in property and equipment, net on the condensed consolidated balance sheets.

Litigation

The Company is currently a party to, and may in the future be involved in, various litigation matters (including intellectual property litigation), legal claims, and government investigations.

The Treasurer & Tax Collector of the City and County of San Francisco (Tax Collector) has issued a decision for fiscal years 2014 and 2015, that the Tax Collector believes the Company’s primary business activity is financial services rather than information services, and accordingly, the Company would be liable for the Gross Receipts Tax and Payroll Expense Tax under the rules for financial services business activities. The Company paid the liability for fiscal years 2014 and 2015 in the first quarter of 2018, as assessed by the Tax Collector. The Company believes its position has merit and intends to vigorously defend its position, including possibly through litigation. Should the Company not prevail, the Company could be obligated to pay additional taxes together with any associated penalties and interest for subsequent years that together, in aggregate, could be material. The Company is currently unable to estimate the range of possible loss given the uncertainties associated with this matter, including uncertainties about the Tax Collector’s rationale for its position and about the amounts that may ultimately be subject to such taxes.

On May 14, 2018, Joshua Woodle, on behalf of a class of couriers who have delivered with Caviar in California, filed a lawsuit in San Francisco County Superior Court against the Company doing business as Caviar, which alleges that Caviar misclassified Mr. Woodle and other similarly situated couriers as independent contractors and, in doing so, violated various provisions of the California Labor Code and California Business and Professions Code. Plaintiffs seek damages and injunctive relief. The Court compelled arbitration of Mr. Woodle’s arbitrable claims on November 5, 2018. On August 24, 2018, Mervyn Cole, on behalf of the State of California and similarly situated couriers who have delivered with Caviar in California filed a lawsuit in Los Angeles County Superior Court against the Company doing business as Caviar. The complaint alleges that Caviar misclassified Mr. Cole and other similarly situated couriers as independent contractors and, in doing so, violated certain provisions of the California Labor Code. The action is being brought as a representative action under the Private Attorneys General Act (“PAGA”). Plaintiffs seek civil penalties and injunctive relief. Given the early stage of these proceedings, it is not yet possible to reliably determine any potential liability that could result from these matters.

In addition, from time to time, the Company is involved in various other litigation matters and disputes arising in the ordinary course of business. The Company cannot at this time fairly estimate a reasonable range of exposure, if any, of the potential liability with respect to these other matters. While the Company does not believe, at this time, that any ultimate liability resulting from any of these other matters will have a material adverse effect on the Company's results of operations, financial position, or liquidity, the Company cannot give any assurance regarding the ultimate outcome of these other matters, and their resolution could be material to the Company's operating results for any particular period.

SEGMENT AND GEOGRAPHICAL INFORMATION

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

SEGMENT AND GEOGRAPHIC INFORMATION

SEGMENT AND GEOGRAPHICAL INFORMATION

Operating segments are defined as components of an enterprise for which discrete financial information is available that is evaluated regularly by the chief operating decision maker (CODM) for purposes of allocating resources and evaluating financial performance. The Company’s CODM is the chief executive officer who reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. As such, the Company’s operations constitute a single operating segment and one reportable segment.

Revenue

Revenue by geography is based on the billing addresses of the sellers or customers. The following table sets forth revenue by geographic area (in thousands):



	Three Months Ended March 31,
	2019		2018
Revenue
United States	$	914,656	$	640,173
International	44,703		28,430
Total net revenue	$	959,359	$	668,603

No individual country from the international markets contributed in excess of 10% of total revenue for the three months ended March 31, 2019 and 2018.

Long-Lived Assets

The following table sets forth long-lived assets by geographic area (in thousands):



	March 31, 2019		December 31, 2018
Long-lived assets
United States	$	579,397	$	471,970
International	12,974		9,239
Total long-lived assets	$	592,371	$	481,209

SUPPLEMENTAL CASH FLOW INFORMATION

3 Months Ended

Mar. 31, 2019

Supplemental Cash Flow Elements [Abstract]

SUPPLEMENTAL CASH FLOW INFORMATION

The supplemental disclosures of cash flow information consist of the following (in thousands):



	Three Months Ended March 31,
	2019		2018
Supplemental Cash Flow Data:
Cash paid for interest	$	538	$	966
Cash paid for income taxes	1,342		658
Right-of-use assets obtained in exchange for operating lease obligations	19,918		—
Supplemental disclosures of non-cash investing and financing activities:
Change in purchases of property and equipment in accounts payable and accrued expenses	13,114		(3,813		)
Unpaid business combination purchase price	6,447		1,151
Recovery of common stock in connection with indemnification settlement agreement	789		—

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements of the Company are unaudited. These interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP) and the applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The December 31, 2018 condensed consolidated balance sheet was derived from the audited financial statements as of that date, but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The accompanying unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company's consolidated financial position, results of operations, comprehensive income (loss), and cash flows for the interim periods. All intercompany transactions and balances have been eliminated in consolidation. The interim results for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019, or for any other future annual or interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and notes thereto included in Items 7, 7A, and 8, respectively, in the Company's Annual Report on Form 10-K for the year ended December 31, 2018.
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, as well as related disclosure of contingent assets and liabilities. Actual results could differ from the Company’s estimates. To the extent that there are material differences between these estimates and actual results, the Company’s financial condition or operating results will be materially affected. The Company bases its estimates on past experience and other assumptions that the Company believes are reasonable under the circumstances, and the Company evaluates these estimates on an ongoing basis. Estimates, judgments, and assumptions in these consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued transaction losses, valuation of the debt component of convertible senior notes, valuation of loans held for sale, goodwill, acquired intangible assets and deferred revenue, income and other taxes, operating and financing lease right-of-use assets and related liabilities, and share-based compensation.
Concentration of Credit Risk	Concentration of Credit Risk For the three months ended March 31, 2019 and 2018, the Company had no customer that accounted for greater than 10% of total net revenue. The Company had three third-party payment processors that represented approximately 55%, 35%, and 6% of settlements receivable as of March 31, 2019. The same three parties represented approximately 45%, 33%, and 9% of settlements receivable as of December 31, 2018. All other third-party processors were insignificant. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, marketable debt securities, settlements receivables, customer funds, and loans held for sale. The associated risk of concentration for cash and cash equivalents and restricted cash is mitigated by banking with creditworthy institutions. At certain times, amounts on deposit exceed federal deposit insurance limits. The associated risk of concentration for marketable debt securities is mitigated by holding a diversified portfolio of highly rated investments. Settlements receivable are amounts due from well-established payment processing companies and normally take one or two business days to settle which mitigates the associated risk of concentration. The associated risk of concentration for loans held for sale is partially mitigated by credit evaluations that are performed prior to facilitating the offering of loans and ongoing performance monitoring of the Company’s loan customers.
New Accounting Policies and Recent Accounting Pronouncements	New Accounting Policies The Company adopted Accounting Standards Codification (ASC) 842, Leases on January 1, 2019, and elected the optional transition method to apply the transition provisions from the effective date of adoption, which requires the Company to report the cumulative effect of the adoption of the standard on the date of adoption with no changes to the prior period balances. Pursuant to the practical expedients, the Company has elected not to reassess: (i) whether expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases, or, (iii) initial direct costs for any existing leases. Additionally, the Company has lease agreements with lease and non-lease components, which are accounted for separately. The Company recognized $112.0 million of operating right-of-use lease assets and $135.6 million of operating lease liabilities on its consolidated balance sheet as of March 31, 2019. Additionally, the Company derecognized $149 million related to the build-to-suit asset and liability upon adoption of this standard because the Company is no longer deemed to be the owner of the related asset under construction under the new standard. Refer to Note 17 for further detail. Except for the adoption of ASC 842, there have been no material changes to the Company’s accounting policies during the three months ended March 31, 2019, as compared to the accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018. Recent Accounting Pronouncements Recently issued accounting pronouncements not yet adopted In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses, which requires measurement and recognition of expected credit losses for financial assets held. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The Company intends to adopt this guidance effective January 1, 2020. The Company is currently evaluating the impact this guidance may have on the consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The new guidance eliminates the requirement to calculate the implied fair value of goodwill assuming a hypothetical purchase price allocation (i.e., Step 2 of the goodwill impairment test) to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value, not to exceed the carrying amount of goodwill. This standard should be adopted when the Company performs its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019, with early adoption permitted. The amendments should be applied on a prospective basis. The Company intends to adopt this guidance effective with its 2019 annual goodwill impairment test which it performs as of December 31. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. In July 2018, the FASB issued ASU 2018-13, Changes to the Disclosure Requirements for Fair Value Measurement, which will remove, modify, and add disclosure requirements for fair value measurements to improve the overall usefulness of such disclosures. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any removed or modified disclosure requirements. Transition is on a prospective basis for the new and modified disclosures, and on a retrospective basis for disclosures that have been eliminated. The Company currently does not intend to early adopt any portion of this disclosure guidance. The Company is currently evaluating the impact this guidance may have on the consolidated financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which is intended to align the requirements for capitalization of implementation costs incurred in a cloud computing arrangement that is a service contract with the existing guidance for internal-use software. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. The guidance provides flexibility in adoption, allowing for either retrospective adjustment or prospective adjustment for all implementation costs incurred after the date of adoption. The Company is currently evaluating whether to early adopt this guidance as well as the impact it may have on the consolidated financial statements and related disclosures.

REVENUE (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

The following table presents the Company's revenue disaggregated by revenue source (in thousands):



	Three Months Ended March 31,
	2019		2018
Revenue from Contracts with Customers:
Transaction-based revenue	$	656,762	$	523,037
Subscription and services-based revenue	190,307		77,215
Hardware revenue	18,212		14,417
Bitcoin revenue	$	65,528	$	34,095
Revenue from other sources:
Subscription and services-based revenue	$	28,550	$	19,839

Schedule of Deferred Revenue

The deferred revenue balances were as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Deferred revenue, beginning of the period	$	36,451	$	5,893
Less: cumulative impact of the adoption of ASC 606	—		(4,303		)
Deferred revenue, beginning of the period, as adjusted	36,451		1,590
Deferred revenue, end of the period	42,160		3,353
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	$	12,306	$	298

INVESTMENTS (Tables)

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Short-term and Long-term Investments

The Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	113,508	$	142	$	(15	)	$	113,635
Corporate bonds	84,832		289		(25		)	85,096
Municipal securities	20,237		54		(18		)	20,273
U.S. government securities	317,787		394		(71		)	318,110
Non-U.S. government securities	29,355		70		—			29,425
Total	$	565,719	$	949	$	(129	)	$	566,539

Long-term debt securities:
U.S. agency securities	$	85,993	$	299	$	(28	)	$	86,264
Corporate bonds	186,674		1,233		(11		)	187,896
Municipal securities	23,267		128		(2		)	23,393
U.S. government securities	174,515		541		(8		)	175,048
Non-U.S. government securities	8,417		45		—			8,462
Total	$	478,866	$	2,246	$	(49	)	$	481,063

The Company's short-term and long-term investments as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	80,160	$	32	$	(70	)	$	80,122
Corporate bonds	109,807		80		(368		)	109,519
Municipal securities	27,839		52		(59		)	27,832
U.S. government securities	292,615		161		(509		)	292,267
Non-U.S. government securities	31,263		4		(16		)	31,251
Total	$	541,684	$	329	$	(1,022	)	$	540,991

Long-term debt securities:
U.S. agency securities	$	114,444	$	194	$	(78	)	$	114,560
Corporate bonds	159,783		419		(950		)	159,252
Municipal securities	28,453		167		(26		)	28,594
U.S. government securities	153,743		553		(172		)	154,124
Non-U.S. government securities	8,122		28		—			8,150
Total	$	464,545	$	1,361	$	(1,226	)	$	464,680

Contractual Maturities of Short-Term and Long-Term Investments

The contractual maturities of the Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	565,719	$	566,539
Due in one to five years	478,866		481,063
Total	$	1,044,585	$	1,047,602

The contractual maturities of the Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	101,888	$	101,924
Due in one to five years	—		—
Total	$	101,888	$	101,924

CUSTOMER FUNDS (Tables)

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Assets Underlying Customer Funds

The following table presents the assets underlying customer funds (in thousands):



	March 31, 2019		December 31, 2018
Cash	$	278,967	$	158,697
Cash Equivalents:
Money market funds	862		18
U.S. agency securities	14,539		39,991
U.S. government securities	49,125		35,349
Short-term debt securities:
U.S. agency securities	22,286		27,291
U.S. government securities	79,638		72,671
Total	$	445,417	$	334,017

Investments within Customer Funds

The Company's investments within customer funds as of December 31, 2018 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	27,293		2		(4		)	27,291
U.S. government securities	72,662		12		(3		)	72,671
Total	$	99,955	$	14	$	(7	)	$	99,962

The Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term debt securities:
U.S. agency securities	$	22,281	$	7	$	(2	)	$	22,286
U.S. government securities	79,607		33		(2		)	79,638
Total	$	101,888	$	40	$	(4	)	$	101,924

Contractual Maturities of Short-Term and Long-Term Investments within Customer Funds

The contractual maturities of the Company's short-term and long-term investments as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	565,719	$	566,539
Due in one to five years	478,866		481,063
Total	$	1,044,585	$	1,047,602

The contractual maturities of the Company's investments within customer funds as of March 31, 2019 are as follows (in thousands):



	Amortized Cost		Fair Value
Due in one year or less	$	101,888	$	101,924
Due in one to five years	—		—
Total	$	101,888	$	101,924

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The estimated fair value and carrying value of the convertible senior notes were as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Value		Fair Value (Level 2)		Carrying Value		Fair Value (Level 2)
2023 Notes	$	725,900	$	1,042,987	$	718,522	$	901,468
2022 Notes	183,402		690,691		181,173		515,693
Total	$	909,302	$	1,733,678	$	899,695	$	1,417,161

The estimated fair value and carrying value of loans held for sale is as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Value		Fair Value (Level 3)		Carrying Value		Fair Value (Level 3)
Loans held for sale	$	123,471	$	128,358	$	89,974	$	93,064
Total	$	123,471	$	128,358	$	89,974	$	93,064

The Company’s financial assets and liabilities that are measured at fair value on a recurring basis are classified as follows (in thousands):



	March 31, 2019						December 31, 2018
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Cash Equivalents:
Money market funds	$	164,457	$	—	$	—	$	218,109	$	—	$	—
U.S. agency securities	—		19,712		—		—		46,423		—
Commercial paper	—		2,997		—		—		—		—
U.S. government securities	102,199		—		—		—		—		—
Municipal securities	—		—		—		86,239		—		—
Non-U.S. government securities	—		—		—		—		23,981		—
Customer funds:
Money market funds	862		—		—		18		—		—
U.S. agency securities	—		36,825		—		—		67,282		—
U.S. government securities	128,763		—		—		108,020		—		—
Short-term debt securities:
U.S. agency securities	—		113,635		—		—		80,122		—
Corporate bonds	—		85,096		—		—		109,519		—
Municipal securities	—		20,273		—		—		27,832		—
U.S. government securities	318,110		—		—		292,267		—		—
Non-U.S. government securities	—		29,425		—		—		31,251		—
Long-term debt securities:
U.S. agency securities	—		86,264		—		—		114,560		—
Corporate bonds	—		187,896		—		—		159,252		—
Municipal securities	—		23,393		—		—		28,594		—
U.S. government securities	175,048		—		—		154,124		—		—
Non-U.S. government securities	—		8,462		—		—		8,150		—
Other:
Equity investment	31,255		—		—		45,342		—		—
Total	$	920,694	$	613,978	$	—	$	904,119	$	696,966	$	—

PROPERTY AND EQUIPMENT, NET (Tables)

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

The following is a summary of property and equipment, less accumulated depreciation and amortization (in thousands):



	March 31, 2019			December 31, 2018
Leasehold improvements	$	105,244		$	107,611
Computer equipment	82,056			80,093
Capitalized software	64,233			58,908
Office furniture and equipment	20,713			20,699
	272,246			267,311
Less: Accumulated depreciation and amortization	(138,540		)	(124,909		)
Property and equipment, net	$	133,706		$	142,402

ACQUISITIONS (Tables)

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

Schedule of Assets Acquired and Liabilities Assumed

The table below summarizes the consideration paid for Weebly and the preliminary assessment of the fair value of the assets acquired and liabilities assumed at the closing date (in thousands, except share data).



Consideration:
Cash	$	132,432
Stock (2,418,271 shares of Class A common stock)	140,107
	$	272,539
Recognized amounts of identifiable assets acquired and liabilities assumed:
Current assets (inclusive of cash acquired of $25,758)	$	46,814
Intangible customer assets	42,700
Intangible technology assets	14,900
Intangible trade name	11,300
Intangible other assets	961
Total liabilities assumed (including deferred revenue of $22,800)	(37,592		)
Total identifiable net assets acquired	79,083
Goodwill	193,456
Total	$	272,539

GOODWILL (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The change in carrying value of goodwill in the period was as follows (in thousands):



Balance at December 31, 2018	$	261,705
Acquisitions	7,437
Other adjustments	(2,130		)
Balance at March 31, 2019	$	267,012

ACQUIRED INTANGIBLE ASSETS (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite Lived Intangible Assets

The changes to the carrying value of intangible assets were as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Acquired intangible assets, net, beginning of the period	$	77,102	$	14,334
Acquisitions	6,082		1,679
Amortization expense	3,487		1,875
Acquired intangible assets, net, end of the period	$	79,697	$	14,138

The following table presents the detail of acquired intangible assets as of the periods presented (in thousands):



	Balance at March 31, 2019
	Cost		Accumulated Amortization			Net
Technology assets	49,007		(29,796		)	19,211
Customer assets	57,109		(9,361		)	47,748
Trade name	11,300		(2,354		)	8,946
Other	5,299		(1,507		)	3,792
Total	$	122,715	$	(43,018	)	$	79,697



	Balance at December 31, 2018
	Cost		Accumulated Amortization			Net
Technology assets	45,978		(28,420		)	17,558
Customer assets	57,109		(8,068		)	49,041
Trade name	11,300		(1,648		)	9,652
Other	2,246		(1,395		)	851
Total	$	116,633	$	(39,531	)	$	77,102

Schedule of Future Amortization Expense of Intangible Assets

The total estimated future amortization expense of these intangible assets as of March 31, 2019 is as follows (in thousands):



2019 (remaining 9 months)	$	11,185
2020	12,611
2021	11,413
2022	9,484
2023	7,953
Thereafter	27,051
Total	$	79,697

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) (Tables)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Other Current Assets

The following table presents the detail of other current assets (in thousands):



	March 31, 2019		December 31, 2018
Inventory, net	$	26,679	$	28,627
Processing costs receivable	59,470		46,102
Prepaid expenses	23,526		21,782
Accounts receivable, net	28,665		22,393
Other	46,781		46,062
Total	$	185,121	$	164,966

Schedule of Accrued Expenses

The following table presents the detail of accrued expenses (in thousands):



	March 31, 2019		December 31, 2018
Accrued facilities expenses	$	5,853	$	13,040
Accrued payroll	18,282		9,612
Accrued professional fees	6,173		5,232
Accrued advertising and other marketing	15,940		12,201
Processing costs payable	13,190		12,683
Accrued non income tax liabilities	6,568		9,503
Accrued hardware costs	5,413		5,125
Other accrued liabilities	16,393		14,958
Total	$	87,812	$	82,354

Schedule of Other Current Liabilities

The following table presents the detail of other current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Accounts payable	$	24,635	$	36,416
Deferred revenue, current	36,343		31,474
Square Capital payable (i)	18,459		6,092
Square Payroll payable (ii)	12,338		7,534
Other	16,869		17,637
Total	$	108,644	$	99,153

⁽ⁱ⁾Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties.

⁽ⁱⁱ⁾Square Payroll payable represents amounts received from Square Payroll product customers that will be utilized to settle the customers' employee payroll and related obligations.

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) (Tables)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Other Non-Current Assets

The following table presents the detail of other non-current assets (in thousands):



	March 31, 2019		December 31, 2018
Equity investment (i)	$	31,255	$	45,342
Other	16,947		13,051
Total	$	48,202	$	58,393

⁽ⁱ⁾ This balance represents the Company's investment in Class B common shares of Eventbrite, Inc. (Eventbrite). The investment is carried at fair value with changes in fair value being recorded on the consolidated statement of operations. During the three months ended March 31, 2019, the Company recorded a loss of $14.1 million to other expense (income), net on the consolidated statements of operations arising from revaluation of this investment.

Schedule of Other Non-Current Liabilities

The following table presents the detail of other non-current liabilities (in thousands):



	March 31, 2019		December 31, 2018
Statutory liabilities (ii)	$	57,839	$	54,748
Deferred rent, non-current (iii)	—		23,003
Deferred revenue, non-current	5,817		4,977
Other	11,929		10,558
Total	$	75,585	$	93,286

⁽ⁱⁱ⁾Statutory liabilities represent loss contingencies that may arise from the Company's interpretation and application of certain guidelines and rules issued by various federal, state, local, and foreign regulatory authorities.

⁽ⁱⁱⁱ⁾The adoption of ASC 842 on January 1, 2019, resulted in the reclassification of deferred rent as an offset to right-of-use lease assets.

INDEBTEDNESS (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Convertible Notes

The net carrying amount of the Notes were as follows (in thousands):



	Principal outstanding		Unamortized debt discount			Unamortized debt issuance costs			Net carrying value
March 31, 2019
2023 Notes	$	862,500	$	(131,767	)	$	(4,833	)	$	725,900
2022 Notes	211,728		(25,563		)	(2,763		)	183,402
Total	$	1,074,228	$	(157,330	)	$	(7,596	)	$	909,302

December 31, 2018
2023 Notes	$	862,500	$	(138,924	)	$	(5,054	)	$	718,522
2022 Notes	211,728		(27,569		)	(2,986		)	181,173
	$	1,074,228	$	(166,493	)	$	(8,040	)	$	899,695

The net carrying amount of the equity component of the 2023 Notes and 2022 Notes were as follows (in thousands):



	Amount allocated to conversion option		Less: allocated issuance costs			Equity component, net
March 31, 2019 and December 31, 2018
2023 Notes	$	155,250	$	(1,231	)	$	154,019
2022 Notes	41,481		(1,108		)	40,373
Total	196,731		(2,339		)	194,392

Interest Expense on Convertible Notes

The Company recognized interest expense on the Notes as follows (in thousands, except for percentages):



	Three Months Ended March 31,
	2019		2018
Contractual interest expense	$	1,277	$	413
Amortization of debt discount and issuance costs	9,608		4,393
Total	$	10,885	$	4,806

ACCRUED TRANSACTION LOSSES (Tables)

3 Months Ended

Mar. 31, 2019

Product Warranties Disclosures [Abstract]

Schedule of Reserve for Transaction Losses

The following table summarizes the activities of the Company’s reserve for transaction losses (in thousands):



	Three Months Ended March 31,
	2019			2018
Accrued transaction losses, beginning of the period	$	33,682		$	26,893
Provision for transaction losses	19,808			14,258
Charge-offs to accrued transaction losses	(17,443		)	(12,842		)
Accrued transaction losses, end of the period	$	36,047		$	28,309

- Definition

Tabular disclosure of the loss contingencies that were reported in the period or disclosed as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14472-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14453-108349

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+ Details

STOCKHOLDERS' EQUITY (Tables)

3 Months Ended

Mar. 31, 2019

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

Summary of Stock Option Activity

A summary of stock option activity for the three months ended March 31, 2019 is as follows (in thousands, except share and per share data):



	Number of Stock Options Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance at December 31, 2018	33,152,881		$	9.52	5.45	$	1,543,793
Granted	97,701		73.94
Exercised	(3,588,052	)	7.06
Forfeited	(95,141	)	11.78
Balance at March 31, 2019	29,567,389		$	10.03	5.41	$	1,918,661
Options exercisable as of
March 31, 2019	27,693,334		$	8.88	5.23	$	1,828,856

Schedule of Restricted Stock Awards and Restricted Stock Units Activity

Activity related to RSAs and RSUs during the three months ended March 31, 2019 is set forth below:



	Number of shares		Weighted Average Grant Date Fair Value
Unvested as of December 31, 2018	17,934,728		$	31.34
Granted	552,596		69.20
Vested	(1,880,545	)	24.12
Forfeited	(559,047	)	29.35
Unvested as of March 31, 2019	16,047,732		$	33.56

Schedule of Fair Value Assumptions for Options

The fair value of stock options granted was estimated using the following weighted-average assumptions:



	Three Months Ended March 31,
	2019
Dividend yield	—	%
Risk-free interest rate	2.59	%
Expected volatility	38.55	%
Expected term (years)	6.08

Summary of the Effect of Share-Based Compensation on the Condensed Consolidated Statements of Operations

The following table summarizes the effects of share-based compensation on the Company's condensed consolidated statements of operations (in thousands):



	Three Months Ended March 31,
	2019		2018
Cost of revenue	$	21	$	31
Product development	42,649		30,482
Sales and marketing	6,202		4,961
General and administrative	12,216		11,350
Total	$	61,088	$	46,824

NET LOSS PER SHARE (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Share

The following table presents the calculation of basic and diluted net loss per share (in thousands, except per share data):



	Three Months Ended March 31,
	2019			2018
Net loss	$	(38,151	)	$	(23,986	)
Basic shares:
Weighted-average common shares outstanding	419,860			397,246
Weighted-average unvested shares	(571		)	(1,298		)
Weighted-average shares used to compute basic net loss per share	419,289			395,948
Diluted shares:
Weighted-average shares used to compute diluted net loss per share	419,289			395,948
Net loss per share:
Basic	$	(0.09	)	$	(0.06	)
Diluted	$	(0.09	)	$	(0.06	)

Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following potential common shares were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):



	Three Months Ended March 31,
	2019	2018
Stock options and restricted stock units	47,833	66,382
Common stock warrants	30,252	19,173
Convertible senior notes	20,305	—
Unvested shares	571	1,298
Employee stock purchase plan	212	264
Total anti-dilutive securities	99,173	87,117

COMMITMENTS AND CONTINGENCIES (Tables)

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Expense Components and Other Information Related to Leases

The components of lease expense were as follows (in thousands):



	Three Months Ended March 31,
	2019
Operating lease costs	$	6,690

Finance lease costs
Amortization of right-of-use assets	1,293
Interest on lease liabilities	—
Total finance lease costs	$	1,293

For the periods presented, costs associated with short-term leases were not material.

Other information related to leases was as follows:



	Three Months Ended March 31,
	2019
Weighted Average Remaining Lease Term:
Operating leases	4.80 years
Finance leases	1.75 years
Weighted Average Discount Rate:
Operating leases	4	%
Finance leases	—	%

Future Minimum Lease Payments under Non-Cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases (with initial lease terms in excess of one year) and future minimum finance lease payments as of March 31, 2019 are as follows (in thousands):



	Finance		Operating
Year:
2019 (remaining 9 months)	$	3,745	$	20,112
2020	2,446		39,182
2021	—		53,426
2022	—		54,229
2023	—		47,952
Thereafter	—		211,056
Total	$	6,191	$	425,957
Less amount representing interest	—		14,323
Less leases executed but not yet commenced	—		276,037
Total	$	6,191	$	135,597

Future Minimum Finance Lease Payments

Future minimum lease payments under non-cancelable operating leases (with initial lease terms in excess of one year) and future minimum finance lease payments as of March 31, 2019 are as follows (in thousands):



	Finance		Operating
Year:
2019 (remaining 9 months)	$	3,745	$	20,112
2020	2,446		39,182
2021	—		53,426
2022	—		54,229
2023	—		47,952
Thereafter	—		211,056
Total	$	6,191	$	425,957
Less amount representing interest	—		14,323
Less leases executed but not yet commenced	—		276,037
Total	$	6,191	$	135,597

SEGMENT AND GEOGRAPHICAL INFORMATION (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Revenue by Geographic Area

Revenue by geography is based on the billing addresses of the sellers or customers. The following table sets forth revenue by geographic area (in thousands):



	Three Months Ended March 31,
	2019		2018
Revenue
United States	$	914,656	$	640,173
International	44,703		28,430
Total net revenue	$	959,359	$	668,603

Long-lived Assets by Geographic Area

The following table sets forth long-lived assets by geographic area (in thousands):



	March 31, 2019		December 31, 2018
Long-lived assets
United States	$	579,397	$	471,970
International	12,974		9,239
Total long-lived assets	$	592,371	$	481,209

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)

3 Months Ended

Mar. 31, 2019

Supplemental Cash Flow Elements [Abstract]

Schedule of Cash Flow, Supplemental Disclosures

The supplemental disclosures of cash flow information consist of the following (in thousands):



	Three Months Ended March 31,
	2019		2018
Supplemental Cash Flow Data:
Cash paid for interest	$	538	$	966
Cash paid for income taxes	1,342		658
Right-of-use assets obtained in exchange for operating lease obligations	19,918		—
Supplemental disclosures of non-cash investing and financing activities:
Change in purchases of property and equipment in accounts payable and accrued expenses	13,114		(3,813		)
Unpaid business combination purchase price	6,447		1,151
Recovery of common stock in connection with indemnification settlement agreement	789		—

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) customer third_party_processor	Mar. 31, 2018 customer	Dec. 31, 2018 USD ($) third_party_processor
Concentration Risk [Line Items]
Operating lease right-of-use assets	$ 111,956
Operating lease liability	135,597
Derecognition of build-to-suit lease asset	0		$ (149,000)
Derecognition of build-to-suit lease liability	$ 0		$ (149,000)
Total Net Revenue \| Customer Concentration Risk
Concentration Risk [Line Items]
Number of customers accoutning for greater than 10% of total net revenue \| customer	0	0
Settlements Receivable \| Credit Concentration Risk
Concentration Risk [Line Items]
Number of third party processors \| third_party_processor	3		3
Settlements Receivable \| Credit Concentration Risk \| Third Party Processor One
Concentration Risk [Line Items]
Concentration risk, settlements receivable	55.00%		45.00%
Settlements Receivable \| Credit Concentration Risk \| Third Party Processor Two
Concentration Risk [Line Items]
Concentration risk, settlements receivable	35.00%		33.00%
Settlements Receivable \| Credit Concentration Risk \| Third Party Processor Three
Concentration Risk [Line Items]
Concentration risk, settlements receivable	6.00%		9.00%
Minimum
Concentration Risk [Line Items]
Settlements receivable period	1 day
Maximum
Concentration Risk [Line Items]
Settlements receivable period	2 days
Accounting Standards Update 2016-02
Concentration Risk [Line Items]
Operating lease right-of-use assets	$ 112,000
Operating lease liability	135,600
Derecognition of build-to-suit lease asset			$ 149,000
Derecognition of build-to-suit lease liability	$ 149,000

REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Transaction-based revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 656,762	$ 523,037
Subscription and services-based revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	190,307	77,215
Revenues from other sources	28,550	19,839
Hardware revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18,212	14,417
Bitcoin revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 65,528	$ 34,095

REVENUE - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, beginning of the period	$ 36,451	$ 1,590
Deferred revenue, end of the period	42,160	3,353
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	12,306	298
Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, beginning of the period	36,451	5,893
Accounting Standards Update 2014-09 \| Effect of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, beginning of the period	$ 0	$ (4,303)

INVESTMENTS - Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,044,585
Fair Value	1,047,602
Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	565,719	$ 541,684
Gross Unrealized Gains	949	329
Gross Unrealized Losses	(129)	(1,022)
Fair Value	566,539	540,991
Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	478,866	464,545
Gross Unrealized Gains	2,246	1,361
Gross Unrealized Losses	(49)	(1,226)
Fair Value	481,063	464,680
U.S. agency securities \| Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	113,508	80,160
Gross Unrealized Gains	142	32
Gross Unrealized Losses	(15)	(70)
Fair Value	113,635	80,122
U.S. agency securities \| Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	85,993	114,444
Gross Unrealized Gains	299	194
Gross Unrealized Losses	(28)	(78)
Fair Value	86,264	114,560
Corporate bonds \| Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	84,832	109,807
Gross Unrealized Gains	289	80
Gross Unrealized Losses	(25)	(368)
Fair Value	85,096	109,519
Corporate bonds \| Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	186,674	159,783
Gross Unrealized Gains	1,233	419
Gross Unrealized Losses	(11)	(950)
Fair Value	187,896	159,252
Municipal securities \| Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,237	27,839
Gross Unrealized Gains	54	52
Gross Unrealized Losses	(18)	(59)
Fair Value	20,273	27,832
Municipal securities \| Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	23,267	28,453
Gross Unrealized Gains	128	167
Gross Unrealized Losses	(2)	(26)
Fair Value	23,393	28,594
U.S. government securities \| Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	317,787	292,615
Gross Unrealized Gains	394	161
Gross Unrealized Losses	(71)	(509)
Fair Value	318,110	292,267
U.S. government securities \| Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	174,515	153,743
Gross Unrealized Gains	541	553
Gross Unrealized Losses	(8)	(172)
Fair Value	175,048	154,124
Non-U.S. government securities \| Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29,355	31,263
Gross Unrealized Gains	70	4
Gross Unrealized Losses	0	(16)
Fair Value	29,425	31,251
Non-U.S. government securities \| Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,417	8,122
Gross Unrealized Gains	45	28
Gross Unrealized Losses	0	0
Fair Value	$ 8,462	$ 8,150

INVESTMENTS - Contractual Maturities of Short-Term and Long-Term Investments (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Amortized Cost
Due in one year or less	$ 565,719
Due in one to five years	478,866
Amortized Cost	1,044,585
Fair Value
Due in one year or less	566,539
Due in one to five years	481,063
Fair Value	$ 1,047,602

CUSTOMER FUNDS - Assets Underlying Customer Funds (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Customer funds	$ 445,417	$ 334,017
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Customer funds	22,286	27,291
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Customer funds	79,638	72,671
Cash
Debt Securities, Available-for-sale [Line Items]
Customer funds	278,967	158,697
Cash Equivalents \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Customer funds	862	18
Cash Equivalents \| U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Customer funds	14,539	39,991
Cash Equivalents \| U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Customer funds	$ 49,125	$ 35,349

CUSTOMER FUNDS - Investments within Customer Funds (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,044,585
Fair Value	1,047,602
Customer funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	101,888	$ 99,955
Gross Unrealized Gains	40	14
Gross Unrealized Losses	(4)	(7)
Fair Value	101,924	99,962
Customer funds \| U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22,281	27,293
Gross Unrealized Gains	7	2
Gross Unrealized Losses	(2)	(4)
Fair Value	22,286	27,291
Customer funds \| U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	79,607	72,662
Gross Unrealized Gains	33	12
Gross Unrealized Losses	(2)	(3)
Fair Value	$ 79,638	$ 72,671

CUSTOMER FUNDS - Contractual Maturities of Short-Term and Long-Term Investments within Customer Funds (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 565,719
Due in one to five years	478,866
Amortized Cost	1,044,585
Fair Value
Due in one year or less	566,539
Due in one to five years	481,063
Fair Value	1,047,602
Customer funds
Amortized Cost
Due in one year or less	101,888
Due in one to five years	0
Amortized Cost	101,888	$ 99,955
Fair Value
Due in one year or less	101,924
Due in one to five years	0
Fair Value	$ 101,924	$ 99,962

FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer funds	$ 445,417	$ 334,017
Short-term debt securities	566,539	540,991
Long-term debt securities	481,063	464,680
Equity investment	31,255	45,342
U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer funds	22,286	27,291
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer funds	79,638	72,671
Fair Value, Measurements, Recurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment	31,255	45,342
Total	920,694	904,119
Fair Value, Measurements, Recurring \| Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	164,457	218,109
Customer funds	862	18
Fair Value, Measurements, Recurring \| Level 1 \| U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	102,199	0
Customer funds	128,763	108,020
Short-term debt securities	318,110	292,267
Long-term debt securities	175,048	154,124
Fair Value, Measurements, Recurring \| Level 1 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	86,239
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment	0	0
Total	613,978	696,966
Fair Value, Measurements, Recurring \| Level 2 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Fair Value, Measurements, Recurring \| Level 2 \| U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	19,712	46,423
Customer funds	36,825	67,282
Short-term debt securities	113,635	80,122
Long-term debt securities	86,264	114,560
Fair Value, Measurements, Recurring \| Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,997	0
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term debt securities	85,096	109,519
Long-term debt securities	187,896	159,252
Fair Value, Measurements, Recurring \| Level 2 \| Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term debt securities	20,273	27,832
Long-term debt securities	23,393	28,594
Fair Value, Measurements, Recurring \| Level 2 \| Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	23,981
Short-term debt securities	29,425	31,251
Long-term debt securities	8,462	8,150
Fair Value, Measurements, Recurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment	0	0
Total	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Customer funds	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term debt securities	0	0
Long-term debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term debt securities	0	0
Long-term debt securities	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Convertible Senior Notes (Details) - Level 2 - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 909,302	$ 899,695
Fair Value (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	1,733,678	1,417,161
2023 Notes \| Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	725,900	718,522
2023 Notes \| Fair Value (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	1,042,987	901,468
2022 Notes \| Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	183,402	181,173
2022 Notes \| Fair Value (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 690,691	$ 515,693

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Loans Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Carrying Value \| Level 3 \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	$ 123,471		$ 89,974
Fair Value (Level 3) \| Level 3 \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	128,358		$ 93,064
Loans Receivable Held-For-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Excess amortized cost over fair value of loans	$ 6,700	$ 2,500

PROPERTY AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 272,246		$ 267,311
Less: Accumulated depreciation and amortization	(138,540)		(124,909)
Property and equipment, net	133,706		142,402
Depreciation and amortization expense	15,500	$ 8,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	105,244		107,611
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	82,056		80,093
Capitalized software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	64,233		58,908
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 20,713		$ 20,699

ACQUISITIONS - Narrative (Details) - Weebly, Inc. - USD ($) $ in Thousands		3 Months Ended
	May 31, 2018	Mar. 31, 2019
Business Acquisition [Line Items]
Percent of outstanding shares acquired	100.00%
Cash consideration	$ 132,432
Equity consideration (in shares)	2,418,271
Equity consideration fair value	$ 140,107
Payment to settle outstanding vested and unvested employee options	17,700
Post-combination compensation expense	$ 2,600
Goodwill adjustment to purchase price allocation		$ 3,900
Tax liabilities adjustment to purchase price allocation		4,800
Cash withheld for indemnification		$ 19,100
Shares withheld for indemnification (in shares)		357,780

ACQUISITIONS - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	May 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Recognized amounts of identifiable assets acquired and liabilities assumed:
Goodwill		$ 267,012	$ 261,705
Weebly, Inc.
Consideration:
Cash	$ 132,432
Stock (2,418,271 shares of Class A common stock)	$ 140,107
Stock (in shares)	2,418,271
Total consideration	$ 272,539
Recognized amounts of identifiable assets acquired and liabilities assumed:
Current assets (inclusive of cash acquired of $25,758)	46,814
Cash acquired	25,758
Total liabilities assumed (including deferred revenue of $22,800)	(37,592)
Deferred revenue	22,800
Total identifiable net assets acquired	79,083
Goodwill	193,456
Total	272,539
Weebly, Inc. \| Intangible customer assets
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangible assets	42,700
Weebly, Inc. \| Intangible technology assets
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangible assets	14,900
Weebly, Inc. \| Intangible trade name
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangible assets	11,300
Weebly, Inc. \| Intangible other assets
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangible assets	$ 961

GOODWILL (Details) - USD ($)	3 Months Ended
GOODWILL (Details) - USD ($)	Mar. 31, 2019	Mar. 31, 2018
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 261,705,000
Acquisitions	7,437,000
Other adjustments	(2,130,000)
Goodwill, ending balance	267,012,000
Goodwill, impairment charges	$ 0	$ 0

ACQUIRED INTANGIBLE ASSETS - Narrative (Details)	3 Months Ended
ACQUIRED INTANGIBLE ASSETS - Narrative (Details)	Mar. 31, 2019
Technology assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	5 years
Customer assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	11 years
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	4 years

ACQUIRED INTANGIBLE ASSETS - Schedule of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	$ 122,715	$ 116,633
Accumulated Amortization	(43,018)	(39,531)
Net	79,697	77,102	$ 14,138	$ 14,334
Technology assets
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	49,007	45,978
Accumulated Amortization	(29,796)	(28,420)
Net	19,211	17,558
Customer assets
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	57,109	57,109
Accumulated Amortization	(9,361)	(8,068)
Net	47,748	49,041
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	11,300	11,300
Accumulated Amortization	(2,354)	(1,648)
Net	8,946	9,652
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	5,299	2,246
Accumulated Amortization	(1,507)	(1,395)
Net	$ 3,792	$ 851

ACQUIRED INTANGIBLE ASSETS - Change in Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Acquired intangible assets, net, beginning of the period	$ 77,102	$ 14,334
Acquisitions	6,082	1,679
Amortization expense	3,487	1,875
Acquired intangible assets, net, end of the period	$ 79,697	$ 14,138

ACQUIRED INTANGIBLE ASSETS - Future Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2019 (remaining 9 months)	$ 11,185
2020	12,611
2021	11,413
2022	9,484
2023	7,953
Thereafter	27,051
Net	$ 79,697	$ 77,102	$ 14,138	$ 14,334

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Inventory, net	$ 26,679	$ 28,627
Processing costs receivable	59,470	46,102
Prepaid expenses	23,526	21,782
Accounts receivable, net	28,665	22,393
Other	46,781	46,062
Total	$ 185,121	$ 164,966

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued facilities expenses	$ 5,853	$ 13,040
Accrued payroll	18,282	9,612
Accrued professional fees	6,173	5,232
Accrued advertising and other marketing	15,940	12,201
Processing costs payable	13,190	12,683
Accrued non income tax liabilities	6,568	9,503
Accrued hardware costs	5,413	5,125
Other accrued liabilities	16,393	14,958
Total	$ 87,812	$ 82,354

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable	$ 24,635	$ 36,416
Deferred revenue, current	36,343	31,474
Square Capital payable	18,459	6,092
Square Payroll payable	12,338	7,534
Other	16,869	17,637
Total	$ 108,644	$ 99,153

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Equity investment	$ 31,255		$ 45,342
Other	16,947		13,051
Total	48,202		$ 58,393
Loss on equity investment	$ 14,087	$ 0

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Statutory liabilities	$ 57,839	$ 54,748
Deferred rent, non-current	0	23,003
Deferred revenue, non-current	5,817	4,977
Other	11,929	10,558
Total	$ 75,585	$ 93,286

INDEBTEDNESS - Revolving Credit Facility Narrative (Details) - Revolving Credit Facility - Line of Credit - USD ($)	1 Months Ended	3 Months Ended
	Nov. 30, 2015	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 375,000,000
Administrative agent fee	$ 100,000
Unused commitment fee percentage	0.15%
Remaining borrowing capacity		$ 375,000,000
Unused commitment fees		$ 100,000	$ 100,000
Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
One Month LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
One Month LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%

INDEBTEDNESS - Convertible Senior Notes Narrative (Details) $ / shares in Units, shares in Millions				12 Months Ended
	Dec. 31, 2018 USD ($)	May 25, 2018 USD ($) day $ / shares	Mar. 06, 2017 USD ($) day $ / shares	Dec. 31, 2018 USD ($) shares	Mar. 31, 2019 USD ($)
Debt Instrument [Line Items]
Principal payment on conversion of senior notes				$ 219,400,000
Convertible Debt
Debt Instrument [Line Items]
Conversion price (in USD per share) \| $ / shares		$ 77.85	$ 22.95
Carrying amount of equity component	$ 194,392,000			194,392,000	$ 194,392,000
Issuance costs attributable to the liability component	8,040,000			8,040,000	7,596,000
Convertible Debt \| Convertible Senior Notes due in 2023
Debt Instrument [Line Items]
Aggregate principal amount		$ 862,500,000.00
Over-allotment option as a percentage of a principal amount		15.00%
Over-allotment option		$ 112,500,000.0
Interest rate		0.50%
Conversion rate		0.0128456
Conversion price (in USD per share) \| $ / shares		$ 77.85
Carrying amount of equity component	154,019,000	$ 155,300,000		154,019,000	$ 154,019,000
Effective interest rate of the liability component		4.69%			4.69%
Discounts and commissions payable		$ 6,000,000
Third party offering costs		800,000
Issuance costs attributable to the liability component	5,054,000	$ 5,600,000		5,054,000	$ 4,833,000
Convertible Debt \| Convertible Senior Notes due in 2023 \| Debt Instrument, Conversion Term One
Debt Instrument [Line Items]
Threshold trading days \| day		20
Threshold consecutive trading days \| day		30
Threshold percentage of stock price trigger		130.00%
Convertible Debt \| Convertible Senior Notes due in 2023 \| Debt Instrument Conversion Term Two
Debt Instrument [Line Items]
Threshold trading days \| day		5
Threshold consecutive trading days \| day		5
Threshold percentage of stock price trigger		98.00%
Convertible Debt \| Convertible Senior Notes due in 2022
Debt Instrument [Line Items]
Aggregate principal amount			$ 440,000,000.0
Over-allotment option as a percentage of a principal amount			10.00%
Over-allotment option			$ 40,000,000.0
Interest rate			0.375%
Conversion rate			0.0435749
Conversion price (in USD per share) \| $ / shares			$ 22.95
Carrying amount of equity component	40,373,000		$ 86,200,000	40,373,000	$ 40,373,000
Effective interest rate of the liability component			5.34%		5.34%
Discounts and commissions payable			$ 11,000,000
Third party offering costs			800,000
Issuance costs attributable to the liability component	2,986,000		$ 9,400,000	2,986,000	$ 2,763,000
Notes converted				$ 228,300,000
Shares issued upon conversion \| shares				7.3
Loss on extinguishment of long-term debt	5,000,000
Reduction to additional paid in capital	$ 21,000,000
Convertible Debt \| Convertible Senior Notes due in 2022 \| Debt Instrument, Conversion Term One
Debt Instrument [Line Items]
Threshold trading days \| day			20
Threshold consecutive trading days \| day			30
Threshold percentage of stock price trigger			130.00%
Convertible Debt \| Convertible Senior Notes due in 2022 \| Debt Instrument Conversion Term Two
Debt Instrument [Line Items]
Threshold trading days \| day			5
Threshold consecutive trading days \| day			5
Threshold percentage of stock price trigger			98.00%

INDEBTEDNESS - Components of Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	May 25, 2018	Mar. 06, 2017
Debt Instrument [Line Items]
Principal outstanding	$ 1,074,228	$ 1,074,228
Unamortized debt discount	(157,330)	(166,493)
Unamortized debt issuance costs	(7,596)	(8,040)
Net carrying value	909,302	899,695
Convertible Senior Notes due in 2023
Debt Instrument [Line Items]
Principal outstanding	862,500	862,500
Unamortized debt discount	(131,767)	(138,924)
Unamortized debt issuance costs	(4,833)	(5,054)	$ (5,600)
Net carrying value	725,900	718,522
Convertible Senior Notes due in 2022
Debt Instrument [Line Items]
Principal outstanding	211,728	211,728
Unamortized debt discount	(25,563)	(27,569)
Unamortized debt issuance costs	(2,763)	(2,986)		$ (9,400)
Net carrying value	$ 183,402	$ 181,173

INDEBTEDNESS - Carrying Amount of Equity Component of Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	May 25, 2018	Mar. 06, 2017
Debt Instrument [Line Items]
Amount allocated to conversion option	$ 196,731	$ 196,731
Less: allocated issuance costs	(2,339)	(2,339)
Equity component, net	194,392	194,392
Convertible Senior Notes due in 2023
Debt Instrument [Line Items]
Amount allocated to conversion option	155,250	155,250
Less: allocated issuance costs	(1,231)	(1,231)
Equity component, net	154,019	154,019	$ 155,300
Convertible Senior Notes due in 2022
Debt Instrument [Line Items]
Amount allocated to conversion option	41,481	41,481
Less: allocated issuance costs	(1,108)	(1,108)
Equity component, net	$ 40,373	$ 40,373		$ 86,200

INDEBTEDNESS - Interest Expense on Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	May 25, 2018	Mar. 06, 2017
Debt Instrument [Line Items]
Contractual interest expense	$ 1,277	$ 413
Amortization of debt discount and issuance costs	9,608	4,393
Total	$ 10,885	$ 4,806
Convertible Senior Notes due in 2023
Debt Instrument [Line Items]
Effective interest rate of the liability component	4.69%		4.69%
Convertible Senior Notes due in 2022
Debt Instrument [Line Items]
Effective interest rate of the liability component	5.34%			5.34%

INDEBTEDNESS - Convertible Note Hedge and Warrant Transactions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 25, 2018	Mar. 06, 2017	Mar. 31, 2019	Dec. 31, 2018
Convertible Debt
Debt Instrument [Line Items]
Conversion price of convertible debt (in USD per share)	$ 77.85	$ 22.95
Conversion price of convertible debt after effect of warrants and note hedge (in USD per share)	$ 109.26	$ 31.18
Common Stock Warrant
Debt Instrument [Line Items]
Warrants to purchase aggregate shares of capital stock (in shares)	11.1	19.2
Warrants, weighted average exercise price (in USD per share)	$ 109.26	$ 31.18
Proceeds from issuance of warrants	$ 112.1	$ 57.2
Shares of common stock received due to exercise of note hedges (in shares)			0.3	6.9
Options
Debt Instrument [Line Items]
Warrants to purchase aggregate shares of capital stock (in shares)	11.1	19.2
Convertible note hedge, option to purchase common stock, price (in USD per share)	$ 77.85	$ 22.95
Cost of convertible note hedge	$ 172.6	$ 92.1

ACCRUED TRANSACTION LOSSES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Loss Contingency Accrual
Accrued transaction losses, beginning of the period	$ 33,682
Provision for transaction losses	27,841	$ 18,031
Accrued transaction losses, end of the period	36,047
Transaction Losses
Loss Contingency Accrual
Accrued transaction losses, beginning of the period	33,682	26,893
Provision for transaction losses	19,808	14,258
Charge-offs to accrued transaction losses	(17,443)	(12,842)
Accrued transaction losses, end of the period	$ 36,047	$ 28,309

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
INCOME TAXES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 129	$ 175
Effective tax rate	(0.30%)	(0.70%)

STOCKHOLDERS' EQUITY - Common Stock and Warrants Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	May 25, 2018	Mar. 06, 2017	Mar. 31, 2019	Dec. 31, 2018
Common Stock Warrant
Class of Stock [Line Items]
Warrants to purchase aggregate shares of capital stock (in shares)	11,100,000	19,200,000
Warrants, weighted average exercise price (in USD per share)	$ 109.26	$ 31.18
Proceeds from issuance of warrants	$ 112.1	$ 57.2
Number of warrants exercised			0
Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			1,000,000,000	1,000,000,000
Common stock, par value (in USD per share)			$ 0.0000001	$ 0.0000001
Common stock, shares outstanding (in shares)			334,650,231	323,546,864
Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			500,000,000	500,000,000
Common stock, par value (in USD per share)			$ 0.0000001	$ 0.0000001
Common stock, shares outstanding (in shares)			86,973,715	93,501,142

STOCKHOLDERS' EQUITY - Stock Plans and Share Based Compensation Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) plan shares	Mar. 31, 2018 USD ($) shares	Nov. 17, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share based compensation plans \| plan	2
Granted (in shares)	97,701	0
Employee stock purchase plan, compensation expense \| $	$ 61,088	$ 46,824
Capitalized share-based compensation expense \| $	1,700	1,500
Unrecognized compensation cost, options \| $	527,000
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, compensation expense \| $	$ 4,300	$ 2,300
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition	2 years 7 months 28 days
2009 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	0
2009 Stock Option Plan \| Stock options, RSAs, and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments outstanding (in shares)	24,792,142
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	86,449,187
Shares reserved for future issuance (in shares)			30,000,000
Shares reserved for future issuance, percentage of annual increase	5.00%
2015 Equity Incentive Plan \| Stock options, RSAs, and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments outstanding (in shares)	20,822,979
2015 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance, amount of annual increase (in shares)	40,000,000

STOCKHOLDERS' EQUITY - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Mar. 31, 2019
Number of Stock Options Outstanding
Beginning balance (in shares)	33,152,881
Granted (in shares)	97,701	0
Exercised (in shares)	(3,588,052)
Forfeited (in shares)	(95,141)
Ending balance (in shares)	29,567,389		33,152,881
Weighted Average Exercise Price
Beginning balance (in USD per share)	$ 9.52
Granted (in USD per share)	73.94
Exercised (in USD per share)	7.06
Forfeited (in USD per share)	11.78
Ending balance (in USD per share)	$ 9.52		$ 9.52	$ 10.03
Options Exercisable
Options exercisable (in shares)				27,693,334
Options exercisable (in USD per share)				$ 8.88
Additional Disclosures
Weighted average remaining contractual term, options outstanding	5 years 4 months 28 days		5 years 5 months 13 days
Weighted average remaining contractual term, options exercisable	5 years 2 months 23 days
Aggregate intrinsic value, options outstanding			$ 1,543,793	$ 1,918,661
Aggregate intrinsic value, options exercisable				$ 1,828,856

STOCKHOLDERS' EQUITY - Restricted Stock Awards and Restricted Stock Units Activity (Details) - RSAs and RSUs	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Number of shares
Beginning balance (in shares) \| shares	17,934,728
Granted (in shares) \| shares	552,596
Vested (in shares) \| shares	(1,880,545)
Forfeited (in shares) \| shares	(559,047)
Ending balance (in shares) \| shares	16,047,732
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) \| $ / shares	$ 31.34
Granted (in USD per share) \| $ / shares	69.20
Vested (in USD per share) \| $ / shares	24.12
Forfeited (in USD per share) \| $ / shares	29.35
Ending balance (in USD per share) \| $ / shares	$ 33.56

STOCKHOLDERS' EQUITY - Stock Option Fair Value Assumptions (Details) - Stock options	3 Months Ended
	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Risk-free interest rate	2.59%
Expected volatility	38.55%
Expected term (years)	6 years 29 days

STOCKHOLDERS' EQUITY - Effects of Share-Based Compensation on Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 61,088	$ 46,824
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	21	31
Product development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	42,649	30,482
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	6,202	4,961
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 12,216	$ 11,350

NET LOSS PER SHARE - Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (38,151)	$ (23,986)
Basic shares:
Weighted-average common shares outstanding (in shares)	419,860	397,246
Weighted-average unvested shares (in shares)	(571)	(1,298)
Weighted-average shares used to compute basic net loss per share (in shares)	419,289	395,948
Diluted shares:
Weighted-average shares used to compute diluted income (loss) per share (in shares)	419,289	395,948
Net loss per share:
Basic (in USD per share)	$ (0.09)	$ (0.06)
Diluted (in USD per share)	$ (0.09)	$ (0.06)

NET LOSS PER SHARE - Antidilutive Securities Excluded from Computation of Diluted Net Income (Loss) Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	99,173	87,117
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	47,833	66,382
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	30,252	19,173
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	20,305	0
Unvested shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	571	1,298
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net income (loss) per share (in shares)	212	264

COMMITMENTS AND CONTINGENCIES - Operating and Finance Leases Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2018 USD ($) ft² renewal_option	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease renewal term		5 years
Operating lease option to terminate term		1 year
Total lease payments over term		$ 425,957
Minimum
Lessee, Lease, Description [Line Items]
Operating lease term		1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease term		12 years
Equipment
Lessee, Lease, Description [Line Items]
Finance lease, remaining lease term		2 years
Oakland, California \| Building
Lessee, Lease, Description [Line Items]
Operating lease term	12 years
Operating lease renewal term	5 years
Leased area of office space (in sq ft) \| ft²	355,762
Operating lease, number of renewal options \| renewal_option	2
Total lease payments over term	$ 276,000

COMMITMENTS AND CONTINGENCIES - Schedule of Lease Expense Components (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 6,690
Finance lease costs
Amortization of right-of-use assets	1,293
Interest on lease liabilities	0
Total finance lease costs	$ 1,293

COMMITMENTS AND CONTINGENCIES - Other Information Related to Leases (Details)	Mar. 31, 2019
Weighted Average Remaining Lease Term:
Operating leases	4 years 9 months 18 days
Finance leases	1 year 9 months
Weighted Average Discount Rate:
Operating leases	4.00%
Finance leases	0.00%

COMMITMENTS AND CONTINGENCIES - Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases and Finance Leases (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Finance
2019 (remaining 9 months)	$ 3,745
2020	2,446
2021	0
2022	0
2023	0
Thereafter	0
Total	6,191
Less amount representing interest	0
Less leases executed but not yet commenced	0
Total	6,191
Operating
2019 (remaining 9 months)	20,112
2020	39,182
2021	53,426
2022	54,229
2023	47,952
Thereafter	211,056
Total	425,957
Less amount representing interest	14,323
Less leases executed but not yet commenced	276,037
Total	$ 135,597

SEGMENT AND GEOGRAPHICAL INFORMATION - Narrative (Details)	3 Months Ended
	Mar. 31, 2019 segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

SEGMENT AND GEOGRAPHICAL INFORMATION - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 959,359	$ 668,603
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	914,656	640,173
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 44,703	$ 28,430

SEGMENT AND GEOGRAPHICAL INFORMATION - Long-lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 592,371	$ 481,209
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	579,397	471,970
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 12,974	$ 9,239

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Data:
Cash paid for interest	$ 538	$ 966
Cash paid for income taxes	1,342	658
Right-of-use assets obtained in exchange for operating lease obligations	19,918
Supplemental disclosures of non-cash investing and financing activities:
Change in purchases of property and equipment in accounts payable and accrued expenses	13,114	(3,813)
Unpaid business combination purchase price	$ 6,447	$ 1,151

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (4,586,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (4,586,000)