Block (XYZ) 10-Q 2 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Square, Inc.
Entity Central Index Key	1,512,673
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		289,951,143
Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		110,743,787

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 738,586	$ 696,474
Short-term investments	200,048	169,576
Restricted cash	27,688	28,805
Settlements receivable	700,646	620,523
Customer funds	152,661	103,042
Loans held for sale	78,821	73,420
Other current assets	91,933	86,454
Total current assets	1,990,383	1,778,294
Property and equipment, net	98,170	91,496
Goodwill	58,327	58,327
Acquired intangible assets, net	14,138	14,334
Long-term investments	176,672	203,667
Restricted cash	9,802	9,802
Other non-current assets	32,120	31,350
Total assets	2,379,612	2,187,270
Current liabilities:
Accounts payable	19,556	16,763
Customers payable	881,754	733,736
Settlements payable	116,902	114,788
Accrued transaction losses	28,309	26,893
Accrued expenses	57,997	52,280
Other current liabilities	27,214	28,367
Total current liabilities	1,131,732	972,827
Long-term debt (Note 11)	362,965	358,572
Other non-current liabilities	74,935	69,538
Total liabilities	1,569,632	1,400,937
Commitments and contingencies (Note 16)
Stockholders’ equity:
Preferred stock, $0.0000001 par value: 100,000,000 shares authorized at March 31, 2018 and December 31, 2017. None issued and outstanding at March 31, 2018 and December 31, 2017.	0	0
Additional paid-in capital	1,682,581	1,630,386
Accumulated other comprehensive loss	(1,294)	(1,318)
Accumulated deficit	(871,307)	(842,735)
Total stockholders’ equity	809,980	786,333
Total liabilities and stockholders’ equity	2,379,612	2,187,270
Class A
Stockholders’ equity:
Common stock	0	0
Class B
Stockholders’ equity:
Common stock	$ 0	$ 0

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Preferred stock, par value (in USD per share)	$ 0.00	$ 0.00
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)	$ 0.00	$ 0.00
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	287,921,742	280,400,813
Common stock, shares outstanding (in shares)	287,921,742	280,400,813
Class B
Class of Stock [Line Items]
Common stock, par value (in USD per share)	$ 0.00	$ 0.00
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	112,462,337	114,793,262
Common stock, shares outstanding (in shares)	112,462,337	114,793,262

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Hardware revenue	$ 14,417	$ 9,016
Bitcoin revenue	34,095	0
Total net revenue	668,603	461,554
Cost of revenue:
Hardware costs	19,702	12,662
Bitcoin costs	33,872	0
Amortization of acquired technology	1,580	1,807
Total cost of revenue	413,433	288,123
Gross profit	255,170	173,431
Operating expenses:
Product development	105,095	68,582
Sales and marketing	77,266	49,900
General and administrative	75,501	56,935
Transaction, loan and advance losses	18,031	11,891
Amortization of acquired customer assets	269	205
Total operating expenses	276,162	187,513
Operating loss	(20,992)	(14,082)
Interest and other expense, net	2,819	499
Loss before income tax	(23,811)	(14,581)
Provision for income taxes	175	509
Net loss	$ (23,986)	$ (15,090)
Net loss per share:
Basic (in USD per share)	$ (0.06)	$ (0.04)
Diluted (in USD per share)	$ (0.06)	$ (0.04)
Weighted-average shares used to compute net loss per share
Basic (in shares)	395,948	366,737
Diluted (in shares)	395,948	366,737
Transaction-based revenue
Revenue:
Transaction and services-based revenue	$ 523,037	$ 403,478
Cost of revenue:
Transaction and services-based costs	327,911	257,778
Subscription and services-based revenue
Revenue:
Transaction and services-based revenue	97,054	49,060
Cost of revenue:
Transaction and services-based costs	$ 30,368	$ 15,876

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (23,986)	$ (15,090)
Net foreign currency translation adjustments	549	757
Net unrealized gain (loss) on revaluation of intercompany loans	665	(29)
Net unrealized gain (loss) on marketable securities	(1,190)	19
Total comprehensive loss	$ (23,962)	$ (14,343)

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (23,986)	$ (15,090)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	10,160	9,437
Non-cash interest and other expense	4,847	1,534
Share-based compensation	46,824	31,670
Transaction, loan and advance losses	18,031	11,891
Deferred provision (benefit) for income taxes	(654)	99
Changes in operating assets and liabilities:
Settlements receivable	(81,452)	54,586
Customer funds	(49,619)	(13,953)
Purchase of loans held for sale	(344,976)	(252,170)
Sales and principal payments of loans held for sale	337,092	242,431
Other current assets	(13,444)	6,105
Other non-current assets	(1,256)	141
Accounts payable	1,990	(1,459)
Customers payable	147,977	(11,132)
Settlements payable	2,114	(15,378)
Charge-offs to accrued transaction losses	(12,842)	(11,178)
Accrued expenses	2,703	3,930
Other current liabilities	3,165	(368)
Other non-current liabilities	5,379	2,902
Net cash provided by operating activities	52,053	43,998
Cash flows from investing activities:
Purchase of marketable securities	(50,221)	(181,851)
Proceeds from maturities of marketable securities	45,450	15,569
Proceeds from sale of marketable securities	0	3,996
Purchase of property and equipment	(8,083)	(6,508)
Purchase of intangible assets	(1,584)	0
Business acquisitions	(1,055)	(1,600)
Net cash used in investing activities	(15,493)	(170,394)
Cash flows from financing activities:
Proceeds from issuance of convertible senior notes, net	0	428,250
Purchase of convertible senior note hedges	0	(92,136)
Proceeds from issuance of warrants	0	57,244
Payment for termination of Starbucks warrant	0	(54,808)
Principal payments on capital lease obligation	(665)	(247)
Proceeds from the exercise of stock options, net	31,354	39,280
Payments for tax withholding related to vesting of restricted stock units	(27,651)	0
Net cash provided by financing activities	3,038	377,583
Effect of foreign exchange rate on cash and cash equivalents	1,397	1,058
Net increase in cash, cash equivalents and restricted cash	40,995	252,245
Cash, cash equivalents and restricted cash, beginning of period	735,081	488,745
Cash, cash equivalents and restricted cash, end of period	$ 776,076	$ 740,990

DESCRIPTION OF BUSINESS AND SUM

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2018
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, next-day settlement, and chargeback protection. Square’s point-of-sale software and other business services help sellers manage inventory, locations, and employees; access financing; engage customers; and grow sales. Cash App is an easy way for businesses and individuals to send and receive money, store their funds as well as use their funds via a Visa debit card, and recently started offering customers the ability to purchase bitcoin (a 'cryptocurrency' or 'digital currency'). Caviar is a food ordering service for pickup and delivery that helps restaurants reach new customers. Square was founded in 2009 and is headquartered in San Francisco, with offices in the United States, Canada, Japan, Australia, Ireland, and the United Kingdom. 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, 2017 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 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, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 , 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, 2017 . 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 and intangible assets, income and other taxes, and share-based compensation. Concentration of Credit Risk For the three months ended March 31, 2018 and 2017 , 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 46% , 42% , and 7% of settlements receivable as of March 31, 2018 . The same three parties represented approximately 46% , 42% , and 8% of settlements receivable as of December 31, 2017 . 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 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 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. Accounting Policies Except for the adoption of ASC 606, Revenue from Contracts with Customers (ASC 606) , described in Note 2, and the accounting policy on cryptocurrency transactions, described below, there have been no material changes to the Company’s accounting policies during the three months ended March 31, 2018 , as compared to the accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . Cryptocurrency transactions During the fourth quarter of 2017, the Company started offering its Cash App customers the ability to purchase bitcoin, a cryptocurrency denominated asset, from the Company. The Company purchases bitcoin from public cryptocurrency exchanges or from customers. Upon purchase, the Company records the cost of bitcoin within other current assets in its consolidated balance sheets. Upon sale, the Company records the total sale amount received from customers as bitcoin revenue and the associated cost as cost of revenue. The carrying value of bitcoin was $0.2 million and $0.3 million as of March 31, 2018 and December 31, 2017 , respectively. The Company assesses the carrying value of bitcoin at each reporting date and records an impairment charge if the cost exceeds the fair value. Losses on bitcoin for the three months ended March 31, 2018 were insignificant. Recent Accounting Pronouncements Recently issued accounting pronouncements not yet adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases , which will require, among other items, lessees to recognize a right of use asset and a related lease liability for most leases on the balance sheet. Qualitative and quantitative disclosures will be enhanced to better understand the amount, timing and uncertainty of cash flows arising from leases. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The new standard should be applied on a modified retrospective basis. The Company does not plan to early adopt this guidance. The Company’s operating leases primarily comprise of office spaces, with the most significant leases relating to corporate headquarters in San Francisco and an office in New York. While the Company continues to evaluate the impact of adopting this guidance on its consolidated financial statements, it does expect to record right to use assets and related lease liabilities on its consolidated balance sheets upon adoption, which will increase total assets and liabilities. In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments , 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, with early adoption permitted. The Company is currently evaluating the impact this new 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 does not expect the adoption of this guidance to have a material the impact on the consolidated financial statements and related disclosures. In March 2017, the FASB issued ASU No. 2017-08, Premium Amortization on Purchased Callable Debt Securities, which amends the amortization period for certain purchased callable debt securities held at a premium, shortening such period to the earliest call date. This standard is effective for annual periods beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The amendments in this guidance should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently evaluating the impact this new guidance may have on the consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . When the Tax Cuts and Jobs Act of 2017 was enacted in December 2017, there was a valuation allowance on the deferred tax assets included within the Company's accumulated other comprehensive income; therefore no tax expense resulted from the change in the federal income tax rate. This guidance allows companies to reclassify such tax effects from accumulated other comprehensive income to retained earnings. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-03, Recognition and Measurement of Financial Assets and Financial Liabilities. This guidance clarifies that an entity that uses the measurement alternative for equity securities without readily determinable fair values can change its measurement approach to fair value. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years beginning after June 15, 2018. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. .

REVENUE

REVENUE	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
REVENUE	REVENUE Adoption of ASC 606, Revenue from Contracts with Customers On January 1, 2018, the Company adopted ASC 606 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with the Company's historic revenue recognition methodology under ASC 605, Revenue Recognition . The Company recorded a net reduction to retained earnings of $4.6 million as of January 1, 2018, due to the cumulative impact of adopting ASC 606, primarily related to impact on revenue and associated cost of revenue from hardware sold through the retail distribution channels and hardware installment sales. The impact to revenue for the three months ended March 31, 2018, was an increase of $1.3 million as a result of applying ASC 606. For the three months ended March 31, 2018, the revenue recognized from contracts with customers was $648.8 million , including $34.1 million from bitcoin sales. Revenue from other sources was $19.8 million . Impairment losses arising from contracts with customers were not significant in the current reporting period. The impact of adoption of ASC 606 on the Company's consolidated statement of operations and balance sheet was as follows (in thousands): Three Months Ended March 31, 2018 As reported Balances without adoption of ASC 606 Effect of change Impact on the Condensed Consolidated Statement of Operations: Subscription and services-based revenue $ 97,054 $ 96,995 $ 59 Hardware revenue 14,417 13,154 1,263 Subscription and services-based costs 30,368 30,368 — Hardware costs 19,702 18,757 945 Impact on the Condensed Consolidated Balance Sheets: Other current assets 91,933 100,573 (8,640 ) Other current liabilities 27,214 31,976 (4,762 ) Other non-current assets 32,120 33,355 (1,235 ) Other non-current liabilities $ 74,935 $ 75,993 $ (1,058 ) Revenue Recognition Revenue is recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The Company's contracts with customers generally do not include multiple performance obligations. The following table presents the Company's revenue from contracts with customers disaggregated by revenue source (in thousands): Three Months Ended March 31, 2018 2017 Revenue from Contracts with Customers: Transaction-based revenue $ 523,037 $ 403,478 Subscription and services-based revenue 77,215 31,321 Hardware revenue $ 14,417 $ 9,016 Bitcoin revenue $ 34,095 $ — Transaction-based revenue The Company charges its sellers a transaction fee for managed payments solutions that is generally calculated as a percentage of the total transaction amount processed. The Company selectively offers custom pricing for certain sellers. The Company collects the transaction amount from the seller's customer's bank, net of acquiring interchange and assessment fees, processing fees and bank settlement fees paid to third-party payment processors and financial institutions. The Company retains its fees and remits the net amount to the sellers. The Company acts as the merchant of record for its sellers and works directly with payment card networks and banks so that its sellers do not need to manage the complex systems, rules, and requirements of the payments industry. The Company satisfies its performance obligations and therefore recognizes the transaction fees as revenue upon authorization of a transaction by the seller's customer's bank. Revenue is recognized net of refunds, which arise from reversals of transactions initiated by sellers. The transaction fees collected from sellers are recognized as revenue on a gross basis as the Company is the principal in the delivery of the managed payments solutions to the sellers. The Company has concluded it is the principal because it controls the services before delivery to the seller, it is primarily responsible for the delivery of the services and it has discretion in setting prices charged to sellers. As the merchant of record, Square is liable for settlement of the transactions the Company processes for its sellers, which is recorded as cost of revenues. Subscription and services-based revenue Subscription and services-based revenue is primarily comprised of revenue the Company generates from Instant Deposit, Caviar and various software as a service (SaaS) products. Instant Deposit is a functionality within the Cash App and the Company's managed payment solutions that enables customers, including individuals and sellers, to instantly deposit funds into their bank accounts. The Company charges a per transaction fee which is recognized as revenue when customers instantly deposit funds to their bank account. Caviar is a food ordering platform that facilitates food delivery services for restaurants. The Company's performance obligation is the delivery of food orders from restaurants to customers. The Company charges fees to restaurants, as sellers, and also charges delivery and service fees to customers. All fees are billed upon delivery of food orders, when the Company considers that it has satisfied its performance obligations. Revenue is also recognized upon delivery of the food orders, net of refunds. Refunds are estimated based on historical experience. SaaS represents software products and solutions that provide customers with access to various technologies for a fee which is recognized ratably as the service is provided. The Company's contracts with customers are generally for a term of one month and renew automatically each month. The Company invoices its customers monthly. The Company considers that it satisfies its performance obligations over time each month as it provides the SaaS services to customers and hence recognizes revenue ratably over the month. Hardware revenue The Company generates revenue through the sale of hardware through e-commerce and through its retail distribution channels. The Company satisfies its performance obligation upon delivery of hardware to its customers who include end user customers, distributors, or retailers. The Company may at times offer concessions to customers and also allows for customer returns, which are accounted for as variable consideration. The Company estimates these amounts based on historical experience, and reduces revenue recognized. The Company invoices end user customers upon delivery of the products to customers and payments from such customers are due upon invoicing. Distributors and retailers have payment terms that range from 30 to 90 days after delivery. The Company offers hardware installment sales to customers with terms ranging from three to twenty four months. The Company allocates a portion of the consideration received from these arrangements to a financing component when it determines that a significant financing component exists. The financing component is subsequently recognized as financing revenue over the terms of the arrangement with the customer. Bitcoin revenue During the fourth quarter of 2017, the Company started offering its Cash App customers the ability to purchase bitcoin, a cryptocurrency denominated asset, from the Company. The Company satisfies its performance obligation and records revenue when bitcoin is transferred to the customer's account. Arrangements with Multiple Performance Obligations Infrequently the Company has offered its hardware customers free managed payment solutions with the purchase of its hardware as part of a marketing promotion. For such arrangements, the Company allocates revenue to each performance obligation based on its relative standalone selling price. We generally determine standalone selling prices based on the prices charged to customers since the Company's products and services are normally sold on a stand alone basis. Deferred revenues Deferred revenue is comprised of unearned revenue related to managed payments services offered in conjunction with hardware sales for which the cash payments from customers are received and due upon the sale of the hardware. The deferred revenue balances were as follows (in thousands): Three Months Ended March 31, 2018 2017 Deferred revenue, beginning of the period $ 5,893 $ 5,407 Deferred revenue, end of the period 3,353 2,965 Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period 298 4,062 Practical Expedients The Company does not recognize a financing component for hardware installment sales that have a term of one year or less.

RESTRICTED CASH

RESTRICTED CASH	3 Months Ended
	Mar. 31, 2018
Cash and Cash Equivalents [Abstract]
RESTRICTED CASH	RESTRICTED CASH As of March 31, 2018 and December 31, 2017 , restricted cash of $27.7 million and $28.8 million , respectively, is related to pledged cash deposited into savings accounts at the financial institutions that process the Company's sellers' payment transactions and as collateral pursuant to an agreement with the originating bank for the Company's loan product. The Company uses the restricted cash to secure letters of credit with the financial institution to provide collateral for cash flow timing differences in the processing of these payments. The Company has recorded this amount as a current asset on the consolidated balance sheets due to the short-term nature of these cash flow timing differences and that there is no minimum time frame during which the cash must remain restricted. Additionally, this balance includes certain amounts held as collateral pursuant to multi-year lease agreements, discussed in the paragraph below, which we expect to become unrestricted within the next year. As of both March 31, 2018 and December 31, 2017 , the remaining restricted cash of $9.8 million , is primarily related to cash deposited into money market funds that is used as collateral pursuant to multi-year lease agreements entered into in 2012 and 2014 (Note 16 ). The Company has recorded this amount as a non-current asset on the consolidated balance sheets as the terms of the related leases extend beyond one year.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The Company measures its cash equivalents and short-term and long-term investments at fair value. The Company classifies its cash equivalents and short-term and long-term 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, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Cash and Cash Equivalents: Money market funds $ 405,813 $ — $ — $ 387,698 $ — $ — Commercial paper — 20,576 — — 24,695 — Short-term securities: U.S. agency securities — 13,583 — — 15,083 — Corporate bonds — 91,672 — — 57,798 — Commercial paper — 14,286 — — 17,428 — Municipal securities — 26,889 — — 23,700 — U.S. government securities 53,618 — 55,567 — — Long-term securities: U.S. agency securities — 20,095 — — 20,169 — Corporate bonds — 71,383 — — 91,413 — Municipal securities — 14,519 — — 26,224 — U.S. government securities 70,675 — — 65,861 — — Total $ 530,106 $ 273,003 $ — $ 509,126 $ 276,510 $ — The carrying amounts of certain financial instruments, including cash equivalents, settlements receivable, customer funds, accounts payable, customers payable, 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, 2018 December 31, 2017 Carrying Value Fair Value (Level 2) Carrying Value Fair Value (Level 2) Convertible senior notes $ 362,965 $ 963,965 $ 358,572 $ 719,356 Total $ 362,965 $ 963,965 $ 358,572 $ 719,356 Loans held for sale are recorded at the lower of amortized cost or fair value determined on an individual loan basis. To determine the fair value the Company utilizes industry-standard valuation modeling, such as discounted cash flow models, taking into account the estimated timing and amounts of periodic repayments. A summary of loans disclosed at fair value on a recurring basis is as follows (in thousands): March 31, 2018 December 31, 2017 Carrying Value Fair Value (Level 3) Carrying Value Fair Value (Level 3) Loans held for sale $ 78,821 $ 81,459 $ 73,420 $ 76,070 Total $ 78,821 $ 81,459 $ 73,420 $ 76,070 The Company recognizes a charge within transaction, loan and advance losses on the consolidated statement of operations whenever the amortized cost of a loan exceeds its fair value, with such charges being reversed for subsequent increases in fair value, but only to the extent that such reversals do not result in the amortized cost of a loan exceeding its fair value. 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 . No charges were recorded for the three months ended March 31, 2017 . 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, 2018 and 2017 , the Company did not have any transfers in or out of Level 1, Level 2, or Level 3 assets or liabilities.

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS The Company determines the appropriate classification of its investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its marketable securities as available-for-sale. The Company's short-term and long-term investments as of March 31, 2018 are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Short-term securities: U.S. agency securities $ 13,581 $ 5 $ (3 ) $ 13,583 Corporate bonds 92,023 11 (362 ) 91,672 Commercial paper 14,286 — — 14,286 Municipal securities 26,950 20 (81 ) 26,889 U.S. government securities 53,615 11 (8 ) 53,618 Total $ 200,455 $ 47 $ (454 ) $ 200,048 Long-term securities: U.S. agency securities $ 20,169 $ 8 $ (82 ) $ 20,095 Corporate bonds 71,741 170 (528 ) 71,383 Municipal securities 14,467 70 (18 ) 14,519 U.S. government securities 71,078 — (403 ) 70,675 Total $ 177,455 $ 248 $ (1,031 ) $ 176,672 The Company's short-term and long-term investments as of December 31, 2017 are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Short-term securities: U.S. agency securities $ 15,122 $ — $ (39 ) $ 15,083 Corporate bonds 57,855 22 (79 ) 57,798 Commercial paper 17,428 — — 17,428 Municipal securities 23,743 8 (51 ) 23,700 U.S. government securities 55,729 1 (163 ) 55,567 Total $ 169,877 $ 31 $ (332 ) $ 169,576 Long-term securities: U.S. agency securities $ 20,288 $ 2 $ (121 ) $ 20,169 Corporate bonds 91,959 25 (571 ) 91,413 Municipal securities 26,371 13 (160 ) 26,224 U.S. government securities 66,362 19 (520 ) 65,861 Total $ 204,980 $ 59 $ (1,372 ) $ 203,667 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 until a recovery of fair value, or 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 contractual maturities of the Company's short-term and long-term investments as of March 31, 2018 are as follows (in thousands): Amortized Cost Fair Value Due in one year or less $ 200,455 $ 200,048 Due in one to five years 177,455 176,672 Total $ 377,910 $ 376,720

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT, NET	PROPERTY AND EQUIPMENT, NET The following is a summary of property and equipment, less accumulated depreciation and amortization (in thousands): March 31, December 31, Leasehold improvements $ 82,425 $ 77,073 Computer equipment 70,818 66,186 Capitalized software 39,268 35,063 Office furniture and equipment 15,152 14,490 207,663 192,812 Less: Accumulated depreciation and amortization (109,493 ) (101,316 ) Property and equipment, net $ 98,170 $ 91,496 Depreciation and amortization expense on property and equipment was $8.3 million for the three months ended March 31, 2018 . Depreciation and amortization expense on property and equipment was $7.3 million for the three months ended March 31, 2017 .

GOODWILL

GOODWILL	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL	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. As of both March 31, 2018 and December 31, 2017 , goodwill was $58.3 million . 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

ACQUIRED INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
ACQUIRED INTANGIBLE ASSETS	ACQUIRED INTANGIBLE ASSETS For the three months ended March 31, 2018 , 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, 2018 Cost Accumulated Amortization Net Patents $ 1,285 $ (585 ) $ 700 Technology Assets 30,837 (22,909 ) 7,928 Customer Assets 10,319 (4,809 ) 5,510 Total $ 42,441 $ (28,303 ) $ 14,138 Balance at December 31, 2017 Cost Accumulated Amortization Net Patents $ 1,285 $ (559 ) $ 726 Technology Assets 29,158 (21,329 ) 7,829 Customer Assets 10,319 (4,540 ) 5,779 Total $ 40,762 $ (26,428 ) $ 14,334 The weighted average amortization periods for acquired patents, acquired technology, and customer intangible assets are approximately 13 years , 4 years , and 9 years , respectively. Amortization expense associated with other intangible assets was $1.9 million for the three months ended March 31, 2018 . Amortization expense associated with other intangible assets was $2.1 million for the three months ended March 31, 2017 . The total estimated future amortization expense of these intangible assets as of March 31, 2018 is as follows (in thousands): 2018 (remaining 9 months) $ 4,864 2019 4,002 2020 2,039 2021 892 2022 611 Thereafter 1,730 Total $ 14,138

OTHER CONSOLIDATED BALANCE SHEE

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)	OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) Other Current Assets The following table presents the detail of other current assets (in thousands): March 31, December 31, Inventory, net $ 20,899 $ 16,777 Processing costs receivable 27,099 21,083 Prepaid expenses 14,743 14,473 Accounts receivable, net 9,876 8,606 Deferred hardware costs (i) — 7,931 Deferred magstripe reader costs (ii) 2,677 2,469 Other 16,639 15,115 Total $ 91,933 $ 86,454 (i) The deferred hardware costs represented costs associated with hardware sold through the retail distribution channels. The adoption of ASC 606 on January 1, 2018, has resulted in the recognition of such costs upon delivery of the hardware to the distribution channel. (ii) The Company capitalizes the cost of its magstripe readers, including packaging and shipping costs, held on-hand by the Company as of each consolidated balance sheet date. Once the readers are shipped to a third-party distributor or an end-customer, they are recorded as marketing expense on the consolidated statements of operations. Accrued Expenses The following table presents the detail of accrued expenses (in thousands): March 31, December 31, Accrued payroll $ 13,833 $ 9,103 Accrued professional fees 5,888 5,638 Accrued advertising and other marketing 7,279 6,723 Processing costs payable 10,166 10,145 Accrued non income tax liabilities 4,677 6,155 Accrued hardware costs 1,305 2,496 Other accrued liabilities 14,849 12,020 Total $ 57,997 $ 52,280 Other Current Liabilities The following table presents the detail of other current liabilities (in thousands): March 31, December 31, Square Capital payable (iii) $ 6,450 $ 7,671 Square Payroll payable (iv) 2,865 2,850 Deferred revenue 3,353 5,893 Current portion of deferred rent 3,252 3,311 Accrued redemptions 1,110 1,036 Other 10,184 7,606 Total $ 27,214 $ 28,367 (iii) Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties. (iv) 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, December 31, Investment in privately held entity $ 25,000 $ 25,000 Deposits 2,379 2,738 Debt issuance costs 719 788 Deferred tax assets 666 519 Other 3,356 2,305 Total $ 32,120 $ 31,350 Other Non-Current Liabilities The following table presents the detail of other non-current liabilities (in thousands): March 31, December 31, Statutory liabilities (i) $ 44,468 $ 40,768 Deferred rent 22,241 20,349 Deferred tax liabilities 139 644 Other 8,087 7,777 Total $ 74,935 $ 69,538 (i) 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.

OTHER CONSOLIDATED BALANCE SH16

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)	3 Months Ended
	Mar. 31, 2018
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, December 31, Inventory, net $ 20,899 $ 16,777 Processing costs receivable 27,099 21,083 Prepaid expenses 14,743 14,473 Accounts receivable, net 9,876 8,606 Deferred hardware costs (i) — 7,931 Deferred magstripe reader costs (ii) 2,677 2,469 Other 16,639 15,115 Total $ 91,933 $ 86,454 (i) The deferred hardware costs represented costs associated with hardware sold through the retail distribution channels. The adoption of ASC 606 on January 1, 2018, has resulted in the recognition of such costs upon delivery of the hardware to the distribution channel. (ii) The Company capitalizes the cost of its magstripe readers, including packaging and shipping costs, held on-hand by the Company as of each consolidated balance sheet date. Once the readers are shipped to a third-party distributor or an end-customer, they are recorded as marketing expense on the consolidated statements of operations. Accrued Expenses The following table presents the detail of accrued expenses (in thousands): March 31, December 31, Accrued payroll $ 13,833 $ 9,103 Accrued professional fees 5,888 5,638 Accrued advertising and other marketing 7,279 6,723 Processing costs payable 10,166 10,145 Accrued non income tax liabilities 4,677 6,155 Accrued hardware costs 1,305 2,496 Other accrued liabilities 14,849 12,020 Total $ 57,997 $ 52,280 Other Current Liabilities The following table presents the detail of other current liabilities (in thousands): March 31, December 31, Square Capital payable (iii) $ 6,450 $ 7,671 Square Payroll payable (iv) 2,865 2,850 Deferred revenue 3,353 5,893 Current portion of deferred rent 3,252 3,311 Accrued redemptions 1,110 1,036 Other 10,184 7,606 Total $ 27,214 $ 28,367 (iii) Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties. (iv) 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, December 31, Investment in privately held entity $ 25,000 $ 25,000 Deposits 2,379 2,738 Debt issuance costs 719 788 Deferred tax assets 666 519 Other 3,356 2,305 Total $ 32,120 $ 31,350 Other Non-Current Liabilities The following table presents the detail of other non-current liabilities (in thousands): March 31, December 31, Statutory liabilities (i) $ 44,468 $ 40,768 Deferred rent 22,241 20,349 Deferred tax liabilities 139 644 Other 8,087 7,777 Total $ 74,935 $ 69,538 (i) 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.

INDEBTEDNESS

INDEBTEDNESS	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
INDEBTEDNESS	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 in unused commitment fees during both the three months ended March 31, 2018 and 2017 . As of March 31, 2018 , the Company was in compliance with all financial covenants associated with this credit facility. Convertible Senior Notes On March 6, 2017, the Company issued an aggregate principal amount of $ 400.0 million of convertible senior notes (Notes) and an additional 10% or $ 40.0 million pursuant to the exercise in full of the option to the initial purchasers to cover over-allotments. The 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 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 Notes, which is equivalent to an initial conversion price of approximately $ 22.95 per share of Class A common stock. Holders may convert their 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 Notes) per $1,000 principal amount of 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 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 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. It is the Company’s current intent and policy to settle conversions through combination settlement with a specified dollar amount of $ 1,000 per $ 1,000 principal amount of Notes. The circumstances required to allow the holders to convert their Notes were met for the quarters commencing January 1, 2018 and April 1, 2018, respectively. As of May 1, 2018, no holders have converted or indicated their intention to convert their Notes. In accounting for the issuance of the Notes, the Company separated the 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 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 Notes at an effective interest rate of 5.34% over the contractual terms of the Notes. Debt issuance costs related to the 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 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 Notes consisted of the following (in thousands): March 31, 2018 December 31, 2017 Principal $ 440,000 $ 440,000 Less: unamortized debt discount (69,425 ) (73,384 ) Less: unamortized debt issuance costs (7,610 ) (8,044 ) Net carrying amount $ 362,965 $ 358,572 The net carrying amount of the equity component of the Notes was as follows (in thousands): March 31, 2018 December 31, 2017 Debt discount related to value of conversion option $ 86,203 $ 86,203 Less: allocated debt issuance costs (2,302 ) (2,302 ) Equity component, net $ 83,901 $ 83,901 The Company recognized interest expense on the Notes as follows (in thousands, except for percentages): Three Months Ended March 31, 2018 2017 Contractual interest expense based on 0.375% per annum $ 413 $ 113 Amortization of debt discount and issuance costs 4,393 1,390 Total $ 4,806 $ 1,503 Effective interest rate of the liability component 5.34 % 5.34 % Convertible Note Hedge and Warrant Transactions In connection with the offering of the Notes, the Company entered into convertible note hedge transactions with certain financial institutions (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 convertible note hedge transactions was $ 92.1 million . In addition, the Company sold warrants to the Counterparties whereby the 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 these warrants. Taken together, the purchase of the convertible note hedges and sale of the warrants are intended to reduce dilution from the conversion of the Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of the converted 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 convertible note hedges and 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 convertible note hedge and warrant transactions were recorded as a reduction to additional paid-in capital on the condensed consolidated balance sheets.

ACCRUED TRANSACTION LOSSES

ACCRUED TRANSACTION LOSSES	3 Months Ended
	Mar. 31, 2018
Product Warranties Disclosures [Abstract]
ACCRUED TRANSACTION LOSSES	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, 2018 2017 Accrued transaction losses, beginning of the period $ 26,893 $ 20,064 Provision for transaction losses 14,258 11,558 Charge-offs to accrued transaction losses (12,842 ) (11,178 ) Accrued transaction losses, end of the period $ 28,309 $ 20,444

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company recorded an income tax expense of $0.2 million for the three months ended March 31, 2018 , compared to income tax expense of $0.5 million for the three months ended March 31, 2017 . The income tax expense recorded for the three months ended March 31, 2018 was primarily due to state and foreign income tax expense. The Company’s effective tax rate was (0.7)% for the three months ended March 31, 2018 , compared to an effective tax rate of (3.5)% for the three months ended March 31, 2017 . The difference between the effective tax rate and the federal statutory tax rate for the three months ended March 31, 2018 and March 31, 2017 primarily relates to the valuation allowance on the Company’s deferred tax assets. 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, 2018 , 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, 2018 and March 31, 2017 , was calculated on a jurisdiction basis. The Company estimated the foreign income tax provision using the effective income tax rate expected to be applicable for the full year. On December 22, 2017, the SEC issued Staff Accounting Bulletin No. 118 to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act of 2017. The accounting for all items is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018. Any differences between what was previously recorded and the final tax return amounts or estimates done for subsequent quarters are not expected to be material.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY The changes in total stockholders’ equity were as follows (in thousands): Total stockholders’ equity Balance at December 31, 2017 $ 786,333 Net loss (23,986 ) Exercise of stock options 31,354 Vesting of early exercised stock options and other 136 Share-based compensation 48,356 Tax withholding related to vesting of restricted stock units (27,651 ) Cumulative adjustment for adoption of ASC 606 (4,586 ) Change in other comprehensive loss 24 Balance at March 31, 2018 $ 809,980 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, 2018 , 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, 2018 , there were 287,921,742 shares of Class A common stock and 112,462,337 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. 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, 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, 2018 , the total number of shares subject to stock options and RSUs outstanding under the 2015 Plan was 24,960,627 , and 65,895,253 shares were available for future issuance. As of March 31, 2018 , the total number of shares subject to stock options and RSUs outstanding under the 2009 Plan was 38,069,996 . A summary of stock option activity for the three months ended March 31, 2018 is as follows (in thousands, except share and per share data): Number of Stock Options Outstanding Weighted Weighted Aggregate Balance at December 31, 2017 47,270,091 $ 8.67 6.52 $ 1,229,103 Exercised (4,213,775 ) 7.44 Forfeited (328,651 ) 12.04 Balance at March 31, 2018 42,727,665 $ 8.76 6.33 $ 1,727,761 Options exercisable as of March 31, 2018 40,039,760 $ 8.47 6.20 $ 1,630,725 Restricted Stock Activity Activity related to RSUs during the three months ended March 31, 2018 is set forth below: Number of Weighted Unvested as of December 31, 2017 21,317,525 $ 17.84 Granted 1,226,422 44.78 Vested (1,625,534 ) 14.54 Forfeited (615,455 ) 15.67 Unvested as of March 31, 2018 20,302,958 $ 19.80 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 RSUs is determined by the closing price of the Company’s common stock on each grant date. There were no stock options granted during the three months ended March 31, 2018 and 2017 . 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, 2018 2017 Cost of revenue $ 31 $ — Product development 30,482 19,356 Sales and marketing 4,961 3,935 General and administrative 11,350 8,379 Total $ 46,824 $ 31,670 The Company recorded $2.3 million of share-based compensation expense related to the Company's 2015 Employee Stock Purchase Plan during the three months ended March 31, 2018 , compared to $1.9 million for the three months ended March 31, 2017 , which are included in the table above. The Company capitalized $1.5 million of share-based compensation expense related to capitalized software costs during the three months ended March 31, 2018 , compared to $0.5 million for the three months ended March 31, 2017 . As of March 31, 2018 , there was $418.7 million of total unrecognized compensation cost related to outstanding stock options that is expected to be recognized over a weighted-average period of 2.74 years .

LOSS PER SHARE

LOSS PER SHARE	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
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 loss per share is the same as basic loss per share for all periods presented 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, 2018 2017 Net loss $ (23,986 ) $ (15,090 ) Basic shares: Weighted-average common shares outstanding 397,246 368,571 Weighted-average unvested shares (1,298 ) (1,834 ) Weighted-average shares used to compute basic net loss per share 395,948 366,737 Diluted shares: Weighted-average shares used to compute diluted loss per share 395,948 366,737 Net loss per share: Basic $ (0.06 ) $ (0.04 ) Diluted $ (0.06 ) $ (0.04 ) Additionally, since the Company expects to settle the principal amount of its outstanding Notes in cash, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The conversion spread will have a dilutive impact on diluted net income per share of common stock when the average market price of the Company’s common stock for a given period exceeds the conversion price of $ 22.95 per share for the Notes. Because the Company has reported a net loss for all periods presented, 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, 2018 2017 Stock options and restricted stock units 66,382 84,909 Common stock warrants 19,173 11,129 Unvested shares 1,298 1,834 Employee stock purchase plan 264 509 Total anti-dilutive securities 87,117 98,381

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Operating and Capital Leases The Company has entered into various non-cancelable operating leases for certain offices with contractual lease periods expiring between 2018 and 2025 . The Company recognized total rental expenses under operating leases of $4.5 million for the three months ended March 31, 2018 , compared to $2.8 million for the three months ended March 31, 2017 . Future minimum lease payments under non-cancelable operating leases (with initial lease terms in excess of one year) and future minimum capital lease payments as of March 31, 2018 are as follows (in thousands): Capital Operating Year: 2018 (remaining 9 months) $ 1,996 $ 15,437 2019 2,549 19,600 2020 1,274 19,388 2021 44 19,009 2022 2 19,105 Thereafter — 23,628 Total $ 5,865 $ 116,167 Less amount representing interest (15 ) Present value of capital lease obligations 5,850 Less current portion of capital lease obligation (2,654 ) Non-current portion of capital lease obligation $ 3,196 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 intends to vigorously defend its position, which it believes has merit. 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. 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 INFORM

SEGMENT AND GEOGRAPHICAL INFORMATION	3 Months Ended
	Mar. 31, 2018
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 merchants or customers. The following table sets forth revenue by geographic area (in thousands): Three Months Ended March 31, 2018 2017 Revenue United States $ 640,173 $ 444,899 International 28,430 16,655 Total net revenue $ 668,603 $ 461,554 No individual country from the international markets contributed in excess of 10% of total revenue for the three months ended March 31, 2018 and 2017 . Long-Lived Assets The following table sets forth long-lived assets by geographic area (in thousands): March 31, December 31, Long-lived assets United States $ 165,530 $ 158,820 International 5,105 5,337 Total long-lived assets $ 170,635 $ 164,157

SUPPLEMENTAL CASH FLOW INFORMAT

SUPPLEMENTAL CASH FLOW INFORMATION	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
SUPPLEMENTAL CASH FLOW INFORMATION	SUPPLEMENTAL CASH FLOW INFORMATION The supplemental disclosures of cash flow information consist of the following (in thousands): Three Months Ended March 31, 2018 2017 Supplemental Cash Flow Data: Cash paid for interest $ 966 $ 142 Cash paid for income taxes 658 334 Supplemental disclosures of non-cash investing and financing activities: Change in purchases of property and equipment in accounts payable and accrued expenses (3,813 ) (468 ) Unpaid business acquisition purchase price 1,151 400

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Release of Caviar Shares Held Back In 2014, in conjunction with the Company's acquisition of Caviar, Inc. (Caviar), 1,292,207 shares of the purchase consideration issuable were withheld for indemnification purposes. In April 2018, the Company reached an agreement with the former owners of Caviar whereby 822,085 of the shares held back would be released to the former owners and 469,894 shares would be forfeited back to the Company to cover any potential future liabilities. Acquisition In April 2018, the Company entered into an agreement to acquire Weebly Inc (Weebly), a technology company that provides customers with tools to build a professional website or online store, for a purchase price of approximately $265 million , comprising an aggregate of approximately $132.5 million in cash and approximately $132.5 million in the Company’s Class A common stock, subject to adjustments based on (i) purchase price adjustment provisions and (ii) indemnification obligations of Weebly stockholders after the closing of the acquisition, as specified in the agreement. The acquisition of Weebly will enable the Company to combine Weebly’s web presence tools with the Company's in-person and online offerings to create one cohesive solution for sellers to start or grow an omnichannel business. The acquisition will also expand the Company’s customer base globally and add a new recurring revenue stream. The acquisition is expected to close in the second quarter of 2018, subject to customary closing conditions including regulatory approvals.

DESCRIPTION OF BUSINESS AND S26

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
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, 2017 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 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, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 , 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, 2017 .
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 and intangible assets, income and other taxes, and share-based compensation.
Concentration of Credit Risk	For the three months ended March 31, 2018 and 2017 , 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 46% , 42% , and 7% of settlements receivable as of March 31, 2018 . The same three parties represented approximately 46% , 42% , and 8% of settlements receivable as of December 31, 2017 . 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 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 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.
Cryptocurrency transactions	During the fourth quarter of 2017, the Company started offering its Cash App customers the ability to purchase bitcoin, a cryptocurrency denominated asset, from the Company. The Company purchases bitcoin from public cryptocurrency exchanges or from customers. Upon purchase, the Company records the cost of bitcoin within other current assets in its consolidated balance sheets. Upon sale, the Company records the total sale amount received from customers as bitcoin revenue and the associated cost as cost of revenue. The carrying value of bitcoin was $0.2 million and $0.3 million as of March 31, 2018 and December 31, 2017 , respectively. The Company assesses the carrying value of bitcoin at each reporting date and records an impairment charge if the cost exceeds the fair value. Losses on bitcoin for the three months ended March 31, 2018 were insignificant.
Recent Accounting Pronouncements	Recently issued accounting pronouncements not yet adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases , which will require, among other items, lessees to recognize a right of use asset and a related lease liability for most leases on the balance sheet. Qualitative and quantitative disclosures will be enhanced to better understand the amount, timing and uncertainty of cash flows arising from leases. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The new standard should be applied on a modified retrospective basis. The Company does not plan to early adopt this guidance. The Company’s operating leases primarily comprise of office spaces, with the most significant leases relating to corporate headquarters in San Francisco and an office in New York. While the Company continues to evaluate the impact of adopting this guidance on its consolidated financial statements, it does expect to record right to use assets and related lease liabilities on its consolidated balance sheets upon adoption, which will increase total assets and liabilities. In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments , 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, with early adoption permitted. The Company is currently evaluating the impact this new 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 does not expect the adoption of this guidance to have a material the impact on the consolidated financial statements and related disclosures. In March 2017, the FASB issued ASU No. 2017-08, Premium Amortization on Purchased Callable Debt Securities, which amends the amortization period for certain purchased callable debt securities held at a premium, shortening such period to the earliest call date. This standard is effective for annual periods beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The amendments in this guidance should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently evaluating the impact this new guidance may have on the consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . When the Tax Cuts and Jobs Act of 2017 was enacted in December 2017, there was a valuation allowance on the deferred tax assets included within the Company's accumulated other comprehensive income; therefore no tax expense resulted from the change in the federal income tax rate. This guidance allows companies to reclassify such tax effects from accumulated other comprehensive income to retained earnings. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with early adoption permitted. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-03, Recognition and Measurement of Financial Assets and Financial Liabilities. This guidance clarifies that an entity that uses the measurement alternative for equity securities without readily determinable fair values can change its measurement approach to fair value. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years beginning after June 15, 2018. The Company does not expect the adoption of this guidance to have a material impact on the consolidated financial statements and related disclosures. .

REVENUE (Tables)

REVENUE (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Impact of Adoption of ASC 606	The impact of adoption of ASC 606 on the Company's consolidated statement of operations and balance sheet was as follows (in thousands): Three Months Ended March 31, 2018 As reported Balances without adoption of ASC 606 Effect of change Impact on the Condensed Consolidated Statement of Operations: Subscription and services-based revenue $ 97,054 $ 96,995 $ 59 Hardware revenue 14,417 13,154 1,263 Subscription and services-based costs 30,368 30,368 — Hardware costs 19,702 18,757 945 Impact on the Condensed Consolidated Balance Sheets: Other current assets 91,933 100,573 (8,640 ) Other current liabilities 27,214 31,976 (4,762 ) Other non-current assets 32,120 33,355 (1,235 ) Other non-current liabilities $ 74,935 $ 75,993 $ (1,058 )
Schedule of Disaggregation of Revenue	The following table presents the Company's revenue from contracts with customers disaggregated by revenue source (in thousands): Three Months Ended March 31, 2018 2017 Revenue from Contracts with Customers: Transaction-based revenue $ 523,037 $ 403,478 Subscription and services-based revenue 77,215 31,321 Hardware revenue $ 14,417 $ 9,016 Bitcoin revenue $ 34,095 $ —
Schedule of Deferred Revenue	The deferred revenue balances were as follows (in thousands): Three Months Ended March 31, 2018 2017 Deferred revenue, beginning of the period $ 5,893 $ 5,407 Deferred revenue, end of the period 3,353 2,965 Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period 298 4,062

FAIR VALUE OF FINANCIAL INSTR28

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	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, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Cash and Cash Equivalents: Money market funds $ 405,813 $ — $ — $ 387,698 $ — $ — Commercial paper — 20,576 — — 24,695 — Short-term securities: U.S. agency securities — 13,583 — — 15,083 — Corporate bonds — 91,672 — — 57,798 — Commercial paper — 14,286 — — 17,428 — Municipal securities — 26,889 — — 23,700 — U.S. government securities 53,618 — 55,567 — — Long-term securities: U.S. agency securities — 20,095 — — 20,169 — Corporate bonds — 71,383 — — 91,413 — Municipal securities — 14,519 — — 26,224 — U.S. government securities 70,675 — — 65,861 — — Total $ 530,106 $ 273,003 $ — $ 509,126 $ 276,510 $ — A summary of loans disclosed at fair value on a recurring basis is as follows (in thousands): March 31, 2018 December 31, 2017 Carrying Value Fair Value (Level 3) Carrying Value Fair Value (Level 3) Loans held for sale $ 78,821 $ 81,459 $ 73,420 $ 76,070 Total $ 78,821 $ 81,459 $ 73,420 $ 76,070 The estimated fair value and carrying value of the convertible senior notes were as follows (in thousands): March 31, 2018 December 31, 2017 Carrying Value Fair Value (Level 2) Carrying Value Fair Value (Level 2) Convertible senior notes $ 362,965 $ 963,965 $ 358,572 $ 719,356 Total $ 362,965 $ 963,965 $ 358,572 $ 719,356

INVESTMENTS (Tables)

INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Short-term securities: U.S. agency securities $ 13,581 $ 5 $ (3 ) $ 13,583 Corporate bonds 92,023 11 (362 ) 91,672 Commercial paper 14,286 — — 14,286 Municipal securities 26,950 20 (81 ) 26,889 U.S. government securities 53,615 11 (8 ) 53,618 Total $ 200,455 $ 47 $ (454 ) $ 200,048 Long-term securities: U.S. agency securities $ 20,169 $ 8 $ (82 ) $ 20,095 Corporate bonds 71,741 170 (528 ) 71,383 Municipal securities 14,467 70 (18 ) 14,519 U.S. government securities 71,078 — (403 ) 70,675 Total $ 177,455 $ 248 $ (1,031 ) $ 176,672 The Company's short-term and long-term investments as of December 31, 2017 are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Short-term securities: U.S. agency securities $ 15,122 $ — $ (39 ) $ 15,083 Corporate bonds 57,855 22 (79 ) 57,798 Commercial paper 17,428 — — 17,428 Municipal securities 23,743 8 (51 ) 23,700 U.S. government securities 55,729 1 (163 ) 55,567 Total $ 169,877 $ 31 $ (332 ) $ 169,576 Long-term securities: U.S. agency securities $ 20,288 $ 2 $ (121 ) $ 20,169 Corporate bonds 91,959 25 (571 ) 91,413 Municipal securities 26,371 13 (160 ) 26,224 U.S. government securities 66,362 19 (520 ) 65,861 Total $ 204,980 $ 59 $ (1,372 ) $ 203,667
Investments Classified by Contractual Maturity Date	The contractual maturities of the Company's short-term and long-term investments as of March 31, 2018 are as follows (in thousands): Amortized Cost Fair Value Due in one year or less $ 200,455 $ 200,048 Due in one to five years 177,455 176,672 Total $ 377,910 $ 376,720

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	3 Months Ended
	Mar. 31, 2018
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, December 31, Leasehold improvements $ 82,425 $ 77,073 Computer equipment 70,818 66,186 Capitalized software 39,268 35,063 Office furniture and equipment 15,152 14,490 207,663 192,812 Less: Accumulated depreciation and amortization (109,493 ) (101,316 ) Property and equipment, net $ 98,170 $ 91,496

ACQUIRED INTANGIBLE ASSETS (Tab

ACQUIRED INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite Lived Intangible Assets	The following table presents the detail of acquired intangible assets as of the periods presented (in thousands): Balance at March 31, 2018 Cost Accumulated Amortization Net Patents $ 1,285 $ (585 ) $ 700 Technology Assets 30,837 (22,909 ) 7,928 Customer Assets 10,319 (4,809 ) 5,510 Total $ 42,441 $ (28,303 ) $ 14,138 Balance at December 31, 2017 Cost Accumulated Amortization Net Patents $ 1,285 $ (559 ) $ 726 Technology Assets 29,158 (21,329 ) 7,829 Customer Assets 10,319 (4,540 ) 5,779 Total $ 40,762 $ (26,428 ) $ 14,334
Schedule of Annual Future Amortization Expense of Intangible Assets	The total estimated future amortization expense of these intangible assets as of March 31, 2018 is as follows (in thousands): 2018 (remaining 9 months) $ 4,864 2019 4,002 2020 2,039 2021 892 2022 611 Thereafter 1,730 Total $ 14,138

OTHER CONSOLIDATED BALANCE SH32

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) (Tables)	3 Months Ended
	Mar. 31, 2018
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, December 31, Inventory, net $ 20,899 $ 16,777 Processing costs receivable 27,099 21,083 Prepaid expenses 14,743 14,473 Accounts receivable, net 9,876 8,606 Deferred hardware costs (i) — 7,931 Deferred magstripe reader costs (ii) 2,677 2,469 Other 16,639 15,115 Total $ 91,933 $ 86,454 (i) The deferred hardware costs represented costs associated with hardware sold through the retail distribution channels. The adoption of ASC 606 on January 1, 2018, has resulted in the recognition of such costs upon delivery of the hardware to the distribution channel. (ii) The Company capitalizes the cost of its magstripe readers, including packaging and shipping costs, held on-hand by the Company as of each consolidated balance sheet date. Once the readers are shipped to a third-party distributor or an end-customer, they are recorded as marketing expense on the consolidated statements of operations.
Schedule of Accrued Expenses	The following table presents the detail of accrued expenses (in thousands): March 31, December 31, Accrued payroll $ 13,833 $ 9,103 Accrued professional fees 5,888 5,638 Accrued advertising and other marketing 7,279 6,723 Processing costs payable 10,166 10,145 Accrued non income tax liabilities 4,677 6,155 Accrued hardware costs 1,305 2,496 Other accrued liabilities 14,849 12,020 Total $ 57,997 $ 52,280
Schedule of Other Current Liabilities	The following table presents the detail of other current liabilities (in thousands): March 31, December 31, Square Capital payable (iii) $ 6,450 $ 7,671 Square Payroll payable (iv) 2,865 2,850 Deferred revenue 3,353 5,893 Current portion of deferred rent 3,252 3,311 Accrued redemptions 1,110 1,036 Other 10,184 7,606 Total $ 27,214 $ 28,367 (iii) Square Capital payable represents unpaid amounts arising from the purchase of loans or loan repayments collected on behalf of third parties. (iv) 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 SH33

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) (Tables)	3 Months Ended
	Mar. 31, 2018
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, December 31, Investment in privately held entity $ 25,000 $ 25,000 Deposits 2,379 2,738 Debt issuance costs 719 788 Deferred tax assets 666 519 Other 3,356 2,305 Total $ 32,120 $ 31,350
Schedule of Other Non-Current Liabilities	The following table presents the detail of other non-current liabilities (in thousands): March 31, December 31, Statutory liabilities (i) $ 44,468 $ 40,768 Deferred rent 22,241 20,349 Deferred tax liabilities 139 644 Other 8,087 7,777 Total $ 74,935 $ 69,538 (i) 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.

INDEBTEDNESS (Tables)

INDEBTEDNESS (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Convertible Notes	The Notes consisted of the following (in thousands): March 31, 2018 December 31, 2017 Principal $ 440,000 $ 440,000 Less: unamortized debt discount (69,425 ) (73,384 ) Less: unamortized debt issuance costs (7,610 ) (8,044 ) Net carrying amount $ 362,965 $ 358,572 The net carrying amount of the equity component of the Notes was as follows (in thousands): March 31, 2018 December 31, 2017 Debt discount related to value of conversion option $ 86,203 $ 86,203 Less: allocated debt issuance costs (2,302 ) (2,302 ) Equity component, net $ 83,901 $ 83,901
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, 2018 2017 Contractual interest expense based on 0.375% per annum $ 413 $ 113 Amortization of debt discount and issuance costs 4,393 1,390 Total $ 4,806 $ 1,503 Effective interest rate of the liability component 5.34 % 5.34 %

ACCRUED TRANSACTION LOSSES (Tab

ACCRUED TRANSACTION LOSSES (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 2017 Accrued transaction losses, beginning of the period $ 26,893 $ 20,064 Provision for transaction losses 14,258 11,558 Charge-offs to accrued transaction losses (12,842 ) (11,178 ) Accrued transaction losses, end of the period $ 28,309 $ 20,444

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Changes in Stockholder's Equity	The changes in total stockholders’ equity were as follows (in thousands): Total stockholders’ equity Balance at December 31, 2017 $ 786,333 Net loss (23,986 ) Exercise of stock options 31,354 Vesting of early exercised stock options and other 136 Share-based compensation 48,356 Tax withholding related to vesting of restricted stock units (27,651 ) Cumulative adjustment for adoption of ASC 606 (4,586 ) Change in other comprehensive loss 24 Balance at March 31, 2018 $ 809,980
Summary of Stock Option Activity	A summary of stock option activity for the three months ended March 31, 2018 is as follows (in thousands, except share and per share data): Number of Stock Options Outstanding Weighted Weighted Aggregate Balance at December 31, 2017 47,270,091 $ 8.67 6.52 $ 1,229,103 Exercised (4,213,775 ) 7.44 Forfeited (328,651 ) 12.04 Balance at March 31, 2018 42,727,665 $ 8.76 6.33 $ 1,727,761 Options exercisable as of March 31, 2018 40,039,760 $ 8.47 6.20 $ 1,630,725
Schedule of RSU Activity	Activity related to RSUs during the three months ended March 31, 2018 is set forth below: Number of Weighted Unvested as of December 31, 2017 21,317,525 $ 17.84 Granted 1,226,422 44.78 Vested (1,625,534 ) 14.54 Forfeited (615,455 ) 15.67 Unvested as of March 31, 2018 20,302,958 $ 19.80
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, 2018 2017 Cost of revenue $ 31 $ — Product development 30,482 19,356 Sales and marketing 4,961 3,935 General and administrative 11,350 8,379 Total $ 46,824 $ 31,670

LOSS PER SHARE (Tables)

LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 2017 Net loss $ (23,986 ) $ (15,090 ) Basic shares: Weighted-average common shares outstanding 397,246 368,571 Weighted-average unvested shares (1,298 ) (1,834 ) Weighted-average shares used to compute basic net loss per share 395,948 366,737 Diluted shares: Weighted-average shares used to compute diluted loss per share 395,948 366,737 Net loss per share: Basic $ (0.06 ) $ (0.04 ) Diluted $ (0.06 ) $ (0.04 )
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, 2018 2017 Stock options and restricted stock units 66,382 84,909 Common stock warrants 19,173 11,129 Unvested shares 1,298 1,834 Employee stock purchase plan 264 509 Total anti-dilutive securities 87,117 98,381

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Payments Under Operating and Capital Leases	Future minimum lease payments under non-cancelable operating leases (with initial lease terms in excess of one year) and future minimum capital lease payments as of March 31, 2018 are as follows (in thousands): Capital Operating Year: 2018 (remaining 9 months) $ 1,996 $ 15,437 2019 2,549 19,600 2020 1,274 19,388 2021 44 19,009 2022 2 19,105 Thereafter — 23,628 Total $ 5,865 $ 116,167 Less amount representing interest (15 ) Present value of capital lease obligations 5,850 Less current portion of capital lease obligation (2,654 ) Non-current portion of capital lease obligation $ 3,196

SEGMENT AND GEOGRAPHICAL INFO39

SEGMENT AND GEOGRAPHICAL INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Revenue from External Customers by Geographic Areas	Revenue by geography is based on the billing addresses of the merchants or customers. The following table sets forth revenue by geographic area (in thousands): Three Months Ended March 31, 2018 2017 Revenue United States $ 640,173 $ 444,899 International 28,430 16,655 Total net revenue $ 668,603 $ 461,554
Long-lived Assets by Geographic Areas	The following table sets forth long-lived assets by geographic area (in thousands): March 31, December 31, Long-lived assets United States $ 165,530 $ 158,820 International 5,105 5,337 Total long-lived assets $ 170,635 $ 164,157

SUPPLEMENTAL CASH FLOW INFORM40

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 2017 Supplemental Cash Flow Data: Cash paid for interest $ 966 $ 142 Cash paid for income taxes 658 334 Supplemental disclosures of non-cash investing and financing activities: Change in purchases of property and equipment in accounts payable and accrued expenses (3,813 ) (468 ) Unpaid business acquisition purchase price 1,151 400

DESCRIPTION OF BUSINESS AND S41

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)customerthird_party_processor	Mar. 31, 2017customer	Dec. 31, 2017USD ($)third_party_processor
Concentration Risk [Line Items]
Cryptocurrency denominated assets | $	$ 0.2		$ 0.3
Total Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Number of customers | 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, percentage	46.00%		46.00%
Settlements Receivable | Credit Concentration Risk | Third Party Processor Two
Concentration Risk [Line Items]
Concentration risk, percentage	42.00%		42.00%
Settlements Receivable | Credit Concentration Risk | Third Party Processor Three
Concentration Risk [Line Items]
Concentration risk, percentage	7.00%		8.00%

REVENUE - Narrative (Details)

REVENUE - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings (accumulated deficit)	$ (871,307)			$ (842,735)
Revenue	668,603	$ 461,554
Revenue, contracts from customers	648,800
Bitcoin revenue	34,095	$ 0
Revenue, other	19,800
Effect of change | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings (accumulated deficit)			$ (4,600)
Revenue	$ 1,300
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Distributors and retailers, payment terms	30 days
Customer installment sales, terms	3 months
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Distributors and retailers, payment terms	90 days
Customer installment sales, terms	24 months

REVENUE - Adoption of ASC 606 (

REVENUE - Adoption of ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Hardware revenue	$ 14,417	$ 9,016
Hardware costs	19,702	12,662
Other current assets	91,933		$ 86,454
Other current liabilities	27,214		28,367
Other non-current assets	32,120		31,350
Other non-current liabilities	74,935		$ 69,538
Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Hardware revenue	13,154
Hardware costs	18,757
Other current assets	100,573
Other current liabilities	31,976
Other non-current assets	33,355
Other non-current liabilities	75,993
ASU 2014-09 | Effect of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Hardware revenue	1,263
Hardware costs	945
Other current assets	(8,640)
Other current liabilities	(4,762)
Other non-current assets	(1,235)
Other non-current liabilities	(1,058)
Subscription and services-based revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction and services-based revenue	97,054	49,060
Transaction and services-based costs	30,368	$ 15,876
Subscription and services-based revenue | Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction and services-based revenue	96,995
Transaction and services-based costs	30,368
Subscription and services-based revenue | ASU 2014-09 | Effect of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction and services-based revenue	59
Transaction and services-based costs	$ 0

REVENUE - Revenue from Contract

REVENUE - Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue, contracts from customers	$ 648,800
Transaction-based revenue
Disaggregation of Revenue [Line Items]
Revenue, contracts from customers	523,037	$ 403,478
Subscription and services-based revenue
Disaggregation of Revenue [Line Items]
Revenue, contracts from customers	77,215	31,321
Hardware revenue
Disaggregation of Revenue [Line Items]
Revenue, contracts from customers	14,417	9,016
Bitcoin revenue
Disaggregation of Revenue [Line Items]
Revenue, contracts from customers	$ 34,095	$ 0

REVENUE - Deferred Revenue (Det

REVENUE - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue from Contract with Customer [Abstract]
Deferred revenue, beginning of the period	$ 5,893	$ 5,407
Deferred revenue, end of the period	3,353	2,965
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	$ 298	$ 4,062

RESTRICTED CASH (Details)

RESTRICTED CASH (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Pledged cash	$ 27,688	$ 28,805
Collateral	$ 9,802	$ 9,802

FAIR VALUE OF FINANCIAL INSTR47

FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	$ 200,048	$ 169,576
Long-term securities	176,672	203,667
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	530,106	509,126
Fair Value, Measurements, Recurring | Level 1 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Long-term securities	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Long-term securities	0	0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Fair Value, Measurements, Recurring | Level 1 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Long-term securities	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]
Short-term securities	53,618	55,567
Long-term securities	70,675	65,861
Fair Value, Measurements, Recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	405,813	387,698
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	273,003	276,510
Fair Value, Measurements, Recurring | Level 2 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	13,583	15,083
Long-term securities	20,095	20,169
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	91,672	57,798
Long-term securities	71,383	91,413
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	14,286	17,428
Fair Value, Measurements, Recurring | Level 2 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	26,889	23,700
Long-term securities	14,519	26,224
Fair Value, Measurements, Recurring | Level 2 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities		0
Long-term securities	0	0
Fair Value, Measurements, Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	20,576	24,695
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	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]
Short-term securities	0	0
Long-term 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 securities	0	0
Long-term securities	0	0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Fair Value, Measurements, Recurring | Level 3 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term securities	0	0
Long-term securities	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]
Short-term securities	0	0
Long-term securities	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 and cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTR48

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Convertible Senior Notes (Details) - Level 2 - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 362,965	$ 358,572
Fair Value (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 963,965	$ 719,356

FAIR VALUE OF FINANCIAL INSTR49

FAIR VALUE OF FINANCIAL INSTRUMENTS - Loans Disclosed at Fair Value (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
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, fair value	$ 78,821,000		$ 73,420,000
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, fair value	81,459,000		$ 76,070,000
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 charge	$ 2,500,000	$ 0

INVESTMENTS - Available for Sa

INVESTMENTS - Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total	$ 377,910
Fair Value	376,720
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	200,455	$ 169,877
Gross Unrealized Gains	47	31
Gross Unrealized Losses	(454)	(332)
Fair Value	200,048	169,576
Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	177,455	204,980
Gross Unrealized Gains	248	59
Gross Unrealized Losses	(1,031)	(1,372)
Fair Value	176,672	203,667
U.S. agency securities | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	13,581	15,122
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(3)	(39)
Fair Value	13,583	15,083
U.S. agency securities | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	20,169	20,288
Gross Unrealized Gains	8	2
Gross Unrealized Losses	(82)	(121)
Fair Value	20,095	20,169
Corporate bonds | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	92,023	57,855
Gross Unrealized Gains	11	22
Gross Unrealized Losses	(362)	(79)
Fair Value	91,672	57,798
Corporate bonds | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	71,741	91,959
Gross Unrealized Gains	170	25
Gross Unrealized Losses	(528)	(571)
Fair Value	71,383	91,413
Commercial paper | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	14,286	17,428
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	14,286	17,428
Municipal securities | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	26,950	23,743
Gross Unrealized Gains	20	8
Gross Unrealized Losses	(81)	(51)
Fair Value	26,889	23,700
Municipal securities | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	14,467	26,371
Gross Unrealized Gains	70	13
Gross Unrealized Losses	(18)	(160)
Fair Value	14,519	26,224
U.S. government securities | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	53,615	55,729
Gross Unrealized Gains	11	1
Gross Unrealized Losses	(8)	(163)
Fair Value	53,618	55,567
U.S. government securities | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Total	71,078	66,362
Gross Unrealized Gains	0	19
Gross Unrealized Losses	(403)	(520)
Fair Value	$ 70,675	$ 65,861

INVESTMENTS - Maturity of Avai

INVESTMENTS - Maturity of Available for Sale Securities (Details) $ in Thousands	Mar. 31, 2018USD ($)
Amortized Cost
Due in one year or less	$ 200,455
Due in one to five years	177,455
Total	377,910
Fair Value
Due in one year or less	200,048
Due in one to five years	176,672
Total	$ 376,720

PROPERTY AND EQUIPMENT, NET (De

PROPERTY AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 207,663		$ 192,812
Less: Accumulated depreciation and amortization	(109,493)		(101,316)
Property and equipment, net	98,170		91,496
Depreciation	8,300	$ 7,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	82,425		77,073
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	70,818		66,186
Capitalized software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,268		35,063
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,152		$ 14,490

GOODWILL (Details)

GOODWILL (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 58,327,000		$ 58,327,000
Goodwill, impairment charges	$ 0	$ 0

ACQUIRED INTANGIBLE ASSETS - S

ACQUIRED INTANGIBLE ASSETS - Schedule of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	$ 42,441	$ 40,762
Accumulated Amortization	(28,303)	(26,428)
Net	14,138	14,334
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	1,285	1,285
Accumulated Amortization	(585)	(559)
Net	700	726
Technology Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	30,837	29,158
Accumulated Amortization	(22,909)	(21,329)
Net	7,928	7,829
Customer Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	10,319	10,319
Accumulated Amortization	(4,809)	(4,540)
Net	$ 5,510	$ 5,779

ACQUIRED INTANGIBLE ASSETS - N

ACQUIRED INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 1.9	$ 2.1
Weighted Average | Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	13 years
Weighted Average | Technology Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	4 years
Weighted Average | Customer Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	9 years

ACQUIRED INTANGIBLE ASSETS - F

ACQUIRED INTANGIBLE ASSETS - Future Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018 (remaining 9 months)	$ 4,864
2,019	4,002
2,020	2,039
2,021	892
2,022	611
Thereafter	1,730
Net	$ 14,138	$ 14,334

OTHER CONSOLIDATED BALANCE SH57

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Inventory, net	$ 20,899	$ 16,777
Processing costs receivable	27,099	21,083
Prepaid expenses	14,743	14,473
Accounts receivable, net	9,876	8,606
Deferred hardware costs	0	7,931
Deferred magstripe reader costs	2,677	2,469
Other	16,639	15,115
Total	$ 91,933	$ 86,454

OTHER CONSOLIDATED BALANCE SH58

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll	$ 13,833	$ 9,103
Accrued professional fees	5,888	5,638
Accrued advertising and other marketing	7,279	6,723
Processing costs payable	10,166	10,145
Accrued non income tax liabilities	4,677	6,155
Accrued hardware costs	1,305	2,496
Other accrued liabilities	14,849	12,020
Total	$ 57,997	$ 52,280

OTHER CONSOLIDATED BALANCE SH59

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Square Capital payable	$ 6,450	$ 7,671
Square Payroll payable	2,865	2,850
Deferred revenue	3,353	5,893
Current portion of deferred rent	3,252	3,311
Accrued redemptions	1,110	1,036
Other	10,184	7,606
Total	$ 27,214	$ 28,367

OTHER CONSOLIDATED BALANCE SH60

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Investment in privately held entity	$ 25,000	$ 25,000
Deposits	2,379	2,738
Debt issuance costs	719	788
Deferred tax assets	666	519
Other	3,356	2,305
Total	$ 32,120	$ 31,350

OTHER CONSOLIDATED BALANCE SH61

OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Statutory liabilities	$ 44,468	$ 40,768
Deferred rent	22,241	20,349
Deferred tax liabilities	139	644
Other	8,087	7,777
Total	$ 74,935	$ 69,538

INDEBTEDNESS - Revolving Credi

INDEBTEDNESS - Revolving Credit Facility, Narrative (Details) - Revolving Credit Facility - Line of Credit - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Nov. 30, 2015
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 | Minimum
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 Seni

INDEBTEDNESS - Convertible Senior Notes, Narrative (Details) - Convertible Debt	Mar. 06, 2017USD ($)day$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)	Mar. 31, 2017
Debt Instrument [Line Items]
Aggregate principal amount	$ 400,000,000
Over-allotment option as a percentage of a principal amount	10.00%
Over-allotment option	$ 40,000,000
Interest rate	0.375%	0.375%
Conversion rate	0.0435749
Conversion price (in USD per share) | $ / shares	$ 22.95	$ 22.95
Conversion amount	$ 1,000
Carrying amount of equity component	86,200,000	$ 83,901,000	$ 83,901,000
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	$ 9,400,000	$ 7,610,000	$ 8,044,000
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%
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 Co

INDEBTEDNESS - Components of Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 06, 2017
Debt Instrument [Line Items]
Principal	$ 440,000	$ 440,000
Less: unamortized debt discount	(69,425)	(73,384)
Less: unamortized debt issuance costs	(7,610)	(8,044)	$ (9,400)
Net carrying amount	$ 362,965	$ 358,572

INDEBTEDNESS - Carrying Amount

INDEBTEDNESS - Carrying Amount of Equity Component of Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 06, 2017
Debt Instrument [Line Items]
Debt discount related to value of conversion option	$ 86,203	$ 86,203
Less: allocated debt issuance costs	(2,302)	(2,302)
Equity component, net	$ 83,901	$ 83,901	$ 86,200

INDEBTEDNESS - Interest Expense

INDEBTEDNESS - Interest Expense (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 06, 2017
Debt Instrument [Line Items]
Contractual interest expense based on 0.375% per annum	$ 413	$ 113
Amortization of debt discount and issuance costs	4,393	1,390
Total	$ 4,806	$ 1,503
Effective interest rate of the liability component	5.34%	5.34%
Interest rate	0.375%		0.375%

INDEBTEDNESS - Convertible Bond

INDEBTEDNESS - Convertible Bond Hedge and Warrant Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Mar. 06, 2017	Mar. 31, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Proceeds from issuance of warrants		$ 0	$ 57,244
Convertible Debt
Debt Instrument [Line Items]
Conversion price of convertible debt (in USD per share)	$ 22.95	$ 22.95
Conversion price of convertible debt after effect of warrants and note hedge (in USD per share)	$ 31.18
Common Stock Warrant
Debt Instrument [Line Items]
Warrants to purchase aggregate shares of capital stock (in shares)	19.2
Warrants, weighted average exercise price (in USD per share)	$ 31.18
Proceeds from issuance of warrants	$ 57,200
Options
Debt Instrument [Line Items]
Convertible note hedge, option to purchase common stock, price (in USD per share)	$ 22.95
Cost of convertible note hedge	$ 92,100

ACCRUED TRANSACTION LOSSES (Det

ACCRUED TRANSACTION LOSSES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Loss Contingency Accrual
Accrued transaction losses, beginning of the period	$ 26,893
Provision for transaction losses	18,031	$ 11,891
Accrued transaction losses, end of the period	28,309
Transaction Losses
Loss Contingency Accrual
Accrued transaction losses, beginning of the period	26,893	20,064
Provision for transaction losses	14,258	11,558
Charge-offs to accrued transaction losses	(12,842)	(11,178)
Accrued transaction losses, end of the period	$ 28,309	$ 20,444

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 175	$ 509
Effective tax rate	(0.70%)	(3.50%)

STOCKHOLDERS' EQUITY - Changes

STOCKHOLDERS' EQUITY - Changes in Stockholder's Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2017	$ 786,333
Net loss	(23,986)	$ (15,090)
Exercise of stock options	31,354
Vesting of early exercised stock options and other	136
Share-based compensation	48,356
Tax withholding related to vesting of restricted stock units	(27,651)
Cumulative adjustment for adoption of ASC 606			$ (4,586)
Change in other comprehensive loss	24
Balance at March 31, 2018	$ 809,980

STOCKHOLDERS' EQUITY - Common

STOCKHOLDERS' EQUITY - Common Stock Narrative (Details) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
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)	$ 0.00	$ 0.00
Common stock, shares outstanding (in shares)	287,921,742	280,400,813
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)	$ 0.00	$ 0.00
Common stock, shares outstanding (in shares)	112,462,337	114,793,262

STOCKHOLDERS' EQUITY - Share B

STOCKHOLDERS' EQUITY - Share Based Compensation Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)planshares	Mar. 31, 2017USD ($)shares	Nov. 17, 2015shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share based compensation plans | plan	2
Stock options granted (in shares)	0	0
Employee stock purchase plan, compensation expense | $	$ 46,824	$ 31,670
Capitalized share-based compensation expense | $	1,500	500
Unrecognized compensation cost, options | $	418,700
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, compensation expense | $	$ 2,300	$ 1,900
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition	2 years 8 months 27 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 and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments outstanding (in shares)	38,069,996
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	65,895,253
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 and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments outstanding (in shares)	24,960,627
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 O

STOCKHOLDERS' EQUITY - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Number of Stock Options Outstanding
Beginning balance (in shares)			47,270,091
Exercised (in shares)			(4,213,775)
Forfeited (in shares)			(328,651)
Ending balance (in shares)	42,727,665	47,270,091	42,727,665
Weighted Average Exercise Price
Beginning balance (in USD per share)			$ 8.67
Exercised (in USD per share)			7.44
Forfeited (in USD per share)			12.04
Ending balance (in USD per share)	$ 8.76	$ 8.67	$ 8.67
Options Exercisable
Options exercisable (in shares)	40,039,760
Options exercisable (in USD per share)	$ 8.47
Additional Disclosures
Weighted average remaining contractual term, options outstanding	6 years 3 months 29 days	6 years 6 months 7 days
Weighted average remaining contractual term, options exercisable	6 years 2 months 13 days
Aggregate intrinsic value, options outstanding	$ 1,727,761	$ 1,229,103
Aggregate intrinsic value, options exercisable	$ 1,630,725

STOCKHOLDERS' EQUITY - RSU Act

STOCKHOLDERS' EQUITY - RSU Activity (Details) - RSUs	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of RSUs
Beginning balance (in shares) | shares	21,317,525
Granted (in shares) | shares	1,226,422
Vested (in shares) | shares	(1,625,534)
Forfeited (in shares) | shares	(615,455)
Ending balance (in shares) | shares	20,302,958
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 17.84
Granted (in USD per share) | $ / shares	44.78
Vested (in USD per share) | $ / shares	14.54
Forfeited (in USD per share) | $ / shares	15.67
Ending balance (in USD per share) | $ / shares	$ 19.80

STOCKHOLDERS' EQUITY - Effects

STOCKHOLDERS' EQUITY - Effects of Share-Based Compensation on Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 46,824	$ 31,670
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	31	0
Product development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	30,482	19,356
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	4,961	3,935
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 11,350	$ 8,379

LOSS PER SHARE - Calculation o

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, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (23,986)	$ (15,090)
Basic shares:
Weighted-average common shares outstanding (in shares)	397,246	368,571
Weighted-average unvested shares (in shares)	(1,298)	(1,834)
Weighted-average shares used to compute basic net loss per share (in shares)	395,948	366,737
Diluted shares:
Weighted-average shares used to compute diluted loss per share (in shares)	395,948	366,737
Net loss per share:
Basic (in USD per share)	$ (0.06)	$ (0.04)
Diluted (in USD per share)	$ (0.06)	$ (0.04)

LOSS PER SHARE - Antidilutive

LOSS PER SHARE - Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 06, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	87,117	98,381
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	66,382	84,909
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	19,173	11,129
Unvested shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,298	1,834
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	264	509
Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion price of convertible debt (in USD per share)	$ 22.95		$ 22.95

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES - Operating and Capital Leases- Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Operating leases, rent expense	$ 4.5	$ 2.8

COMMITMENTS AND CONTINGENCIES79

COMMITMENTS AND CONTINGENCIES - Schedule of Future Payments Under Operating and Capital Leases (Details) $ in Thousands	Mar. 31, 2018USD ($)
Capital
2018 (remaining 9 months)	$ 1,996
2,019	2,549
2,020	1,274
2,021	44
2,022	2
Thereafter	0
Total	5,865
Less amount representing interest	(15)
Present value of capital lease obligations	5,850
Less current portion of capital lease obligation	(2,654)
Non-current portion of capital lease obligation	3,196
Operating
2018 (remaining 9 months)	15,437
2,019	19,600
2,020	19,388
2,021	19,009
2,022	19,105
Thereafter	23,628
Total	$ 116,167

SEGMENT AND GEOGRAPHICAL INFO80

SEGMENT AND GEOGRAPHICAL INFORMATION - Narrative (Details)	3 Months Ended
	Mar. 31, 2018segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

SEGMENT AND GEOGRAPHICAL INFO81

SEGMENT AND GEOGRAPHICAL INFORMATION - Revenue by Geography (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 668,603	$ 461,554
Revenue, contracts from customers	648,800
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	640,173	444,899
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 28,430	$ 16,655

SEGMENT AND GEOGRAPHICAL INFO82

SEGMENT AND GEOGRAPHICAL INFORMATION - Long-lived Assets by Geography (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 170,635	$ 164,157
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	165,530	158,820
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 5,105	$ 5,337

SUPPLEMENTAL CASH FLOW INFORM83

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Data:
Cash paid for interest	$ 966	$ 142
Cash paid for income taxes	658	334
Supplemental disclosures of non-cash investing and financing activities:
Change in purchases of property and equipment in accounts payable and accrued expenses	(3,813)	(468)
Unpaid business acquisition purchase price	$ 1,151	$ 400

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2018	Dec. 31, 2014
Caviar, Inc.
Subsequent Event [Line Items]
Shares issued for consideration withheld for indemnification purposes (in shares)		1,292,207
Subsequent Event | Caviar, Inc.
Subsequent Event [Line Items]
Shares issued for consideration withheld for indemnification purposes, released to former owners (in shares)	822,085
Shares issued for consideration withheld for indemnification purposes, forfeited back to Company (in shares)	469,894
Subsequent Event | Webbly Inc
Subsequent Event [Line Items]
Purchase price	$ 265
Cash paid to acquire company	132.5
Stock issued to acquire company	$ 132.5