Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (47,735)	$ (21,336)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	11,392	8,480
Net amortization of investment premium and discount	(237)	107
Amortization of debt issuance costs	211
Accretion of debt discount on convertible senior notes	2,484
Stock-based compensation	38,546	21,785
Amortization of deferred commissions	478	140
Provision for doubtful accounts	1,515	282
Write-off of internal-use software	515	96
Gain on lease termination		(295)
Changes in operating assets and liabilities:
Accounts receivable	(26,048)	(9,365)
Prepaid expenses and other current assets	(2,847)	1,933
Other long-term assets	(1,908)	(932)
Accounts payable	12,566	(1,282)
Accrued expenses and other current liabilities	28,040	(6,311)
Customer deposits	7,842
Deferred revenue	(4,542)	2,353
Long-term liabilities	(1,047)	296
Net cash provided by (used in) operating activities	19,225	(4,049)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(184,364)	(220,914)
Maturities of marketable securities	58,520	23,000
Capitalized software development costs	(9,958)	(8,000)
Purchases of property and equipment	(2,066)	(6,772)
Purchases of intangible assets	(249)	(154)
Acquisition, net of cash acquired		(22,621)
Net cash used in investing activities	(138,117)	(235,461)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of convertible senior notes	550,000
Payment of debt issuance costs	(12,513)
Purchase of capped call	(58,465)
Payments of costs related to public offerings		(430)
Proceeds from exercises of stock options	13,715	18,154
Proceeds from shares issued under ESPP	4,474	7,404
Value of equity awards withheld for tax liabilities	(910)	(311)
Net cash provided by financing activities	496,301	24,817
Effect of exchange rate changes on cash, cash equivalents and restricted cash	818	42
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	378,227	(214,651)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH-Beginning of period	120,788	314,280
CASH, CASH EQUIVALENTS AND RESTRICTED CASH -End of period	499,015	99,629
Cash paid for income taxes	321	373
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property, equipment and intangible assets, accrued but not paid	572	376
Stock-based compensation capitalized in software development costs	2,909	$ 1,557
Debt offering costs, accrued but not paid	$ 467