Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (39,118)	$ (37,710)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	13,192	10,172
Amortization of deferred costs	5,486	3,928
Accretion of interest on convertible senior notes	3,667	3,435
Provision for doubtful accounts and sales reserve	642	158
Stock-based compensation	24,094	20,007
Other non-cash adjustments	(47)	(345)
Changes in operating assets and liabilities:
Accounts receivable	(8,405)	1,524
Prepaid expenses	(5,144)	(2,439)
Deferred costs	(8,438)	(6,991)
Other assets	924	(1,584)
Accounts payable	7,318	(113)
Accrued payroll and employee related liabilities	1,974	2,109
Accrued expenses	(296)	(621)
Deferred revenue	12,373	7,237
Other liabilities	632	457
Net cash provided by (used in) operating activities	8,854	(776)
Cash flows from investing activities:
Capital expenditures	(4,417)	(855)
Proceeds from landlord reimbursement	1,143
Payments for acquisition of business, net of acquired cash	(58,419)	(35,857)
Purchase of short-term investments	(1,975)	(57,709)
Maturities of short-term investments	47,765	74,069
Additions to intangibles		(184)
Additions to capitalized software development costs	(5,867)	(6,722)
Net cash used in investing activities	(21,770)	(27,258)
Cash flows from financing activities:
Restricted stock units withheld to settle employee tax withholding liability	(4,531)	(7,921)
Proceeds from public offering, net of costs	139,110
Proceeds from employee stock purchase plan	2,337	1,758
Proceeds from stock option exercises	15,822	8,821
Other	(548)	(635)
Net cash provided by financing activities	152,190	2,023
Effect of exchange rates on cash, cash equivalents and restricted cash	(227)	(746)
Net increase (decrease) in cash, cash equivalents and restricted cash	139,047	(26,757)
Cash, cash equivalents and restricted cash—beginning of period	60,068	103,051
Cash, cash equivalents and restricted cash—end of period	199,115	76,294
Supplemental disclosures of cash flow information:
Interest	863	771
Taxes, net of refunds received		43
Supplemental disclosure of non-cash activities:
Capitalized assets included in accounts payable and accrued expenses	122	278
Capitalized development costs included in accounts payable and accrued expenses	7
Common stock issued in connection with acquisition	32,838
Contingent consideration in connection with acquisition	550
Note payable issued for asset acquisition		52
Stock-based compensation capitalized for software development	$ 420	$ 250