Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss		$ (13,396)	$ (14,051)	[1]
Adjustments to reconcile net loss to net cash provided by operating activities
Depreciation and amortization		2,684	3,082	[1]
(Accretion of discounts)/amortization of premiums on investments		(237)	54	[1]
Amortization of acquisition-related intangible assets		1,492
Amortization of deferred costs		7,950	6,616	[1]
Amortization of debt discount and issuance costs		1,774	18	[1]
Loss (gain) on disposal of property and equipment		47	(4)	[1]
Stock-based compensation		10,531	7,310	[1]
Foreign exchange loss (gain)		462	(66)	[1]
Change in operating assets and liabilities, net of impact of business combination
Accounts receivable		15,508	7,330	[1]
Prepaid expenses and other assets		89	1,481	[1]
Deferred costs		(8,163)	(6,119)	[1]
Accounts payable		839	1,037	[1]
Accrued expenses		(1,328)	(1,727)	[1]
Deferred revenue		(9,674)	(2,820)	[1]
Deferred rent		(446)	(398)	[1]
Net cash provided by operating activities		8,132	1,743	[1]
Cash flows from investing activities
Business combination, net of cash acquired		(39,041)
Purchases of property and equipment		(1,396)	(2,236)	[1]
Proceeds from sales of equipment	[1]		9
Proceeds from maturities of investments		81,550	19,700	[1]
Purchases of investments		(67,218)	(28,898)	[1]
Return of (payments for) security deposits		50	(29)	[1]
Net cash used in investing activities		(26,055)	(11,454)	[1]
Cash flows from financing activities
Proceeds from borrowings on convertible notes, net of discounts		139,438
Purchase of capped calls		(17,092)
Proceeds from exercises of common stock options		13,942	5,495	[1]
Payment of issuance costs on convertible notes		(465)
Proceeds from purchases of stock under employee stock purchase plan		2,391	2,251	[1]
Payment of initial public offering costs	[1]		(243)
Principal payments on capital lease obligations		(13)	(21)	[1]
Net cash provided by financing activities		138,201	7,482	[1]
Foreign currency effect on cash, cash equivalents and restricted cash		(353)	56	[1]
Net increase (decrease) in cash, cash equivalents and restricted cash		119,925	(2,173)	[1]
Cash, cash equivalents and restricted cash
Beginning of period		55,069	42,007	[1]
End of period		174,994	39,834	[1]
Supplemental non-cash disclosures
Debt issuance costs in accounts payable and accrued expenses		4
Purchases under capital lease obligations		144
Property and equipment additions in accounts payable and accrued expenses		347	$ 742	[1]
Class A Common Stock
Supplemental non-cash disclosures
Class A Common stock issued in business combination		$ 4,617

[1] See Note 1 for a summary of adjustments