CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (48,134)	$ (50,071)	$ (44,426)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	4,160	3,781	3,546
Stock-based compensation expense	35,784	30,841	19,476
(Recovery of) provision for doubtful accounts	(92)	550	(517)
Amortization of premiums and discounts on marketable securities, net	13	(141)	101
Amortization of debt discount and issuance costs	3,262	0	0
Recognition of deferred government grant obligation	0	0	(1,578)
Deferred income tax	(65)	(9)	0
Changes in assets and liabilities:
Accounts receivable	5,166	(20,216)	(5,546)
Deferred commissions	(10,268)	(11,155)	(498)
Operating lease right-of-use asset	2,552
Other receivables	(1,250)	(205)	577
Prepaid expenses and other	(2,084)	2,020	2,952
Other assets	(1,860)	276	618
Accounts payable	2,153	1,699	2,206
Deferred revenue	32,039	40,144	29,367
Operating lease liability	(3,035)
Accrued expenses and other liabilities	12,225	8,886	(758)
Net cash provided by operating activities	30,566	6,400	5,520
Cash flows from investing activities
Purchase of property and equipment	(3,104)	(1,122)	(1,188)
Purchase of marketable securities	(112,565)	(24,659)	(14,369)
Maturities of marketable securities	26,840	20,400	9,281
Sale of marketable securities	498	0	0
Purchase of intangible assets	(734)	(251)	(197)
Other investments	(1,000)	0	0
Net cash used in investing activities	(90,065)	(5,632)	(6,473)
Cash flows from financing activities
Proceeds from option exercises	24,152	16,662	12,485
Taxes paid related to net share settlements of stock-based compensation awards	(390)	(1,861)	(1,125)
Proceeds from shares issued in connection with employee stock purchase plan	4,922	3,216	0
Proceeds from the issuance of convertible senior notes, net of issuance costs	335,899	0	0
Repayment of other long-term debt	0	0	(73)
Principal payments on financing obligations	(1,213)
Principal payments on capital lease obligations		(1,163)	(1,435)
Proceeds from government grants	0	22	51
Deferred financing costs	0	0	(81)
Net cash provided by financing activities	363,370	16,876	9,822
Effect of foreign exchange rates on cash	287	(393)	183
Net increase in cash and cash equivalents	304,158	17,251	9,052
Cash and cash equivalents at beginning of year	77,584	60,333	51,281
Cash and cash equivalents at end of year	381,742	77,584	60,333
Supplemental cash flow disclosure
Cash paid for interest	1,692	1,734	1,627
Cash paid for income taxes, net of refunds	371	67	42
Supplemental disclosure of noncash investing and financing activities
Allowance for tenant improvements	270	2,192	0
Purchases of property and equipment, accrued but not paid	$ 588	$ 1,287	$ 0