Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (25,093)	$ (30,694)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,371	5,077
Amortization of debt discount and issuance costs	5,104	0
Stock-based compensation expense	19,064	13,575
Provision for doubtful accounts	1,353	456
Deferred income taxes	(761)	0
Foreign currency re-measurement loss	191	471
Other non-cash (income) expense	(1,290)	(71)
Changes in operating assets and liabilities:
Accounts receivable	4,549	24,586
Deferred contract acquisition and fulfillment costs	(3,172)	(4,531)
Prepaid expenses and other assets	(9,334)	(3,602)
Accounts payable	2,184	2,391
Accrued expenses	(7,312)	(7,806)
Deferred revenue	(5,066)	(1,001)
Other liabilities	1,129	(669)
Net cash used in operating activities	(11,083)	(1,818)
Cash flows from investing activities:
Business acquisition, net of cash acquired	(14,621)	0
Purchases of property and equipment	(17,712)	(5,650)
Capitalization of internal-use software costs	(3,152)	(1,413)
Purchases of investments	(72,432)	(10,655)
Sales/maturities of investments	140,302	33,128
Net cash provided by investing activities	32,385	15,410
Cash flows from financing activities:
Proceeds from follow-on public offering, net of offering costs of $608	0	30,907
Taxes paid related to net share settlement of equity awards	(2,839)	(1,005)
Proceeds from employee stock purchase plan	2,634	1,632
Proceeds from stock option exercises	6,058	4,657
Net cash provided by financing activities	5,853	36,191
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(151)	(314)
Net increase in cash, cash equivalents and restricted cash	27,004	49,469
Cash, cash equivalents and restricted cash, beginning of period	99,565	51,762
Cash, cash equivalents and restricted cash, end of period	126,569	101,231
Supplemental cash flow information:
Cash paid for interest on convertible senior notes	1,342	0
Cash paid for income taxes, net of refunds	319	315
Non-cash investing activities:
Leasehold improvements acquired through tenant improvement allowance	14,016	0
Reconciliation of cash, cash equivalents and restricted cash:
Total cash, cash equivalents and restricted cash	$ 99,565	$ 51,762