CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows used in operating activities:
Net loss	$ (23,862)	$ (15,654)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8,253	2,607
Allowance for doubtful accounts	1,148	306
Stock-based compensation	7,832	3,097
Deferred income taxes	(585)	150
Accretion of interest	3,018	(18)
Changes in operating assets and liabilities:
Accounts receivable	(4,738)	(1,809)
Prepaid expenses and other current assets	599	(430)
Other assets	31	(9)
Accounts payable	(533)	(287)
Accrued expenses and other current liabilities	1,836	966
Accrued compensation	(7,917)	(1,921)
Other liabilities	1,047	495
Net cash used in operating activities	(13,871)	(12,507)
Cash flows (used in) provided by investing activities:
Purchase of property and equipment	(557)	(620)
Purchase of internal-use software	(471)	(152)
Purchase of marketable securities		(34,957)
Proceeds from marketable securities	25,000	14,740
Net cash provided by (used in) investing activities	23,972	(20,989)
Cash flows provided by financing activities:
Net proceeds from the exercise of stock options	8,643	1,195
Repayment of bank borrowings and other debt		(2,000)
Proceeds from issuance of common stock		123,928
Cash for withholding taxes on stock-based awards, net	3,555	306
Net cash provided by financing activities	12,198	123,429
Net increase in cash and cash equivalents	22,299	89,933
Foreign exchange difference	63
Cash and cash equivalents at beginning of the period	42,817	50,015
Cash and cash equivalents at end of the period	65,179	139,948
Income taxes paid	52	994
Interest paid	$ 2	$ 2,387