Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (10,545)	$ (15,580)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	1,624	1,711
Stock-based compensation expense	4,279	5,519
Provision for doubtful accounts	316	124
Foreign currency re-measurement loss (gain)	44	(223)
Other non-cash expenses	97	78
Changes in assets and liabilities:
Accounts receivable	15,182	14,048
Prepaid expenses and other assets	1,466	(716)
Accounts payable	(244)	(500)
Accrued expenses	(7,216)	(7,427)
Deferred revenue	(1,416)	1,540
Other liabilities	(266)	(166)
Net cash provided by (used in) operating activities	3,321	(1,592)
Cash flows from investing activities:
Purchases of property and equipment	(1,335)	(1,092)
Purchases of investments	(7,401)	0
Maturities of investments	900	0
Net cash used in investing activities	(7,836)	(1,092)
Cash flows from financing activities:
Payments of capital lease obligations	0	(68)
Taxes paid related to net share settlement of equity awards	(169)	(3,087)
Proceeds from employee stock purchase plan	1,499	2,096
Proceeds from stock option exercises	775	547
Net cash provided by (used in) financing activities	2,105	(512)
Effect of exchange rate changes on cash and cash equivalents	(76)	151
Net decrease in cash and cash equivalents	(2,486)	(3,045)
Cash and cash equivalents, beginning of period	53,148	86,553
Cash and cash equivalents, end of period	50,662	83,508
Supplemental cash flow information:
Cash paid for income taxes	65	274
Cash paid for interest	$ 0	$ 1