Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Net loss	$ (23,636)	$ (28,271)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	4,487	4,916
Amortization of premiums on investments	20	67
Loss (gain) on disposal of property and equipment	26	(12)
Stock-based compensation	6,902	5,877
Accretion of capitalized loan fees	127	39
Loss on extinguishment of debt	722
Remeasurement of preferred stock warrant liability	202	57
Change in operating assets and liabilities
Accounts receivable	10,302	14,689
Prepaid expenses and other assets	(660)	(2,167)
Accounts payable	1,648	812
Accrued expenses	(2,442)	(2,199)
Deferred revenue	535	(2,959)
Deferred rent	(421)	391
Net cash used in operating activities	(2,188)	(8,760)
Cash flows from investing activities
Purchases of property and equipment	(3,518)	(6,636)
Proceeds from maturities of investments	6,245	13,309
Purchases of investments	(10,826)	(2,017)
(Payment) return of security deposits	(43)	157
Return of restricted cash	2,500	85
Net cash (used in) provided by investing activities	(5,642)	4,898
Cash flows from financing activities
Proceeds from initial public offering, net of underwriting discounts	102,672
Payment of deferred initial public offering costs	(574)	(418)
Proceeds from long-term debt	20,000
Principal payments on long-term debt	(20,000)
Payment of debt prepayment fees	(200)
Proceeds from exercise of common stock options	1,000	2,335
Principal payments on capital lease obligations	(33)	(36)
Payment of capitalized loan fees	(248)	(78)
Net cash provided by financing activities	102,617	1,803
Foreign currency effect on cash and cash equivalents	(331)	(77)
Net increase (decrease) in cash and cash equivalents	94,456	(2,136)
Cash and cash equivalents
Beginning of year	17,256	19,686
End of year	111,712	17,550
Supplemental disclosures
Purchases under capital lease obligations		102
Property and equipment additions in accounts payable and accrued expenses	419	37
Leasehold improvements paid directly by lessor	356
Non-cash debt issuance costs	285	90
Deferred initial public offering cost accruals	1,004	$ 1,163
Non-cash preferred stock warrant exercise	$ 616