Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (41,708)	$ (64,911)	$ (48,429)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	23,169	17,267	12,979
Deferred income taxes	581	581	577
Bad debt expense and other reserves	1,285	925	300
Stock-based compensation	24,739	42,563	29,333
Common stock warrant expense (benefit)	46	(803)	9,861
Non-cash interest expense on lease financing obligation	396	0	0
Imputed interest on notes receivable	0	0	(3)
Interest income on notes receivable	0	0	(4)
Accretion of beneficial conversion feature on convertible notes payable and discount on revolving line of credit	0	0	236
Write-off and loss on disposal of fixed assets	474	1,631	233
Changes in operating assets and liabilities:
Accounts receivable	(4,391)	(5,938)	(10,372)
Prepaid expenses	4	(855)	(1,643)
Other current assets	(846)	1,087	(1,316)
Other assets	(613)	(458)	(26)
Accounts payable	(4,552)	5,312	3,399
Accrued employee expenses	1,152	(6,510)	3,883
Accrued expenses and other liabilities	1,531	(1,781)	4,253
Other liabilities	1,501	521	(157)
Net cash provided by (used in) operating activities	2,768	(11,369)	3,104
Cash flows from investing activities
Change in restricted cash	0	0	2,000
Purchase of property and equipment	(16,639)	(29,836)	(15,531)
Purchase of intangible assets	0	0	(365)
Notes receivable from related parties	0	0	(60)
Repayment of notes receivable from related parties	0	0	4,133
Net cash used in investing activities	(16,639)	(29,836)	(9,823)
Cash flows from financing activities
Proceeds from initial public offering, net of underwriting discounts and offering costs	0	0	69,702
Proceeds from follow-on public offering, net of underwriting discounts and offering costs	0	0	30,950
Proceeds from short swing profits	0	0	14
Proceeds from borrowings under credit agreement	0	0	5,000
Repayments under credit agreement	0	0	(10,000)
Repurchase of common stock option awards	(100)	0	0
Proceeds from exercise of common stock options	9,112	6,328	5,851
Taxes paid related to net share settlement of equity awards	(1,312)	(908)	(539)
Proceeds from exercise of warrants	0	0	9,461
Proceeds from financing obligation drawdown	1,521	622	0
Payments for lease financing obligation	0	(5)	0
Net cash provided by financing activities	9,221	6,037	110,439
Net (decrease) increase in cash and cash equivalents	(4,650)	(35,168)	103,720
Cash and cash equivalents at beginning of period	112,371	147,539	43,819
Cash and cash equivalents at end of period	107,721	112,371	147,539
Cash paid during the year for:
Interest	2,133	617	139
Income taxes	82	48	20
Supplemental disclosures of non-cash activities
Conversion of Series A convertible preferred stock in connection with initial public offering	0	0	29,224
Initial public offering costs paid in the prior year	0	0	551
Stock-based compensation capitalized for software development	1,012	1,325	1,249
Recognition of leased facility asset and lease financing obligation	0	23,683	6,591
Accrued offering costs included in accounts payable and accrued expenses	0	0	(188)
Capitalized assets included in accounts payable, accrued employee expenses and other accrued expenses	$ 1,078	$ 1,635	$ 795