Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Cash Flows
Net loss	$ (48,429)	$ (25,056)	$ (74,495)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	12,979	10,835	10,275
Deferred income taxes	577	579	(606)
Bad debt expense and other reserves	300	280	668
Stock-based compensation	29,333	9,346	10,320
Legal expense settled in stock			307
Legal settlement paid in stock		326
Increase in fair value of contingent consideration liability		95	1,370
Common stock warrant expense	9,861	3,740	1,990
Imputed interest on notes receivable	(3)	127	126
Interest income on notes receivable	(4)	(107)	(107)
Interest expense on note payable		805	1,508
Accretion of beneficial conversion feature on convertible notes payable and discount on revolving line of credit	236	1,117	1,770
Loss on disposal of fixed assets	233	734	1,493
Changes in operating assets and liabilities, net of effect of acquisitions:
Accounts receivable	(10,372)	(8,196)	2,506
Prepaid expenses	(1,643)	(1,955)	(104)
Other current assets	(1,316)	(29)	163
Other assets	(26)	(281)	10,082
Accounts payable	3,399	1,382	(2,053)
Accrued employee expenses	3,883	3,973	(376)
Accrued expenses and other liabilities	4,253	(1,204)	2,655
Other liabilities	(157)	(422)	(210)
Net cash used in operating activities	3,104	(3,911)	(32,718)
Cash flows from investing activities
Change in restricted cash	2,000	2,500	(4,500)
Sales of short term investments			31,061
Purchase of property and equipment	(15,531)	(8,404)	(6,200)
Purchase of intangible assets	(365)
Notes receivable from related parties	(60)
Repayment of notes receivable from related parties	4,133	421	13
Net cash (used in) provided by investing activities	(9,823)	(5,483)	20,374
Cash flows from financing activities
Proceeds from initial public offering net of underwriting discounts	69,702
Proceeds from follow-on public offering, net of underwriting discounts and offering costs	30,950
Proceeds from short swing profits	14
Proceeds from revolving line of credit	5,000	5,000
Repayments under credit agreement	(10,000)
Proceeds from the issuance of preferred stock and common stock warrants, net of issuance costs		29,901
Proceeds from the issuance of common stock, net of issuance costs			116
Issuance of convertible note payable			23,133
Payments of initial public offering costs		(551)
Payment of contingent consideration		(428)
Repurchase of common stock		(1,000)	(1,648)
Repurchase of vested common stock option awards		(2,000)
Proceeds from exercise of common stock options	5,851	229	313
Taxes paid related to net share settlement of equity awards	(539)
Proceeds from exercise of warrants	9,461		637
Net cash provided by financing activities	110,439	31,151	22,551
Net increase in cash and cash equivalents	103,720	21,757	10,207
Cash and cash equivalents at beginning of period	43,819	22,062	11,855
Cash and cash equivalents at end of period	147,539	43,819	22,062
Cash paid during the year for:
Interest	139	64
Income taxes	20
Supplemental disclosures of non-cash activities
Conversion of Series A convertible preferred stock in connection with initial public offering	29,224
Payments of initial public offering costs paid in the prior year	551
Issuance of common stock in settlement of liability			850
Issuance of common stock in lieu of cash bonus			626
Conversion of convertible note payable and accrued interest to common stock		25,447
Contingently redeemable common stock			(1,000)
Beneficial conversion feature related to convertible notes payable, net of tax			1,618
Deferred offering costs included in accounts payable and accrued expenses		1,143
Tenant incentive for purchase of leasehold improvements		519
Stock-based compensation capitalized for software development	1,249	540	214
Recognition of leased facility asset and lease financing obligation	6,591
Accrued offering costs included in accounts payable and accrued expenses	(188)
Capitalized assets included in accounts payable, accrued employee expenses and other accrued expenses	$ 795	$ 109