Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Consolidated Statements of Cash Flows
Net loss	$ (11,623)	$ (9,921)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,897	2,919
Deferred income taxes	203	250
Bad debt expense and other reserves	65	37
Stock-based compensation	9,453	4,144
Common stock warrant expense	(147)	2,388
Imputed interest on notes receivable		10
Interest income on notes receivable		(14)
Accretion of beneficial conversion feature on convertible notes payable and discount on revolving line of credit		129
Loss on disposal of fixed assets	28	195
Changes in operating assets and liabilities:
Accounts receivable	(256)	(2,217)
Prepaid expenses	608	648
Other current assets	1,338	280
Other assets	(206)
Accounts payable	(683)	(780)
Accrued employee expenses	(7,407)	(4,941)
Accrued expenses and other liabilities	1,508	4,629
Other liabilities	65	(39)
Net cash used in operating activities	(3,157)	(2,283)
Cash flows from investing activities
Purchase of property and equipment	(5,174)	(2,215)
Purchase of intangible assets		(350)
Repayment of notes receivable from related parties		3,761
Net cash (used in) provided by investing activities	(5,174)	1,196
Cash flows from financing activities
Payments of initial public offering costs		(714)
Proceeds from exercise of common stock options	3,893	557
Taxes paid related to net share settlement of equity awards	(362)
Proceeds from financing obligation drawdown	345
Payments of build-to-suit financing obligations	(15)
Net cash provided by (used in) financing activities	3,861	(157)
Net increase in cash and cash equivalents	(4,470)	(1,244)
Cash and cash equivalents at beginning of period	147,539
Cash and cash equivalents at end of period	143,069	42,575
Supplemental disclosures of non-cash activities
Deferred offering costs included in accounts payable and accrued expenses		2,310
Recognition of leased facility asset acquired and lease financing obligation	22,412
Stock-based compensation capitalized for software development	331	294
Capitalized assets included in accounts payable, accrued employee expenses and other accrued expenses	$ 1,181	$ 239