Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net loss	$ (11,226)	$ (9,158)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	5,778	4,295
Share-based compensation	8,652	5,370
Provision for doubtful accounts	197	52
Amortization of premiums on marketable securities	635	670
Deferred income tax benefit	(7,498)	(6,026)
Other	46	82
Change in operating assets and liabilities:
Trade and other receivables	467	(295)
Prepaid expenses and other current assets	(1,360)	(4,319)
Other non-current assets	27	(44)
Accounts payable	(12,293)	2,563
Accrued expenses and other liabilities	7,991	4,556
Deferred revenue	19,203	22,777
Other non-current liabilities	246	7
Net cash provided by operating activities	10,865	20,530
Investing activities
Acquisition of property and equipment, including capitalization of internal use software	(4,830)	(2,816)
Purchases of marketable securities	(25,521)	(39,379)
Sales and maturities of marketable securities	65,071	33,438
Net cash provided by (used in) investing activities	34,720	(8,757)
Financing activities
Proceeds from stock-based compensation plans	1,956	1,773
Payments related to the repurchases of common stock	(51,923)	0
Payments for employee tax withholdings related to restricted stock units and awards	(950)	(230)
Net cash provided by (used in) financing activities	(50,917)	1,543
Net increase (decrease) in cash and cash equivalents	(5,332)	13,316
Cash and cash equivalents at beginning of period	50,239	146,569
Cash and cash equivalents at end of period	$ 44,907	$ 159,885