Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating activities
Net loss	$ (18,792)	$ (8,638)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	12,025	8,860
Share-based compensation	16,897	12,424
Provision for doubtful accounts	309	45
Amortization of premiums on marketable securities	1,161	1,498
Deferred income tax benefit	(12,328)	(5,709)
Other	213	82
Change in operating assets and liabilities:
Trade and other receivables	(2,818)	(2,655)
Prepaid expenses and other current assets	(673)	(653)
Other non-current assets	(280)	304
Accounts payable	(15,629)	7,229
Accrued expenses and other liabilities	10,117	7,284
Deferred revenue	30,374	34,450
Other non-current liabilities	58	376
Net cash provided by operating activities	20,634	54,897
Investing activities
Acquisition of property and equipment, including capitalization of internal use software	(9,337)	(4,973)
Purchases of marketable securities	(38,400)	(115,274)
Sales and maturities of marketable securities	107,986	72,345
Premiums paid for company-owned life insurance policies	4,337	4,337
Net cash provided by (used in) investing activities	55,912	(52,239)
Financing activities
Proceeds from stock-based compensation plans	5,469	8,032
Payments related to the repurchases of common stock	(100,000)	0
Payments for employee tax withholdings related to restricted stock units and awards	(2,582)	(1,230)
Net cash provided by (used in) financing activities	(97,113)	6,802
Net increase (decrease) in cash and cash equivalents	(20,567)	9,460
Cash and cash equivalents at beginning of period	50,239	146,569
Cash and cash equivalents at end of period	29,672	156,029
Supplemental cash flow information:
Building in progress - leased facility acquired under financing obligation	$ 10,746	$ 0