Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes
Accrued interest and penalties related to the timing of certain tax payments	$ 300
Percent of pre-tax income:
U.S. federal statutory income tax rate (as a percent)	35.00%	35.00%	35.00%
State taxes, net of federal benefit (as a percent)	7.40%	6.80%
Permanent items (as a percent)	(0.50%)	2.30%	(2.20%)
Impact of state rate changes (as a percent)	0.90%
Research and development credit (as a percent)			2.70%
Change in valuation allowance (as a percent)	(29.10%)	(89.50%)	(35.50%)
Effective income tax rate (as a percent)	13.70%	(45.40%)	0.00%
Current:
Federal	$ 136	$ 29,505
State	91	11,440
Deferred:
Federal	(17,014)	(4,469)
Income tax (benefit) expense	(16,787)	36,476
Deferred tax assets (liabilities)
Deferred revenue	142,675	120,611
License and technology payments	13,150	14,251
Share-based compensation	11,427	5,679
Accrued expenses	743	442
Depreciation	(617)	(328)
Federal and state net operating loss carryforwards	26,065
Excess tax benefits related to share-based compensation	1,630
Charitable contribution carryforwards	5
Deferred income tax assets	195,078	140,655
Valuation allowance	(171,965)	(136,138)
Net deferred tax assets	$ 23,113	$ 4,517