Income Taxes - Additional Information (Details) (USD $)	3 Months Ended					9 Months Ended
	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S federal statutory rate	35.00%		35.00%			35.00%	35.00%
Discrete tax benefits realized on disqualifying dispositions of stock	$ 700,000		$ 500,000			$ 2,200,000	$ 1,500,000
Stock-based compensation expense adjustments related to certain terminated employees	3,016,000	900,000	7,960,000			6,778,000	24,663,000
Reinstatement of the federal research and development tax credit					2,200,000
Non-deductible acquisition related expenses				1,000,000
Tax benefit related to the expiration of certain statutes	800,000
Tax benefit related to the expiration of certain statutes			2,000,000
Unrecognized tax benefits	21,300,000					21,300,000
Accrued interest and penalties related to uncertain tax positions	1,600,000					1,600,000		1,500,000
Anticipated reduction in uncertain tax positions	$ 600,000					$ 600,000