Convertible Senior Notes - Schedule of Convertible Senior Notes (Details) - USD ($)	Sep. 30, 2015	Dec. 31, 2014	Feb. 28, 2014
Liability component:
Principal	$ 690,000,000	$ 690,000,000	$ 690,000,000
Less: debt discount, net of amortization	(70,635,000)	(85,149,000)
Net carrying amount	619,365,000	604,851,000
Convertible senior notes
Liability component:
Equity component:	$ 101,276,000	$ 101,276,000