Convertible Senior Notes - Schedule of Convertible Senior Notes (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Feb. 28, 2014
Liability component:
Principal	$ 690,000,000	$ 690,000,000	$ 690,000,000
Less: debt discount and issuance costs, net of amortization	(32,869,000)	(49,913,000)
Net carrying amount	657,131,000	640,087,000
Convertible senior notes
Liability component:
Equity component:	$ 101,276,000	$ 101,276,000