Convertible Senior Notes (Liability Component) (Details) - Senior Notes [Member] - USD ($)	Sep. 30, 2015	Jan. 31, 2015	Dec. 31, 2014	Jun. 30, 2012
Convertible Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Principal	$ 400,000,000	$ 400,000,000	$ 0
Less: Debt discount, net	(81,536,000)		0
Net carrying amount	318,464,000		0
Convertible Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Principal	275,000,000		275,000,000	$ 275,000,000
Less: Debt discount, net	(19,953,000)		(28,324,000)
Net carrying amount	$ 255,047,000		$ 246,676,000