Long-Term Debt - Details of the Liability Component (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Principal amount	$ 851,551	$ 737,000
Unamortized discount	147,454	138,760
Net carrying amount	704,097	598,240
1.125% Notes
Debt Instrument [Line Items]
Principal amount	550,000	550,000
Unamortized discount	114,670	133,632
Net carrying amount	435,330	416,368
1.625% Notes
Debt Instrument [Line Items]
Principal amount	301,551
Unamortized discount	32,784
Net carrying amount	268,767
3.75% Convertible Senior Notes due 2014
Debt Instrument [Line Items]
Principal amount		187,000
Unamortized discount		5,128
Net carrying amount		$ 181,872