Stockholders' Equity (Details 4) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income	$ 104,644	$ 464,425	$ 99,211	$ (16,641)	$ 115,935	$ (25,237)	$ 111,852	$ 137,524	$ 651,639	$ 340,074	$ 174,560
Denominator:
Weighted average outstanding shares - basic									46,000	48,176	50,076
Effect of dilutive securities:
Convertible notes (in shares)									915	2,630	1,736
Warrants (in shares)									3,009	1,910	276
Stock options and employee stock purchase plan (in shares)									1,297	1,439	1,143
Weighted average shares - diluted									51,221	54,155	53,231
Basic
Net (loss) income per share-basic (in dollars per share)	$ 2.29	$ 10.20	$ 2.15	$ (0.36)	$ 2.44	$ (0.53)	$ 2.35	$ 2.73	$ 14.17	$ 7.06	$ 3.49
Diluted
Net (loss) income per share-diluted (in dollars per share)	$ 2.10	$ 9.24	$ 1.91	$ (0.36)	$ 2.17	$ (0.53)	$ 2.10	$ 2.43	$ 12.72	$ 6.28	$ 3.28
Stock options, warrants and shares of our common stock issued under our Convertible Notes excluded from calculation									3,800	9,273	11,210