Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income	$ 99,211	$ 111,852	$ 82,570	$ 249,376
Denominator:
Weighted average outstanding shares - basic	46,091	47,617	46,397	49,002
Effect of dilutive securities:
Convertible notes (in shares)	1,059	2,643	1,471	2,721
Warrants (in shares)	3,274	1,560	3,096	1,671
Stock options and employee stock purchase plan (in shares)	1,481	1,432	1,493	1,554
Weighted average shares - diluted	51,905	53,252	52,457	54,948
Loss (earnings) per common share:
Basic (in dollars per share)	$ 2.15	$ 2.35	$ 1.78	$ 5.09
Diluted (in dollars per share)	$ 1.91	$ 2.10	$ 1.57	$ 4.54
Stock options, warrants and shares of our common stock issued under our Convertible Notes excluded from calculation	3,699	9,925	4,655	9,814