Stockholders' Equity (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:
Income from continuing operations									$ 174,560	$ 304,442	$ 217,243
Income from discontinued operations											625
Net income	$ (30,314)	$ 62,685	$ 79,864	$ 62,325	$ 83,255	$ 78,111	$ 72,316	$ 70,760	$ 174,560	$ 304,442	$ 217,868
Denominator:
Weighted average outstanding shares - basic									50,076	52,093	57,163
Effect of dilutive securities:
Convertible notes (in shares)									1,736	218	569
Warrants (in shares)									276		263
Stock options and employee stock purchase plan (in shares)									1,143	969	1,400
Weighted average shares - diluted									53,231	53,280	59,395
Basic
Continuing operations (in dollars per share)									$ 3.49	$ 5.84	$ 3.80
Discontinued operations (in dollars per share)									$ 0.00	$ 0.00	$ 0.01
Net income per basic common share (in dollars per share)	$ (0.60)	$ 1.25	$ 1.60	$ 1.24	$ 1.65	$ 1.52	$ 1.37	$ 1.32	$ 3.49	$ 5.84	$ 3.81
Diluted
Continuing operations (in dollars per share)									$ 3.28	$ 5.71	$ 3.66
Discontinued operations (in dollars per share)									$ 0.00	$ 0.00	$ 0.01
Net income per diluted common share (in dollars per share)	$ (0.60)	$ 1.17	$ 1.52	$ 1.24	$ 1.60	$ 1.46	$ 1.34	$ 1.29	$ 3.28	$ 5.71	$ 3.67
Stock options and warrants excluded from calculation (in shares)									11,210	11,862	16,299