Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Net income	$ 98,874	$ 11,651
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares - basic (in shares)	96,878	93,446
Effect of dilutive securities (in shares):
Stock options	10,276	13,630
Restricted stock	325	658
Warrants	1,890
Dilutive potential shares	12,491	14,288
Weighted average shares - diluted (in shares)	109,369	107,734
Earnings Per Share, Basic and Diluted [Abstract]
Net income per share - basic (in dollars per share)	$ 1.02	$ 0.12
Net income per share - diluted (in dollars per share)	$ 0.90	$ 0.11
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	3,868	89
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	4,761	4,761
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares		4,761