Per Share Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net income (loss)	$ 191,468	$ (62,365)	$ 279,862	$ (168,317)
Effect of dilutive securities:
Convertible senior notes - interest expense related to contractual coupon interest rate and amortization of discount and note issuance costs	7,374
Net income (loss) - diluted	$ 198,842	$ (62,365)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares - basic	95,012	91,046	94,349	90,215
Effect of dilutive securities (in shares):
Stock options	14,106		14,080
Restricted stock	797		699
Convertible senior notes	4,761
Warrants	1,154		652
Dilutive potential shares	20,818		15,431
Weighted average shares - diluted	115,830	91,046	109,780	90,215
Earnings Per Share, Basic and Diluted [Abstract]
Net income (loss) per share - basic	$ 2.02	$ (0.68)	$ 2.97	$ (1.87)
Net income (loss) per share - diluted	$ 1.72	$ (0.68)	$ 2.55	$ (1.87)
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	175	20,395	91	21,239
Restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares		854		848
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares			4,761
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	3,607		4,109