Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Net income (loss)	$ (405,132)		$ 167,454		$ (297,428)		$ 304,063
Number of common shares, Weighted average outstanding	348,162,723		347,132,830		348,081,399		346,984,194
Number of common shares, Issued upon assumed exercise of outstanding stock options			2,583,711				2,643,537
Number Of Common Shares Effect Of Issuance On Nonvested Restricted Common Stock			254,278				212,313
Number of common shares, Weighted average and potential dilutive outstanding	348,162,723	[1]	349,970,819	[1]	348,081,399	[1]	349,840,044	[1]
Basic	$ (1.16)		$ 0.48		$ (0.85)		$ 0.88
Diluted	$ (1.16)		$ 0.48		$ (0.85)		$ 0.87
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,723,316		749,910		1,783,073		813,878
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	156,047		3,421		121,078		3,041

[1] Due to the net loss for the three months ended June 30, 2012, options for 1,723,316 shares and 156,047 shares of restricted stock were antidilutive and excluded from the calculation. Options for 749,910 shares and 3,421 shares of restricted stock were excluded from the calculation for the three months ended June 30, 2011 because they would have had an antidilutive effect. Due to the net loss for the six months ended June 30, 2012, options for 1,783,073 shares and 121,078 shares of restricted stock were antidilutive and excluded from the calculation. Options for 813,878 shares and 3,041 shares of restricted stock were excluded from the calculation for the six months ended June 30, 2011 because they would have had an antidilutive effect.