Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ 185,867		$ (54,053)		$ 559,013		$ (351,481)
Number of common shares, Weighted average outstanding	350,517,337		348,649,630		350,334,634		348,272,192
Number of common shares, Issued upon assumed exercise of outstanding stock options	373,152				442,678
Number of common shares, Effect of issuance of nonvested restricted common stock	332,341				237,662
Number of common shares, Weighted average and potential dilutive outstanding	351,222,830	[1]	348,649,630	[1]	351,014,974	[1]	348,272,192	[1]
Basic	$ 0.53		$ (0.16)		$ 1.60		$ (1.01)
Diluted	$ 0.53		$ (0.16)		$ 1.59		$ (1.01)
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	1,550,838		1,664,232		1,848,566		1,685,398
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	15,703		560,848		169,261		580,227
Parent [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ 185,867		$ (54,053)		$ 559,013		$ (351,481)

[1] Options for 1,550,838 shares and 15,703 shares of restricted stock were excluded from the calculation for the three months ended September 30, 2013 because they would have had an antidilutive effect. Due to the net loss for the three months ended September 30, 2012, options for 1,664,232 shares and 560,848 shares of restricted stock were antidilutive and excluded from the calculation. Options for 1,848,566 shares and 169,261 shares of restricted stock were excluded from the calculation for the nine months ended September 30, 2013 because they would have had an antidilutive effect. Due to the net loss for the nine months ended September 30, 2012, options for 1,685,398 shares and 580,227 shares of restricted stock were antidilutive and excluded from the calculation.