Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 194,190		$ 127,515
Number of common shares, Weighted average outstanding	351,222,538		350,032,430
Number of common shares, Issued upon assumed exercise of outstanding stock options	348,798		579,022
Diluted	351,985,821	[1]	350,738,309	[1]
Basic	$ 0.55		$ 0.36
Diluted	$ 0.55		$ 0.36
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,179,914		2,112,679
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of common shares, Effect of issuance of nonvested shares	349,608		126,857
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	29,688		271,674
Performance Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of common shares, Effect of issuance of nonvested shares	64,877

[1] Options for 1,179,914 shares and 29,688 shares of restricted stock were excluded from the calculation for the three months ended March 31, 2014 because they would have had an antidilutive effect. Options for 2,112,679 shares and 271,674 shares of restricted stock were excluded from the calculation for the three months ended March 31, 2013 because they would have had an antidilutive effect.