Net Income Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator for Basic and Diluted Earnings per Share - [Abstract]
Net Income	$ 570,279	$ 1,091,123	$ 160,654
Denominator for Basic Earnings per Share - [Abstract]
Weighted Average Shares	267,577,000	262,735,000	250,876,000
Potential Dilutive Common Shares -[Abstract]
Stock Options/SARs	1,456,000	1,707,000	1,991,000
Restricted Stock/Units and Performance Units/Stock	1,729,000	1,826,000	1,633,000
Denominator for Diluted Earnings per Share - [Abstract]
Adjusted Diluted Weighted Average Shares	270,762,000	266,268,000	254,500,000
Net Income Per Share [Abstract]
Basic	$ 2.13	$ 4.15	$ 0.64
Diluted	$ 2.11	$ 4.10	$ 0.63
Antidilutive Stock Options and SARs excluded from Diluted Earnings Per Share Calculation	500,000	400,000	300,000