Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share [Abstract]
Income from continuing operations used in computing basic and diluted earnings per share	$ 548,078	$ 259,669	$ 70,641
Denominator for basic earnings per share-weighted-average common shares	232,889,000	233,312,000	232,577,000
Effect of dilutive securities - employee stock compensation plan	2,029,000	1,475,000	996,000
Denominator for diluted earnings per share-adjusted weighted-average shares outstanding	234,918,000	234,787,000	233,573,000
Basic	$ 2.35	$ 1.11	$ 0.30
Diluted	$ 2.33	$ 1.11	$ 0.30
Shares considered anti-dilutive and excluded from computation	3,800,000	4,200,000	5,000,000