Earnings Per Share (Details) (USD $) In Thousands, except Per Share data	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Reconciliation of the numerators and the denominators of basic and diluted per-share computations
Net income - basic (numerator):	$ 256,854	$ 198,524	$ 774,052	$ 713,770
Effect of dilutive potential shares
Convertible debentures				56
Net income including conversions - diluted (numerator)	$ 256,854	$ 198,524	$ 774,052	$ 713,826
Weighted average shares - basic (denominator):	139,027	139,027	139,027	139,026
Effect of dilutive potential shares
Convertible debentures				28
Stock options and stock appreciation rights	14	10	21	27
Weighted average shares including conversions - diluted (denominator)	139,041	139,037	139,048	139,081
Earnings per share:
Basic	$ 1.85	$ 1.43	$ 5.57	$ 5.13
Diluted	$ 1.85	$ 1.43	$ 5.57	$ 5.13

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