Earnings Per Share (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Reconciliation of the numerators and the denominators of basic and diluted per-share computations
Net income - basic (numerator):	$ 266,586	$ 224,393	$ 517,198	$ 515,246
Effect of dilutive potential shares
Convertible Debentures		32		56
Net income including conversions - diluted (numerator)	$ 266,586	$ 224,425	$ 517,198	$ 515,302
Weighted average shares - basic (denominator):	139,027	139,026	139,027	139,026
Effect of dilutive potential shares
Convertible Debentures		32		42
Stock options and stock appreciation rights	25	21	25	36
Weighted average shares including conversions - diluted (denominator)	139,052	139,079	139,052	139,104
Earnings per share:
Basic	$ 1.92	$ 1.61	$ 3.72	$ 3.71
Diluted	$ 1.92	$ 1.61	$ 3.72	$ 3.70