Income Taxes Income Tax Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Amount
Statutory U.S. Federal Income Tax Rate	$ 275,784	$ 163,770	$ 275,921
Excess Depletion	(91,470)	(70,812)	(68,787)
Effect of Domestic Production Activities Deduction	22,209	5,633	12,707
Income Tax Reconciliation, Prior Year Income Taxes	2,257	4,609	(1,256)
Income Tax Reconciliation, Tax Settlements	(5,188)	0	0
Net Effect of State Income Taxes	14,197	12,022	27,362
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance	(22,618)	0	0
Income Tax Reconciliation, Tax Credits, Foreign	(1,822)	(3,424)	(5,502)
Other	6,525	8,755	6,172
Income Tax Expense / Effective Rate	$ 155,456	$ 109,287	$ 221,203
Percent
Statutory U.S. Federal Income Tax Rate	35.00%	35.00%	35.00%
Excess Tax Depletion	(11.60%)	(15.10%)	(8.70%)
Effect of Domestic Production Activities Deduction	(2.80%)	(1.20%)	(1.60%)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes	0.30%	1.00%	(0.20%)
Effective Income Tax Rate Reconciliation, Tax Settlements	(0.70%)	0.00%	0.00%
Net Effect of State Income Taxes	1.80%	2.60%	3.50%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance	(2.90%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential	(0.20%)	(0.70%)	(0.70%)
Other	0.80%	1.80%	0.80%
Income Tax Expense / Effective Rate	19.70%	23.40%	28.10%