Income Taxes (Details 4) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets:
Net operating loss carryforwards	$ 2,009,318	$ 1,848,956
Equity compensation	25,937	19,262
Deferred revenue	32,200	13,428
Tax credit and other attribute carryforwards	90,297	89,141
Insurance loss reserve	24,598	28,537
Other	114,043	62,324
Subtotal	2,296,393	2,061,648
Valuation allowance	(1,485,540)	(1,514,153)
Deferred tax assets	810,853	547,495
Deferred tax liabilities:
Depreciation, amortization and depletion for tax in excess of book expense	1,317,256	1,123,622
Variable interest investments	116,005	75,204
Other	34,822	54,738
Deferred tax liability	1,468,083	1,253,564
Net deferred assets (liabilities)	(657,230)	(706,069)
Balance Sheet Summary
Net current deferred asset	127,874	31,510
Net noncurrent deferred asset	13,090	33,694
Current deferred tax liability	(269)	(1,027)
Net noncurrent deferred liability	(797,925)	(770,247)
Net deferred asset (liability)	$ (657,230)	$ (706,069)