Income Taxes (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred Tax Assets Related to
Pensions	$ 58,193	$ 21,630
Other postretirement benefits	52,433	52,366
Accruals for asset retirement obligations and environmental accruals	37,145	28,605
Accounts receivable, principally allowance for doubtful accounts	2,194	2,770
Deferred compensation, vacation pay and incentives	97,741	89,246
Interest rate swaps	22,273	27,022
Self-insurance reserves	16,467	31,445
Inventory	6,984	0
Federal net operating loss carryforwards	48,496	25,629
State net operating loss carryforwards	36,912	26,663
Valuation allowance on state net operating loss carryforwards	(29,757)	(20,721)
Foreign tax credit carryforwards	22,395	22,816
Other	38,866	35,740
Total deferred tax assets	410,342	343,211
Deferred Tax Liabilities Related to
Inventory	0	1,768
Fixed assets	799,632	843,630
Intangible assets	286,317	273,711
Other	13,889	12,997
Total deferred tax liabilities	1,099,838	1,132,106
Net deferred tax liability	$ 689,496	$ 788,895