Components of Net Deferred Income Tax Liability (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Tax Assets Related to
Pensions	$ 84,869	$ 58,193
Other postretirement benefits	44,030	52,433
Accruals for asset retirement obligations and environmental accruals	40,202	37,145
Accounts receivable, principally allowance for doubtful accounts	1,910	2,194
Deferred compensation, vacation pay and incentives	102,048	97,741
Interest rate swaps	19,585	22,273
Self-insurance reserves	18,165	16,467
Inventory	8,011	6,984
Federal net operating loss carryforwards	57,679	48,496
State net operating loss carryforwards	45,929	36,912
Valuation allowance on state net operating loss carryforwards	(38,837)	(29,757)
Foreign tax credit carryforwards	22,409	22,395
Alternative minimum tax credit carryforwards	15,711	10,724
Charitable contribution carryforwards	9,953	9,523
Other	20,561	18,619
Total deferred tax assets	452,225	410,342
Deferred Tax Liabilities Related to
Fixed assets	754,697	799,632
Intangible assets	295,429	286,317
Other	18,770	13,889
Total deferred tax liabilities	1,068,896	1,099,838
Net deferred tax liability	$ 616,671	$ 689,496