Income Taxes - Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Postretirement and other benefits	$ 52,097	$ 75,927
Capitalized expenditures	3,563	5,365
Net operating loss and tax credit carryforwards	143,182	138,905
All other items	48,302	42,418
Total deferred tax assets	247,144	262,615
Deferred tax liabilities:
Property, plant and equipment	(56,200)	(47,480)
Intangibles	(32,130)	(37,015)
All other items	(3,864)	(2,662)
Total deferred tax liabilities	(92,194)	(87,157)
Valuation allowances	(122,771)	(97,285)
Net deferred tax assets	$ 32,179	$ 78,173