Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Components Of Deferred Tax Assets And Liabilities [Abstract]
Accrued liabilities and reserves	$ 171,998	$ 146,658
Allowance for doubtful accounts	16,434	18,479
Inventory	62,755	79,363
Post-retirement benefits	12,714	10,288
Commodity hedges	4,033	5,164
Net operating loss carryforward	63,952	59,083
Tax credit carryforwards	187,267	164,132
Other deferred tax assets	10,674	8,508
Valuation allowance	(207,653)	(192,295)
Total deferred tax assets	322,174	299,380
Holdbacks and amounts not due under contracts	(14,051)	(12,930)
Intangibles	(177,061)	(171,531)
Property, plant and equipment	(680,688)	(545,890)
Book/Tax differences on debt modifications	(46,813)
Total deferred tax liabilities	(918,613)	(730,351)
Total net deferred tax liabilities	$ (596,439)	$ (430,971)