Income Taxes - Deferred Income Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax credit carryforwards	$ 71,428	$ 59,640
Research and development expenses	41,862	58,340
Net operating loss carryforwards	161,846	153,866
Interest expense	108,069	80,774
Allowances and reserves	92,372	100,896
Deferred compensation	60,665	67,689
Postretirement benefits	38,182	33,839
Intangible assets	231,527	245,138
Lease liabilities	74,600	77,948
Other	42,058	33,619
Gross deferred income tax assets	922,609	911,749
Intangible assets	(187,001)	(190,677)
Right-of-use assets	(66,404)	(68,082)
Other	(25,500)	(31,024)
Gross deferred income tax liabilities	(278,905)	(289,783)
Deferred income tax asset valuation allowances	(631,914)	(610,560)
Net deferred income tax assets	$ 11,790	$ 11,406