Income Taxes - Deferred Income Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax credit carryforwards	$ 59,640	$ 64,895
Research and development expenses	58,340	76,906
Net operating loss carryforwards	234,640	187,741
Allowances and reserves	100,896	94,168
Deferred compensation	67,689	63,641
Postretirement benefits	33,839	24,666
Intangible assets	245,138	419
Other	43,485	48,262
Gross deferred income tax assets	843,667	560,698
Intangible assets	(190,677)	(196,012)
Other	(31,024)	(15,782)
Gross deferred income tax liabilities	(221,701)	(211,794)
Deferred income tax asset valuation allowances	(610,560)	(365,820)
Net deferred income tax assets	$ 11,406
Net deferred income tax liabilities		$ (16,916)