Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Balance at beginning of period	$ 1,036,994	$ 1,036,258	$ 828,051
Acquisitions and adjustments	0	736	208,787
Divestitures	0	0	(580)
Balance at end of period	$ 1,036,994	$ 1,036,994	$ 1,036,258