Valuation and Qualifying Accounts (Detail) - Valuation Allowance for Deferred Tax Assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 75,277	$ 79,264	$ 70,227
Charges to costs and expenses (income)	(7,274)	(3,987)	9,037
Balance at end of period	$ 68,003	$ 75,277	$ 79,264