Income Taxes - Reconciliation of Beginning and Ending Amount of Uncertain Tax Positions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 519	$ 577	$ 618
Reductions for tax positions of prior years	(55)	(58)	(41)
Balance at end of year	$ 464	$ 519	$ 577