Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at January 1,	$ 2,164	$ 1,553	$ 1,096
Additions based on tax positions related to the current year	500	500	500
Additions for tax positions of prior years	142	113	62
Reductions for tax positions of prior years	0	0	0
Settlements	0	(2)	(105)
Balance at December 31,	$ 2,806	$ 2,164	$ 1,553