Income Taxes - Schedule of Unrecognized Tax Benefits (Excluding Interest and Federal Income Tax Benefit of Unrecognized State Tax Benefits) (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	$ 434	$ 465	$ 467
Additions based on tax positions related to the current year		58	68
Reductions for tax positions of prior years	0	0	0
Reductions due to the statute of limitations	(110)	(89)	(70)
Settlements	0	0	0
Balance at end of year	$ 324	$ 434	$ 465