Income Taxes - Components of Consolidated Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 17,760	$ 20,658	$ 16,407
State	900	1,297	1,004
Total Current	18,660	21,955	17,411
Deferred:
Federal	1,403	732	(1,389)
State	254	140	(73)
Total Deferred	1,657	872	(1,462)
Income tax expense, Total	$ 20,317	$ 22,827	$ 15,949