Loans and Allowance for Credit Losses - Schedule of Activity in Related Party Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at beginning of period	$ 2,345	$ 9,310	$ 9,481
New loans	1,848	1,218	9,152
Repayments	(1,715)	(2,063)	(8,721)
Officer and director changes	(34)	(6,120)	(602)
Balance at end of period	$ 2,444	$ 2,345	$ 9,310