Intangible Assets and Goodwill - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 36,761	$ 39,247
Accumulated Amortization	(17,762)	(16,639)
Net Carrying Amount	18,999	22,608
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	33,411	35,856
Accumulated Amortization	(15,076)	(14,131)
Net Carrying Amount	18,335	21,725
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,350	3,391
Accumulated Amortization	(2,686)	(2,508)
Net Carrying Amount	$ 664	$ 883