Goodwill and Other Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 36,746	$ 34,767
Accumulated amortization	27,880	24,483
Net carrying amount	8,866	10,284
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	6,788	6,788
Accumulated amortization	4,787	4,026
Net carrying amount	2,001	2,762
Customer Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	7,604	8,819
Accumulated amortization	7,147	7,923
Net carrying amount	457	896
Servicing Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	22,354	19,160
Accumulated amortization	15,946	12,534
Net carrying amount	$ 6,408	$ 6,626