Loans and the Allowance for Credit Losses - Recorded Investment in Non-Accrual Loans and TDRs (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Non-accrual loans	$ 35,742	$ 36,880
TDRs	5,293	5,755
Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	3,746	3,927
Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	1,547	1,828
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	5,064	3,302
TDRs	192	111
Commercial and Industrial [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	192	111
Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	5,163	5,345
TDRs	535	663
Home Equity [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	277	363
Home Equity [Member] | Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	258	300
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	7,788	9,963
TDRs	507	820
Commercial Real Estate [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	374	655
Commercial Real Estate [Member] | Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	133	165
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	73	469
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	7,715	9,494
TDRs	507	820
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	374	655
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member] | Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	133	165
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	17,190	17,925
TDRs	4,031	4,133
Residential Real Estate [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	2,875	2,779
Residential Real Estate [Member] | Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	1,156	1,354
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	537	345
TDRs	28	28
Consumer [Member] | Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	$ 28	19
Consumer [Member] | Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs		$ 9