Loans and Allowance for Credit Losses - Summary of TDR Loans on Accrual and Nonaccrual (Detail) $ in Thousands	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 contract	Sep. 30, 2022 USD ($) loan	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 contract	Dec. 31, 2021 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	21	2	255	38	4	249
Balance of Loans	$ 51,730		$ 51,730	$ 51,730		$ 47,535
TDRs on Accrual Status | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			182			197
Balance of Loans	36,275		$ 36,275	36,275		$ 33,336
TDRs on Non-Accrual Status | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			73			52
Balance of Loans	$ 15,455		$ 15,455	$ 15,455		$ 14,199
Commercial and industrial | Commercial Portfolio Segment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	3		12	4		7
Balance of Loans	$ 17,335		$ 17,335	$ 17,335		$ 13,728
Commercial and industrial | TDRs on Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			2			1
Balance of Loans	7,087		$ 7,087	7,087		$ 3,745
Commercial and industrial | TDRs on Non-Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			10			6
Balance of Loans	10,248		$ 10,248	10,248		$ 9,983
Commercial real estate | Commercial Portfolio Segment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			1
Balance of Loans	3,520		$ 3,520	3,520		$ 3,520
Commercial real estate | TDRs on Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			1
Balance of Loans	3,520		$ 3,520	3,520		$ 3,520
Commercial real estate | TDRs on Non-Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			0			0
Balance of Loans	$ 0		$ 0	$ 0		$ 0
Business banking | Commercial Portfolio Segment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	9	0	27	20	1	8
Balance of Loans	$ 4,727		$ 4,727	$ 4,727		$ 4,213
Business banking | TDRs on Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			7			5
Balance of Loans	3,729		$ 3,729	3,729		$ 3,830
Business banking | TDRs on Non-Accrual Status | Commercial Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			20			3
Balance of Loans	$ 998		$ 998	$ 998		$ 383
Residential real estate | Residential Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	5	0	143	8	1	148
Balance of Loans	$ 21,608		$ 21,608	$ 21,608		$ 22,134
Residential real estate | TDRs on Accrual Status | Residential Real Estate | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			117			121
Balance of Loans	18,268		$ 18,268	18,268		$ 19,119
Residential real estate | TDRs on Non-Accrual Status | Residential Real Estate | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			26			27
Balance of Loans	$ 3,340		$ 3,340	$ 3,340		$ 3,015
Consumer home equity | Consumer Portfolio Segment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans	4	2	71	6	2	83
Balance of Loans	$ 4,526		$ 4,526	$ 4,526		$ 3,922
Consumer home equity | TDRs on Accrual Status | Consumer Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			55			67
Balance of Loans	3,671		$ 3,671	3,671		$ 3,104
Consumer home equity | TDRs on Non-Accrual Status | Consumer Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			16			16
Balance of Loans	855		$ 855	855		$ 818
Other Consumer | Consumer Portfolio Segment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			2
Balance of Loans	14		$ 14	14		$ 18
Other Consumer | TDRs on Accrual Status | Consumer Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			0			2
Balance of Loans	0		$ 0	0		$ 18
Other Consumer | TDRs on Non-Accrual Status | Consumer Portfolio Segment | Special mention | Contractual Obligation Modification
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			1			0
Balance of Loans	$ 14		$ 14	$ 14		$ 0