Summary of Significant Accounting Policies - Impact of Change from Incurred Loss Model to Current Expected Credit Loss Model (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Jan. 01, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	$ 6,691	$ 6,559		$ 6,838	$ 7,008	$ 7,268	$ 7,618
ACL for off-balance sheet commitments	492			141
ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			$ 6,279
ACL for off-balance sheet commitments			493
Total allowance for credit losses			6,772
Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			6,838	6,838
Total allowance for credit losses			6,838
Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			(559)	(559)
ACL for off-balance sheet commitments			493
Total allowance for credit losses			(66)
Commercial and Industrial [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	1,963	2,119		1,110	1,249	1,213	1,240
Commercial and Industrial [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			1,768
Commercial and Industrial [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			1,110
Commercial and Industrial [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			658
Commercial Real Estate [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	2,129	1,882		2,760	2,112	2,422	2,838
Commercial Real Estate [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			2,219
Commercial Real Estate [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			2,760
Commercial Real Estate [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			(541)
Commercial Lessors of Buildings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	1,226	1,237
Commercial Lessors of Buildings [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			974
Commercial Lessors of Buildings [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			974
Construction [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	255	283		803
Construction [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			288
Construction [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			803
Construction [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			(515)
Consumer Mortgage [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	775	714		1,268
Consumer Mortgage [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			688
Consumer Mortgage [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			1,268
Consumer Mortgage [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			(580)
Home Equity Line of Credit [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	187	178
Home Equity Line of Credit [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			201
Home Equity Line of Credit [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			201
Consumer Installment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	57	52		233
Consumer Installment [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			50
Consumer Installment [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			233
Consumer Installment [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			(183)
Consumer Indirect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans	$ 99	$ 94
Consumer Indirect [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			91
Consumer Indirect [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			91
Unallocated [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans				$ 664	$ 814	$ 454	$ 747
Unallocated [Member] | Pre-adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			664
Unallocated [Member] | Cumulative Effect of Adoption [Memnber] | Adoption Impact [Member] | ASU 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for credit losses - loans			$ (664)