Loans Receivable - Summary of loans by year of origination, internally assigned credit grades and risk characteristics (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 1,500,864		$ 1,500,864		$ 1,372,824
Current period recoveries Total	27	$ 212	30	$ 246
Home Equity Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current period gross charge-offs 2023			0
Current period gross charge-offs 2022			0
Current period gross charge-offs 2021			0
Current period gross charge-offs 2020			0
Current period gross charge-offs 2019			0
Current period gross charge-offs Prior			(1,868)
Current period gross charge-offs Revolving Loans			0
Current period gross charge-offs Total			(1,868)
Current period recoveries 2023			0
Current period recoveries 2022			0
Current period recoveries 2021			0
Current period recoveries 2020			0
Current period recoveries 2019			0
Current period recoveries Prior			30
Current period recoveries Revolving Loans			0
Current period recoveries Total			30
Total net-charge-off 2023			0
Total net-charge-off 2022			0
Total net-charge-off 2021			0
Total net-charge-off 2020			0
Total net-charge-off 2019			0
Total net-charge-off Prior			(1,838)
Total net-charge-off Revolving Loans			0
Total net-charge-off Total			(1,838)
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total					1,362,973
Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total					3,392
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total					$ 6,459
Loans Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	8,031		8,031
2022	248,711		248,711
2021	237,996		237,996
2020	100,642		100,642
2019	192,652		192,652
Prior	507,024		507,024
Revolving Loans	205,808		205,808
Total	1,500,864		1,500,864
Loans Receivable [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,260		6,260
2022	235,799		235,799
2021	88,066		88,066
2020	54,349		54,349
2019	174,659		174,659
Prior	458,213		458,213
Revolving Loans	5,608		5,608
Total	1,022,954		1,022,954
Loans Receivable [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,771		1,771
2022	4,054		4,054
2021	2,466		2,466
2020	2,298		2,298
2019	16,367		16,367
Prior	5,927		5,927
Revolving Loans	13,139		13,139
Total	46,022		46,022
Loans Receivable [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	6,904		6,904
2021	141,342		141,342
2020	41,042		41,042
2019	48		48
Prior	10,837		10,837
Revolving Loans	183,442		183,442
Total	383,615		383,615
Loans Receivable [Member] | Residential FirstLien Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	1,006		1,006
2021	5,707		5,707
2020	2,886		2,886
2019	1,578		1,578
Prior	29,067		29,067
Revolving Loans	0		0
Total	40,244		40,244
Loans Receivable [Member] | Residential FirstLien Mortgage [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	1,006		1,006
2021	5,707		5,707
2020	2,886		2,886
2019	1,578		1,578
Prior	28,956		28,956
Revolving Loans	0		0
Total	40,133		40,133
Loans Receivable [Member] | Residential FirstLien Mortgage [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	111		111
Revolving Loans	0		0
Total	111		111
Loans Receivable [Member] | Home Equity Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	948		948
2021	415		415
2020	67		67
2019	0		0
Prior	2,980		2,980
Revolving Loans	3,619		3,619
Total	8,029		8,029
Loans Receivable [Member] | Home Equity Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	948		948
2021	415		415
2020	67		67
2019	0		0
Prior	2,980		2,980
Revolving Loans	3,619		3,619
Total	8,029		8,029
Loans Receivable [Member] | Home Equity Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	0		0
Revolving Loans	0		0
Total	0		0
Loans Receivable [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	8,031		8,031
2022	248,711		248,711
2021	237,996		237,996
2020	97,717		97,717
2019	192,652		192,652
Prior	496,363		496,363
Revolving Loans	205,808		205,808
Total	1,487,278		1,487,278
Loans Receivable [Member] | Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,260		6,260
2022	235,799		235,799
2021	88,066		88,066
2020	54,349		54,349
2019	174,659		174,659
Prior	450,916		450,916
Revolving Loans	5,608		5,608
Total	1,015,657		1,015,657
Loans Receivable [Member] | Pass [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,771		1,771
2022	4,054		4,054
2021	2,466		2,466
2020	2,298		2,298
2019	16,367		16,367
Prior	2,674		2,674
Revolving Loans	13,139		13,139
Total	42,769		42,769
Loans Receivable [Member] | Pass [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	6,904		6,904
2021	141,342		141,342
2020	38,117		38,117
2019	48		48
Prior	10,837		10,837
Revolving Loans	183,442		183,442
Total	380,690		380,690
Loans Receivable [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	3,509		3,509
Revolving Loans	0		0
Total	3,509		3,509
Loans Receivable [Member] | Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	2,812		2,812
Revolving Loans	0		0
Total	2,812		2,812
Loans Receivable [Member] | Special Mention [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	697		697
Revolving Loans	0		0
Total	697		697
Loans Receivable [Member] | Special Mention [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	0		0
Revolving Loans	0		0
Total	0		0
Loans Receivable [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	2,925		2,925
2019	0		0
Prior	7,152		7,152
Revolving Loans	0		0
Total	10,077		10,077
Loans Receivable [Member] | Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	4,485		4,485
Revolving Loans	0		0
Total	4,485		4,485
Loans Receivable [Member] | Substandard [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	0		0
2019	0		0
Prior	2,556		2,556
Revolving Loans	0		0
Total	2,556		2,556
Loans Receivable [Member] | Substandard [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0		0
2022	0		0
2021	0		0
2020	2,925		2,925
2019	0		0
Prior	0		0
Revolving Loans	0		0
Total	$ 2,925		$ 2,925