Loans Receivable - Summary of loans by year of origination, internally assigned credit grades and risk characteristics (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 1,573,556	$ 1,550,133
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current period gross charge-offs Prior	(237)	1,718
Current period gross charge-offs Total	(237)	1,718
Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current period gross charge-offs Prior	(46)	55
Current period gross charge-offs Total	(46)	55
Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current period gross charge-offs Prior		148
Current period gross charge-offs Total		148
Residential First lien Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Current period gross charge-offs Prior		2
Current period gross charge-offs Total		2
Loans Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	32,777	141,917
2023 and 2022	141,078	256,114
2022 and 2021	266,567	226,499
2021 and 2020	215,966	77,591
2020 and 2019	76,666	178,669
Prior	631,104	479,111
Revolving Loans	209,398	190,232
Total	1,573,556	1,550,133
Loans Receivable [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023		0
2023 and 2022		0
2022 and 2021		0
2021 and 2020		0
2020 and 2019		0
Prior		6,632
Revolving Loans		0
Total		6,632
Loans Receivable [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	25,851	132,834
2023 and 2022	134,137	233,436
2022 and 2021	244,778	116,836
2021 and 2020	116,312	53,574
2020 and 2019	61,828	175,991
Prior	574,323	424,642
Revolving Loans	5,512	5,551
Total	1,162,741	1,142,864
Loans Receivable [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	653	2,098
2023 and 2022	563	2,304
2022 and 2021	1,615	11,925
2021 and 2020	11,702	1,962
2020 and 2019	648	1,133
Prior	18,519	16,494
Revolving Loans	12,230	15,045
Total	45,930	50,961
Loans Receivable [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	6,050	5,832
2023 and 2022	5,832	18,379
2022 and 2021	17,809	91,774
2021 and 2020	83,849	19,216
2020 and 2019	11,371	0
Prior	7,391	8,484
Revolving Loans	188,707	166,502
Total	321,009	310,187
Loans Receivable [Member] | Residential First lien Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	979
2022 and 2021	966	4,792
2021 and 2020	3,805	2,839
2020 and 2019	2,816	1,545
Prior	28,978	27,885
Revolving Loans	0	0
Total	36,565	38,040
Loans Receivable [Member] | Residential First lien Mortgage [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	979
2022 and 2021	966	4,792
2021 and 2020	3,805	2,839
2020 and 2019	2,816	1,545
Prior	28,846	27,778
Revolving Loans	0	0
Total	36,433	37,933
Loans Receivable [Member] | Residential First lien Mortgage [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	132	107
Revolving Loans	0	0
Total	132	107
Loans Receivable [Member] | Home Equity Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	223	1,153
2023 and 2022	546	1,016
2022 and 2021	1,399	1,172
2021 and 2020	298	0
2020 and 2019	3	0
Prior	1,893	1,606
Revolving Loans	2,949	3,134
Total	7,311	8,081
Loans Receivable [Member] | Home Equity Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	223	1,153
2023 and 2022	546	1,016
2022 and 2021	1,371	1,172
2021 and 2020	298	0
2020 and 2019	3	0
Prior	1,893	1,606
Revolving Loans	2,949	3,134
Total	7,283	8,081
Loans Receivable [Member] | Home Equity Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	28	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	0	0
Revolving Loans	0	0
Total	28	0
Loans Receivable [Member] | Pass [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	32,777	141,917
2023 and 2022	141,078	256,114
2022 and 2021	266,539	226,499
2021 and 2020	215,966	77,591
2020 and 2019	76,166	178,669
Prior	624,611	469,239
Revolving Loans	209,398	190,232
Total	1,566,535	1,540,261
Loans Receivable [Member] | Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	25,851	132,834
2023 and 2022	134,137	233,436
2022 and 2021	244,778	116,836
2021 and 2020	116,312	53,574
2020 and 2019	61,828	175,991
Prior	574,323	417,417
Revolving Loans	5,512	5,551
Total	1,162,741	1,135,639
Loans Receivable [Member] | Pass [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	653	2,098
2023 and 2022	563	2,304
2022 and 2021	1,615	11,925
2021 and 2020	11,702	1,962
2020 and 2019	148	1,133
Prior	12,158	13,954
Revolving Loans	12,230	15,045
Total	39,069	48,421
Loans Receivable [Member] | Pass [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	6,050	5,832
2023 and 2022	5,832	18,379
2022 and 2021	17,809	91,774
2021 and 2020	83,849	19,216
2020 and 2019	11,371	0
Prior	7,391	8,484
Revolving Loans	188,707	166,502
Total	321,009	310,187
Loans Receivable [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	4,508	3,240
Revolving Loans	0	0
Total	4,508	3,240
Loans Receivable [Member] | Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	0	2,740
Revolving Loans	0	0
Total	0	2,740
Loans Receivable [Member] | Special Mention [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	4,508	500
Revolving Loans	0	0
Total	4,508	500
Loans Receivable [Member] | Special Mention [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 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]
2024 and 2023	0
2023 and 2022	0
2022 and 2021	28
2021 and 2020	0
2020 and 2019	500
Prior	1,985
Revolving Loans	0
Total	2,513
Loans Receivable [Member] | Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	0	4,485
Revolving Loans	0	0
Total	0	4,485
Loans Receivable [Member] | Substandard [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	500	0
Prior	1,853	2,040
Revolving Loans	0	0
Total	2,353	2,040
Loans Receivable [Member] | Substandard [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2024 and 2023	0	0
2023 and 2022	0	0
2022 and 2021	0	0
2021 and 2020	0	0
2020 and 2019	0	0
Prior	0	0
Revolving Loans	0	0
Total	$ 0	$ 0