Loans - Details and Delinquency Status of Nonperforming Loans (detail, and delinquency status, of non-performing loans (Non-Accrual Loans and Loans Past Due 90 Days or More and Still Accruing) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	$ 4,229,974	$ 4,243,693
Non-accrual loans	9,570	9,813
90 Days or More Past Due and Accruing	592	425
Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	3,073	3,285
Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	5,435	5,184
Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	106	118
Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	98	262
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	848	964
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	10
Non-Performing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	10,162	10,238
Non-accrual loans	9,570	9,813
90 Days or More Past Due and Accruing	592	425
Non-Performing Loans | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	9,289	9,245
Non-accrual loans	8,712	8,849
90 Days or More Past Due and Accruing	577	396
Non-Performing Loans | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	3,282	3,518
Non-accrual loans	3,073	3,285
90 Days or More Past Due and Accruing	209	233
Non-Performing Loans | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	5,549	5,192
Non-accrual loans	5,435	5,184
90 Days or More Past Due and Accruing	114	8
Non-Performing Loans | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	245	273
Non-accrual loans	106	118
90 Days or More Past Due and Accruing	139	155
Non-Performing Loans | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	213	262
Non-accrual loans	98	262
90 Days or More Past Due and Accruing	115	0
Non-Performing Loans | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	863	988
Non-accrual loans	848	964
90 Days or More Past Due and Accruing	15	24
Non-Performing Loans | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	10	5
Non-accrual loans	10	0
90 Days or More Past Due and Accruing	0	5
Non-Performing Loans | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	3,282	3,518
Non-accrual loans	3,073	3,285
90 Days or More Past Due and Accruing	209	233
Non-Performing Loans | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	5,549	5,192
Non-accrual loans	5,435	5,184
90 Days or More Past Due and Accruing	114	8
Non-Performing Loans | Substandard | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	245	273
Non-accrual loans	106	118
90 Days or More Past Due and Accruing	139	155
Non-Performing Loans | Substandard | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	174	262
Non-accrual loans	98	262
90 Days or More Past Due and Accruing	76	0
Non-Performing Loans | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	848	988
Non-accrual loans	848	964
90 Days or More Past Due and Accruing	0	24
Non-Performing Loans | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	10
Non-accrual loans	10
90 Days or More Past Due and Accruing	0
Non-Performing Loans | Pass | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	39
Non-accrual loans	0
90 Days or More Past Due and Accruing	39
Non-Performing Loans | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	15
Non-accrual loans	0
90 Days or More Past Due and Accruing	15
Non-Performing Loans | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment		5
Non-accrual loans		0
90 Days or More Past Due and Accruing		5
Non-Performing Loans | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	5,321	4,915
Non-Performing Loans | Current | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	5,224	4,915
Non-Performing Loans | Current | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,248	1,923
Non-Performing Loans | Current | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,875	2,806
Non-Performing Loans | Current | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	79	0
Non-Performing Loans | Current | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	22	186
Non-Performing Loans | Current | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	97	0
Non-Performing Loans | Current | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | Current | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,248	1,923
Non-Performing Loans | Current | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,875	2,806
Non-Performing Loans | Current | Substandard | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	79	0
Non-Performing Loans | Current | Substandard | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	22	186
Non-Performing Loans | Current | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	97	0
Non-Performing Loans | Current | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | Current | Pass | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | Current | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | Current | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment		0
Non-Performing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	457
Non-Performing Loans | 30-89 Days Past Due | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	431
Non-Performing Loans | 30-89 Days Past Due | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	431
Non-Performing Loans | 30-89 Days Past Due | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	26
Non-Performing Loans | 30-89 Days Past Due | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	431
Non-Performing Loans | 30-89 Days Past Due | Substandard | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0	26
Non-Performing Loans | 30-89 Days Past Due | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | 30-89 Days Past Due | Pass | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | 30-89 Days Past Due | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | 30-89 Days Past Due | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment		0
Non-Performing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	4,249	4,441
Non-Performing Loans | 90 Days or More Past Due | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	3,488	3,503
Non-Performing Loans | 90 Days or More Past Due | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	825	1,362
Non-Performing Loans | 90 Days or More Past Due | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,560	1,947
Non-Performing Loans | 90 Days or More Past Due | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	27	118
Non-Performing Loans | 90 Days or More Past Due | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	76	76
Non-Performing Loans | 90 Days or More Past Due | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	751	938
Non-Performing Loans | 90 Days or More Past Due | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	10	0
Non-Performing Loans | 90 Days or More Past Due | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	825	1,362
Non-Performing Loans | 90 Days or More Past Due | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	2,560	1,947
Non-Performing Loans | 90 Days or More Past Due | Substandard | Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	27	118
Non-Performing Loans | 90 Days or More Past Due | Substandard | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	76	76
Non-Performing Loans | 90 Days or More Past Due | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	751	938
Non-Performing Loans | 90 Days or More Past Due | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	10
Non-Performing Loans | 90 Days or More Past Due | Pass | Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	0
Non-Performing Loans | 90 Days or More Past Due | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment	$ 0
Non-Performing Loans | 90 Days or More Past Due | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held-for-investment		$ 0