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Loans - Details and Delinquency Status Of Nonperforming Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	$ 3,817,273	$ 3,823,238
Non-accrual loans	8,124	8,500
90 Days or More Past Due and Accruing	731	1,100
Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	5,028
Real estate loans: | One-to-four family residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	320
Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,107
Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,131
Real estate loans: | Home equity and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	128
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	407
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	3
Non-Performing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	8,855	9,629
Non-accrual loans	8,124	8,516
90 Days or More Past Due and Accruing	731	1,113
Non-Performing Loans | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	8,251	9,153
Non-accrual loans	7,714	8,479
90 Days or More Past Due and Accruing	537	674
Non-Performing Loans | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	5,244	6,729
Non-accrual loans	5,028	6,229
90 Days or More Past Due and Accruing	216	500
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, net	543	1,080
Non-accrual loans	320	906
90 Days or More Past Due and Accruing	223	174
Non-Performing Loans | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,107
Non-accrual loans	1,107
90 Days or More Past Due and Accruing	0
Non-Performing Loans | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,131	1,153
Non-accrual loans	1,131	1,153
90 Days or More Past Due and Accruing	0	0
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, net	226	191
Non-accrual loans	128	191
90 Days or More Past Due and Accruing	98	0
Non-Performing Loans | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	601	473
Non-accrual loans	407	37
90 Days or More Past Due and Accruing	194	436
Non-Performing Loans | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	3	3
Non-accrual loans	3	0
90 Days or More Past Due and Accruing	0	3
Non-Performing Loans | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	5,244	6,229
Non-accrual loans	5,028	6,229
90 Days or More Past Due and Accruing	216	0
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, net	543	1,080
Non-accrual loans	320	906
90 Days or More Past Due and Accruing	223	174
Non-Performing Loans | Substandard | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,107
Non-accrual loans	1,107
90 Days or More Past Due and Accruing	0
Non-Performing Loans | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,131	1,153
Non-accrual loans	1,131	1,153
90 Days or More Past Due and Accruing	0	0
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, net	226	191
Non-accrual loans	128	191
90 Days or More Past Due and Accruing	98	0
Non-Performing Loans | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	601	287
Non-accrual loans	407	37
90 Days or More Past Due and Accruing	194	250
Non-Performing Loans | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	3
Non-accrual loans	3
90 Days or More Past Due and Accruing	0
Non-Performing Loans | Pass | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		500
Non-accrual loans		0
90 Days or More Past Due and Accruing		500
Non-Performing Loans | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		101
Non-accrual loans		0
90 Days or More Past Due and Accruing		101
Non-Performing Loans | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		3
Non-accrual loans		0
90 Days or More Past Due and Accruing		3
Non-Performing Loans | Special Mention | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		85
Non-accrual loans		0
90 Days or More Past Due and Accruing		85
Non-Performing Loans | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	2,840	3,302
Non-Performing Loans | Current | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	2,805	3,302
Non-Performing Loans | Current | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	2,805	2,829
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, net	0	413
Non-Performing Loans | Current | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0
Non-Performing Loans | Current | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0	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, net	0	60
Non-Performing Loans | Current | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	35	0
Non-Performing Loans | Current | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0	0
Non-Performing Loans | Current | Substandard | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	2,805	2,829
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, net	0	413
Non-Performing Loans | Current | Substandard | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0
Non-Performing Loans | Current | Substandard | Real estate loans: | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0	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, net	0	60
Non-Performing Loans | Current | Substandard | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	35	0
Non-Performing Loans | Current | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0
Non-Performing Loans | Current | Pass | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		0
Non-Performing Loans | Current | Pass | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		0
Non-Performing Loans | Current | Pass | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		0
Non-Performing Loans | Current | Special Mention | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		0
Non-Performing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	74	537
Non-Performing Loans | 30-89 Days Past Due | Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	74	537
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, net	74	537
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, net	0	0
Non-Performing Loans | 30-89 Days Past Due | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0
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, net	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, net	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, net	0	0
Non-Performing Loans | 30-89 Days Past Due | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	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, net	74	537
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, net	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	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, net	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, net	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, net	0	0
Non-Performing Loans | 30-89 Days Past Due | Substandard | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	0
Non-Performing Loans | 30-89 Days Past Due | Pass | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		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, net		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, net		0
Non-Performing Loans | 30-89 Days Past Due | Special Mention | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		0
Non-Performing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	5,210	4,677
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, net	4,835	4,640
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, net	2,149	2,863
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, net	320	493
Non-Performing Loans | 90 Days or More Past Due | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,107
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, net	1,131	1,153
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, net	128	131
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, net	372	37
Non-Performing Loans | 90 Days or More Past Due | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	3	0
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, net	2,149	2,863
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, net	320	493
Non-Performing Loans | 90 Days or More Past Due | Substandard | Real estate loans: | Construction and land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net	1,107
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, net	1,131	1,153
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, net	128	131
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, net	372	37
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, net	$ 3
Non-Performing Loans | 90 Days or More Past Due | Pass | Real estate loans: | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		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, net		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, net		0
Non-Performing Loans | 90 Days or More Past Due | Special Mention | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans held-for-investment, net		$ 0

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