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Loans - Investment of Originated Loans Held-for-Investment by Loan Type and Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	$ 3,806,617	$ 3,823,238
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	3,790,798	3,804,720
Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	3,647,778	3,610,210
Commercial and Industrial | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	141,005	191,481
Other loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	2,015	3,029
Pass | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		3,731,891
Pass | Commercial and Industrial | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	133,873	189,372
Pass | Other loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	2,015	3,026
Special Mention | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		24,145
Special Mention | Commercial and Industrial | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	572	498
Special Mention | Other loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		0
Substandard | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		48,684
Substandard | Commercial and Industrial | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	6,560	1,611
Substandard | Other loans | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		3
Multifamily | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	2,518,065	2,512,934
Multifamily | Pass | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	2,502,531	2,497,556
Multifamily | Special Mention | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	425	458
Multifamily | Substandard | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	15,109	14,920
Commercial | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	808,597	717,566
Commercial | Pass | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	765,448	667,568
Commercial | Special Mention | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	10,159	20,422
Commercial | Substandard | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	32,990	29,576
One-to-Four Family | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	183,665	212,222
One-to-Four Family | Pass | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	177,607	207,633
One-to-Four Family | Special Mention | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	2,803	2,456
One-to-Four Family | Substandard | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	3,255	2,133
Home Equity and Lines of Credit | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	109,956	93,137
Home Equity and Lines of Credit | Pass | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	109,319	92,385
Home Equity and Lines of Credit | Special Mention | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	103	311
Home Equity and Lines of Credit | Substandard | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	534	441
Construction and Land | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	27,495	74,351
Construction and Land | Pass | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net	$ 27,495	74,351
Construction and Land | Special Mention | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		0
Construction and Land | Substandard | Real Estate | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment [Line Items]
Total loans held-for-investment, net		$ 0

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