Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Loans - Net Loans Held-for-Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Loans held-for-investment, net	$ 3,509,137	$ 3,437,085
Allowance for loan losses	(36,800)	(28,707)	$ (27,486)	$ (27,497)
Net loans held-for-investment	3,472,337	3,408,378
Originated
Loans and Leases Receivable Disclosure [Line Items]
Loans	50,415	47,411
Deferred loan cost, net	7,680	7,614
Loans held-for-investment, net	3,098,760	2,987,067
Allowance for loan losses	(35,956)	(27,783)	(26,476)	(26,487)
Purchased Credit-Impaired
Loans and Leases Receivable Disclosure [Line Items]
Loans held-for-investment, net	16,886	17,365
Allowance for loan losses	(789)	(789)	(1,010)	(1,010)
Acquired Loans
Loans and Leases Receivable Disclosure [Line Items]
Loans	393,491	432,653
Loans held-for-investment, net	393,491	432,653
Allowance for loan losses	(55)	(135)	0	0
Real Estate \| Originated
Loans and Leases Receivable Disclosure [Line Items]
Loans	3,040,665	2,932,042
Real Estate \| Originated \| Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Loans	2,300,974	2,196,407
Loans held-for-investment, net	2,304,387	2,199,734
Allowance for loan losses	(26,889)	(20,203)	(18,346)	(18,084)
Real Estate \| Originated \| Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	527,498	528,681
Loans held-for-investment, net	528,104	529,287
Allowance for loan losses	(5,389)	(4,756)	(5,382)	(5,630)
Real Estate \| Originated \| One-to-Four Family
Loans and Leases Receivable Disclosure [Line Items]
Loans	84,880	83,742
Loans held-for-investment, net	86,404	85,355
Allowance for loan losses	(312)	(180)	(370)	(342)
Real Estate \| Originated \| Home equity and lines of credit
Loans and Leases Receivable Disclosure [Line Items]
Loans	87,391	84,928
Loans held-for-investment, net	89,349	86,848
Allowance for loan losses	(574)	(317)	(336)	(291)
Real Estate \| Originated \| Construction and Land
Loans and Leases Receivable Disclosure [Line Items]
Loans	39,922	38,284
Loans held-for-investment, net	39,953	38,303
Allowance for loan losses	(671)	(536)	(574)	(463)
Real Estate \| Acquired Loans
Loans and Leases Receivable Disclosure [Line Items]
Loans	384,435	423,964
Real Estate \| Acquired Loans \| Multifamily
Loans and Leases Receivable Disclosure [Line Items]
Loans	102,176	108,417
Real Estate \| Acquired Loans \| Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	102,284	113,027
Real Estate \| Acquired Loans \| One-to-Four Family
Loans and Leases Receivable Disclosure [Line Items]
Loans	167,934	187,975
Real Estate \| Acquired Loans \| Home equity and lines of credit
Loans and Leases Receivable Disclosure [Line Items]
Loans	10,653	12,008
Real Estate \| Acquired Loans \| Construction and Land
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,388	2,537
Commercial and Industrial \| Originated
Loans and Leases Receivable Disclosure [Line Items]
Loans	49,210	45,328
Loans held-for-investment, net	49,358	45,456
Allowance for loan losses	(2,035)	(1,640)	(1,376)	(1,569)
Commercial and Industrial \| Acquired Loans
Loans and Leases Receivable Disclosure [Line Items]
Loans	9,056	8,689
Other \| Originated
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,205	2,083
Loans held-for-investment, net	1,205	2,084
Allowance for loan losses	$ (86)	$ (151)	$ (92)	$ (108)