Loans - Amount of Loans Receivable Held-for-Investment and Related Allowances Per Loan Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Allowance for loan losses:
Beginning Balance	$ 27,486	$ 26,172	$ 27,497	$ 26,160
Charge-offs	(233)	0	(324)	(64)
Recoveries	88	40	109	82
Provisions (credit)	491	670	550	704
Ending balance	27,832	26,882	27,832	26,882
Ending balance: individually evaluated for impairment	252		252		$ 26
Ending balance: collectively evaluated for impairment	27,580		27,580		27,471
Loans, net:
Loans held-for-investment, net	3,338,778		3,338,778		3,245,170
Ending balance: individually evaluated for impairment	22,295		22,295		22,329
Ending balance: collectively evaluated for impairment	3,316,483		3,316,483		3,222,841
Originated
Allowance for loan losses:
Beginning Balance	26,476	25,218	26,487	25,172
Charge-offs	(180)	0	(212)	(63)
Recoveries	86	38	98	74
Provisions (credit)	305	675	314	748
Ending balance	26,687	25,931	26,687	25,931
Ending balance: individually evaluated for impairment	117		117		26
Ending balance: collectively evaluated for impairment	26,570		26,570		26,461
Loans, net:
Loans held-for-investment, net	2,800,816		2,800,816		2,678,877
Ending balance: individually evaluated for impairment	17,346		17,346		18,547
Ending balance: collectively evaluated for impairment	2,783,470		2,783,470		2,660,330
Purchased Credit-Impaired
Allowance for loan losses:
Beginning Balance	1,010	951	1,010	951
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provisions (credit)	0	0	0	0
Ending balance	1,010	951	1,010	951
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	1,010		1,010		1,010
Loans, net:
Loans held-for-investment, net	18,077		18,077		20,143
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	18,077		18,077		20,143
Acquired Loans
Allowance for loan losses:
Beginning Balance	0	3	0	37
Charge-offs	(53)	0	(112)	(1)
Recoveries	2	2	11	8
Provisions (credit)	186	(5)	236	(44)
Ending balance	135	0	135	0
Ending balance: individually evaluated for impairment	135		135		0
Ending balance: collectively evaluated for impairment	0		0		0
Loans, net:
Loans held-for-investment, net	519,885		519,885		546,150
Ending balance: individually evaluated for impairment	4,949		4,949		3,782
Ending balance: collectively evaluated for impairment	514,936		514,936		542,368
Real Estate \| Commercial \| Originated
Allowance for loan losses:
Beginning Balance	5,382	5,213	5,630	5,196
Charge-offs	0	0	(6)	(3)
Recoveries	13	12	25	28
Provisions (credit)	(64)	493	(318)	497
Ending balance	5,331	5,718	5,331	5,718
Ending balance: individually evaluated for impairment	104		104		0
Ending balance: collectively evaluated for impairment	5,227		5,227		5,630
Loans, net:
Loans held-for-investment, net	512,308		512,308		499,860
Ending balance: individually evaluated for impairment	14,362		14,362		15,252
Ending balance: collectively evaluated for impairment	497,946		497,946		484,608
Real Estate \| One-to-Four Family \| Originated
Allowance for loan losses:
Beginning Balance	370	455	342	503
Charge-offs	0	0	0	0
Recoveries	72	0	72	0
Provisions (credit)	(208)	(71)	(180)	(119)
Ending balance	234	384	234	384
Ending balance: individually evaluated for impairment	1		1		18
Ending balance: collectively evaluated for impairment	233		233		324
Loans, net:
Loans held-for-investment, net	90,232		90,232		92,433
Ending balance: individually evaluated for impairment	1,854		1,854		1,893
Ending balance: collectively evaluated for impairment	88,378		88,378		90,540
Real Estate \| Construction and Land \| Originated
Allowance for loan losses:
Beginning Balance	574	463	463	610
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provisions (credit)	10	(25)	121	(172)
Ending balance	584	438	584	438
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	584		584		463
Loans, net:
Loans held-for-investment, net	33,573		33,573		26,613
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	33,573		33,573		26,613
Real Estate \| Multifamily \| Originated
Allowance for loan losses:
Beginning Balance	18,346	17,412	18,084	17,374
Charge-offs	0	0	0	0
Recoveries	0	26	0	26
Provisions (credit)	38	165	300	203
Ending balance	18,384	17,603	18,384	17,603
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	18,384		18,384		18,084
Loans, net:
Loans held-for-investment, net	2,032,518		2,032,518		1,933,946
Ending balance: individually evaluated for impairment	1,007		1,007		1,268
Ending balance: collectively evaluated for impairment	2,031,511		2,031,511		1,932,678
Real Estate \| Home equity and lines of credit \| Originated
Allowance for loan losses:
Beginning Balance	336	225	291	122
Charge-offs	0	0	0	(60)
Recoveries	0	0	0	0
Provisions (credit)	81	54	126	217
Ending balance	417	279	417	279
Ending balance: individually evaluated for impairment	8		8		5
Ending balance: collectively evaluated for impairment	409		409		286
Loans, net:
Loans held-for-investment, net	87,389		87,389		80,315
Ending balance: individually evaluated for impairment	58		58		61
Ending balance: collectively evaluated for impairment	87,331		87,331		80,254
Commercial and Industrial \| Originated
Allowance for loan losses:
Beginning Balance	1,376	1,337	1,569	1,273
Charge-offs	(57)	0	(83)	0
Recoveries	0	0	0	20
Provisions (credit)	272	65	105	109
Ending balance	1,591	1,402	1,591	1,402
Ending balance: individually evaluated for impairment	4		4		3
Ending balance: collectively evaluated for impairment	1,587		1,587		1,566
Loans, net:
Loans held-for-investment, net	42,768		42,768		44,190
Ending balance: individually evaluated for impairment	65		65		73
Ending balance: collectively evaluated for impairment	42,703		42,703		44,117
Other \| Originated
Allowance for loan losses:
Beginning Balance	92	113	108	94
Charge-offs	(123)	0	(123)	0
Recoveries	1	0	1	0
Provisions (credit)	176	(6)	160	13
Ending balance	146	$ 107	146	$ 107
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	146		146		108
Loans, net:
Loans held-for-investment, net	2,028		2,028		1,520
Ending balance: individually evaluated for impairment	0		0		0
Ending balance: collectively evaluated for impairment	$ 2,028		$ 2,028		$ 1,520

Originated loans, net.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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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 and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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