Loans and Allowance for Loan Losses - Allowance For Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Allowance for loan losses
Balance, beginning of period	$ 10,588	$ 6,865	$ 8,311	$ 6,250
Provision (credit) for loan losses	617	592	3,021	1,072
Loans charged to the allowance	74		(89)
Recoveries of loans previously charged off	(36)			(135)
Balance, end of period	11,243	7,457	11,243	7,457
Ending balance: individually evaluated for impairment	541		541		$ 362
Ending balance: collectively evaluated for impairment	10,702		10,702		7,949
Loans
Ending balance	1,917,102		1,917,102		1,374,660
Ending balance individually evaluated for impairment	9,267		9,267		7,336
Ending balance: collectively evaluated for impairment	1,907,835		1,907,835		1,367,324
Mortgage warehouse lines of credit
Allowance for loan losses
Balance, beginning of period	646	281	283	373
Provision (credit) for loan losses	73	(8)	436	(100)
Balance, end of period	719	273	719	273
Ending balance: individually evaluated for impairment	175		175
Ending balance: collectively evaluated for impairment	544		544		283
Loans
Ending balance	406,287		406,287		224,937
Ending balance individually evaluated for impairment	579		579
Ending balance: collectively evaluated for impairment	405,708		405,708		224,937
Residential real estate
Allowance for loan losses
Balance, beginning of period	1,812	1,938	1,587	2,170
Provision (credit) for loan losses	96	(414)	305	(646)
Recoveries of loans previously charged off	(16)
Balance, end of period	1,892	1,524	1,892	1,524
Ending balance: collectively evaluated for impairment	1,892		1,892		1,587
Loans
Ending balance	399,970		399,970		330,410
Ending balance individually evaluated for impairment	1,048		1,048		729
Ending balance: collectively evaluated for impairment	398,922		398,922		329,681
Multi-family and healthcare financing
Allowance for loan losses
Balance, beginning of period	4,662	2,426	3,502	1,962
Provision (credit) for loan losses	240	276	1,400	740
Balance, end of period	4,902	2,702	4,902	2,702
Ending balance: collectively evaluated for impairment	4,902		4,902		3,502
Loans
Ending balance	738,879		738,879		529,259
Ending balance individually evaluated for impairment	109		109
Ending balance: collectively evaluated for impairment	738,770		738,770		529,259
Commercial and commercial real estate
Allowance for loan losses
Balance, beginning of period	2,803	1,845	2,362	1,374
Provision (credit) for loan losses	184	688	759	1,058
Loans charged to the allowance	46		(89)
Recoveries of loans previously charged off	(1)			(101)
Balance, end of period	3,032	2,533	3,032	2,533
Ending balance: individually evaluated for impairment	200		200		200
Ending balance: collectively evaluated for impairment	2,832		2,832		2,162
Loans
Ending balance	290,126		290,126		228,668
Ending balance individually evaluated for impairment	6,974		6,974		6,179
Ending balance: collectively evaluated for impairment	283,152		283,152		222,489
Agricultural production and real estate
Allowance for loan losses
Balance, beginning of period	392	271	320	269
Provision (credit) for loan losses	35	36	107	38
Balance, end of period	427	307	427	307
Ending balance: individually evaluated for impairment	20		20		16
Ending balance: collectively evaluated for impairment	407		407		304
Loans
Ending balance	70,280		70,280		51,966
Ending balance individually evaluated for impairment	370		370		282
Ending balance: collectively evaluated for impairment	69,910		69,910		51,684
Consumer and margin loans
Allowance for loan losses
Balance, beginning of period	273	104	257	102
Provision (credit) for loan losses	(11)	14	14	(18)
Loans charged to the allowance	28
Recoveries of loans previously charged off	(19)			(34)
Balance, end of period	271	$ 118	271	$ 118
Ending balance: individually evaluated for impairment	146		146		146
Ending balance: collectively evaluated for impairment	125		125		111
Loans
Ending balance	11,560		11,560		9,420
Ending balance individually evaluated for impairment	187		187		146
Ending balance: collectively evaluated for impairment	$ 11,373		$ 11,373		$ 9,274

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

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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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The balance of financing receivables 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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