Loans and Allowance for Loan Losses - Allowance For Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan losses
Balance, beginning of period	$ 6,250	$ 5,422	$ 4,458
Provision for loan losses	2,472	960	960
Transfer out		(132)
Loans charged to the allowance	(546)
Recoveries of loans previously charged off	135		4
Balance, end of period	8,311	6,250	5,422
Ending balance: individually evaluated for impairment	362	41
Ending balance: collectively evaluated for impairment	7,949	6,209
Loans
Ending balance	1,374,660	941,796
Ending balance individually evaluated for impairment	7,336	5,568
Ending balance: collectively evaluated for impairment	1,367,324	936,228
Mortgage warehouse lines of credit
Allowance for loan losses
Balance, beginning of period	373	704	475
Provision for loan losses	(90)	(331)	229
Balance, end of period	283	373	704
Ending balance: collectively evaluated for impairment	283	373
Loans
Ending balance	224,937	275,039
Ending balance: collectively evaluated for impairment	224,937	275,039
Residential real estate
Allowance for loan losses
Balance, beginning of period	2,170	2,212	1,806
Provision for loan losses	(583)	90	405
Transfer out		(132)
Recoveries of loans previously charged off			1
Balance, end of period	1,587	2,170	2,212
Ending balance: individually evaluated for impairment		30
Ending balance: collectively evaluated for impairment	1,587	2,140
Loans
Ending balance	330,410	235,759
Ending balance individually evaluated for impairment	729	343
Ending balance: collectively evaluated for impairment	329,681	235,416
Multi-family and healthcare financing
Allowance for loan losses
Balance, beginning of period	1,962	1,308	689
Provision for loan losses	1,540	654	619
Balance, end of period	3,502	1,962	1,308
Ending balance: collectively evaluated for impairment	3,502	1,962
Loans
Ending balance	529,259	261,031
Ending balance: collectively evaluated for impairment	529,259	261,031
Commercial and commercial real estate
Allowance for loan losses
Balance, beginning of period	1,374	908	1,163
Provision for loan losses	1,399	466	(258)
Loans charged to the allowance	(546)
Recoveries of loans previously charged off	135		3
Balance, end of period	2,362	1,374	908
Ending balance: individually evaluated for impairment	200
Ending balance: collectively evaluated for impairment	2,162	1,374
Loans
Ending balance	228,668	113,812
Ending balance individually evaluated for impairment	6,179	5,022
Ending balance: collectively evaluated for impairment	222,489	108,790
Agricultural production and real estate
Allowance for loan losses
Balance, beginning of period	269	222	275
Provision for loan losses	51	47	(53)
Balance, end of period	320	269	222
Ending balance: individually evaluated for impairment	16	11
Ending balance: collectively evaluated for impairment	304	258
Loans
Ending balance	51,966	46,763
Ending balance individually evaluated for impairment	282	203
Ending balance: collectively evaluated for impairment	51,684	46,560
Consumer and margin loans
Allowance for loan losses
Balance, beginning of period	102	68	50
Provision for loan losses	155	34	18
Balance, end of period	257	102	$ 68
Ending balance: individually evaluated for impairment	146
Ending balance: collectively evaluated for impairment	111	102
Loans
Ending balance	9,420	9,392
Ending balance individually evaluated for impairment	146
Ending balance: collectively evaluated for impairment	$ 9,274	$ 9,392

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 other addition (reduction) in allowance reserve for credit loss.

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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 valuation allowance for financing receivables that are expected to be uncollectible that were individually 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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