Loans and Allowance for Loan Losses - Allowance for loan losses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	$ 7,725	$ 6,452
Charge-offs	(565)	(77)
Recoveries	79	150
Provision	1,920	1,200
Loans and Leases Receivable, Allowance, Ending Balance	9,159	7,725
Ending Balance: Individually evaluated for impairment	373
Ending Balance: Collectively evaluated for impairment	8,786	7,725
Loans receivables:
Ending Balance: Individually evaluated for impairment	4,457	5,320
Ending Balance: Collectively evaluated for impairment	1,132,150	884,089
Loans receivables	1,138,008	889,409
Purchased credit impaired
Loans receivables:
Ending Balance: Individually evaluated for impairment	1,401
Loans receivables	1,401
Commercial \| Real Estate
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	4,832	4,266
Provision	716	566
Loans and Leases Receivable, Allowance, Ending Balance	5,548	4,832
Ending Balance: Collectively evaluated for impairment	5,548	4,832
Loans receivables:
Ending Balance: Individually evaluated for impairment	1,306	1,882
Ending Balance: Collectively evaluated for impairment	682,157	524,775
Loans receivables	683,602	526,657
Commercial \| Real Estate \| Purchased credit impaired
Loans receivables:
Loans receivables	139
Commercial \| Commercial and Industrial
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	768	1,032
Charge-offs	(86)	(44)
Recoveries	26	117
Provision	766	(337)
Loans and Leases Receivable, Allowance, Ending Balance	1,474	768
Ending Balance: Individually evaluated for impairment	372
Ending Balance: Collectively evaluated for impairment	1,102	768
Loans receivables:
Ending Balance: Individually evaluated for impairment	2,969	2,846
Ending Balance: Collectively evaluated for impairment	133,892	95,304
Loans receivables	137,328	98,150
Commercial \| Commercial and Industrial \| Purchased credit impaired
Loans receivables:
Loans receivables	467
Commercial \| Construction
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	1,191	375
Provision	94	816
Loans and Leases Receivable, Allowance, Ending Balance	1,285	1,191
Ending Balance: Collectively evaluated for impairment	1,285	1,191
Loans receivables:
Ending Balance: Collectively evaluated for impairment	152,918	123,444
Loans receivables	153,339	123,444
Commercial \| Construction \| Purchased credit impaired
Loans receivables:
Loans receivables	421
Consumer \| Residential
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	626	500
Charge-offs	(187)
Recoveries	1
Provision	78	126
Loans and Leases Receivable, Allowance, Ending Balance	518	626
Ending Balance: Individually evaluated for impairment	1
Ending Balance: Collectively evaluated for impairment	517	626
Loans receivables:
Ending Balance: Individually evaluated for impairment	182	587
Ending Balance: Collectively evaluated for impairment	130,875	108,339
Loans receivables	131,431	108,926
Consumer \| Residential \| Purchased credit impaired
Loans receivables:
Loans receivables	374
Consumer \| Nonresidential
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	268	121
Charge-offs	(292)	(33)
Recoveries	52	33
Provision	306	147
Loans and Leases Receivable, Allowance, Ending Balance	334	268
Ending Balance: Collectively evaluated for impairment	334	268
Loans receivables:
Ending Balance: Individually evaluated for impairment		5
Ending Balance: Collectively evaluated for impairment	32,308	32,227
Loans receivables	32,308	32,232
Unallocated
Allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	40	158
Provision	$ (40)	(118)
Loans and Leases Receivable, Allowance, Ending Balance		40
Ending Balance: Collectively evaluated for impairment		$ 40

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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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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually 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 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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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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