Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Allowance for loan losses:
Beginning balance	$ 15,771	$ 15,219	$ 15,767	$ 15,442
Provision for loan losses	0	0	0	0
Charge-offs	(5)	0	(5)	(287)
Recoveries	47	13	51	77
Ending balance	15,813	15,232	15,813	15,232
Ending ALLL related to loans collectively evaluated for impairment	15,310		15,310		$ 15,254
Ending ALLL related to loans individually evaluated for impairment	503		503		513
Ending ALLL	15,813		15,813		15,767
Collectively evaluated for impairment	1,699,592		1,699,592		1,659,972
Individually evaluated for impairment	15,879		15,879		16,926
Total loans	$ 1,717,611		$ 1,717,611		$ 1,679,013
Ratio of allowance for loan losses to total loans	0.92%		0.92%		0.94%
Allowance for loan losses to non-accrual loans	4107.00%		4107.00%		3883.00%
Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	2,140		2,140		2,115
Commercial loans \| Commercial and industrial
Allowance for loan losses:
Beginning balance	3,693	4,413	3,654	3,248
Provision for loan losses	(1,098)	(490)	(1,063)	896
Charge-offs	(3)	0	(3)	(284)
Recoveries	5	9	9	72
Ending balance	2,597	3,932	2,597	3,932
Ending ALLL related to loans collectively evaluated for impairment	2,365		2,365		3,604
Ending ALLL related to loans individually evaluated for impairment	232		232		50
Ending ALLL	2,597		2,597		3,654
Collectively evaluated for impairment	240,035		240,035		233,605
Individually evaluated for impairment	1,917		1,917		2,165
Total loans	$ 241,994		$ 241,994		$ 235,835
Ratio of allowance for loan losses to total loans	1.07%		1.07%		1.55%
Commercial loans \| Commercial and industrial \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	42		42		65
Commercial real estate loans \| Commercial real estate, owner-occupied
Allowance for loan losses:
Beginning balance	2,080	1,992	2,294	1,753
Provision for loan losses	259	90	45	329
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	2,339	2,082	2,339	2,082
Ending ALLL related to loans collectively evaluated for impairment	2,213		2,213		2,106
Ending ALLL related to loans individually evaluated for impairment	126		126		188
Ending ALLL	2,339		2,339		2,294
Collectively evaluated for impairment	309,376		309,376		292,798
Individually evaluated for impairment	7,002		7,002		6,999
Total loans	$ 317,587		$ 317,587		$ 300,963
Ratio of allowance for loan losses to total loans	0.74%		0.74%		0.76%
Commercial real estate loans \| Commercial real estate, owner-occupied \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	1,209		1,209		1,166
Commercial real estate loans \| Commercial real estate, investor
Allowance for loan losses:
Beginning balance	6,455	6,133	6,475	6,320
Provision for loan losses	935	(68)	915	(255)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	7,390	6,065	7,390	6,065
Ending ALLL related to loans collectively evaluated for impairment	7,343		7,343		6,316
Ending ALLL related to loans individually evaluated for impairment	47		47		159
Ending ALLL	7,390		7,390		6,475
Collectively evaluated for impairment	837,022		837,022		820,023
Individually evaluated for impairment	1,844		1,844		2,171
Total loans	$ 839,667		$ 839,667		$ 822,984
Ratio of allowance for loan losses to total loans	0.88%		0.88%		0.79%
Commercial real estate loans \| Commercial real estate, investor \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	801		801		790
Commercial real estate loans \| Construction
Allowance for loan losses:
Beginning balance	697	546	681	781
Provision for loan losses	(189)	(135)	(173)	(370)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	508	411	508	411
Ending ALLL related to loans collectively evaluated for impairment	508		508		674
Ending ALLL related to loans individually evaluated for impairment	0		0		7
Ending ALLL	508		508		681
Collectively evaluated for impairment	54,324		54,324		60,859
Individually evaluated for impairment	2,691		2,691		2,969
Total loans	$ 57,015		$ 57,015		$ 63,828
Ratio of allowance for loan losses to total loans	0.89%		0.89%		1.07%
Commercial real estate loans \| Construction \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	0		0		0
Residential loans \| Home equity
Allowance for loan losses:
Beginning balance	979	990	1,031	973
Provision for loan losses	(27)	(9)	(79)	8
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	952	981	952	981
Ending ALLL related to loans collectively evaluated for impairment	946		946		1,025
Ending ALLL related to loans individually evaluated for impairment	6		6		6
Ending ALLL	952		952		1,031
Collectively evaluated for impairment	125,211		125,211		131,620
Individually evaluated for impairment	732		732		753
Total loans	$ 126,031		$ 126,031		$ 132,467
Ratio of allowance for loan losses to total loans	0.76%		0.76%		0.78%
Allowance for loan losses to non-accrual loans	247.00%		247.00%		254.00%
Residential loans \| Home equity \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	88		88		94
Residential loans \| Other residential
Allowance for loan losses:
Beginning balance	543	444	536	454
Provision for loan losses	203	65	210	55
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	746	509	746	509
Ending ALLL related to loans collectively evaluated for impairment	746		746		535
Ending ALLL related to loans individually evaluated for impairment	0		0		1
Ending ALLL	746		746		536
Collectively evaluated for impairment	107,840		107,840		94,378
Individually evaluated for impairment	989		989		1,148
Total loans	$ 108,829		$ 108,829		$ 95,526
Ratio of allowance for loan losses to total loans	0.69%		0.69%		0.56%
Residential loans \| Other residential \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	0		0		0
Consumer loans \| Installment and other consumer
Allowance for loan losses:
Beginning balance	351	359	378	372
Provision for loan losses	(66)	(23)	(93)	(34)
Charge-offs	(2)	0	(2)	(3)
Recoveries	42	4	42	5
Ending balance	325	340	325	340
Ending ALLL related to loans collectively evaluated for impairment	233		233		276
Ending ALLL related to loans individually evaluated for impairment	92		92		102
Ending ALLL	325		325		378
Collectively evaluated for impairment	25,784		25,784		26,689
Individually evaluated for impairment	704		704		721
Total loans	$ 26,488		$ 26,488		$ 27,410
Ratio of allowance for loan losses to total loans	1.23%		1.23%		1.38%
Consumer loans \| Installment and other consumer \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0		$ 0
Purchased credit-impaired	0		0		0
Unallocated
Allowance for loan losses:
Beginning balance	973	342	718	1,541
Provision for loan losses	(17)	570	238	(629)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	956	$ 912	956	$ 912
Ending ALLL related to loans collectively evaluated for impairment	956		956		718
Ending ALLL related to loans individually evaluated for impairment	0		0		0
Ending ALLL	956		956		718
Collectively evaluated for impairment	0		0		0
Individually evaluated for impairment	0		0		0
Total loans	0		0		0
Unallocated \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	0		0		0
Purchased credit-impaired	$ 0		$ 0		$ 0

Allowance as percentage of non-accrual loans.

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Allowance as percentage of total loans.

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

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A valuation allowance for financing receivables that are expected to be uncollectible.

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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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