Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Allowance for loan losses:
Beginning balance	$ 15,767	$ 15,442
Provision for loan losses	0	0
Charge-offs	0	(287)
Recoveries	4	64
Ending balance	15,771	15,219
Ending ALLL related to loans collectively evaluated for impairment	15,417		$ 15,254
Ending ALLL related to loans individually evaluated for impairment	354		513
Ending ALLL	15,771		15,767
Collectively evaluated for impairment	1,653,058		1,659,972
Individually evaluated for impairment	16,547		16,926
Total loans	$ 1,671,740		$ 1,679,013
Ratio of allowance for loan losses to total loans	0.94%		0.94%
Allowance for loan losses to non-accrual loans	4023.00%		3883.00%
Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	2,135		2,115
Commercial loans \| Commercial and industrial
Allowance for loan losses:
Beginning balance	3,654	3,248
Provision for loan losses	35	1,386
Charge-offs	0	(284)
Recoveries	4	63
Ending balance	3,693	4,413
Ending ALLL related to loans collectively evaluated for impairment	3,658		3,604
Ending ALLL related to loans individually evaluated for impairment	35		50
Ending ALLL	3,693		3,654
Collectively evaluated for impairment	229,361		233,605
Individually evaluated for impairment	2,267		2,165
Total loans	$ 231,680		$ 235,835
Ratio of allowance for loan losses to total loans	1.59%		1.55%
Commercial loans \| Commercial and industrial \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	52		65
Commercial real estate loans \| Commercial real estate, owner-occupied
Allowance for loan losses:
Beginning balance	2,294	1,753
Provision for loan losses	(214)	239
Charge-offs	0	0
Recoveries	0	0
Ending balance	2,080	1,992
Ending ALLL related to loans collectively evaluated for impairment	1,918		2,106
Ending ALLL related to loans individually evaluated for impairment	162		188
Ending ALLL	2,080		2,294
Collectively evaluated for impairment	292,176		292,798
Individually evaluated for impairment	7,007		6,999
Total loans	$ 300,377		$ 300,963
Ratio of allowance for loan losses to total loans	0.69%		0.76%
Commercial real estate loans \| Commercial real estate, owner-occupied \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	1,194		1,166
Commercial real estate loans \| Commercial real estate, investor
Allowance for loan losses:
Beginning balance	6,475	6,320
Provision for loan losses	(20)	(187)
Charge-offs	0	0
Recoveries	0	0
Ending balance	6,455	6,133
Ending ALLL related to loans collectively evaluated for impairment	6,407		6,316
Ending ALLL related to loans individually evaluated for impairment	48		159
Ending ALLL	6,455		6,475
Collectively evaluated for impairment	826,294		820,023
Individually evaluated for impairment	1,854		2,171
Total loans	$ 828,945		$ 822,984
Ratio of allowance for loan losses to total loans	0.78%		0.79%
Commercial real estate loans \| Commercial real estate, investor \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	797		790
Commercial real estate loans \| Construction
Allowance for loan losses:
Beginning balance	681	781
Provision for loan losses	16	(235)
Charge-offs	0	0
Recoveries	0	0
Ending balance	697	546
Ending ALLL related to loans collectively evaluated for impairment	686		674
Ending ALLL related to loans individually evaluated for impairment	11		7
Ending ALLL	697		681
Collectively evaluated for impairment	62,002		60,859
Individually evaluated for impairment	2,976		2,969
Total loans	$ 64,978		$ 63,828
Ratio of allowance for loan losses to total loans	1.07%		1.07%
Commercial real estate loans \| Construction \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	0		0
Residential loans \| Home equity
Allowance for loan losses:
Beginning balance	1,031	973
Provision for loan losses	(52)	17
Charge-offs	0	0
Recoveries	0	0
Ending balance	979	990
Ending ALLL related to loans collectively evaluated for impairment	973		1,025
Ending ALLL related to loans individually evaluated for impairment	6		6
Ending ALLL	979		1,031
Collectively evaluated for impairment	123,868		131,620
Individually evaluated for impairment	739		753
Total loans	$ 124,699		$ 132,467
Ratio of allowance for loan losses to total loans	0.79%		0.78%
Allowance for loan losses to non-accrual loans	250.00%		254.00%
Residential loans \| Home equity \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	92		94
Residential loans \| Other residential
Allowance for loan losses:
Beginning balance	536	454
Provision for loan losses	7	(10)
Charge-offs	0	0
Recoveries	0	0
Ending balance	543	444
Ending ALLL related to loans collectively evaluated for impairment	543		535
Ending ALLL related to loans individually evaluated for impairment	0		1
Ending ALLL	543		536
Collectively evaluated for impairment	94,629		94,378
Individually evaluated for impairment	992		1,148
Total loans	$ 95,621		$ 95,526
Ratio of allowance for loan losses to total loans	0.57%		0.56%
Residential loans \| Other residential \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	0		0
Consumer loans \| Installment and other consumer
Allowance for loan losses:
Beginning balance	378	372
Provision for loan losses	(27)	(11)
Charge-offs	0	(3)
Recoveries	0	1
Ending balance	351	359
Ending ALLL related to loans collectively evaluated for impairment	259		276
Ending ALLL related to loans individually evaluated for impairment	92		102
Ending ALLL	351		378
Collectively evaluated for impairment	24,728		26,689
Individually evaluated for impairment	712		721
Total loans	$ 25,440		$ 27,410
Ratio of allowance for loan losses to total loans	1.38%		1.38%
Consumer loans \| Installment and other consumer \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	$ 0		$ 0
Purchased credit-impaired	0		0
Unallocated
Allowance for loan losses:
Beginning balance	718	1,541
Provision for loan losses	255	(1,199)
Charge-offs	0	0
Recoveries	0	0
Ending balance	973	$ 342
Ending ALLL related to loans collectively evaluated for impairment	973		718
Ending ALLL related to loans individually evaluated for impairment	0		0
Ending ALLL	973		718
Collectively evaluated for impairment	0		0
Individually evaluated for impairment	0		0
Total loans	0		0
Unallocated \| Purchased credit-impaired
Allowance for loan losses:
Ending ALLL	0		0
Purchased credit-impaired	$ 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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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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