Loans and Allowance for Loan Losses, Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ 5,094	$ 4,525	$ 4,525
Charge-offs	(51)	(99)	(691)
Recoveries	57	1	740
Provision (recovery)	300	50	520
Ending balance	5,400	4,477	5,094
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	1,019		912
Ending balances collectively evaluated for impairment	4,381		4,182
Loans receivable, individually evaluated for impairment	10,734		10,862
Loans receivable, collectively evaluated for impairment	492,357		491,937
Total financing receivables	503,091		502,799
Commercial and Industrial [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	518	561	561
Charge-offs	(39)	(15)	(19)
Recoveries	6	0	154
Provision (recovery)	160	(75)	(178)
Ending balance	645	471	518
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	286		247
Ending balances collectively evaluated for impairment	359		271
Loans receivable, individually evaluated for impairment	875		758
Loans receivable, collectively evaluated for impairment	24,166		23,655
Total financing receivables	25,041		24,413
Commercial Real Estate [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	1,609	1,569	1,569
Charge-offs	0	0	(476)
Recoveries	0	0	575
Provision (recovery)	99	59	(59)
Ending balance	1,708	1,628	1,609
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	310		257
Ending balances collectively evaluated for impairment	1,398		1,352
Loans receivable, individually evaluated for impairment	3,616		3,631
Loans receivable, collectively evaluated for impairment	170,550		173,196
Total financing receivables	174,166		176,827
Construction and Land [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	879	661	661
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (recovery)	72	(28)	218
Ending balance	951	633	879
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	375		357
Ending balances collectively evaluated for impairment	575		522
Loans receivable, individually evaluated for impairment	5,013		5,234
Loans receivable, collectively evaluated for impairment	50,863		48,928
Total financing receivables	55,876		54,162
Consumer [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	105	21	21
Charge-offs	(3)	(29)	(114)
Recoveries	3	1	2
Provision (recovery)	(2)	52	196
Ending balance	103	45	105
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	0		0
Ending balances collectively evaluated for impairment	103		105
Loans receivable, individually evaluated for impairment	0		0
Loans receivable, collectively evaluated for impairment	4,624		5,068
Total financing receivables	4,624		5,068
Student [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	72	76	76
Charge-offs	(9)	(4)	(31)
Recoveries	0	0	0
Provision (recovery)	10	0	27
Ending balance	73	72	72
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	0		0
Ending balances collectively evaluated for impairment	73		72
Loans receivable, individually evaluated for impairment	0		0
Loans receivable, collectively evaluated for impairment	10,212		10,677
Total financing receivables	10,212		10,677
Residential Real Estate [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	1,174	943	943
Charge-offs	0	(51)	(51)
Recoveries	47	0	6
Provision (recovery)	(36)	77	276
Ending balance	1,185	969	1,174
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	0		0
Ending balances collectively evaluated for impairment	1,185		1,174
Loans receivable, individually evaluated for impairment	575		581
Loans receivable, collectively evaluated for impairment	189,272		186,523
Total financing receivables	189,847		187,104
Home Equity Lines of Credit [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	387	307	307
Charge-offs	0	0	0
Recoveries	1	0	3
Provision (recovery)	4	(3)	77
Ending balance	392	304	387
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	48		51
Ending balances collectively evaluated for impairment	345		336
Loans receivable, individually evaluated for impairment	655		658
Loans receivable, collectively evaluated for impairment	42,670		43,890
Total financing receivables	43,325		44,548
Unallocated [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	350	387	387
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (recovery)	(7)	(32)	(37)
Ending balance	343	$ 355	350
Additional Information on Allowance for Loan Losses and Recorded Investment in Loans Receivable [Abstract]
Ending balances individually evaluated for impairment	0		0
Ending balances collectively evaluated for impairment	343		350
Loans receivable, individually evaluated for impairment	0		0
Loans receivable, collectively evaluated for impairment	0		0
Total financing receivables	$ 0		$ 0

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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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 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 to estimated loss from loan and lease transactions.

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