Loans - Allowance for Credit Losses by Loan Category (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment loan	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of loan portfolio segment | segment			10
Number of loans entity experienced losses over past twelve quarters | loan			3
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	$ 8,452	$ 8,425	$ 8,395	$ 9,267
Provision (recovery of provision) for credit losses	5	(373)	15	(1,699)
Charge-offs	(299)	(52)	(418)	(151)
Recoveries	72	798	238	1,381
Net recoveries (charge-offs)	(227)	746	(180)	1,230
Ending balance	8,230	8,798	8,230	8,798
Period-end amount allocated to:
Loans individually evaluated for impairment					$ 1,142		$ 1,717
Loans collectively evaluated for impairment					7,088		7,081
Ending balance	8,452	8,425	$ 8,395	9,267	8,230	$ 8,395	8,798
Loans Individually Evaluated for Impairment					18,362		19,242
Loans Collectively Evaluated for Impairment					551,766		557,873
Total Loans					570,128	587,933	577,115
Consumer Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of segments | segment			3
Total commercial and industrial
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	1,457	1,547	$ 1,673	1,408
Provision (recovery of provision) for credit losses	(168)	(734)	(441)	(915)
Charge-offs	0	0	0	(88)
Recoveries	7	678	64	1,086
Net recoveries (charge-offs)	7	678	64	998
Ending balance	1,296	1,491	1,296	1,491
Period-end amount allocated to:
Loans individually evaluated for impairment					525		633
Loans collectively evaluated for impairment					771		858
Ending balance	1,457	1,547	1,673	1,408	1,296	1,673	1,491
Loans Individually Evaluated for Impairment					1,918		3,039
Loans Collectively Evaluated for Impairment					46,219		52,484
Total Loans					48,137	56,978	55,523
Commercial and business loans
Period-end amount allocated to:
Loans Individually Evaluated for Impairment					1,652		2,738
Loans Collectively Evaluated for Impairment					45,703		51,901
Total Loans					47,355	55,929	54,639
Government program loans
Period-end amount allocated to:
Loans Individually Evaluated for Impairment					266		301
Loans Collectively Evaluated for Impairment					516		583
Total Loans					782	1,049	884
Total real estate mortgage
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	864	1,213	1,015	1,182
Provision (recovery of provision) for credit losses	(109)	(81)	(263)	(70)
Charge-offs	0	(47)	(5)	(47)
Recoveries	52	4	60	24
Net recoveries (charge-offs)	52	(43)	55	(23)
Ending balance	807	1,089	807	1,089
Period-end amount allocated to:
Loans individually evaluated for impairment					361		464
Loans collectively evaluated for impairment					446		625
Ending balance	864	1,213	1,015	1,182	807	1,015	1,089
Loans Individually Evaluated for Impairment					4,179		3,524
Loans Collectively Evaluated for Impairment					271,780		277,711
Total Loans					275,959	289,200	281,235
Commercial real estate loans
Period-end amount allocated to:
Loans Individually Evaluated for Impairment					3,105		1,314
Loans Collectively Evaluated for Impairment					221,608		211,325
Total Loans					224,713	229,448	212,639
Residential mortgages
Period-end amount allocated to:
Loans Individually Evaluated for Impairment					1,074		2,210
Loans Collectively Evaluated for Impairment					49,988		66,053
Total Loans					51,062	59,431	68,263
Home Improvement and Home Equity
Period-end amount allocated to:
Loans Individually Evaluated for Impairment					0		0
Loans Collectively Evaluated for Impairment					184		333
Total Loans					184	321	333
Real estate construction and development
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	2,330	2,687	2,424	2,903
Provision (recovery of provision) for credit losses	(3)	(215)	(97)	(431)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net recoveries (charge-offs)	0	0	0	0
Ending balance	2,327	2,472	2,327	2,472
Period-end amount allocated to:
Loans individually evaluated for impairment					0		0
Loans collectively evaluated for impairment					2,327		2,472
Ending balance	2,330	2,687	2,424	2,903	2,327	2,424	2,472
Loans Individually Evaluated for Impairment					11,529		11,713
Loans Collectively Evaluated for Impairment					104,914		97,441
Total Loans					116,443	108,795	109,154
Agricultural
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	1,132	1,301	1,131	1,631
Provision (recovery of provision) for credit losses	(227)	(69)	(226)	(399)
Charge-offs	(36)	0	(36)	0
Recoveries	0	0	0	0
Net recoveries (charge-offs)	(36)	0	(36)	0
Ending balance	869	1,232	869	1,232
Period-end amount allocated to:
Loans individually evaluated for impairment					256		620
Loans collectively evaluated for impairment					613		612
Ending balance	1,132	1,301	1,131	1,631	869	1,131	1,232
Loans Individually Evaluated for Impairment					736		914
Loans Collectively Evaluated for Impairment					59,364		58,741
Total Loans					60,100	61,149	59,655
Installment and Student Loans
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	1,991	840	1,559	887
Provision (recovery of provision) for credit losses	388	687	833	496
Charge-offs	(263)	(5)	(377)	(16)
Recoveries	13	116	114	271
Net recoveries (charge-offs)	(250)	111	(263)	255
Ending balance	2,129	1,638	2,129	1,638
Period-end amount allocated to:
Loans individually evaluated for impairment					0		0
Loans collectively evaluated for impairment					2,129		1,638
Ending balance	1,991	840	1,559	887	2,129	1,559	1,638
Loans Individually Evaluated for Impairment					0		52
Loans Collectively Evaluated for Impairment					69,489		71,496
Total Loans					69,489	71,811	71,548
Unallocated
Summarizes activity in allowance for credit losses by loan category [Roll Forward]
Beginning balance	678	837	593	1,256
Provision (recovery of provision) for credit losses	124	39	209	(380)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net recoveries (charge-offs)	0	0	0	0
Ending balance	802	876	802	876
Period-end amount allocated to:
Loans individually evaluated for impairment					0		0
Loans collectively evaluated for impairment					802		876
Ending balance	$ 678	$ 837	$ 593	$ 1,256	$ 802	$ 593	$ 876