Allowance for Loan Losses and Credit Quality of Loans, Average Recorded Investments on Loans Specifically Evaluated for Impairment and Interest Income Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	$ 19,733	$ 20,429	$ 23,238
Interest income recognized accrual	891	901	924
Originated Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	19,733	20,429	23,145
Interest income recognized accrual	891	901	924
Originated Loans [Member] | Commercial Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	4,642	5,549	8,183
Interest income recognized accrual	148	155	171
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	242	453	0
Interest income recognized accrual	1	1	0
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	3,311	4,078	0
Interest income recognized accrual	123	128	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	1,841
Interest income recognized accrual	0	0	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	3,534
Interest income recognized accrual	0	0	115
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	224
Interest income recognized accrual	0	0	1
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	1,709
Interest income recognized accrual	0	0	43
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	1,089	1,018	875
Interest income recognized accrual	24	26	12
Originated Loans [Member] | Consumer Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,586	8,101	8,439
Interest income recognized accrual	393	441	457
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	192	179	0
Interest income recognized accrual	10	10	0
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,387	7,922	0
Interest income recognized accrual	382	431	0
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7	0	0
Interest income recognized accrual	1	0	0
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	35
Interest income recognized accrual	0	0	3
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	8,226
Interest income recognized accrual	0	0	446
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	178
Interest income recognized accrual	0	0	8
Originated Loans [Member] | Residential Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,505	6,779	6,523
Interest income recognized accrual	350	305	296
Acquired Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	0	0	0
Acquired Loans [Member] | Commercial Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	0	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	$ 0	$ 0	$ 0