Loans & Leases and Allowance for Credit Losses, Aging Analysis of Loan & Lease Portfolio by the Time Past Due (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	$ 0	$ 0	$ 0
Nonaccrual	0	0	81
Total Past Due	727	1,438	186
Current	2,563,241	2,569,803	2,234,897
Total Loans & Leases	2,563,968	2,571,241	2,235,083
30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	727	707	42
60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	731	63
Commercial Real Estate [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	731	0
Current	815,366	825,818	698,349
Total Loans & Leases	815,366	826,549	698,349
Commercial Real Estate [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	731	0
Agricultural Real Estate [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	0
Current	603,601	584,625	508,400
Total Loans & Leases	603,601	584,625	508,400
Agricultural Real Estate [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Agricultural Real Estate [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Real Estate Construction [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	327	0
Current	99,837	98,241	96,315
Total Loans & Leases	99,837	98,568	96,315
Real Estate Construction [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	327	0
Real Estate Construction [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Residential 1st Mortgages [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	81
Total Past Due	707	367	144
Current	257,652	259,369	263,993
Total Loans & Leases	258,359	259,736	264,137
Residential 1st Mortgages [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	707	367	14
Residential 1st Mortgages [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	49
Home Equity Lines & Loans [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	20
Current	40,072	40,789	34,671
Total Loans & Leases	40,072	40,789	34,691
Home Equity Lines & Loans [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	20
Home Equity Lines & Loans [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Agricultural [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	0
Current	257,004	290,463	261,427
Total Loans & Leases	257,004	290,463	261,427
Agricultural [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Agricultural [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Commercial [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	14
Current	364,439	343,834	274,668
Total Loans & Leases	364,439	343,834	274,682
Commercial [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Commercial [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	14
Consumer & Other [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	20	13	8
Current	18,398	19,399	6,677
Total Loans & Leases	18,418	19,412	6,685
Consumer & Other [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	20	13	8
Consumer & Other [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Leases [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	0
Current	106,872	107,265	90,397
Total Loans & Leases	106,872	107,265	90,397
Leases [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	0	0	0
Leases [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Past Due	$ 0	$ 0	$ 0