Allowance for Credit Losses, Allocation of The Allowance For Loan Losses by Portfolio Segment and By Impairment Methodology (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 41,523	$ 35,401
Charge-Offs	(172)	(96)
Recoveries	233	5,468
Provision	6,335	750	$ 1,175
Ending Balance	47,919	41,523	35,401
Ending Balance Individually Evaluated for Impairment	831	1,213
Ending Balance Collectively Evaluated for Impairment	47,088	40,310
Loans & Leases [Abstract]
Ending Balance	2,177,601	1,996,359
Ending Balance Individually Evaluated for Impairment	10,863	12,044
Ending Balance Collectively Evaluated for Impairment	2,166,738	1,984,315
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	10,063	7,842
Charge-Offs	0	0
Recoveries	2	2,939
Provision	1,045	(718)
Ending Balance	11,110	10,063	7,842
Ending Balance Individually Evaluated for Impairment	0	61
Ending Balance Collectively Evaluated for Impairment	11,110	10,002
Loans & Leases [Abstract]
Ending Balance	668,046	603,650
Ending Balance Individually Evaluated for Impairment	1,932	3,420
Ending Balance Collectively Evaluated for Impairment	666,114	600,230
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	6,881	4,185
Charge-Offs	0	0
Recoveries	0	0
Provision	2,569	2,696
Ending Balance	9,450	6,881	4,185
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	9,450	6,881
Loans & Leases [Abstract]
Ending Balance	467,685	424,034
Ending Balance Individually Evaluated for Impairment	1,304	0
Ending Balance Collectively Evaluated for Impairment	466,381	424,034
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,485	1,669
Charge-Offs	0	0
Recoveries	0	2,225
Provision	738	(1,409)
Ending Balance	3,223	2,485	1,669
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	3,223	2,485
Loans & Leases [Abstract]
Ending Balance	176,462	151,974
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	176,462	151,974
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	789	1,022
Charge-Offs	(21)	0
Recoveries	26	8
Provision	71	(241)
Ending Balance	865	789	1,022
Ending Balance Individually Evaluated for Impairment	70	69
Ending Balance Collectively Evaluated for Impairment	795	720
Loans & Leases [Abstract]
Ending Balance	242,247	206,405
Ending Balance Individually Evaluated for Impairment	2,126	2,010
Ending Balance Collectively Evaluated for Impairment	240,121	204,395
Home Equity Lines and Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,146	2,426
Charge-Offs	(46)	0
Recoveries	103	87
Provision	(63)	(367)
Ending Balance	2,140	2,146	2,426
Ending Balance Individually Evaluated for Impairment	18	35
Ending Balance Collectively Evaluated for Impairment	2,122	2,111
Loans & Leases [Abstract]
Ending Balance	31,625	33,056
Ending Balance Individually Evaluated for Impairment	402	1,214
Ending Balance Collectively Evaluated for Impairment	31,223	31,842
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	6,308	6,104
Charge-Offs	0	0
Recoveries	0	4
Provision	1,073	200
Ending Balance	7,381	6,308	6,104
Ending Balance Individually Evaluated for Impairment	128	115
Ending Balance Collectively Evaluated for Impairment	7,253	6,193
Loans & Leases [Abstract]
Ending Balance	295,325	293,966
Ending Balance Individually Evaluated for Impairment	625	606
Ending Balance Collectively Evaluated for Impairment	294,700	293,360
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,836	8,195
Charge-Offs	0	(12)
Recoveries	47	136
Provision	632	(483)
Ending Balance	8,515	7,836	8,195
Ending Balance Individually Evaluated for Impairment	608	905
Ending Balance Collectively Evaluated for Impairment	7,907	6,931
Loans & Leases [Abstract]
Ending Balance	217,577	210,804
Ending Balance Individually Evaluated for Impairment	4,464	4,760
Ending Balance Collectively Evaluated for Impairment	213,113	206,044
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	175	218
Charge-Offs	(105)	(84)
Recoveries	55	69
Provision	75	(28)
Ending Balance	200	175	218
Ending Balance Individually Evaluated for Impairment	7	28
Ending Balance Collectively Evaluated for Impairment	193	147
Loans & Leases [Abstract]
Ending Balance	6,913	6,592
Ending Balance Individually Evaluated for Impairment	10	34
Ending Balance Collectively Evaluated for Impairment	6,903	6,558
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,294	2,211
Charge-Offs	0	0
Recoveries	0	0
Provision	292	1,083
Ending Balance	3,586	3,294	2,211
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	3,586	3,294
Loans & Leases [Abstract]
Ending Balance	71,721	65,878
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	71,721	65,878
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,546	1,529
Charge-Offs	0	0
Recoveries	0	0
Provision	(97)	17
Ending Balance	1,449	1,546	$ 1,529
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	1,449	1,546
Loans & Leases [Abstract]
Ending Balance	0	0
Ending Balance Individually Evaluated for Impairment	0	0
Ending Balance Collectively Evaluated for Impairment	0	0
Restructured Loans [Member]
Loans & Leases [Abstract]
Ending Balance Individually Evaluated for Impairment	$ 3,300	$ 4,900