Loans & Leases and Allowance for Credit Losses, Allocation of The Allowance For Credit Losses by Portfolio Segment and By Impairment Methodology (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 39,037	$ 34,290	$ 35,401	$ 34,274	$ 34,274
Charge-Offs	(21)	(61)	(67)	(204)	(276)
Recoveries	74	38	3,106	197	228
Provision	0	0	650	0	1,175
Ending Balance	39,090	34,267	39,090	34,267	35,401
Ending Balance Individually Evaluated for Impairment	1,196	2,201	1,196	2,201	2,197
Ending Balance Collectively Evaluated for Impairment	37,894	32,066	37,894	32,066	33,204
Loans & Leases [Abstract]
Ending Balance	1,910,270	1,615,771	1,910,270	1,615,771	1,712,244
Ending Balance Individually Evaluated for Impairment	17,191	33,536	17,191	33,536	33,584
Ending Balance Collectively Evaluated for Impairment	1,893,079	1,582,235	1,893,079	1,582,235	1,678,660
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,591	6,991	7,842	5,178	5,178
Charge-Offs	0	0	0	0	0
Recoveries	0	12	2,939	12	11
Provision	654	795	(1,536)	2,608	2,653
Ending Balance	9,245	7,798	9,245	7,798	7,842
Ending Balance Individually Evaluated for Impairment	61	190	61	190	377
Ending Balance Collectively Evaluated for Impairment	9,184	7,608	9,184	7,608	7,465
Loans & Leases [Abstract]
Ending Balance	558,743	473,505	558,743	473,505	491,903
Ending Balance Individually Evaluated for Impairment	4,120	20,175	4,120	20,175	20,066
Ending Balance Collectively Evaluated for Impairment	554,623	453,330	554,623	453,330	471,837
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,272	3,677	4,185	3,576	3,576
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	208	269	3,295	370	609
Ending Balance	7,480	3,946	7,480	3,946	4,185
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	7,480	3,946	7,480	3,946	4,185
Loans & Leases [Abstract]
Ending Balance	432,610	364,161	432,610	364,161	357,207
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	432,610	364,161	432,610	364,161	357,207
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,177	1,290	1,669	654	654
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	211	390	719	1,026	1,015
Ending Balance	2,388	1,680	2,388	1,680	1,669
Ending Balance Individually Evaluated for Impairment	0	239	0	239	0
Ending Balance Collectively Evaluated for Impairment	2,388	1,441	2,388	1,441	1,669
Loans & Leases [Abstract]
Ending Balance	161,762	104,463	161,762	104,463	96,519
Ending Balance Individually Evaluated for Impairment	4,307	4,419	4,307	4,419	4,386
Ending Balance Collectively Evaluated for Impairment	157,455	100,044	157,455	100,044	92,133
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	731	1,094	1,022	1,108	1,108
Charge-Offs	0	(25)	0	(58)	(73)
Recoveries	3	0	4	0	0
Provision	18	73	(274)	92	(13)
Ending Balance	752	1,142	752	1,142	1,022
Ending Balance Individually Evaluated for Impairment	70	370	70	370	422
Ending Balance Collectively Evaluated for Impairment	682	772	682	772	600
Loans & Leases [Abstract]
Ending Balance	196,893	168,310	196,893	168,310	171,880
Ending Balance Individually Evaluated for Impairment	2,036	1,847	2,036	1,847	2,108
Ending Balance Collectively Evaluated for Impairment	194,857	166,463	194,857	166,463	169,772
Home Equity Lines and Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,073	2,737	2,426	2,767	2,767
Charge-Offs	0	(5)	0	(70)	(70)
Recoveries	37	3	85	54	58
Provision	45	(60)	(356)	(76)	(329)
Ending Balance	2,155	2,675	2,155	2,675	2,426
Ending Balance Individually Evaluated for Impairment	35	328	35	328	329
Ending Balance Collectively Evaluated for Impairment	2,120	2,347	2,120	2,347	2,097
Loans & Leases [Abstract]
Ending Balance	31,833	33,283	31,833	33,283	33,017
Ending Balance Individually Evaluated for Impairment	1,264	1,658	1,264	1,658	1,643
Ending Balance Collectively Evaluated for Impairment	30,569	31,625	30,569	31,625	31,374
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	5,046	8,291	6,104	12,205	12,205
Charge-Offs	0	0	0	0	0
Recoveries	1	1	3	3	8
Provision	91	(2,510)	(969)	(6,426)	(6,109)
Ending Balance	5,138	5,782	5,138	5,782	6,104
Ending Balance Individually Evaluated for Impairment	120	120	120	120	114
Ending Balance Collectively Evaluated for Impairment	5,018	5,662	5,018	5,662	5,990
Loans & Leases [Abstract]
Ending Balance	249,783	237,521	249,783	237,521	281,963
Ending Balance Individually Evaluated for Impairment	630	518	630	518	461
Ending Balance Collectively Evaluated for Impairment	249,153	237,003	249,153	237,003	281,502
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,878	7,377	8,195	5,697	5,697
Charge-Offs	0	0	(12)	0	(1)
Recoveries	20	6	24	83	86
Provision	(653)	532	38	2,135	2,413
Ending Balance	8,245	7,915	8,245	7,915	8,195
Ending Balance Individually Evaluated for Impairment	879	912	879	912	914
Ending Balance Collectively Evaluated for Impairment	7,366	7,003	7,366	7,003	7,281
Loans & Leases [Abstract]
Ending Balance	210,491	192,804	210,491	192,804	230,819
Ending Balance Individually Evaluated for Impairment	4,797	4,877	4,797	4,877	4,874
Ending Balance Collectively Evaluated for Impairment	205,694	187,927	205,694	187,927	225,945
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	217	193	218	176	176
Charge-Offs	(21)	(31)	(55)	(76)	(132)
Recoveries	13	16	51	45	65
Provision	7	43	2	76	109
Ending Balance	216	221	216	221	218
Ending Balance Individually Evaluated for Impairment	31	42	31	42	41
Ending Balance Collectively Evaluated for Impairment	185	179	185	179	177
Loans & Leases [Abstract]
Ending Balance	6,735	4,816	6,735	4,816	4,719
Ending Balance Individually Evaluated for Impairment	37	42	37	42	46
Ending Balance Collectively Evaluated for Impairment	6,698	4,774	6,698	4,774	4,673
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,532	1,108	2,211	639	639
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	539	737	860	1,206	1,572
Ending Balance	3,071	1,845	3,071	1,845	2,211
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	3,071	1,845	3,071	1,845	2,211
Loans & Leases [Abstract]
Ending Balance	61,420	36,908	61,420	36,908	44,217
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	61,420	36,908	61,420	36,908	44,217
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,520	1,532	1,529	2,274	2,274
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	(1,120)	(269)	(1,129)	(1,011)	(745)
Ending Balance	400	1,263	400	1,263	1,529
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	400	1,263	400	1,263	1,529
Loans & Leases [Abstract]
Ending Balance	0	0	0	0	0
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	0	0	0	0	0
Restructured Loans [Member]
Loans & Leases [Abstract]
Ending Balance Individually Evaluated for Impairment	$ 9,300	$ 26,600	$ 9,300	$ 26,600	$ 26,400