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, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 35,401	$ 34,274	$ 34,274
Charge-Offs	(29)	(30)	(276)
Recoveries	2,968	33	228
Provision	600	0	1,175
Ending Balance	38,940	34,277	35,401
Ending Balance Individually Evaluated for Impairment	1,470	2,104	2,197
Ending Balance Collectively Evaluated for Impairment	37,470	32,173	33,204
Loans & Leases [Abstract]
Ending Balance	1,705,320	1,363,030	1,712,244
Ending Balance Individually Evaluated for Impairment	17,025	36,010	33,584
Ending Balance Collectively Evaluated for Impairment	1,688,295	1,327,020	1,678,660
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,842	5,178	5,178
Charge-Offs	0	0	0
Recoveries	2,938	0	11
Provision	(2,826)	1,248	2,653
Ending Balance	7,954	6,426	7,842
Ending Balance Individually Evaluated for Impairment	61	245	377
Ending Balance Collectively Evaluated for Impairment	7,893	6,181	7,465
Loans & Leases [Abstract]
Ending Balance	529,550	402,865	491,903
Ending Balance Individually Evaluated for Impairment	3,573	22,046	20,066
Ending Balance Collectively Evaluated for Impairment	525,977	380,819	471,837
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	4,185	3,576	3,576
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	2,716	(189)	609
Ending Balance	6,901	3,387	4,185
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	6,901	3,387	4,185
Loans & Leases [Abstract]
Ending Balance	351,866	326,112	357,207
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	351,866	326,112	357,207
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,669	654	654
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	247	423	1,015
Ending Balance	1,916	1,077	1,669
Ending Balance Individually Evaluated for Impairment	0	226	0
Ending Balance Collectively Evaluated for Impairment	1,916	851	1,669
Loans & Leases [Abstract]
Ending Balance	101,616	55,751	96,519
Ending Balance Individually Evaluated for Impairment	4,363	4,473	4,386
Ending Balance Collectively Evaluated for Impairment	97,253	51,278	92,133
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,022	1,108	1,108
Charge-Offs	0	(3)	(73)
Recoveries	0	0	0
Provision	(349)	(5)	(13)
Ending Balance	673	1,100	1,022
Ending Balance Individually Evaluated for Impairment	72	340	422
Ending Balance Collectively Evaluated for Impairment	601	760	600
Loans & Leases [Abstract]
Ending Balance	182,431	156,094	171,880
Ending Balance Individually Evaluated for Impairment	2,080	1,701	2,108
Ending Balance Collectively Evaluated for Impairment	180,351	154,393	169,772
Home Equity Lines and Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,426	2,767	2,767
Charge-Offs	0	0	(70)
Recoveries	5	12	58
Provision	(335)	(131)	(329)
Ending Balance	2,096	2,648	2,426
Ending Balance Individually Evaluated for Impairment	53	313	329
Ending Balance Collectively Evaluated for Impairment	2,043	2,335	2,097
Loans & Leases [Abstract]
Ending Balance	31,724	34,289	33,017
Ending Balance Individually Evaluated for Impairment	1,668	2,055	1,643
Ending Balance Collectively Evaluated for Impairment	30,056	32,234	31,374
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	6,104	12,205	12,205
Charge-Offs	0	0	0
Recoveries	1	1	8
Provision	(1,503)	(2,605)	(6,109)
Ending Balance	4,602	9,601	6,104
Ending Balance Individually Evaluated for Impairment	129	118	114
Ending Balance Collectively Evaluated for Impairment	4,473	9,483	5,990
Loans & Leases [Abstract]
Ending Balance	216,231	209,228	281,963
Ending Balance Individually Evaluated for Impairment	457	587	461
Ending Balance Collectively Evaluated for Impairment	215,774	208,641	281,502
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,195	5,697	5,697
Charge-Offs	(12)	0	(1)
Recoveries	2	5	86
Provision	756	724	2,413
Ending Balance	8,941	6,426	8,195
Ending Balance Individually Evaluated for Impairment	1,118	814	914
Ending Balance Collectively Evaluated for Impairment	7,823	5,612	7,281
Loans & Leases [Abstract]
Ending Balance	236,141	155,802	230,819
Ending Balance Individually Evaluated for Impairment	4,840	5,100	4,874
Ending Balance Collectively Evaluated for Impairment	231,301	150,702	225,945
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	218	176	176
Charge-Offs	(17)	(27)	(132)
Recoveries	22	15	65
Provision	(11)	7	109
Ending Balance	212	171	218
Ending Balance Individually Evaluated for Impairment	37	48	41
Ending Balance Collectively Evaluated for Impairment	175	123	177
Loans & Leases [Abstract]
Ending Balance	4,915	4,721	4,719
Ending Balance Individually Evaluated for Impairment	44	48	46
Ending Balance Collectively Evaluated for Impairment	4,871	4,673	4,673
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,211	639	639
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	288	282	1,572
Ending Balance	2,499	921	2,211
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	2,499	921	2,211
Loans & Leases [Abstract]
Ending Balance	50,846	18,168	44,217
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	50,846	18,168	44,217
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,529	2,274	2,274
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	1,617	246	(745)
Ending Balance	3,146	2,520	1,529
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	3,146	2,520	1,529
Loans & Leases [Abstract]
Ending Balance	0	0	0
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	0	0	0
Restructured loans [Member]
Loans & Leases [Abstract]
Ending Balance Individually Evaluated for Impairment	$ 9,800	$ 28,900	$ 26,400