Allowance for Loan Losses, Allocation of The Allowance For Loan Losses by Portfolio Segment and By Impairment Methodology (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	$ 33,098	$ 32,942	$ 33,017	$ 32,261	$ 32,261
Charge-Offs	(136)	(903)	(779)	(4,731)	(6,146)
Recoveries	42	24	266	83	127
Provision	600	900	1,100	5,350	6,775
Ending Balance	33,604	32,963	33,604	32,963	33,017
Ending Balance Individually Evaluated for Impairment	962	1,742	962	1,742	1,636
Ending Balance Collectively Evaluated for Impairment	32,642	31,221	32,642	31,221	31,381
Loans:
Ending Balance	1,210,027	1,177,505	1,210,027	1,177,505	1,163,078
Ending Balance Individually Evaluated for Impairment	7,316	8,833	7,316	8,833	8,938
Ending Balance Collectively Evaluated for Impairment	1,202,711	1,168,672	1,202,711	1,168,672	1,154,140
Commercial Real Estate [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	4,377	5,726	5,823	7,631	7,631
Charge-Offs	0	(12)	0	(25)	(25)
Recoveries	0	0	0	0	0
Provision	(44)	102	(1,490)	(1,790)	(1,783)
Ending Balance	4,333	5,816	4,333	5,816	5,823
Ending Balance Individually Evaluated for Impairment	0	702	0	702	686
Ending Balance Collectively Evaluated for Impairment	4,333	5,114	4,333	5,114	5,137
Loans:
Ending Balance	335,664	300,918	335,664	300,918	305,704
Ending Balance Individually Evaluated for Impairment	295	3,841	295	3,841	4,562
Ending Balance Collectively Evaluated for Impairment	335,369	297,077	335,369	297,077	301,142
Agricultural Real Estate [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	2,633	2,813	2,583	1,539	1,539
Charge-Offs	0	(384)	0	(384)	(384)
Recoveries	0	0	89	0	18
Provision	1,029	(41)	990	1,233	1,410
Ending Balance	3,662	2,388	3,662	2,388	2,583
Ending Balance Individually Evaluated for Impairment	0	46	0	46	0
Ending Balance Collectively Evaluated for Impairment	3,662	2,342	3,662	2,342	2,583
Loans:
Ending Balance	293,864	284,149	293,864	284,149	280,139
Ending Balance Individually Evaluated for Impairment	2,551	1,413	2,551	1,413	954
Ending Balance Collectively Evaluated for Impairment	291,313	282,736	291,313	282,736	279,185
Real Estate Construction [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	1,900	2,362	1,933	2,160	2,160
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	(39)	(6)	(72)	196	(227)
Ending Balance	1,861	2,356	1,861	2,356	1,933
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	1,861	2,356	1,861	2,356	1,933
Loans:
Ending Balance	32,701	28,979	32,701	28,979	29,607
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	32,701	28,979	32,701	28,979	29,607
Residential 1st Mortgages [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	1,451	1,198	1,251	1,164	1,164
Charge-Offs	(80)	(58)	(81)	(398)	(449)
Recoveries	16	0	16	3	4
Provision	155	(30)	356	341	532
Ending Balance	1,542	1,110	1,542	1,110	1,251
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	1,542	1,110	1,542	1,110	1,251
Loans:
Ending Balance	137,464	104,130	137,464	104,130	107,421
Ending Balance Individually Evaluated for Impairment	493	1,273	493	1,273	1,194
Ending Balance Collectively Evaluated for Impairment	136,971	102,857	136,971	102,857	106,227
Home Equity Lines and Loans [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	3,514	3,450	3,746	3,724	3,724
Charge-Offs	(22)	(239)	(138)	(701)	(751)
Recoveries	2	5	12	11	13
Provision	21	315	(105)	497	760
Ending Balance	3,515	3,531	3,515	3,531	3,746
Ending Balance Individually Evaluated for Impairment	248	40	248	40	80
Ending Balance Collectively Evaluated for Impairment	3,267	3,491	3,267	3,491	3,666
Loans:
Ending Balance	43,990	52,451	43,990	52,451	50,956
Ending Balance Individually Evaluated for Impairment	1,048	262	1,048	262	576
Ending Balance Collectively Evaluated for Impairment	42,942	52,189	42,942	52,189	50,380
Agricultural [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	7,834	6,284	8,127	6,733	6,733
Charge-Offs	0	0	(240)	(2,750)	(3,559)
Recoveries	0	0	61	10	10
Provision	425	355	311	2,646	4,943
Ending Balance	8,259	6,639	8,259	6,639	8,127
Ending Balance Individually Evaluated for Impairment	548	827	548	827	793
Ending Balance Collectively Evaluated for Impairment	7,711	5,812	7,711	5,812	7,334
Loans:
Ending Balance	193,053	219,670	193,053	219,670	217,227
Ending Balance Individually Evaluated for Impairment	2,652	1,671	2,652	1,671	1,337
Ending Balance Collectively Evaluated for Impairment	190,401	217,999	190,401	217,999	215,890
Commercial [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	9,538	10,794	8,733	9,084	9,084
Charge-Offs	0	(148)	(198)	(324)	(788)
Recoveries	9	5	41	14	21
Provision	113	(1,139)	1,084	738	416
Ending Balance	9,660	9,512	9,660	9,512	8,733
Ending Balance Individually Evaluated for Impairment	146	103	146	103	54
Ending Balance Collectively Evaluated for Impairment	9,514	9,409	9,514	9,409	8,679
Loans:
Ending Balance	167,777	180,329	167,777	180,329	165,089
Ending Balance Individually Evaluated for Impairment	257	349	257	349	292
Ending Balance Collectively Evaluated for Impairment	167,520	179,980	167,520	179,980	164,797
Consumer & Other [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	140	252	207	216	216
Charge-Offs	(34)	(62)	(122)	(149)	(190)
Recoveries	15	14	47	45	61
Provision	23	(12)	12	80	120
Ending Balance	144	192	144	192	207
Ending Balance Individually Evaluated for Impairment	20	24	20	24	23
Ending Balance Collectively Evaluated for Impairment	124	168	124	168	184
Loans:
Ending Balance	5,514	6,879	5,514	6,879	6,935
Ending Balance Individually Evaluated for Impairment	20	24	20	24	23
Ending Balance Collectively Evaluated for Impairment	5,494	6,855	5,494	6,855	6,912
Unallocated [Member]
Year To Date Allowance for Loan Losses [Abstract]
Beginning Balance	1,711	63	614	10	10
Charge-Offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision	(1,083)	1,356	14	1,409	604
Ending Balance	628	1,419	628	1,419	614
Ending Balance Individually Evaluated for Impairment	0	0	0	0	0
Ending Balance Collectively Evaluated for Impairment	628	1,419	628	1,419	614
Loans:
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