Loans and Allowance for Loan Losses (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 alternative	Sep. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 898,307,000		$ 898,307,000		$ 859,732,000
Less [Abstract]
Net deferred loan fees, premiums and discounts	330,000		330,000		704,000
Allowance for loan losses	11,645,000	10,429,000	11,645,000	10,429,000	11,120,000
Net loans	886,332,000		886,332,000		847,908,000
Loans held for sale	1,390,000		1,390,000		1,046,000
Impaired Loans [Abstract]
Minimum value of loans individually measured for impairment			100,000
Number of alternatives for measuring impaired loans receivable			3
Adversely Classified Loans [Abstract]
Minimum balance of adversely classified loan in which a detailed analysis is performed			0
Non-classified and Watch Loans [Abstract]
Time period used a a base for loss estimations			five-year
Allowance for Loan Losses [Abstract]
Balance, beginning of period	11,455,000	10,695,000	11,120,000	10,393,000	10,393,000
Provision charged to expense	720,000	728,000	1,751,000	2,584,000	3,101,000
Losses charged off	(585,000)	(1,058,000)	(1,495,000)	(2,766,000)	(3,760,000)
Recoveries	55,000	64,000	269,000	218,000	1,386,000
Balance, end of period	11,645,000	10,429,000	11,645,000	10,429,000	11,120,000
Ending Balance [Abstract]
Individually evaluated for impairment	768,000	978,000	768,000	978,000	575,000
Collectively evaluated for impairment	10,877,000	9,451,000	10,877,000	9,451,000	10,545,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	899,367,000	815,491,000	899,367,000	815,491,000	860,074,000
Ending Balance [Abstract]
Individually evaluated for impairment	6,526,000	8,074,000	6,526,000	8,074,000	5,868,000
Collectively evaluated for impairment	892,841,000	807,417,000	892,841,000	807,417,000	854,206,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	25,117,000		25,117,000		23,136,000
Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	83,413,000		83,413,000		72,586,000
1-4 Family Residential Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	188,768,000		188,768,000		180,738,000
Ending Balance [Abstract]
Period When Loans are Charged-down			180 days
Multifamily Residential Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	44,292,000		44,292,000		19,847,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	313,621,000		313,621,000		321,908,000
Loans Receivable Additional Information [Abstract]
Debt coverage ratio			1.20x
Amortization period of loans			twenty years
Commercial Real Estate [Member] | Minimum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			65.00%
Commercial Real Estate [Member] | Maximum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Loans Secured by Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	655,211,000		655,211,000		618,215,000
Agricultural Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	63,294,000		63,294,000		63,182,000
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	154,190,000		154,190,000		150,631,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			seven years
Loans Receivable, Time Period			one year
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	16,242,000		16,242,000		16,274,000
Less [Abstract]
Allowance for loan losses	389,000	390,000	389,000	390,000	378,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	395,000	396,000	378,000	392,000	392,000
Provision charged to expense	8,000	50,000	60,000	83,000	122,000
Losses charged off	(45,000)	(82,000)	(140,000)	(158,000)	(254,000)
Recoveries	31,000	26,000	91,000	73,000	118,000
Balance, end of period	389,000	390,000	389,000	390,000	378,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	389,000	390,000	389,000	390,000	378,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	16,014,000	17,001,000	16,014,000	17,001,000	16,270,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	16,014,000	17,001,000	16,014,000	17,001,000	16,270,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	9,370,000		9,370,000		11,430,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	146,700,000		146,700,000		135,800,000
Less [Abstract]
Decrease in loans receivable			10,900,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			65.00%
Amortization period of loans			twenty five years
Loans Receivable, Time Period			one year
Other Grain Farming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	125,800,000		125,800,000		120,100,000
Less [Abstract]
Decrease in loans receivable			5,700,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	46,200,000		46,200,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	92,800,000		92,800,000
Residential Real Estate [Member]
Less [Abstract]
Allowance for loan losses	745,000	464,000	745,000	464,000	636,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			twenty five years
Balloon period			five years
Allowance for Loan Losses [Abstract]
Balance, beginning of period	743,000	462,000	636,000	440,000	440,000
Provision charged to expense	232,000	139,000	523,000	223,000	546,000
Losses charged off	(232,000)	(137,000)	(437,000)	(200,000)	(363,000)
Recoveries	2,000	0	23,000	1,000	13,000
Balance, end of period	745,000	464,000	745,000	464,000	636,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	745,000	464,000	745,000	464,000	636,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	182,234,000	187,361,000	182,234,000	187,361,000	185,151,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	182,234,000	187,361,000	182,234,000	187,361,000	185,151,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	60,500,000		60,500,000
Unallocated [Member]
Less [Abstract]
Allowance for loan losses	404,000	572,000	404,000	572,000	769,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	609,000	969,000	769,000	850,000	850,000
Provision charged to expense	(205,000)	(397,000)	(365,000)	(278,000)	(81,000)
Losses charged off	0	0	0	0	0
Recoveries	0	0	0	0	0
Balance, end of period	404,000	572,000	404,000	572,000	769,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	404,000	572,000	404,000	572,000	769,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	210,000	405,000	210,000	405,000	22,365,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	210,000	405,000	210,000	405,000	22,365,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Unsecured Open-end Loans [Member]
Ending Balance [Abstract]
Period When Loans are Charged-down			180 days
Other Secured Loans [Member]
Ending Balance [Abstract]
Period When Loans are Charged-down			120 days
Commercial/Commercial Real Estate [Member]
Less [Abstract]
Allowance for loan losses	9,500,000	8,424,000	9,500,000	8,424,000	8,791,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	9,007,000	8,312,000	8,791,000	8,307,000	8,307,000
Provision charged to expense	782,000	866,000	1,530,000	2,334,000	2,309,000
Losses charged off	(308,000)	(789,000)	(906,000)	(2,358,000)	(3,077,000)
Recoveries	19,000	35,000	85,000	141,000	1,252,000
Balance, end of period	9,500,000	8,424,000	9,500,000	8,424,000	8,791,000
Ending Balance [Abstract]
Individually evaluated for impairment	768,000	978,000	768,000	978,000	575,000
Collectively evaluated for impairment	8,732,000	7,446,000	8,732,000	7,446,000	8,216,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	556,026,000	485,504,000	556,026,000	485,504,000	505,693,000
Ending Balance [Abstract]
Individually evaluated for impairment	5,627,000	6,925,000	5,627,000	6,925,000	4,719,000
Collectively evaluated for impairment	550,399,000	478,579,000	550,399,000	478,579,000	500,974,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Agriculture/Agricultural Real Estate [Member]
Less [Abstract]
Allowance for loan losses	607,000	579,000	607,000	579,000	546,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	701,000	556,000	546,000	404,000	404,000
Provision charged to expense	(97,000)	70,000	3,000	222,000	205,000
Losses charged off	0	(50,000)	(12,000)	(50,000)	(66,000)
Recoveries	3,000	3,000	70,000	3,000	3,000
Balance, end of period	607,000	579,000	607,000	579,000	546,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	607,000	579,000	607,000	579,000	546,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	144,883,000	125,220,000	144,883,000	125,220,000	130,595,000
Ending Balance [Abstract]
Individually evaluated for impairment	899,000	1,149,000	899,000	1,149,000	1,149,000
Collectively evaluated for impairment	143,984,000	124,071,000	143,984,000	124,071,000	129,446,000
Loans acquired with deteriorated credit quality	$ 0	$ 0	$ 0	$ 0	$ 0