Loans and Allowance for Loan Losses (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 alternative	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 942,523,000		$ 942,523,000		$ 911,597,000
Less [Abstract]
Net deferred loan fees, premiums and discounts	533,000		533,000		744,000
Allowance for loan losses	12,977,000	11,645,000	12,977,000	11,645,000	11,776,000
Net loans	929,013,000		929,013,000		899,077,000
Loans held for sale	1,101,000		1,101,000		212,000
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			100,000
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	12,131,000	11,455,000	11,776,000	11,120,000	11,120,000
Provision charged to expense	975,000	720,000	1,707,000	1,751,000	2,647,000
Losses charged off	(274,000)	(585,000)	(824,000)	(1,495,000)	(2,371,000)
Recoveries	145,000	55,000	318,000	269,000	380,000
Balance, end of period	12,977,000	11,645,000	12,977,000	11,645,000	11,776,000
Ending Balance [Abstract]
Individually evaluated for impairment	540,000	768,000	540,000	768,000	511,000
Collectively evaluated for impairment	12,437,000	10,877,000	12,437,000	10,877,000	11,265,000
Loans [Abstract]
Ending balance	943,091,000	899,367,000	943,091,000	899,367,000	911,065,000
Ending Balance [Abstract]
Individually evaluated for impairment	4,877,000	6,526,000	4,877,000	6,526,000	6,564,000
Collectively evaluated for impairment	938,214,000	892,841,000	938,214,000	892,841,000	904,501,000
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	20,058,000		20,058,000		31,341,000
Agricultural real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	101,832,000		101,832,000		86,256,000
1-4 Family residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	188,256,000		188,256,000		186,205,000
Ending Balance [Abstract]
Period When Loans are Charged-down			180 days
Multifamily residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	42,342,000		42,342,000		44,863,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	343,404,000		343,404,000		317,321,000
Loans Receivable Additional Information [Abstract]
Debt coverage ratio			1.20x
Amortization period of loans			twenty years
Commercial real estate | Minimum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			65.00%
Commercial real estate | Maximum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Loans secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	695,892,000		695,892,000		665,986,000
Agricultural loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	60,512,000		60,512,000		60,948,000
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	159,608,000		159,608,000		160,193,000
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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	15,296,000		15,296,000		16,264,000
Less [Abstract]
Allowance for loan losses	407,000	389,000	407,000	389,000	403,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	397,000	395,000	403,000	378,000	378,000
Provision charged to expense	50,000	8,000	64,000	60,000	116,000
Losses charged off	(72,000)	(45,000)	(169,000)	(140,000)	(249,000)
Recoveries	32,000	31,000	109,000	91,000	158,000
Balance, end of period	407,000	389,000	407,000	389,000	403,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	407,000	389,000	407,000	389,000	403,000
Loans [Abstract]
Ending balance	15,296,000	16,014,000	15,296,000	16,014,000	16,066,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	15,296,000	16,014,000	15,296,000	16,014,000	16,066,000
All other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	11,215,000		11,215,000		8,206,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	162,300,000		162,300,000		147,200,000
Less [Abstract]
Decrease in loans receivable			15,100,000
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	135,600,000		135,600,000		124,400,000
Less [Abstract]
Decrease in loans receivable			11,200,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	45,200,000		45,200,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	98,500,000		98,500,000
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	56,400,000		56,400,000
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
Less [Abstract]
Allowance for loan losses	10,703,000	9,500,000	10,703,000	9,500,000	9,301,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	9,304,000	9,007,000	9,301,000	8,791,000	8,791,000
Provision charged to expense	1,475,000	782,000	1,759,000	1,530,000	1,979,000
Losses charged off	(184,000)	(308,000)	(551,000)	(906,000)	(1,586,000)
Recoveries	108,000	19,000	194,000	85,000	117,000
Balance, end of period	10,703,000	9,500,000	10,703,000	9,500,000	9,301,000
Ending Balance [Abstract]
Individually evaluated for impairment	540,000	768,000	540,000	768,000	457,000
Collectively evaluated for impairment	10,163,000	8,732,000	10,163,000	8,732,000	8,844,000
Loans [Abstract]
Ending balance	575,912,000	556,026,000	575,912,000	556,026,000	569,717,000
Ending Balance [Abstract]
Individually evaluated for impairment	4,540,000	5,627,000	4,540,000	5,627,000	5,334,000
Collectively evaluated for impairment	571,372,000	550,399,000	571,372,000	550,399,000	564,383,000
Agricultural/ Agricultural Real Estate
Less [Abstract]
Allowance for loan losses	460,000	607,000	460,000	607,000	558,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	414,000	701,000	558,000	546,000	546,000
Provision charged to expense	43,000	(97,000)	(102,000)	3,000	(47,000)
Losses charged off	0	0	0	(12,000)	(12,000)
Recoveries	3,000	3,000	4,000	70,000	71,000
Balance, end of period	460,000	607,000	460,000	607,000	558,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	54,000
Collectively evaluated for impairment	460,000	607,000	460,000	607,000	504,000
Loans [Abstract]
Ending balance	162,443,000	144,883,000	162,443,000	144,883,000	145,695,000
Ending Balance [Abstract]
Individually evaluated for impairment	337,000	899,000	337,000	899,000	1,230,000
Collectively evaluated for impairment	162,106,000	143,984,000	162,106,000	143,984,000	144,465,000
Residential Real Estate
Less [Abstract]
Allowance for loan losses	794,000	745,000	794,000	745,000	726,000
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	793,000	743,000	726,000	636,000	636,000
Provision charged to expense	17,000	232,000	161,000	523,000	580,000
Losses charged off	(18,000)	(232,000)	(104,000)	(437,000)	(524,000)
Recoveries	2,000	2,000	11,000	23,000	34,000
Balance, end of period	794,000	745,000	794,000	745,000	726,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	794,000	745,000	794,000	745,000	726,000
Loans [Abstract]
Ending balance	189,440,000	182,234,000	189,440,000	182,234,000	179,309,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	189,440,000	182,234,000	189,440,000	182,234,000	179,309,000
Unallocated
Less [Abstract]
Allowance for loan losses	613,000	404,000	613,000	404,000	788,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	1,223,000	609,000	788,000	769,000	769,000
Provision charged to expense	(610,000)	(205,000)	(175,000)	(365,000)	19,000
Losses charged off	0		0	0	0
Recoveries	0		0	0	0
Balance, end of period	613,000	404,000	613,000	404,000	788,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	613,000	404,000	613,000	404,000	788,000
Loans [Abstract]
Ending balance	0	210,000	0	210,000	278,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	$ 0	$ 210,000	$ 0	$ 210,000	$ 278,000