Loans and Allowance for Loan Losses (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 alternative	Jun. 30, 2012	Dec. 31, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 914,278,000		$ 914,278,000		$ 911,597,000
Less [Abstract]
Net deferred loan fees, premiums and discounts	533,000		533,000		744,000
Allowance for loan losses	12,131,000	11,455,000	12,131,000	11,455,000	11,776,000
Net loans	901,614,000		901,614,000		899,077,000
Loans held for sale	2,068,000		2,068,000		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			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	11,984,000	11,293,000	11,776,000	11,120,000	11,120,000
Provision charged to expense	252,000	416,000	732,000	1,031,000	2,647,000
Losses charged off	(168,000)	(398,000)	(550,000)	(910,000)	(2,371,000)
Recoveries	63,000	144,000	173,000	214,000	380,000
Balance, end of period	12,131,000	11,455,000	12,131,000	11,455,000	11,776,000
Ending Balance [Abstract]
Individually evaluated for impairment	439,000	734,000	439,000	734,000	511,000	734,000
Collectively evaluated for impairment	11,692,000	10,721,000	11,692,000	10,721,000	11,265,000	10,721,000
Loans [Abstract]
Ending balance	915,813,000	845,925,000	915,813,000	845,925,000	911,065,000
Ending Balance [Abstract]
Individually evaluated for impairment	5,544,000	5,434,000	5,544,000	5,434,000	6,564,000
Collectively evaluated for impairment	910,269,000	840,491,000	910,269,000	840,491,000	904,501,000
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	22,602,000		22,602,000		31,341,000
Agricultural real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	95,255,000		95,255,000		86,256,000
1-4 Family residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	186,104,000		186,104,000		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	44,207,000		44,207,000		44,863,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	335,628,000		335,628,000		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	683,796,000		683,796,000		665,986,000
Agricultural loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	51,864,000		51,864,000		60,948,000
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	152,955,000		152,955,000		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	15,814,000		15,814,000		16,264,000
Less [Abstract]
Allowance for loan losses	397,000	395,000	397,000	395,000	403,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	422,000	386,000	403,000	378,000	378,000
Provision charged to expense	(15,000)	27,000	14,000	52,000	116,000
Losses charged off	(51,000)	(47,000)	(97,000)	(95,000)	(249,000)
Recoveries	41,000	29,000	77,000	60,000	158,000
Balance, end of period	397,000	395,000	397,000	395,000	403,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0	0
Collectively evaluated for impairment	397,000	395,000	397,000	395,000	403,000	395,000
Loans [Abstract]
Ending balance	15,814,000	15,600,000	15,814,000	15,600,000	16,066,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	15,814,000	15,600,000	15,814,000	15,600,000	16,066,000
All other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	9,849,000		9,849,000		8,206,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	147,100,000		147,100,000		147,200,000
Less [Abstract]
Decrease in loans receivable			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	123,600,000		123,600,000		124,400,000
Less [Abstract]
Decrease in loans receivable			800,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	45,300,000		45,300,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	96,500,000		96,500,000
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	56,500,000		56,500,000
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	9,304,000	9,007,000	9,304,000	9,007,000	9,301,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	9,341,000	8,810,000	9,301,000	8,791,000	8,791,000
Provision charged to expense	40,000	453,000	284,000	748,000	1,979,000
Losses charged off	(98,000)	(295,000)	(367,000)	(598,000)	(1,586,000)
Recoveries	21,000	39,000	86,000	66,000	117,000
Balance, end of period	9,304,000	9,007,000	9,304,000	9,007,000	9,301,000
Ending Balance [Abstract]
Individually evaluated for impairment	439,000	645,000	439,000	645,000	457,000	645,000
Collectively evaluated for impairment	8,865,000	8,362,000	8,865,000	8,362,000	8,844,000	8,362,000
Loans [Abstract]
Ending balance	564,526,000	517,406,000	564,526,000	517,406,000	569,717,000
Ending Balance [Abstract]
Individually evaluated for impairment	5,232,000	4,487,000	5,232,000	4,487,000	5,334,000
Collectively evaluated for impairment	559,294,000	512,919,000	559,294,000	512,919,000	564,383,000
Agricultural/ Agricultural Real Estate
Less [Abstract]
Allowance for loan losses	414,000	701,000	414,000	701,000	558,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	417,000	570,000	558,000	546,000	546,000
Provision charged to expense	(3,000)	76,000	(145,000)	100,000	(47,000)
Losses charged off	0	(12,000)	0	(12,000)	(12,000)
Recoveries	0	67,000	1,000	67,000	71,000
Balance, end of period	414,000	701,000	414,000	701,000	558,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	89,000	0	89,000	54,000	89,000
Collectively evaluated for impairment	414,000	612,000	414,000	612,000	504,000	612,000
Loans [Abstract]
Ending balance	147,218,000	132,611,000	147,218,000	132,611,000	145,695,000
Ending Balance [Abstract]
Individually evaluated for impairment	312,000	947,000	312,000	947,000	1,230,000
Collectively evaluated for impairment	146,906,000	131,664,000	146,906,000	131,664,000	144,465,000
Residential Real Estate
Less [Abstract]
Allowance for loan losses	793,000	743,000	793,000	743,000	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	719,000	710,000	726,000	636,000	636,000
Provision charged to expense	92,000	68,000	144,000	291,000	580,000
Losses charged off	(19,000)	(44,000)	(86,000)	(205,000)	(524,000)
Recoveries	1,000	9,000	9,000	21,000	34,000
Balance, end of period	793,000	743,000	793,000	743,000	726,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0	0
Collectively evaluated for impairment	793,000	743,000	793,000	743,000	726,000	743,000
Loans [Abstract]
Ending balance	188,255,000	179,577,000	188,255,000	179,577,000	179,309,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	188,255,000	179,577,000	188,255,000	179,577,000	179,309,000
Unallocated
Less [Abstract]
Allowance for loan losses	1,223,000	609,000	1,223,000	609,000	788,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	1,085,000	817,000	788,000	769,000	769,000
Provision charged to expense	138,000	(208,000)	435,000	(160,000)	19,000
Losses charged off	0		0	0	0
Recoveries	0		0	0	0
Balance, end of period	1,223,000	609,000	1,223,000	609,000	788,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0	0
Collectively evaluated for impairment	1,223,000	609,000	1,223,000	609,000	788,000	609,000
Loans [Abstract]
Ending balance	0	731,000	0	731,000	278,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	$ 0	$ 731,000	$ 0	$ 731,000	$ 278,000