Loans and Allowance for Loan Losses (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 844,875,000		$ 844,875,000		$ 859,732,000
Less [Abstract]
Net deferred loan fees, premiums and discounts	(435,000)		(435,000)		(704,000)
Allowance for loan losses	11,455,000	10,695,000	11,455,000	10,695,000	11,120,000
Net loans	832,985,000		832,985,000		847,908,000
Loans held for sale	1,485,000		1,485,000		1,046,000
Number of borrowers limited by federal regulations			1
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			5 years
Allowance for Loan Losses [Abstract]
Balance, beginning of period	11,293,000	10,651,000	11,120,000	10,393,000	10,393,000
Provision charged to expense	416,000	916,000		1,856,000	3,101,000
Losses charged off	(398,000)	(966,000)		(1,708,000)	(3,760,000)
Recoveries	144,000	94,000		154,000	1,386,000
Balance, end of period	11,455,000	10,695,000	11,455,000	10,695,000	11,120,000
Ending Balance [Abstract]
Individually evaluated for impairment	734,000	661,000	734,000	661,000	575,000
Collectively evaluated for impairment	10,721,000	10,034,000	10,721,000	10,034,000	10,545,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	845,925,000	800,492,000	845,925,000	800,492,000	860,074,000
Ending Balance [Abstract]
Individually evaluated for impairment	5,434,000	8,560,000	5,434,000	8,560,000	5,868,000
Collectively evaluated for impairment	840,491,000	791,932,000	840,491,000	791,932,000	854,206,000
Loans acquired with deteriorated credit quality		0		0	0
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	18,663,000		18,663,000		23,136,000
Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	78,274,000		78,274,000		72,586,000
1-4 Family Residential Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	186,684,000		186,684,000		180,738,000
Multifamily Residential Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	31,067,000		31,067,000		19,847,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	304,369,000		304,369,000		321,908,000
Loans Receivable Additional Information [Abstract]
Debt coverage ratio			1.2x
Amortization period of loans			25 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	619,057,000		619,057,000		618,215,000
Agricultural Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	56,436,000		56,436,000		63,182,000
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	144,673,000		144,673,000		150,631,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			7 years
Loans Receivable, Time Period			1 year
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	15,839,000		15,839,000		16,274,000
Less [Abstract]
Allowance for loan losses	395,000	396,000	395,000	396,000	378,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	386,000	403,000	378,000	392,000	392,000
Provision charged to expense	27,000	14,000	52,000	33,000	122,000
Losses charged off	(47,000)	(40,000)	(95,000)	(76,000)	(254,000)
Recoveries	29,000	19,000	60,000	47,000	118,000
Balance, end of period	395,000	396,000	395,000	396,000	378,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	395,000	396,000	395,000	396,000	378,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	15,600,000	17,471,000	15,600,000	17,471,000	16,270,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	15,600,000	17,471,000	15,600,000	17,471,000	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	8,870,000		8,870,000		11,430,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	134,700,000		134,700,000		135,800,000
Less [Abstract]
Decrease in loans receivable			1,100,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			70.00%
Amortization period of loans			25 years
Loans Receivable, Time Period			1 year
Other Grain Farming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	117,400,000		117,400,000		120,100,000
Less [Abstract]
Decrease in loans receivable			2,700,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	46,100,000		46,100,000
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	89,700,000		89,700,000
Less [Abstract]
Allowance for loan losses	743,000	462,000	743,000	462,000	636,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			25 years
Balloon period			5 years
Allowance for Loan Losses [Abstract]
Balance, beginning of period	710,000	448,000	636,000	440,000	440,000
Provision charged to expense	68,000	63,000	291,000	84,000	546,000
Losses charged off	(44,000)	(49,000)	(205,000)	(63,000)	(363,000)
Recoveries	9,000	0	21,000	1,000	13,000
Balance, end of period	743,000	462,000	743,000	462,000	636,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	743,000	462,000	743,000	462,000	636,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	179,577,000	186,522,000	179,577,000	186,522,000	185,151,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	179,577,000	186,522,000	179,577,000	186,522,000	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	43,600,000		43,600,000
Unallocated [Member]
Less [Abstract]
Allowance for loan losses	609,000	969,000	609,000	969,000	769,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	817,000	703,000	769,000	850,000	850,000
Provision charged to expense	(208,000)	266,000	(160,000)	119,000	(81,000)
Losses charged off	0	0	0	0	0
Recoveries	0	0	0	0	0
Balance, end of period	609,000	969,000	609,000	969,000	769,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	609,000	969,000	609,000	969,000	769,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	731,000	20,379,000	731,000	20,379,000	22,365,000
Ending Balance [Abstract]
Individually evaluated for impairment	0	0	0	0	0
Collectively evaluated for impairment	731,000	20,379,000	731,000	20,379,000	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	9,007,000	8,312,000	9,007,000	8,312,000	8,791,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	8,810,000	8,737,000	8,791,000	8,307,000	8,307,000
Provision charged to expense	453,000	377,000	748,000	1,468,000	2,309,000
Losses charged off	(295,000)	(877,000)	(598,000)	(1,569,000)	(3,077,000)
Recoveries	39,000	75,000	66,000	106,000	1,252,000
Balance, end of period	9,007,000	8,312,000	9,007,000	8,312,000	8,791,000
Ending Balance [Abstract]
Individually evaluated for impairment	645,000	661,000	645,000	661,000	575,000
Collectively evaluated for impairment	8,362,000	7,651,000	8,362,000	7,651,000	8,216,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	517,406,000	466,332,000	517,406,000	466,332,000	505,693,000
Ending Balance [Abstract]
Individually evaluated for impairment	4,487,000	7,411,000	4,487,000	7,411,000	4,719,000
Collectively evaluated for impairment	512,919,000	458,921,000	512,919,000	458,921,000	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	701,000	556,000	701,000	556,000	546,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	570,000	360,000	546,000	404,000	404,000
Provision charged to expense	76,000	196,000	100,000	152,000	205,000
Losses charged off	(12,000)	0	(12,000)	0	(66,000)
Recoveries	67,000	0	67,000	0	3,000
Balance, end of period	701,000	556,000	701,000	556,000	546,000
Ending Balance [Abstract]
Individually evaluated for impairment	89,000	0	89,000	0	0
Collectively evaluated for impairment	612,000	556,000	612,000	556,000	546,000
Loans acquired with deteriorated credit quality	0	0	0	0	0
Loans [Abstract]
Ending balance	132,611,000	109,788,000	132,611,000	109,788,000	130,595,000
Ending Balance [Abstract]
Individually evaluated for impairment	947,000	1,149,000	947,000	1,149,000	1,149,000
Collectively evaluated for impairment	131,664,000	108,639,000	131,664,000	108,639,000	129,446,000
Loans acquired with deteriorated credit quality	$ 0	$ 0	$ 0	$ 0	$ 0