Long-Term Debt (Details) (USD $)	1 Months Ended	3 Months Ended
	Jan. 31, 2012	Mar. 31, 2013 acre	Dec. 31, 2012
Long-Term Debt
Long-term debt		$ 50,968,000	$ 49,268,000
Less current portion		4,068,000	4,068,000
Long-term debt		46,900,000	45,200,000
Minimum
Long-Term Debt
Required liquidity under financial covenants		4,000,000
Maximum
Long-Term Debt
Required total liabilities under financial covenants		175,000,000
Wells Fargo revolving loans
Long-Term Debt
Long-term debt		26,900,000	25,200,000
Interest rate (as a percent)		4.05%	4.05%
Maximum borrowing capacity		34,500,000
Variable rate basis		LIBOR
Interest rate margin (as a percent)		3.80%
Area of the company's real estate pledged as collateral (in acres)		880
Commitment fees on the unused portion of the revolving facility		0
Available borrowing capacity		7,100,000
Irrevocable letters of credit		500,000
Wells Fargo revolving loans | Minimum
Long-Term Debt
Required liquidity under financial covenants		4,000,000
Wells Fargo revolving loans | Maximum
Long-Term Debt
Required total liabilities under financial covenants		175,000,000
American AgCredit term loan, 5.25%
Long-Term Debt
Long-term debt		24,068,000	24,068,000
Interest rate (as a percent)		5.25%	5.25%
Variable rate basis		30-day LIBOR
Interest rate margin (as a percent)		4.25%
Area of the company's real estate pledged as collateral (in acres)		3,100
Interest rate, variable interest rate floor (as a percent)		1.00%
Mandatory principal repayment		4,100,000
Mandatory principal prepayment as percentage of the net proceeds of the sale of any real property pledged as collateral		100.00%
Repayment of principal	353,000
Sale of non-collateralized real estate parcel	1,500,000
American AgCredit term loan, 5.25% | Minimum
Long-Term Debt
Required liquidity under financial covenants		4,000,000
Mandatory principal prepayment as percentage of the net proceeds of the sale of non collateralized real property		10.00%
American AgCredit term loan, 5.25% | Maximum
Long-Term Debt
Required total liabilities under financial covenants		$ 175,000,000
Applicable spread after tiered reduction (as a percent)		0.0375
Mandatory principal prepayment as percentage of the net proceeds of the sale of non collateralized real property		75.00%