Long-Term Debt and Revolving Lines of Credit (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 Facility Institution	Dec. 31, 2013
Debt Instrument [Line Items]
Long term debt	$ 224,250,000
Current maturities	23,000,000	5,750,000
Total long-term debt	201,250,000	224,250,000
Minimum percentage of aggregate principal balance on which entity obtain interest rate protection (in hundredths)	33.00%
Minimum days to obtain interest rate protection	90 days
Minimum time to maintain interest rate protection	3 years
Number of additional farm credit institutions	16
Number of facilities included in Credit Agreement	3
Aggregate principal amount of incremental term loan facilities, maximum	100,000,000
Derivative asset, fair value	1,900,000	4,300,000
Percentage of principal amount of loan on which entity entered in pay fixed receive fixed interest rate swap (in hundredths)	76.00%
Derivative effective interest rate (in hundredths)	2.50%
Derivative fixed interest rate (in hundredths)	3.63%
Percentage of effective interest rate on portion of debt (in hundredths)	1.13%
Financial covenants in its credit agreements [Abstract]
Total Leverage Ratio, Actual	1.67
Debt Service Coverage Ratio, Actual	8.57
Equity to Assets Ratio, Actual	41.7
Total Leverage Ratio, Covenant Requirement	2.50
Debt Service Coverage Ratio, Covenant Requirement	2.50
Equity to Assets Ratio, Covenant Requirement	32.5
Aggregate maturities of long-term debt [Abstract]
2015	23,000,000
2016	23,000,000
2017	23,000,000
2018	23,000,000
2019	132,250,000
Long term debt, Total	224,250,000
Accrued in anticipation of early 2014 distribution of patronage credit	1,600,000
Percentage of patronage credit paid in cash (in hundredths)	75.00%
Percentage of patronage credit paid in shares (in hundredths)	25.00%
CoBank Term Loan [Member]
Debt Instrument [Line Items]
Long term debt	224,250,000	230,000,000
Interest rate (in hundredths)	2.67%
Basis spread on variable rate (in hundredths)	2.50%
Required periodic installments	5,750,000
Expected final payment	120,750,000
Maturity date	Sep. 30, 2019
Debt Instrument, Description of Variable Rate Basis	30-day LIBOR
Trailing month basis of financial covenants	12 months
Aggregate maturities of long-term debt [Abstract]
Long term debt, Total	224,250,000	230,000,000
CoBank Term Loan [Member] | Amendment date through December 31, 2013 [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in hundredths)	0.17%
CoBank Term Loan [Member] | January 1, 2015 and Thereafter [Member]
Financial covenants in its credit agreements [Abstract]
Equity to Assets Ratio, Actual	0.35
CoBank Term Loan [Member] | April 1, 2014 through March 31, 2015 [Member]
Financial covenants in its credit agreements [Abstract]
Total Leverage Ratio, Covenant Requirement	2.50
CoBank Term Loan [Member] | April 1, 2015 and Thereafter [Member]
Financial covenants in its credit agreements [Abstract]
Total Leverage Ratio, Covenant Requirement	2.00
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000