Debt and Other Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Long-term debt	$ 135,133,000	$ 118,828,000
Long-term debt, current maturities	1,420,000	1,200,000
Capital lease obligations, current maturities	228,000	207,000
Maximum borrowing capacity under credit facility	150,000,000
Maturity date	Dec. 31, 2016
Accrued patronage refunds	707,000	529,000	525,000
Period of time interest rate protection must exist on term loans (in years)	2 years
Effective interest rate (in hundredths)	4.20%	4.10%	4.10%
Long-term Debt, Fiscal Year Maturity [Abstract]
2013	1,420,000
2014	1,420,000
2015	1,420,000
2016	132,075,000
Interest Rate Swap Agreement [Member]
Debt Instrument [Line Items]
Amount of interest rate swaps	72,000,000
Minimum [Member] | Interest Rate Swap Agreement [Member]
Debt Instrument [Line Items]
Percentage of credit facility required to be covered with interest rate swaps (in hundredths)	50.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity under credit facility	30,000,000
Unused amount under credit facility	29,980,000	29,965,000
Term Loan B Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity under credit facility	120,000,000
Credit facility amount outstanding	116,500,000	119,700,000
Periodic principal payment	300,000
Incremental Term [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity under credit facility	22,000,000
Credit facility amount outstanding	19,835,000
Periodic principal payment	55,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility amount outstanding	$ 20,000	$ 35,000