BORROWINGS (Details) (USD $)	9 Months Ended
	Sep. 30, 2012 item	Dec. 31, 2011
Borrowings
Amounts outstanding	$ 17,000,000	$ 17,000,000
Letters of credit, outstanding amount	1,900,000	2,000,000
Revolving credit facility
Borrowings
Maximum borrowing capacity	20,000,000
Deposit maintained with U.S. Bank	20,000,000
Fixed charges coverage ratio calculation, number of prior quarters	4
Variable rate basis	one-month Libor
Interest rate margin on variable rate basis (as a percent)	2.50%
Interest rate (as a percent)	2.75%
Floor interest rate (as a percent)	0.50%
Amounts outstanding	17,000,000	17,000,000
Compensating cash balances	20,000,000
Revolving credit facility | Maximum
Borrowings
Annual capital expenditure	20,000,000
Revolving credit facility | Minimum
Borrowings
Deposit to be maintained with U.S. Bank	20,000,000
Fixed charges coverage ratio	1.10
Revolving credit facility, cash-collateralized
Borrowings
Maximum borrowing capacity	3,000,000
Revolving credit facility, non-cash collateralized
Borrowings
Maximum borrowing capacity	17,000,000
Purchasing Card
Borrowings
Outstanding balance	2,200,000	3,400,000
Unused borrowing capacity	$ 2,800,000	$ 1,600,000