Long-term Debt (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Long-term debt [Abstract]
Borrowings under credit facility	$ 23,899,000	$ 23,899,000		$ 19,888,000
Notes payable	6,841,000	6,841,000		7,989,000
Capitalized lease obligations	2,581,000	2,581,000		2,848,000
Total long-term debt	33,321,000	33,321,000		30,725,000
Less: Current maturities	(2,060,000)	(2,060,000)		(1,936,000)
Total maturities due after one year	31,261,000	31,261,000		28,789,000
Aggregate availability of credit facility	50,000,000	50,000,000
Maturity date of credit facility		Mar. 29, 2015
Borrowing base availability under the credit facility	43,800,000	43,800,000	49,200,000
Remaining borrowing availability under credit facility	15,200,000	15,200,000
Standby letters of credit issued	4,700,000	4,700,000
Decrease in borrowing base availability	(5,400,000)
Decrease in eligible receivables	(1,800,000)
Decrease in equipment	(3,600,000)
Line of Credit Facility [Line Items]
Basis spread on Federal Funds Rate (in hundredths)		0.50%
Term of interest period for LIBOR		30 days
Basis spread on LIBOR (in hundredths)		1.00%
Number of days interest will accrue		1 day
Effective percentage rate on promissory note, range, minimum (in hundredths)		5.50%
Effective percentage rate on promissory note, range , maximum (in hundredths)		7.60%
Revenue generating equipment under capital lease	$ 3,000,000	$ 3,000,000
Term of rental agreement under capital lease obligation		60 months
Effective interest rate on the capital lease (in hundredths)	6.80%	6.80%
LIBOR Loan [Member]
Line of Credit Facility [Line Items]
Interest rate of loans outstanding under credit facility (in hundredths)	2.80%	2.80%
Bank Base Rate Loan [Member]
Line of Credit Facility [Line Items]
Interest rate of loans outstanding under credit facility (in hundredths)	4.80%	4.80%