Debt - Senior Secured Credit Facility due 2015 (Details) (USD $)	0 Months Ended			9 Months Ended							9 Months Ended
	Mar. 28, 2013	Sep. 30, 2013 2012 Credit Facility [Member] Letter of Credit [Member]	Sep. 30, 2013 Discretionary Over-Advances [Member] Senior secured credit facility due 2015 [Member]	Sep. 30, 2013 Senior secured credit facility due 2015 [Member]	Mar. 28, 2013 Senior secured credit facility due 2015 [Member]	Dec. 31, 2012 Senior secured credit facility due 2015 [Member]	Aug. 31, 2012 Senior secured credit facility due 2015 [Member]	Sep. 30, 2013 Senior secured credit facility due 2015 [Member] Swingline Loan [Member]	Sep. 30, 2013 Letter of Credit [Member]	Sep. 30, 2013 Accordion Feature [Member]	Sep. 30, 2013 Federal Funds Rate Plus Percentage [Member] Senior secured credit facility due 2015 [Member]	Sep. 30, 2013 London Interbank Offered Rate Plus Percentage [Member] Senior secured credit facility due 2015 [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreements		$ 30,000,000.0	$ 8,000,000		$ 102,500,000.0		$ 80,000,000.0	$ 10,000,000		$ 125,000,000.0
Line of Credit Facility, Increase, Additional Borrowings	22,500,000.0
Outstanding borrowings				18,000,000
Letters of Credit Outstanding, Amount									11,300,000
Unused borrowing capacity under 2012 credit agreement				69,400,000		52,400,000
Basis spread on variable rates basis loans				2.75%							0.50%	1.00%
Second basis spread on base rate loans				1.50%
Duration in which interest rate is applicable				30 days
Letter of credit fee percentage		2.75%
Fronting fee percentage		0.125%
Line of Credit Facility, Commitment Fee Percentage				0.375%
Limitation on borrowing base, accounts receivable, percentage				90.00%
Limitation on borrowing base, accounts receivable, reduction in percentage				85.00%
Limitation on borrowing base, value of eligible inventory, percentage				55.00%
Limitation on borrowing base, product, percentage				85.00%
Limitation on borrowing base, amount, value of eligible trucks				$ 20,000,000.0
Limitation on borrowing base, net orderly liquidation value, percentage				85.00%
Limitation on borrowing base, cost of newly acquired trucks net of a provisions for depreciation on eligible trucks and liquidation of eligible trucks, percentage				80.00%
Reduction to limitation on borrowing base, newly acquired trucks to be reduced by orderly liquidation value of eligible trucks, percentage				85.00%
Reduction to limitation on borrowing base, newly acquired trucks to be reduced by depreciation of eligible trucks since last appraisal, percentage				85.00%
Fixed charge coverage ratio				100.00%
Coverage ratio, measurement period				12 months
Fixed charge coverage ratio				425.00%