XML 19 R31.htm IDEA: XBRL DOCUMENT v2.4.0.6
Capital Lease and Financing Arrangements - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2012
Aug. 01, 2011
Y
Debt Instrument [Line Items]      
Outstanding letters of credit $ 3.0 $ 3.0  
Unused and available borrowings under bank revolving line of credit 47.0 47.0  
Number of chassis leased     3,126
Chassis, lease agreement period (years)     10
Capital lease, interest paid $ 0.2 $ 0.7  
Beginning
     
Debt Instrument [Line Items]      
Letters of credit expiration, year   2012  
Ending
     
Debt Instrument [Line Items]      
Letters of credit expiration, year   2013