XML 54 R59.htm IDEA: XBRL DOCUMENT v2.4.0.6
Property and Equipment - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Property, Plant and Equipment [Line Items]      
Transportation equipment $ 162,461,000 $ 136,691,000  
Equipment, capital lease obligation   26,400,000  
Equipment, capital lease obligation, net 22,600,000 25,300,000  
Depreciation and amortization expense related to property and equipment 19,600,000 14,800,000 8,000,000
Amortization expense under capital lease obligation $ 2,600,000 $ 1,100,000  
Transportation Equipment And Automobiles | Maximum
     
Property, Plant and Equipment [Line Items]      
Property and equipment estimated life 15 years