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Leases, User Charges and Commitments - Additional Information (Detail)
 1 Months Ended 12 Months Ended
Dec. 31, 2015
USD ($)
Container
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Lease and Rental Expense [Line Items]        
Rental expense   $ 8,000,000 $ 8,100,000 $ 10,100,000
Rail transportation charges   74,300,000 67,800,000 69,100,000
Minimum commitments on rail owned chassis and containers       0
Purchase contract units, containers | Container 1,000      
Cost of purchasing containers $ 9,000,000      
Transportation Costs [Member]        
Lease and Rental Expense [Line Items]        
Rental expense   $ 11,900,000 $ 13,100,000 $ 10,200,000