Annual report pursuant to Section 13 and 15(d)

Lease Obligations - Additional Information (Detail)

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Lease Obligations - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Leases [Abstract]      
Rental expense $ 60,000,000us-gaap_LeaseAndRentalExpense $ 57,500,000us-gaap_LeaseAndRentalExpense $ 52,500,000us-gaap_LeaseAndRentalExpense
Property, plant and equipment under capital leases $ 0us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet $ 0us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet