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Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]    
Rent expense for operating leases $ 7.7us-gaap_OperatingLeasesRentExpenseNet $ 6.5us-gaap_OperatingLeasesRentExpenseNet