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Employee Pension Plans - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]      
Contribution to defined contribution plans $ 4.0us-gaap_DefinedContributionPlanCostRecognized $ 3.6us-gaap_DefinedContributionPlanCostRecognized $ 3.2us-gaap_DefinedContributionPlanCostRecognized