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Property and Equipment - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Property, Plant and Equipment [Line Items]      
Depreciation expense $ 28.5us-gaap_Depreciation $ 26.8us-gaap_Depreciation $ 30.2us-gaap_Depreciation