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Employee Benefit Plans - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]      
Percentage of employee contribution 30.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent    
Defined contribution plan, cost recognized $ 4.3us-gaap_DefinedContributionPlanCostRecognized $ 3.8us-gaap_DefinedContributionPlanCostRecognized $ 3.3us-gaap_DefinedContributionPlanCostRecognized
Maximum [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Percentage of employer contribution 3.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
/ us-gaap_RangeAxis
= us-gaap_MaximumMember