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Benefit Plans - Additional Information (Detail) (USD $)
 3 Months Ended
Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]  
Number of highest-paid consecutive years for benefits 5 years
Defined Benefit Pension Plan [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Minimum eligibility for full-time employees, age 21 years
Amount contributed to pension plan, Expected in future 0us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInCurrentFiscalYear
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Amount contributed to pension plan 0us-gaap_DefinedBenefitPlanContributionsByEmployer
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Defined Benefit Pension Plan [Member] | Minimum [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Period of service credit by employee 1 year