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Stock Plans - Summary of Performance Stock Unit Activity (Detail) (Performance Stock Unit Activity, USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Performance Stock Unit Activity
     
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]      
Unvested Shares, Beginning Balance 149,389us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
137,672us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
125,443us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Granted, Shares 46,242us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
53,357us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
54,928us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Vested, Shares (91,696)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
(45,809)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
(47,706)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Performance adjustments, Shares 41,428msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
4,169msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
5,679msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Forfeited, Shares (1,402)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
  (672)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Unvested Shares, Ending Balance 143,961us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
149,389us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
137,672us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Unvested Weighted Average Grant Date Fair value, Beginning Balance $ 46.32us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 35.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 25.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Granted, Weighted Average Grant Date Fair Value $ 57.42us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 57.58us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 41.33us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Vested, Weighted Average Grant Date Fair Value $ 39.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 26.08us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 18.23us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Performance adjustments, Weighted Average Grant Date Fair value $ 39.42msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 25.84msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 26.39msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Forfeited, Weighted Average Grant Date Fair value $ 48.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
  $ 41.45us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
Unvested Weighted Average Grant Date Fair value, Ending Balance $ 52.42us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 46.32us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember
$ 35.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ msa_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardPlanNameAxis
= msa_PerformanceStockUnitMember