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Affiliated Companies (Details)
Dec. 31, 2014
The West Company Mexico, S.A. de C.V. [Member]  
Schedule of Equity Method Investments [Line Items]  
Ownership interest 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= wst_WestCompanyMexicoSADeCVMember
Aluplast S.A. de C.V. [Member]  
Schedule of Equity Method Investments [Line Items]  
Ownership interest 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= wst_AluplastSADeCVMember
Pharma Tap S.A de C.V. [Member]  
Schedule of Equity Method Investments [Line Items]  
Ownership interest 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= wst_PharmaTapSADeCVMember
Pharma Rubber S.A. de C.V. [Member]  
Schedule of Equity Method Investments [Line Items]  
Ownership interest 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= wst_PharmaRubberSADeCVMember
Daikyo Seiko, Ltd. [Member]  
Schedule of Equity Method Investments [Line Items]  
Ownership interest 25.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= wst_DaikyoSeikoLtdDaikyoMember