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Number of non-option equity instruments exercised by participants.

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Data Type:	xbrli:sharesItemType
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Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

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Data Type:	xbrli:sharesItemType
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Net number of non-option equity instruments granted to participants.

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Data Type:	xbrli:sharesItemType
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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Data Type:	xbrli:durationItemType
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Number of cash-settled stock appreciation rights outstanding.

No definition available.

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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Exercisable, Number

No definition available.

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Data Type:	xbrli:sharesItemType
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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures in Period, Weighted Average Exercise Price

No definition available.

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Data Type:	num:perShareItemType
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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Grants in Period, Weighted Average Exercise Price

No definition available.

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Data Type:	num:perShareItemType
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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Weighted Average Exercise Price

No definition available.

Name:	wst_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice
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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Weighted Average Exercise Price [Roll Forward]

No definition available.

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Data Type:	xbrli:stringItemType
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Share-based Compensation Arrangements by Share-based Payment Award, Non-Option Equity Instruments, Exercisable, Weighted Average Exercise Price

No definition available.

Name:	wst_ShareBasedCompensationArrangementsByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableWeightedAverageExercisePrice
Namespace Prefix:	wst_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Share-based Compensation Arrangements by Share-based Payment Award, Non-Option Equity Instruments, Exercises in Period, Weighted Average Exercise Price

No definition available.

Name:	wst_ShareBasedCompensationArrangementsByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisesInPeriodWeightedAverageExercisePrice
Namespace Prefix:	wst_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Number of stock-settled stock appreciation rights outstanding.

No definition available.