Document and Entity Information	9 Months Ended
	Sep. 30, 2017 shares
Document and Entity Information [Abstract]
Entity Registrant Name	WEST PHARMACEUTICAL SERVICES INC
Entity Central Index Key	0000105770
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	74,252,923
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false