Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016
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 Public Float		$ 5,555,781,688
Entity Common Stock, Shares Outstanding	73,260,436
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016