Document and Entity Information	9 Months Ended
	Sep. 30, 2019 shares
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	1-8036
Entity Registrant Name	WEST PHARMACEUTICAL SERVICES, INC.
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-1210010
Entity Address, Address Line One	530 Herman O. West Drive,
Entity Address, City or Town	Exton,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19341-0645
City Area Code	610
Local Phone Number	594-2900
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of each class	Common Stock, par value $0.25 per share
Trading Symbol	WST
Security Exchange Name	NYSE
Entity Central Index Key	0000105770
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	73,990,675