v3.19.2
Cover Page - shares
9 Months Ended
Jun. 30, 2019
Jul. 26, 2019
Cover page.    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 1-37644  
Entity Registrant Name VERSUM MATERIALS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 47-5632014  
Entity Address, Address Line One 8555 South River Parkway  
Entity Address, City or Town Tempe  
Entity Address, State or Province AZ  
Entity Address, Postal Zip Code 85284  
City Area Code 602  
Local Phone Number 282-1000  
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  
Entity Common Stock, Shares Outstanding (In shares)   109,269,216
Entity Central Index Key 0001660690  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Amendment Flag false