Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information Document

Document and Entity Information Document - shares
9 Months Ended
Sep. 30, 2017
Nov. 10, 2017
Document And Entity Information [Abstract]    
Entity Registrant Name PQ Group Holdings Inc.  
Entity Central Index Key 0001708035  
Document Type 10-Q  
Document Period End Date Sep. 30, 2017  
Amendment Flag false  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   135,240,826