Quarterly report pursuant to Section 13 or 15(d)

Investments in Affiliated Companies - Ownership Percentage (Details)

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Investments in Affiliated Companies - Ownership Percentage (Details)
Sep. 30, 2017
PQ Silicates Ltd.  
Schedule of Equity Method Investments [Line Items]  
Ownership percentage 50.00%
Zeolyst International  
Schedule of Equity Method Investments [Line Items]  
Ownership percentage 50.00%
Zeolyst C.V.  
Schedule of Equity Method Investments [Line Items]  
Ownership percentage 50.00%
Quaker Holdings  
Schedule of Equity Method Investments [Line Items]  
Ownership percentage 49.00%