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Business Segment, Geographic and Major Customer Information - Additional Disclosures (Details) - segment
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Segment Reporting Information [Line Items]    
Number of reportable segments (segment) 2  
Customer Concentration Risk | Sales | Major Customers | Energy Chemistry Technologies    
Segment Reporting Information [Line Items]    
Percentage of revenue by major customers   95.00%