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Preferred Share Issuance and Merger (Narrative) (Details) - USD ($)
 3 Months Ended 12 Months Ended
Aug. 11, 2015
May 18, 2015
Mar. 31, 2016
Dec. 31, 2016
May 17, 2015
Business Acquisition [Line Items]          
Max Reimbursement to Acquiror $ 500,000        
Common stock, par value         $ 0.01
Goodwill, purchase accounting adjustments     $ 1,100,000    
Purchase price adjustment, inventory       $ 2,000,000  
purchase price adjustment, deferred taxes     $ 900,000    
BCP IV GrafTech Holdings LP [Member]          
Business Acquisition [Line Items]          
Amount   $ 854,337,000      
Convertible Preferred Stock [Member] | BCP IV GrafTech Holdings LP [Member]          
Business Acquisition [Line Items]          
Number of Shares   150,000      
Amount $ 150,000,000 $ 150,000,000      
Convertible Preferred Stock [Member] | BCP IV GrafTech Holdings LP [Member] | Series A Preferred Stock [Member]          
Business Acquisition [Line Items]          
Number of Shares   136,616      
Preferred stock, par value $ 0.01        
Business Combination, Equity Interest Transferred, Percentage of Common Stock Outstanding Before Transaction 19.90%        
Convertible Preferred Stock [Member] | BCP IV GrafTech Holdings LP [Member] | Series B Preferred Stock [Member]          
Business Acquisition [Line Items]          
Number of Shares   13,384      
Preferred stock, par value $ 0.01        
Notes Payable, Other Payables [Member] | Term Loan Facility [Member]          
Business Acquisition [Line Items]          
Debt Instrument, Unused Borrowing Capacity, Amount $ 40,000,000        
Senior Notes [Member] | Senior Subordinated Notes Due Nov 2015 [Member]          
Business Acquisition [Line Items]          
Early Repayment of Subordinated Debt $ 200,000,000        
Preferred Stock [Member]          
Business Acquisition [Line Items]          
Convertible Preferred Stock, Conversion Price         $ 5.05