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Organization And Summary Of Significant Accounting Policies (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
May 26, 2021
Mar. 31, 2020
USD ($)
Jun. 30, 2021
USD ($)
Dec. 31, 2020
USD ($)
Mar. 31, 2021
USD ($)
Jun. 30, 2020
USD ($)
major_product_categories
Dec. 31, 2019
USD ($)
Apr. 26, 2018
$ / shares
shares
Accounting Policies [Abstract]                
Shares, Issued | shares               38,097,525
Sale of Stock, Price Per Share | $ / shares               $ 15.00
Number of major product categories | major_product_categories           2    
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                
Accounting Standards Update [Extensible List]   us-gaap:AccountingStandardsUpdate201613Member            
Total stockholders' equity   $ 574,714 $ 176,560 $ 329,385 $ 233,841 $ 680,379 $ 691,073  
GrafTech International Ltd | Brookfield                
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                
Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions 24.00%   23.90% 55.30%        
Retained Earnings (Accumulated Deficit)                
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                
Total stockholders' equity   $ 1,284,756 $ 952,400 $ 1,070,770 $ 974,852 $ 1,374,844 $ 1,451,836