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Share-Based Compensation (Stock Option and Performance Share Units Grants) (Details) - SunCoke LTPEP - Stock Options - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares granted (shares) 0 267,897 78,447
Weighted average exercise price (in USD per share)   $ 9.87 $ 10.49
Weighted-average fair value stock option (in dollars per share)   $ 4.09 $ 5.38