Share-Based Compensation (Liability Classified Awards Narrative) (Details) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Dec. 31, 2017 shares	Feb. 28, 2017 shares	Dec. 31, 2019 USD ($) Installment $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Restricted Stock Units Settled in Cash
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (shares) | shares			147,851	108,522	98,364
Number of annual installment in which stock option exercisable | Installment			3
Period from grant date for annual installment (in years)			1 year
Granted (in USD per share)			$ 9.66	$ 10.71	$ 9.82
Closing price (USD per share)			$ 6.23
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (shares) | shares	148,148	237,610	227,378	96,389	385,758
Granted (in USD per share)			$ 10.79	$ 11.36	$ 11.61
Cash Incentive Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of annual installment in which stock option exercisable | Installment			3
Suncoke LTCIP | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Measurement period			3 years
Suncoke LTCIP | Cash Incentive Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value award | $			$ 0.6	$ 1.0	$ 0.7
Percent of award allocation			50.00%
Measurement period			3 years