Share-Based Compensation - Compensation Expense and Unrecognized Compensation Costs (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	$ 2.4
Weighted Average Remaining Recognition Period	1 year 2 months 12 days
RSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	$ 0.3	$ 0.3
PSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	$ 3.7
Weighted Average Remaining Recognition Period	1 year 1 month 6 days
PSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	$ 0.7	0.1
Total equity awards \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	1.0	0.4
Cash RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	$ 3.1
Weighted Average Remaining Recognition Period	2 years 1 month 6 days
Cash RSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	$ 0.7	0.8
Cash incentive award \| Suncoke LTCIP
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	$ 5.7
Weighted Average Remaining Recognition Period	1 year 6 months
Cash incentive award \| Selling, General and Administrative Expenses \| Suncoke LTCIP
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	$ 1.0	0.2
Total liability awards \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation expense	$ 1.7	$ 1.0

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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