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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479830/718-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=sxc_EquityClassifiedAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=sxc_RestrictedStockUnitsSettledinCashMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=sxc_CashIncentiveAwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=sxc_SuncokeLTCIPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=sxc_LiabilityClassifiedAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Share-Based Compensation - Compensation Expense and Unrecognized Compensation Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	$ 1.4		$ 1.4
Weighted Average Remaining Recognition Period			1 year 1 month 6 days
RSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	0.8	$ 0.6	$ 1.8	$ 1.6
PSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	0.9		$ 0.9
Weighted Average Remaining Recognition Period			1 year 8 months 12 days
PSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	0.3	1.2	$ 1.8	3.0
Total equity awards \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	1.1	1.8	3.6	4.6
Cash RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	2.0		$ 2.0
Weighted Average Remaining Recognition Period			1 year 8 months 12 days
Cash RSUs \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	0.9	0.1	$ 1.9	1.0
Cash incentive award \| Suncoke LTCIP
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized Compensation Cost	2.0		$ 2.0
Weighted Average Remaining Recognition Period			1 year 8 months 12 days
Cash incentive award \| Selling, General and Administrative Expenses \| Suncoke LTCIP
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	0.6	1.5	$ 2.3	3.9
Total liability awards \| Selling, General and Administrative Expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense	$ 1.5	$ 1.6	$ 4.2	$ 4.9