Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2018
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual amounts could differ from these estimates.
Reclassifications	Reclassifications Certain amounts in the prior period consolidated financial statements have been reclassified to conform to the current year presentation.
Revenue Recognition	Revenue Recognition The Company sells coke as well as steam and electricity and also provides mixing and/or handling services of coal and other aggregates. The Company also receives fees for operating the cokemaking plant in Brazil and for the licensing of its proprietary technology for use at this facility as well as reimbursement of substantially all of its operating costs. See Note 18. Substantially all of the coke produced by the Company is sold pursuant to long-term contracts with its customers. The Company evaluates each of its contracts to determine whether the arrangement contains a lease under the applicable accounting standards. If the specific facts and circumstances indicate that it is remote that parties other than the contracted customer will take more than a minor amount of the coke that will be produced by the property, plant and equipment during the term of the coke supply agreement, and the price that the customer is paying for the coke is neither contractually fixed per unit nor equal to the current market price per unit at the time of delivery, then the long-term contract is deemed to contain a lease. The lease component of the price of coke represents the rental payment for the use of the property, plant and equipment, and all such payments are accounted for as contingent rentals as they are only earned by the Company when the coke is delivered and title passes to the customer. The total amount of revenue recognized by the Company for these contingent rentals represents less than 10 percent of consolidated sales and other operating revenues for each of the years ended December 31, 2018, 2017 and 2016. Upon adoption of Accounting Standard Codification ("ASC") 842, "Leases", in 2019, these long-term contracts to sell coke will no longer be deemed to contain operating leases.
Cash Equivalents	Cash Equivalents The Company considers all highly liquid investments with a remaining maturity of three months or less at the time of purchase to be cash equivalents. These cash equivalents consist principally of certificates of deposit.
Inventories	Inventories Inventories are valued at the lower of cost or net realizable value. Cost is determined using the first-in, first-out method, except for the Company’s materials and supplies inventory, which are determined using the average-cost method. The Company utilizes the selling prices under its long-term coke supply contracts to record lower of cost or net realizable value inventory adjustments.
Properties, Plants and Equipment	Properties, Plants and Equipment Plants and equipment are depreciated on a straight-line basis over their estimated useful lives. Coke and energy plant, machinery and equipment are generally depreciated over 25 to 30 years. Logistics plant and equipment are generally depreciated over 15 to 35 years. Depreciation and amortization is excluded from cost of products sold and operating expenses and is presented separately on the Consolidated Statements of Income. Gains and losses on the disposal or retirement of fixed assets are reflected in earnings when the assets are sold or retired. Amounts incurred that extend an asset’s useful life, increase its productivity or add production capacity are capitalized. The Company accounts for changes in useful lives, when appropriate, as a change in estimate, with prospective application only. The Company capitalized interest of $3.2 million, $1.1 million, and $5.0 million in 2018, 2017 and 2016, respectively. Direct costs, such as outside labor, materials, internal payroll and benefits costs incurred during capital projects are capitalized; indirect costs are not capitalized. Normal repairs and maintenance costs are expensed as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. A long-lived asset, or group of assets, is considered to be impaired when the undiscounted net cash flows expected to be generated by the asset are less than its carrying amount. Such estimated future cash flows are highly subjective and are based on numerous assumptions about future operations and market conditions. The impairment recognized is the amount by which the carrying amount exceeds the fair market value of the impaired asset, or group of assets. It is also difficult to precisely estimate fair market value because quoted market prices for our long-lived assets may not be readily available. Therefore, fair market value is generally based on the present values of estimated future cash flows using discount rates commensurate with the risks associated with the assets being reviewed for impairment.
Goodwill and Other Intangibles	Goodwill and Other Intangibles Goodwill, which represents the excess of the purchase price over the fair value of net assets acquired, is tested for impairment as of October 1 of each year, or when events occur or circumstances change that would, more likely than not, reduce the fair value of a reporting unit to below its carrying value. The Company performs its annual goodwill impairment test by comparing the fair value of the reporting unit with its carrying amount. The Company would recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. See Note 8. Intangible assets are primarily comprised of permits, customer contracts and customer relationships. Intangible assets are amortized over their useful lives in a manner that reflects the pattern in which the economic benefit of the intangible asset is consumed. Intangible assets are assessed for impairment when a triggering event occurs.
Investment in Brazilian Cokemaking Operations	Investment in Brazilian Cokemaking Operations On November 28, 2016, ArcelorMittal Brazil redeemed SunCoke’s indirectly held preferred and common equity interest in Sol Coqueria Tubarão S.A. ("Brazil Investment"), previously accounted for at cost, for consideration of $41.0 million. The Company received $20.5 million in cash at closing in 2016 and received the remaining $20.5 million in cash, plus interest of $0.2 million, in 2017. Starting in 2016, SunCoke receives $5.1 million in licensing fees per year, in addition to our per ton licensing fee, through 2023 related to the addition of certain patents to its existing intellectual property licensing agreement, which are currently in use by ArcelorMittal Brazil at the Brazil facility. The Company also extended the life of its patents with the Brazilian authorities through 2033, providing opportunity to extend the existing licensing agreement beyond 2023. Licensing fees are included in sales and other operating revenue on the Consolidated Statements of Income.
Income Taxes	Income Taxes Deferred tax asset and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those differences are projected to be recovered or settled. See Note 5. The Company recognizes uncertain tax positions in its financial statements when minimum recognition threshold and measurement attributes are met in accordance with current accounting guidance.
Black Lung Benefit Liabilities	Black Lung Benefit Liabilities The Company has obligations related to coal workers’ pneumoconiosis, or black lung, benefits to certain of our former coal miners and their dependents. Such benefits are provided for under Title IV of the Federal Coal Mine and Safety Act of 1969 and subsequent amendments, as well as for black lung benefits provided in the states of Virginia, Kentucky and West Virginia pursuant to workers’ compensation legislation. The Patient Protection and Affordable Care Act (“PPACA”), which was implemented in 2010, amended previous legislation related to coal workers’ black lung obligations. PPACA provides for the automatic extension of awarded lifetime benefits to surviving spouses and changes the legal criteria used to assess and award claims. We act as a self-insurer for both state and federal black lung benefits and adjust our liability each year based upon actuarial calculations of our expected future payments for these benefits.
Postretirement Benefit Plan Liabilities	Postretirement Benefit Plan Liabilities The postretirement benefit plans, which are frozen, are unfunded and the accumulated postretirement benefit obligation is fully recognized on the Consolidated Balance Sheets. Actuarial gains (losses) and prior service costs (benefits) which have not yet been recognized in net income are recognized as a credit (charge) to accumulated other comprehensive income (loss). The credit (charge) to accumulated other comprehensive income (loss), which is reflected net of related tax effects, is subsequently recognized in net income when amortized as a component of postretirement benefit plans expense included in interest expense, net on the Consolidated Statements of Income.
Asset Retirement Obligations	Asset Retirement Obligations The fair value of a liability for an asset retirement obligation is recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. The associated asset retirement costs are capitalized as part of the carrying amount of the asset and depreciated over its remaining estimated useful life. The Company’s asset retirement obligations primarily relate to costs associated with restoring land to its original state.
Shipping and Handling Costs	Shipping and Handling Costs Shipping and handling costs are included in cost of products sold and operating expenses on the Consolidated Statements of Income and are generally passed through to our customers. The Company has elected the practical expedient under ASC 606, "Revenue from Contracts with Customers", to account for shipping and handling activities as a promise to fulfill the transfer of coke.
Share-based Compensation	Share-Based Compensation We measure the cost of employee services in exchange for equity instrument awards and cash awards based on the grant-date fair value of the award. The cash awards and performance metrics of equity awards are remeasured on a quarterly basis. The market metrics of equity awards are not remeasured. The total cost is recognized over the requisite service period. Award forfeitures are accounted for as they occur. The costs of equity awards and cash awards were recorded to additional paid-in capital and accrued liabilities, respectively, on the Consolidated Balance Sheets.
Fair Value Measurements	Fair Value Measurements The Company determines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As required, the Company utilizes valuation techniques that maximize the use of observable inputs (levels 1 and 2) and minimize the use of unobservable inputs (level 3) within the fair value hierarchy included in current accounting guidance. Assets and liabilities are classified within the fair value hierarchy based on the lowest level (least observable) input that is significant to the measurement in its entirety.
Currency Transactions	Currency Translation The functional currency of the Company’s Brazilian operations is the Brazilian real. The Company’s Brazil operations translate its assets and liabilities into U.S. dollars at the current exchange rates in effect at the end of the fiscal period. The gains or losses that result from this process are shown as cumulative translation adjustments within accumulated other comprehensive loss in the Consolidated Balance Sheets. The revenue and expense accounts of foreign operations are translated into U.S. dollars at the average exchange rates during the period.
Recently Adopted Accounting Pronouncements and Recently Issued Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, “Revenue from Contracts with Customers (Topic 606),” which supersedes the revenue recognition requirements in “Revenue Recognition (Topic 605),” and requires entities to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company adopted this standard on January 1, 2018, using the modified retrospective method with no material impact on our revenue recognition model on an annual basis. See Note 18. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted cash.” The Company retrospectively adopted this ASU in the first quarter 2018 and modified the Company's cash flow presentation to include restricted cash with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. Historical restricted cash balances were related to cash withheld from the 2015 acquisition of CMT to fund the completion of certain expansion capital improvements, and the related immaterial impacts have been reclassified on the statement of cash flows for the years ended December 31, 2017 and 2016. The restricted cash balance was zero at both December 31, 2018 and December 31, 2017. In March 2017, the FASB issued ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The Company adopted this ASU in the first quarter 2018 and retrospectively presented net periodic postretirement benefit cost in the income statement separately from the service cost component and outside a subtotal of income from operations. In conjunction with the adoption of this standard, expense of $1.3 million was reclassified from operating income and was recorded in interest expense, net on the Consolidated Statements of Income for both the years ended December 31, 2017 and 2016, respectively. See Note 10. In February 2018, the FASB issued ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The Company adopted this ASU in the first quarter 2018 and reclassified $1.1 million of deferred tax adjustments to accumulated other comprehensive income (loss) from retained earnings on the December 31, 2017 balance sheet for the tax effects resulting from the Tax Cuts and Jobs Act of 2017. Recently Issued Pronouncements In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)." ASU 2016-02 requires leases to be recognized as assets and liabilities on the balance sheet for the rights and obligations created by all leases with terms of more than 12 months. Subsequently, the FASB has issued various ASUs to provide further clarification around certain aspects of ASC 842, "Leases". This standard is effective for annual and interim periods in fiscal years beginning after December 15, 2018, with early adoption permitted. A multi-disciplined implementation team has gained an understanding of the accounting and disclosure provisions of the standard and analyzed the impacts to our business, including the development of new accounting processes to account for our leases and support the required disclosures. We have implemented a technology tool to assist with the accounting and reporting requirements of this standard. While we are still finalizing the impact of adopting this standard, we expect that upon adoption the right-of-use assets and lease liabilities, such as land, the lease of our corporate office space and certain equipment rentals, will increase the reported assets and liabilities on our Consolidated Balance Sheets by approximately $5 million to $10 million. The Company adopted this standard on January 1, 2019, by applying the modified retrospective transition approach and electing not to adjust prior comparative periods.