Supplemental Condensed Consolidating Financial Information - Consolidating Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Millions | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 |
Assets | | | | | | | | |
Cash and cash equivalents | $ 93.7 | | | $ 145.7 | | | | |
Receivables, net | 62.7 | | | 75.4 | | | | |
Inventories | 157 | | | 110.4 | | | | |
Income tax receivable | 3.1 | | | 0.7 | | | | |
Other current assets | 4.2 | | | 2.8 | | | | |
Advances to affiliate | 0 | | | 0 | | | | |
Total current assets | 320.7 | | | 335 | | | | |
Notes receivable from affiliate | 0 | | | 0 | | | | |
Properties, plants and equipment, net | 1,389.5 | | | 1,471.1 | | | | |
Goodwill | 3.4 | | | 76.9 | | | | |
Other intangible assets, net | 35.4 | | | 156.8 | | | | |
Deferred income taxes | 0 | | | 0 | | | | |
Deferred charges and other assets | 17.2 | | | 5.5 | | | | |
Total assets | 1,766.2 | | | 2,045.3 | | | | |
Liabilities and Equity | | | | | | | | |
Advances from affiliate | 0 | | | 0 | | | | |
Accounts payable | 119.8 | | | 115 | | | | |
Accrued liabilities | 46.1 | | | 45.6 | | | | |
Deferred revenue | 2.1 | | | 3 | | | | |
Current portion of long-term debt and financing obligation | 2.9 | | | 3.9 | | | | |
Interest payable | 14.4 | | | 3.6 | | | | |
Income taxes payable | 0 | | | 0 | | | | |
Total current liabilities | 185.3 | | | 171.1 | | | | |
Long-term debt and financing obligation | 780 | | | 834.5 | | | | |
Payable to affiliate | 0 | | | 0 | | | | |
Accrual for black lung benefits | 46.9 | | | 44.9 | | | | |
Retirement benefit liabilities | 23.7 | | | 25.2 | | | | |
Deferred income taxes | 146.9 | | | 254.7 | | | | |
Asset retirement obligations | 13.5 | | | 14.6 | | | | |
Other deferred credits and liabilities | 23.1 | | | 17.6 | | | | |
Total liabilities | 1,219.4 | | | 1,362.6 | | | | |
Equity | | | | | | | | |
Preferred stock, $0.01 par value. Authorized 50,000,000 shares; no issued shares at both September 30, 2019 and December 31, 2018 | 0 | | | 0 | | | | |
Common stock, $0.01 par value. Authorized 300,000,000 shares; issued 98,040,372 and 72,233,750 shares at September 30, 2019 and December 31, 2018, respectively | 1 | | | 0.7 | | | | |
Treasury stock, 9,544,132 and 7,477,657 shares at September 30, 2019 and December 31, 2018, respectively | (153.9) | | | (140.7) | | | | |
Additional paid-in capital | 710.9 | | | 488.8 | | | | |
Accumulated other comprehensive loss | (13.9) | | | (13.1) | | | | |
Retained (deficit) earnings | (23.5) | | | 127.4 | | | | |
Equity investment eliminations | 0 | | | 0 | | | | |
Total SunCoke Energy, Inc. stockholders’ equity | 520.6 | | | 463.1 | | | | |
Noncontrolling interests | 26.2 | | | 219.6 | | | | |
Total equity | 546.8 | $ 722.8 | $ 687 | 682.7 | $ 682.6 | $ 672.4 | $ 659.5 | $ 659.6 |
Total liabilities and equity | $ 1,766.2 | | | $ 2,045.3 | | | | |
Preferred stock, par value (in dollars per share) | $ 0.01 | | | $ 0.01 | | | | |
Preferred stock, shares authorized (in shares) | 50,000,000 | | | 50,000,000 | | | | |
Preferred stock, shares issued (in shares) | 0 | | | 0 | | | | |
Common stock, par value (in dollars per share) | $ 0.01 | | | $ 0.01 | | | | |
Common stock, shares authorized (in shares) | 300,000,000 | | | 300,000,000 | | | | |
Common stock, shares, issued (in shares) | 98,040,372 | | | 72,233,750 | | | | |
Treasury stock, shares (in shares) | 9,544,132 | | | 7,477,657 | | | | |
Reportable Legal Entities | Issuer | | | | | | | | |
Assets | | | | | | | | |
Cash and cash equivalents | $ 0 | | | $ 0 | | | | |
Receivables, net | 0 | | | 0 | | | | |
Inventories | 0 | | | 0 | | | | |
Income tax receivable | 0 | | | 0 | | | | |
Other current assets | 0 | | | 0 | | | | |
Advances to affiliate | 0 | | | 0 | | | | |
Total current assets | 0 | | | 0 | | | | |
Notes receivable from affiliate | 0 | | | 0 | | | | |
Properties, plants and equipment, net | 0 | | | 0 | | | | |
Goodwill | 0 | | | 0 | | | | |
Other intangible assets, net | 0 | | | 0 | | | | |
Deferred income taxes | 8.6 | | | 7 | | | | |
Deferred charges and other assets | 0 | | | 0 | | | | |
Total assets | 8.6 | | | 7 | | | | |
Liabilities and Equity | | | | | | | | |
Advances from affiliate | 147.8 | | | 167.3 | | | | |
Accounts payable | 0 | | | 0 | | | | |
Accrued liabilities | 1.1 | | | 1.8 | | | | |
Deferred revenue | 0 | | | 0 | | | | |
Current portion of long-term debt and financing obligation | 0 | | | 1.1 | | | | |
Interest payable | 0 | | | 0.4 | | | | |
Income taxes payable | 0.3 | | | 1.9 | | | | |
Total current liabilities | 149.2 | | | 172.5 | | | | |
Long-term debt and financing obligation | 140.5 | | | 41.2 | | | | |
Payable to affiliate | 0 | | | 0 | | | | |
Accrual for black lung benefits | 0 | | | 0 | | | | |
Retirement benefit liabilities | 0 | | | 0 | | | | |
Deferred income taxes | 0 | | | 0 | | | | |
Asset retirement obligations | 0 | | | 0 | | | | |
Other deferred credits and liabilities | 3.1 | | | 3.5 | | | | |
Total liabilities | 292.8 | | | 217.2 | | | | |
Equity | | | | | | | | |
Preferred stock, $0.01 par value. Authorized 50,000,000 shares; no issued shares at both September 30, 2019 and December 31, 2018 | 0 | | | 0 | | | | |
Common stock, $0.01 par value. Authorized 300,000,000 shares; issued 98,040,372 and 72,233,750 shares at September 30, 2019 and December 31, 2018, respectively | 1 | | | 0.7 | | | | |
Treasury stock, 9,544,132 and 7,477,657 shares at September 30, 2019 and December 31, 2018, respectively | (153.9) | | | (140.7) | | | | |
Additional paid-in capital | 710.9 | | | 488.9 | | | | |
Accumulated other comprehensive loss | (13.9) | | | (13.1) | | | | |
Retained (deficit) earnings | (23.5) | | | 127.5 | | | | |
Equity investment eliminations | (804.8) | | | (673.5) | | | | |
Total SunCoke Energy, Inc. stockholders’ equity | (284.2) | | | (210.2) | | | | |
Noncontrolling interests | 0 | | | 0 | | | | |
Total equity | (284.2) | | | (210.2) | | | | |
Total liabilities and equity | 8.6 | | | 7 | | | | |
Reportable Legal Entities | Guarantor Subsidiaries | | | | | | | | |
Assets | | | | | | | | |
Cash and cash equivalents | 71.8 | | | 123.2 | | | | |
Receivables, net | 11.9 | | | 13.3 | | | | |
Inventories | 16.5 | | | 10.6 | | | | |
Income tax receivable | 0 | | | 0 | | | | |
Other current assets | 3.8 | | | 1.8 | | | | |
Advances to affiliate | 290.5 | | | 281.1 | | | | |
Total current assets | 394.5 | | | 430 | | | | |
Notes receivable from affiliate | 0 | | | 0 | | | | |
Properties, plants and equipment, net | 51.1 | | | 54.3 | | | | |
Goodwill | 3.4 | | | 3.4 | | | | |
Other intangible assets, net | 0.6 | | | 1.1 | | | | |
Deferred income taxes | 0 | | | 0 | | | | |
Deferred charges and other assets | 5.3 | | | 5.1 | | | | |
Total assets | 454.9 | | | 493.9 | | | | |
Liabilities and Equity | | | | | | | | |
Advances from affiliate | 0 | | | 0 | | | | |
Accounts payable | 17 | | | 14.7 | | | | |
Accrued liabilities | 12 | | | 13.7 | | | | |
Deferred revenue | 0 | | | 0 | | | | |
Current portion of long-term debt and financing obligation | 0 | | | 0 | | | | |
Interest payable | 0 | | | 0 | | | | |
Income taxes payable | 98.5 | | | 93.5 | | | | |
Total current liabilities | 127.5 | | | 121.9 | | | | |
Long-term debt and financing obligation | 0 | | | 0 | | | | |
Payable to affiliate | 200 | | | 200 | | | | |
Accrual for black lung benefits | 11.2 | | | 10.9 | | | | |
Retirement benefit liabilities | 11.4 | | | 12.2 | | | | |
Deferred income taxes | 146.1 | | | 194.9 | | | | |
Asset retirement obligations | 0 | | | 0 | | | | |
Other deferred credits and liabilities | 7.9 | | | 6.6 | | | | |
Total liabilities | 504.1 | | | 546.5 | | | | |
Equity | | | | | | | | |
Preferred stock, $0.01 par value. Authorized 50,000,000 shares; no issued shares at both September 30, 2019 and December 31, 2018 | 0 | | | 0 | | | | |
Common stock, $0.01 par value. Authorized 300,000,000 shares; issued 98,040,372 and 72,233,750 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Treasury stock, 9,544,132 and 7,477,657 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Additional paid-in capital | 533.4 | | | 61 | | | | |
Accumulated other comprehensive loss | (2.2) | | | (2) | | | | |
Retained (deficit) earnings | 386.5 | | | 526.1 | | | | |
Equity investment eliminations | (966.9) | | | (637.7) | | | | |
Total SunCoke Energy, Inc. stockholders’ equity | (49.2) | | | (52.6) | | | | |
Noncontrolling interests | 0 | | | 0 | | | | |
Total equity | (49.2) | | | (52.6) | | | | |
Total liabilities and equity | 454.9 | | | 493.9 | | | | |
Reportable Legal Entities | Non- Guarantor Subsidiaries | | | | | | | | |
Assets | | | | | | | | |
Cash and cash equivalents | 21.9 | | | 22.5 | | | | |
Receivables, net | 50.8 | | | 62.1 | | | | |
Inventories | 140.5 | | | 99.8 | | | | |
Income tax receivable | 101.9 | | | 96.1 | | | | |
Other current assets | 0.4 | | | 1 | | | | |
Advances to affiliate | 0 | | | 0 | | | | |
Total current assets | 315.5 | | | 281.5 | | | | |
Notes receivable from affiliate | 200 | | | 200 | | | | |
Properties, plants and equipment, net | 1,338.4 | | | 1,416.8 | | | | |
Goodwill | 0 | | | 73.5 | | | | |
Other intangible assets, net | 34.8 | | | 155.7 | | | | |
Deferred income taxes | 0 | | | 0 | | | | |
Deferred charges and other assets | 11.9 | | | 0.4 | | | | |
Total assets | 1,900.6 | | | 2,127.9 | | | | |
Liabilities and Equity | | | | | | | | |
Advances from affiliate | 142.7 | | | 113.8 | | | | |
Accounts payable | 102.8 | | | 100.3 | | | | |
Accrued liabilities | 33 | | | 30.1 | | | | |
Deferred revenue | 2.1 | | | 3 | | | | |
Current portion of long-term debt and financing obligation | 2.9 | | | 2.8 | | | | |
Interest payable | 14.4 | | | 3.2 | | | | |
Income taxes payable | 0 | | | 0 | | | | |
Total current liabilities | 297.9 | | | 253.2 | | | | |
Long-term debt and financing obligation | 639.5 | | | 793.3 | | | | |
Payable to affiliate | 0 | | | 0 | | | | |
Accrual for black lung benefits | 35.7 | | | 34 | | | | |
Retirement benefit liabilities | 12.3 | | | 13 | | | | |
Deferred income taxes | 9.4 | | | 66.8 | | | | |
Asset retirement obligations | 13.5 | | | 14.6 | | | | |
Other deferred credits and liabilities | 12.1 | | | 7.5 | | | | |
Total liabilities | 1,020.4 | | | 1,182.4 | | | | |
Equity | | | | | | | | |
Preferred stock, $0.01 par value. Authorized 50,000,000 shares; no issued shares at both September 30, 2019 and December 31, 2018 | 0 | | | 0 | | | | |
Common stock, $0.01 par value. Authorized 300,000,000 shares; issued 98,040,372 and 72,233,750 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Treasury stock, 9,544,132 and 7,477,657 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Additional paid-in capital | 915.1 | | | 612.8 | | | | |
Accumulated other comprehensive loss | (11.7) | | | (11.1) | | | | |
Retained (deficit) earnings | (49.4) | | | 124.2 | | | | |
Equity investment eliminations | 0 | | | 0 | | | | |
Total SunCoke Energy, Inc. stockholders’ equity | 854 | | | 725.9 | | | | |
Noncontrolling interests | 26.2 | | | 219.6 | | | | |
Total equity | 880.2 | | | 945.5 | | | | |
Total liabilities and equity | 1,900.6 | | | 2,127.9 | | | | |
Combining and Consolidating Adjustments | | | | | | | | |
Assets | | | | | | | | |
Cash and cash equivalents | 0 | | | 0 | | | | |
Receivables, net | 0 | | | 0 | | | | |
Inventories | 0 | | | 0 | | | | |
Income tax receivable | (98.8) | | | (95.4) | | | | |
Other current assets | 0 | | | 0 | | | | |
Advances to affiliate | (290.5) | | | (281.1) | | | | |
Total current assets | (389.3) | | | (376.5) | | | | |
Notes receivable from affiliate | (200) | | | (200) | | | | |
Properties, plants and equipment, net | 0 | | | 0 | | | | |
Goodwill | 0 | | | 0 | | | | |
Other intangible assets, net | 0 | | | 0 | | | | |
Deferred income taxes | (8.6) | | | (7) | | | | |
Deferred charges and other assets | 0 | | | 0 | | | | |
Total assets | (597.9) | | | (583.5) | | | | |
Liabilities and Equity | | | | | | | | |
Advances from affiliate | (290.5) | | | (281.1) | | | | |
Accounts payable | 0 | | | 0 | | | | |
Accrued liabilities | 0 | | | 0 | | | | |
Deferred revenue | 0 | | | 0 | | | | |
Current portion of long-term debt and financing obligation | 0 | | | 0 | | | | |
Interest payable | 0 | | | 0 | | | | |
Income taxes payable | (98.8) | | | (95.4) | | | | |
Total current liabilities | (389.3) | | | (376.5) | | | | |
Long-term debt and financing obligation | 0 | | | 0 | | | | |
Payable to affiliate | (200) | | | (200) | | | | |
Accrual for black lung benefits | 0 | | | 0 | | | | |
Retirement benefit liabilities | 0 | | | 0 | | | | |
Deferred income taxes | (8.6) | | | (7) | | | | |
Asset retirement obligations | 0 | | | 0 | | | | |
Other deferred credits and liabilities | 0 | | | 0 | | | | |
Total liabilities | (597.9) | | | (583.5) | | | | |
Equity | | | | | | | | |
Preferred stock, $0.01 par value. Authorized 50,000,000 shares; no issued shares at both September 30, 2019 and December 31, 2018 | 0 | | | 0 | | | | |
Common stock, $0.01 par value. Authorized 300,000,000 shares; issued 98,040,372 and 72,233,750 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Treasury stock, 9,544,132 and 7,477,657 shares at September 30, 2019 and December 31, 2018, respectively | 0 | | | 0 | | | | |
Additional paid-in capital | (1,448.5) | | | (673.9) | | | | |
Accumulated other comprehensive loss | 13.9 | | | 13.1 | | | | |
Retained (deficit) earnings | (337.1) | | | (650.4) | | | | |
Equity investment eliminations | 1,771.7 | | | 1,311.2 | | | | |
Total SunCoke Energy, Inc. stockholders’ equity | 0 | | | 0 | | | | |
Noncontrolling interests | 0 | | | 0 | | | | |
Total equity | 0 | | | 0 | | | | |
Total liabilities and equity | $ (597.9) | | | $ (583.5) | | | | |