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Income Taxes Effective Tax Rate (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax [Line Items] |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Domestic | $ (449.0) | $ (1,096.2) | $ 322.7 |
Income (Loss) from Continuing Operations before Income Taxes, Foreign | 629.9 | (159.9) | 228.8 |
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest | $ 180.9 | $ (1,256.1) | $ 551.5 |
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation |  |  |  |
Computed tax at the U.S. federal statutory rate | 21.00% | 21.00% | 21.00% | 35.00%
State and local income taxes, net of federal income tax benefit | (7.00%) | 2.60% | 2.00% |
Percentage depletion in excess of basis | (10.30%) | 2.50% | (6.70%) |
Impact of non-U.S. earnings | 42.10% | 5.30% | 11.80% |
Change in valuation allowance | (330.00%) | (3.10%) | (15.20%) |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Percent | 0.00% | (5.00%) | 0.00% |
Share-based excess cost/(benefits) | 0.00% | 0.00% | 0.70% |
Other items (none in excess of 5% of computed tax) | 0.00% | (5.40%) | 0.40% |
Effective tax rate | (319.80%) | 17.90% | 14.00% |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount | $ (609.0) | $ (355.6) | $ 0.7 |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount |  | (79.6) |  |
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount |  | 14.0 |  |
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount | 2.7 | 4.8 | 1.0 |
Refund of Future Alternative Minimum Tax Credits | (5.5) |  | (8.6) |
Effective Income Tax Rate Reconciliation, CARES Act, Amount | (23.6) |  |  |
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount | (774.1) | (73.4) | (945.8) |
Valuation allowance | 683.0 | 1,457.1 |  |
Alternative minimum tax credit carryforwards |  |  | 100.4 |
Sequestration Rules, amount of AMT refunded |  |  | 8.6 |
Undistributed earnings withholding taxes |  |  | 15.0 |
United States Tax Cuts and Jobs Act Law |  |  |  |
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation |  |  |  |
Computed tax at the U.S. federal statutory rate |  |  |  | 21.00%
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount |  |  | 12.2 |
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount |  | 21.2 | 21.2 |
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount |  | 12.5 |  |
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount |  |  | 12.2 | $ 2.3
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit |  |  |  | 457.5
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Transition Tax on Accumulated Foreign Earnings, Amount |  |  |  | 107.7
Reduction of Deferred Tax Liability Related to Undistributed Earnings of Non-U.S. Subsidiaries |  |  |  | 202.6
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) |  |  | 9.0 |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount |  | (30.7) |  |
Alternative minimum tax credit carryforwards |  |  |  | 121.5
Sequestration Rules, amount of AMT refunded |  |  |  | 8.6
Foreign Tax Credit Carryforward |  |  |  |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount |  |  | 30.6 |
Foreign and Domestic Tax Authority |  |  |  |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount |  | $ (15.9) |  |
Foreign Tax Authority |  |  |  |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ 582.6 |  | $ (11.7) |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent | (35.60%) | 0.00% | 0.00% |
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount | $ (32.2) | $ (9.2) |  |
Colonsay Mine Idle |  |  |  |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Restructuring Charges, Amount |  | (263.4) |  |
Plant City Closure |  |  |  |
Effective Income Tax Rate Reconciliation, Amounts |  |  |  |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Restructuring Charges, Amount |  | (81.0) |  |
US Branch Basket Foreign Tax Credits [Member] |  |  |  |
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
Valuation allowance |  |  | $ 156.8 |
Foreign Tax Credit Carryforward |  |  |  |
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount |  |  | 105.8 | (105.8)
Valuation allowance | 249.6 |  |  |
Tax Credit Carryforward, Amount | 628.6 |  |  |
Anticipatory Foreign Tax Credit Carryforward |  |  |  |
Effect of Tax Cuts and Jobs Act [Abstract] |  |  |  |
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount |  |  |  | $ (440.3)
Valuation allowance | $ 235.5 | $ 224.6 | $ 361.6 |

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