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INCOME TAXES (Schedule of Effective Rate Reconciliation) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount | $ 65.5 | $ 118.6 | $ 37.9
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent | 21.00% | 21.00% | 35.00%
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion | $ (49.3) | $ (54.6) | $ (61.6)
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion percent | (15.80%) | (9.70%) | (56.90%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount | $ 0.0 | $ 0.0 | $ 407.5
Impact Of Tax Law Change Percent | 0.00% | 0.00% | 376.60%
Effective Income Tax Rate Reconciliation, Disposition of Business, Amount | $ 846.0 | $ 161.7 | $ 0.0
Effective Income Tax Rate Reconciliation, Disposition of Business, Percent | 271.10% | 28.60% | 0.00%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount | $ 0.2 | $ 0.1 | $ 477.9
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent | 0.10% | 0.00% | 441.70%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount | $ 1.2 | $ 0.8 | $ (1.5)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent | 0.40% | 0.20% | (1.40%)
Income Tax Expense (Benefit) | $ 17.6 | $ (475.2) | $ (252.4)
Effective Income Tax Rate Reconciliation, Percent | 5.70% | (84.10%) | (233.30%)
Tax Law Change [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ 0.0 | $ 0.0 | $ (407.5)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent | 0.00% | 0.00% | (376.60%)
Current year activity [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ 0.0 | $ (79.6) | $ (469.8)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent | 0.00% | (14.10%) | (434.20%)
valuation allowance reversal [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ 0.0 | $ (460.5) | $ 0.0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent | 0.00% | (81.50%) | 0.00%
Repeal of AMT [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ 0.0 | $ 0.0 | $ (235.3)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent | 0.00% | 0.00% | (217.50%)
Dissolution of entities [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | $ (846.0) | $ (161.7) | $ 0.0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent | (271.10%) | (28.60%) | 0.00%

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