Annual report pursuant to Section 13 and 15(d)

INCOME TAXES (Schedule of Effective Rate Reconciliation) (Details)

v3.10.0.1
INCOME TAXES (Schedule of Effective Rate Reconciliation) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount $ 118.6 $ 37.9 $ 38.6
Effective Income Tax Rate Reconciliation, Percent (84.10%) (233.30%) (11.10%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount $ 0.0 $ 407.5 $ 149.1
Impact Of Tax Law Change Percent 0.00% 376.60% 135.10%
Effective Income Tax Rate Reconciliation, Disposition of Business, Amount $ 161.7 $ 0.0 $ 0.0
Effective Income Tax Rate Reconciliation, Disposition of Business, Percent 28.60% 0.00% 0.00%
Prior year adjustments made in current year, amount $ (1.0) $ (1.1) $ (11.8)
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion $ (54.6) $ (61.6) $ (36.1)
Income Tax Reconciliation Tax Deduction for percentage depletion in excess of cost depletion percent (9.70%) (56.90%) (32.70%)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount $ 0.1 $ 477.9 $ (40.6)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent 0.00% 441.70% (36.80%)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent 21.00% 35.00% 35.00%
Tax Adjustments, Settlements, and Unusual Provisions $ (1.3) $ (1.4) $ (11.3)
Tax Adjustments Settlements And Unusual Provisions Percent (0.20%) (1.30%) (10.20%)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent (0.20%) (1.00%) (10.70%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount $ 3.1 $ 1.0 $ (9.8)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent 0.60% 0.90% (8.90%)
Income Tax Expense (Benefit) $ (475.2) $ (252.4) $ (12.2)
Worthless Stock Deduction, Amount $ 0.0 $ 0.0 $ (73.4)
Worthless Stock Deduction, Percent 0.00% 0.00% (66.50%)
Tax Law Change [Member]      
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount $ 0.0 $ (407.5) $ (149.1)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent 0.00% (376.60%) (135.10%)
Current year activity [Member]      
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount $ (80.6) $ (466.3) $ 122.9
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent (14.30%) (431.00%) 111.30%
valuation allowance reversal [Member]      
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount $ (460.5) $ 0.0 $ 0.0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent (81.50%) 0.00% 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 $ (235.3) $ 0.0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent 0.00% (217.50%) 0.00%
Dissolution of entities [Member]      
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount $ (161.7) $ 0.0 $ 0.0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent (28.60%) 0.00% 0.00%
Prior year adjustment in current year [Member]      
Income Tax Contingency [Line Items]      
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount $ 1.0 $ (3.5) $ 9.3
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent 0.20% (3.20%) 8.40%