Annual report pursuant to Section 13 and 15(d)

SUPPLEMENTARY GUARANTOR INFORMATION (Supplementary Statements of Condensed Consolidating Financial Position) (Details)

v3.10.0.1
SUPPLEMENTARY GUARANTOR INFORMATION (Supplementary Statements of Condensed Consolidating Financial Position) (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Jan. 01, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
CURRENT ASSETS          
Cash and cash equivalents $ 823.2 $ 978.3 $ 978.3    
Accounts receivable, net 226.7 183.3 106.7    
Inventories 87.9 87.0 138.4    
Supplies and other inventories 93.2 88.8 88.8    
Derivative assets 91.5 49.5 37.9    
Income tax receivable, current 117.3 13.3 13.3    
Loans to and accounts receivables from the Canadian Entities 0.0 51.6 51.6    
Current assets of discontinued operations 12.4 118.5 118.5    
Other current assets 27.4 11.1 11.1    
TOTAL CURRENT ASSETS 1,479.6 1,581.4 1,544.6    
OTHER ASSETS          
PROPERTY, PLANT AND EQUIPMENT, NET 1,286.0 1,033.8 1,033.8    
Deposits for property, plant and equipment 83.0 17.8 17.8    
Income tax receivable, non-current 121.3 235.3 235.3    
Deferred income taxes 464.8   0.0    
Investment in subsidiaries 0.0   0.0    
Long-term intercompany notes 0.0   0.0    
Non-current assets of discontinued operations 0.0 20.3 20.3    
Other non-current assets 94.9 101.6 101.6    
TOTAL OTHER ASSETS 764.0 375.0 375.0    
TOTAL ASSETS 3,529.6 2,990.2 2,953.4 $ 1,923.9  
CURRENT LIABILITIES          
Accounts payable 186.8 100.9 99.5    
Accrued employment costs 74.0 52.7 52.7    
State and local taxes payable 35.5 30.2 30.2    
Accrued interest 38.4 31.4 31.4    
Contingent claims 0.0 55.6 55.6    
Partnership distribution payable 43.5 44.2 44.2    
Current liabilities of discontinued operations 6.7 75.0 75.0    
Other current liabilities 83.3 65.0 63.6    
TOTAL CURRENT LIABILITIES 468.2 455.0 452.2    
POSTEMPLOYMENT BENEFIT LIABILITIES          
Pensions 218.4   222.8    
Other postretirement benefits 30.3   34.9    
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES 248.7 257.7 257.7    
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS 172.0 167.7 167.7    
LONG-TERM DEBT 2,092.9 2,304.2 2,304.2    
LONG-TERM INTERCOMPANY NOTES 0.0   0.0    
NON-CURRENT LIABILITIES OF DISCONTINUED OPERATIONS 8.3 52.2 52.2    
OTHER LIABILITIES 115.3 163.5 163.5    
TOTAL LIABILITIES 3,105.4 3,400.3 3,397.5    
CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)          
TOTAL CLIFFS SHAREHOLDERS' EQUITY (DEFICIT) 424.2 (410.3) (444.3)    
NONCONTROLLING INTEREST 0.0 0.2 0.2    
TOTAL EQUITY (DEFICIT) 424.2 (410.1) (444.1) $ (1,330.5) $ (1,811.6)
TOTAL LIABILITIES AND EQUITY (DEFICIT) 3,529.6 $ 2,990.2 2,953.4    
Consolidation, Eliminations [Member]          
CURRENT ASSETS          
Cash and cash equivalents 0.0   0.0    
Accounts receivable, net (4.1)   (0.7)    
Inventories 0.0   0.0    
Supplies and other inventories 0.0   0.0    
Derivative assets 0.0   0.0    
Income tax receivable, current 0.0   0.0    
Loans to and accounts receivables from the Canadian Entities     0.0    
Current assets of discontinued operations 0.0   0.0    
Other current assets 0.0   0.0    
TOTAL CURRENT ASSETS (4.1)   (0.7)    
OTHER ASSETS          
PROPERTY, PLANT AND EQUIPMENT, NET 0.0   0.0    
Deposits for property, plant and equipment 0.0   0.0    
Income tax receivable, non-current 0.0   0.0    
Deferred income taxes 0.0        
Investment in subsidiaries (1,313.1)   (1,054.2)    
Long-term intercompany notes (121.3)   (242.0)    
Non-current assets of discontinued operations     0.0    
Other non-current assets 0.0   0.0    
TOTAL OTHER ASSETS (1,434.4)   (1,296.2)    
TOTAL ASSETS (1,438.5)   (1,296.9)    
CURRENT LIABILITIES          
Accounts payable (4.1)   (0.7)    
Accrued employment costs 0.0   0.0    
State and local taxes payable 0.0   0.0    
Accrued interest 0.0   0.0    
Contingent claims     0.0    
Partnership distribution payable 0.0   0.0    
Current liabilities of discontinued operations 0.0   0.0    
Other current liabilities 0.0   0.0    
TOTAL CURRENT LIABILITIES (4.1)   (0.7)    
POSTEMPLOYMENT BENEFIT LIABILITIES          
Pensions 0.0   0.0    
Other postretirement benefits 0.0   0.0    
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES 0.0   0.0    
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS 0.0   0.0    
LONG-TERM DEBT 0.0   0.0    
LONG-TERM INTERCOMPANY NOTES (121.3)   (242.0)    
NON-CURRENT LIABILITIES OF DISCONTINUED OPERATIONS 0.0   0.0    
OTHER LIABILITIES 0.0   0.0    
TOTAL LIABILITIES (125.4)   (242.7)    
CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)          
TOTAL CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)     (1,054.2)    
NONCONTROLLING INTEREST     0.0    
TOTAL EQUITY (DEFICIT) (1,313.1)   (1,054.2)    
TOTAL LIABILITIES AND EQUITY (DEFICIT) (1,438.5)   (1,296.9)    
Parent [Member] | Reportable Legal Entities [Member]          
CURRENT ASSETS          
Cash and cash equivalents 819.8   948.9    
Accounts receivable, net 9.2   4.5    
Inventories 0.0   0.0    
Supplies and other inventories 0.0   0.0    
Derivative assets 0.1   0.0    
Income tax receivable, current 117.3   11.4    
Loans to and accounts receivables from the Canadian Entities     44.7    
Current assets of discontinued operations 0.0   0.0    
Other current assets 10.0   5.0    
TOTAL CURRENT ASSETS 956.4   1,014.5    
OTHER ASSETS          
PROPERTY, PLANT AND EQUIPMENT, NET 13.3   17.5    
Deposits for property, plant and equipment 0.0   0.0    
Income tax receivable, non-current 117.2   235.3    
Deferred income taxes 463.6        
Investment in subsidiaries 1,262.3   1,024.3    
Long-term intercompany notes 0.0   0.0    
Non-current assets of discontinued operations     0.0    
Other non-current assets 8.0   7.8    
TOTAL OTHER ASSETS 1,851.1   1,267.4    
TOTAL ASSETS 2,820.8   2,299.4    
CURRENT LIABILITIES          
Accounts payable 5.3   7.1    
Accrued employment costs 28.5   13.7    
State and local taxes payable 0.0   0.0    
Accrued interest 38.4   31.4    
Contingent claims     55.6    
Partnership distribution payable 0.0   0.0    
Current liabilities of discontinued operations 0.0   0.0    
Other current liabilities 30.6   7.4    
TOTAL CURRENT LIABILITIES 102.8   115.2    
POSTEMPLOYMENT BENEFIT LIABILITIES          
Pensions 58.3   59.2    
Other postretirement benefits 6.0   7.2    
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES 64.3   66.4    
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS 0.0   0.0    
LONG-TERM DEBT 2,092.9   2,304.2    
LONG-TERM INTERCOMPANY NOTES 121.3   242.0    
NON-CURRENT LIABILITIES OF DISCONTINUED OPERATIONS 0.0   0.0    
OTHER LIABILITIES 15.3   15.7    
TOTAL LIABILITIES 2,396.6   2,743.5    
CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)          
TOTAL CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)     (444.1)    
NONCONTROLLING INTEREST     0.0    
TOTAL EQUITY (DEFICIT) 424.2   (444.1)    
TOTAL LIABILITIES AND EQUITY (DEFICIT) 2,820.8   2,299.4    
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]          
CURRENT ASSETS          
Cash and cash equivalents 0.7   2.1    
Accounts receivable, net 221.3   102.9    
Inventories 87.9   138.4    
Supplies and other inventories 93.2   88.8    
Derivative assets 91.4   37.9    
Income tax receivable, current 0.0   1.9    
Loans to and accounts receivables from the Canadian Entities     6.9    
Current assets of discontinued operations 0.0   0.0    
Other current assets 16.9   5.6    
TOTAL CURRENT ASSETS 511.4   384.5    
OTHER ASSETS          
PROPERTY, PLANT AND EQUIPMENT, NET 1,221.9   965.5    
Deposits for property, plant and equipment 68.4   8.2    
Income tax receivable, non-current 4.1   0.0    
Deferred income taxes 0.0        
Investment in subsidiaries 50.8   29.9    
Long-term intercompany notes 0.0   0.0    
Non-current assets of discontinued operations     0.0    
Other non-current assets 85.4   91.8    
TOTAL OTHER ASSETS 208.7   129.9    
TOTAL ASSETS 1,942.0   1,479.9    
CURRENT LIABILITIES          
Accounts payable 181.4   92.3    
Accrued employment costs 45.4   38.9    
State and local taxes payable 35.4   30.0    
Accrued interest 0.0   0.0    
Contingent claims     0.0    
Partnership distribution payable 43.5   44.2    
Current liabilities of discontinued operations 0.0   0.0    
Other current liabilities 51.3   54.5    
TOTAL CURRENT LIABILITIES 357.0   259.9    
POSTEMPLOYMENT BENEFIT LIABILITIES          
Pensions 390.5   403.6    
Other postretirement benefits 23.9   27.0    
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES 414.4   430.6    
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS 152.1   140.6    
LONG-TERM DEBT 0.0   0.0    
LONG-TERM INTERCOMPANY NOTES 0.0   0.0    
NON-CURRENT LIABILITIES OF DISCONTINUED OPERATIONS 0.0   0.0    
OTHER LIABILITIES 99.5   147.2    
TOTAL LIABILITIES 1,023.0   978.3    
CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)          
TOTAL CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)     501.6    
NONCONTROLLING INTEREST     0.0    
TOTAL EQUITY (DEFICIT) 919.0   501.6    
TOTAL LIABILITIES AND EQUITY (DEFICIT) 1,942.0   1,479.9    
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]          
CURRENT ASSETS          
Cash and cash equivalents 2.7   27.3    
Accounts receivable, net 0.3   0.0    
Inventories 0.0   0.0    
Supplies and other inventories 0.0   0.0    
Derivative assets 0.0   0.0    
Income tax receivable, current 0.0   0.0    
Loans to and accounts receivables from the Canadian Entities     0.0    
Current assets of discontinued operations 12.4   118.5    
Other current assets 0.5   0.5    
TOTAL CURRENT ASSETS 15.9   146.3    
OTHER ASSETS          
PROPERTY, PLANT AND EQUIPMENT, NET 50.8   50.8    
Deposits for property, plant and equipment 14.6   9.6    
Income tax receivable, non-current 0.0   0.0    
Deferred income taxes 1.2        
Investment in subsidiaries 0.0   0.0    
Long-term intercompany notes 121.3   242.0    
Non-current assets of discontinued operations     20.3    
Other non-current assets 1.5   2.0    
TOTAL OTHER ASSETS 138.6   273.9    
TOTAL ASSETS 205.3   471.0    
CURRENT LIABILITIES          
Accounts payable 4.2   0.8    
Accrued employment costs 0.1   0.1    
State and local taxes payable 0.1   0.2    
Accrued interest 0.0   0.0    
Contingent claims     0.0    
Partnership distribution payable 0.0   0.0    
Current liabilities of discontinued operations 6.7   75.0    
Other current liabilities 1.4   1.7    
TOTAL CURRENT LIABILITIES 12.5   77.8    
POSTEMPLOYMENT BENEFIT LIABILITIES          
Pensions (230.4)   (240.0)    
Other postretirement benefits 0.4   0.7    
TOTAL POSTEMPLOYMENT BENEFIT LIABILITIES (230.0)   (239.3)    
ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS 19.9   27.1    
LONG-TERM DEBT 0.0   0.0    
LONG-TERM INTERCOMPANY NOTES 0.0   0.0    
NON-CURRENT LIABILITIES OF DISCONTINUED OPERATIONS 8.3   52.2    
OTHER LIABILITIES 0.5   0.6    
TOTAL LIABILITIES (188.8)   (81.6)    
CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)          
TOTAL CLIFFS SHAREHOLDERS' EQUITY (DEFICIT)     552.4    
NONCONTROLLING INTEREST     0.2    
TOTAL EQUITY (DEFICIT) 394.1   552.6    
TOTAL LIABILITIES AND EQUITY (DEFICIT) $ 205.3   $ 471.0