Quarterly report pursuant to Section 13 or 15(d)

PROPERTY, PLANT AND EQUIPMENT (Details)

v3.20.2
PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross $ 5,958.0   $ 5,958.0   $ 3,027.4
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment 1,407.3   1,407.3   1,098.4
Property, plant and equipment, net 4,550.7   4,550.7   1,929.0
Finance Lease, Right-of-Use Asset 97.1   97.1   49.0
Interest Costs Capitalized 14.7 $ 7.0 38.0 $ 16.9  
Depreciation and depletion expense 71.8 $ 22.0 182.5 $ 62.5  
Land, Land Improvements and Mineral Rights [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 653.2   653.2   582.2
Building [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 454.4   454.4   157.8
Steel and Manufacturing Equipment [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 2,128.0   2,128.0   42.0
Mining and Pelletizing Equipment [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 1,455.2   1,455.2   1,413.6
Other Assets [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross 121.3   121.3   101.5
Construction in Progress [Member]          
Property, Plant and Equipment [Line Items]          
Property, Plant and Equipment, Gross $ 1,145.9   $ 1,145.9   $ 730.3