Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

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BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
12 Months Ended
Dec. 31, 2021
USD ($)
employee
segment
Nov. 18, 2021
segment
Dec. 31, 2020
USD ($)
Dec. 09, 2020
Dec. 31, 2019
Basis of Presentation and Significant Accounting Policies [Line Items]          
Number of employees | employee 26,000        
Number of operating segments 4        
Number of reportable segments 1        
Other Noncurrent Assets          
Basis of Presentation and Significant Accounting Policies [Line Items]          
Investment in affiliates | $ $ 128   $ 105    
Ferrous Processing and Trading          
Basis of Presentation and Significant Accounting Policies [Line Items]          
Number of facilities acquired   22      
Hibbing          
Basis of Presentation and Significant Accounting Policies [Line Items]          
Ownership interest, equity method investment 85.30%   85.30% 62.30% 23.00%
Workforce represented by labor unions          
Basis of Presentation and Significant Accounting Policies [Line Items]          
Number of employees | employee 18,500