Annual report pursuant to Section 13 and 15(d)

ACQUISITIONS - Pro Forma (Details)

v3.22.4
ACQUISITIONS - Pro Forma (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
ArcelorMittal USA and AK Steel    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Revenues, pro forma   $ 12,837
Net income (loss) attributable to Cliffs shareholders, pro forma   (520)
Expenses, pro forma   $ 32
Statutory tax rate, pro forma   24.30%
Income tax benefit (expense), pro forma   $ 170
ArcelorMittal USA and AK Steel | Intersegment Eliminations    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Revenues, pro forma   844
Ferrous Processing and Trading    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Revenues, pro forma $ 21,701 13,549
Net income (loss) attributable to Cliffs shareholders, pro forma $ 3,074 (526)
Franchise | ArcelorMittal USA and AK Steel    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Net income (loss) attributable to Cliffs shareholders, pro forma   140
Fair Value Adjustment to Inventory | ArcelorMittal USA and AK Steel    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Net income (loss) attributable to Cliffs shareholders, pro forma   96
Acquisition-related costs | ArcelorMittal USA and AK Steel    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Net income (loss) attributable to Cliffs shareholders, pro forma   93
Restructuring Costs | ArcelorMittal USA    
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]    
Net income (loss) attributable to Cliffs shareholders, pro forma   $ 1,820