Cleveland-Cliffs Inc. Annual report pursuant to Section 13 and 15(d)

SEGMENT REPORTING - Depreciation, Depletion and Amortization and Capital Additions By Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	$ 308	$ 85	$ 89
Depreciation, Depletion and Amortization excluding Depreciation, Amortization and Depletion expense for Discontinued Operations			74
Property, Plant and Equipment, Additions	483	690	395
Steelmaking [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	276	80	68
Property, Plant and Equipment, Additions	436	687	393
Other businesses
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	27	0	0
Property, Plant and Equipment, Additions	45	0	0
Corporate and Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization	5	5	6
Property, Plant and Equipment, Additions	$ 2	$ 3	$ 2