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

STOCK COMPENSATION PLANS (Schedule of Compensation Costs) (Details)

v3.19.3.a.u2

STOCK COMPENSATION PLANS (Schedule of Compensation Costs) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense, Tax Benefit									$ (3.7)	$ 0.0	$ 0.0
Share-based Payment Arrangement, Expense, after Tax									$ 13.9	$ 15.1	$ 18.2
Earnings (loss) per common share attributable to Cliffs common shareholders - basic:	$ 0.23	$ 0.34	$ 0.59	$ (0.08)	$ 2.06	$ 1.47	$ 0.55	$ (0.29)	$ 1.06	$ 3.80	$ 1.28
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:	$ 0.23	$ 0.33	$ 0.57	$ (0.08)	$ 1.98	$ 1.41	$ 0.55	$ (0.29)	1.03	3.71	1.26
Share-based Payment Arrangement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Earnings (loss) per common share attributable to Cliffs common shareholders - basic:									0.05	0.05	0.06
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:									$ 0.05	$ 0.05	$ 0.06
Cost of goods sold and operating expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Costs and Expenses									$ 2.0	$ 1.7	$ 1.9
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Costs and Expenses									15.6	13.4	16.3
Operating Income (Loss) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Costs and Expenses									$ 17.6	$ 15.1	$ 18.2

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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