Statements Of Unaudited Condensed Consolidated Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Revenues	$ 4,569	$ 5,605	$ 14,860	$ 16,884
Operating costs:
Cost of goods sold	(4,673)	(5,125)	(14,517)	(15,661)
Selling, general and administrative expenses	(112)	(139)	(347)	(415)
Acquisition-related costs	14	5	14	5
Restructuring and other charges	(2)	0	(131)	0
Asset impairments	0	0	(79)	0
Miscellaneous – net	(27)	(11)	(63)	(26)
Total operating costs	(4,828)	(5,280)	(15,151)	(16,107)
Operating income (loss)	(259)	325	(291)	777
Other income (expense):
Interest expense, net	(102)	(70)	(235)	(226)
Loss on extinguishment of debt	0	0	(27)	0
Net periodic benefit credits other than service cost component	62	50	184	150
Changes in fair value of foreign currency contracts, net	(7)	0	(7)	0
Other non-operating income (expense)	0	(2)	3	4
Total other expense	(47)	(22)	(82)	(72)
Income (loss) from continuing operations before income taxes	(306)	303	(373)	705
Income tax benefit (expense)	76	(29)	99	(118)
Income (loss) from continuing operations	(230)	274	(274)	587
Income from discontinued operations, net of tax	0	1	0	2
Net income (loss)	(230)	275	(274)	589
Income attributable to noncontrolling interests	(12)	(11)	(33)	(35)
Net income (loss) attributable to Cliffs shareholders	$ (242)	$ 264	$ (307)	$ 554
Earnings (loss) per common share attributable to Cliffs shareholders - basic
Continuing operations (in dollars per share)	$ (0.52)	$ 0.52	$ (0.64)	$ 1.08
Discontinued operations (in dollars per share)	0	0	0	0
Earnings per Common Share - Basic (in dollars per share)	(0.52)	0.52	(0.64)	1.08
Earnings (loss) per common share attributable to Cliffs shareholders - diluted
Continuing operations (in dollars per share)	(0.52)	0.52	(0.64)	1.08
Discontinued operations (in dollars per share)	0	0	0	0
Earnings per Common Share - Diluted (in dollars per share)	$ (0.52)	$ 0.52	$ (0.64)	$ 1.08