Segment Information - Schedule of Reconciling Items to EBIT (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	$ 4,946	$ (1,075)	$ (230)
Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	145	(270)	(325)
Restructuring and other charges (Note 25) | Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	(128)	(138)	(275)
Asset impairment charges | Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	(273)	(287)	0
Big River Steel - acquisition-related items | Reconciling Items and Eliminations | Big River Steel
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	(35)	(3)	0
Losses (gains) on assets sold & previously held investments | Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	118	170	0
Gain on sale of Transtar (Note 5) | Reconciling Items and Eliminations | Transtar, LLC
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	506	0	0
Environmental remediation charges | Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	(43)	0	0
Other items | Reconciling Items and Eliminations
Other items not allocated to segments:
Earnings (loss) before interest and income taxes	$ 0	$ (12)	$ (50)