Segment Information - Schedule of Assets by Segment (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 17,816	$ 12,059
Corporate, reconciling items, and eliminations (b)
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	(1,489)	(2,340)
Flat-Rolled
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	7,337	7,099
Mini Mill (a)
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,715	0
Mini Mill #2
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	347
USSE
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,111	5,502
Tubular
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,054	887
Total reportable segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,217	13,488
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 88	$ 911