SEGMENT REPORTING - Net Income (Loss) to Total Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Net income (loss)	$ (230)			$ 275	$ (274)	$ 589
Interest expense, net	(102)			(70)	(235)	(226)
Income tax benefit (expense)	76			(29)	99	(118)
Depreciation, depletion and amortization	(235)			(249)	(693)	(738)
EBITDA	31			623	555	1,671
Weirton indefinite idle	(2)	$ (40)	$ (170)
Loss on extinguishment of debt	0			0	(27)	0
Acquisition-related costs	(14)			(5)	(14)	(5)
Changes in fair value of foreign currency contracts, net	(7)			0	(7)	0
Adjusted EBITDA	124			614	861	1,632
Net income attributable to noncontrolling interests	12			11	33	35
EBITDA Calculation
Segment Reporting Information [Line Items]
Interest expense, net	(102)			(70)	(235)	(226)
Income tax benefit (expense)	76			(29)	99	(118)
Depreciation, depletion and amortization	(235)			(249)	(693)	(738)
Adjusted EBITDA Calculation
Segment Reporting Information [Line Items]
EBITDA of noncontrolling interests	20			20	56	60
Weirton indefinite idle	(2)			0	(219)	0
Loss on extinguishment of debt	0			0	(27)	0
Acquisition-related costs	(14)			(3)	(14)	(5)
Changes in fair value of foreign currency contracts, net	(7)			0	(7)	0
Arbitration decision	71			0	71	0
Other, net	(19)			(8)	(24)	(16)
Net income attributable to noncontrolling interests	12			11	33	35
Depreciation, depletion and amortization attributable to noncontrolling interests	$ 8			$ 9	$ 23	$ 25