Quarterly Data (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
Segment Reporting Information [Line Items]
Sales	$ 3,401	$ 3,559	$ 3,691	$ 3,541	$ 3,472	$ 3,524	$ 3,573	$ 3,445	$ 14,192	$ 14,014	$ 12,960
Net income (loss)	$ 309	$ 95	$ (121)	$ 187	$ 218	$ 161	$ 120	$ 143	$ 470	$ 642	$ (74)
Basic
Net loss per share-basic (in usd per share)	$ 0.71	$ 0.22	$ (0.27)	$ 0.40	$ 0.45	$ 0.33	$ 0.25	$ 0.30	$ 1.05	$ 1.33	$ (0.28)
Diluted
Net loss per share-diluted (in usd per share)	$ 0.70	$ 0.21	$ (0.27)	$ 0.39	$ 0.44	$ 0.32	$ 0.24	$ 0.29	$ 1.03	$ 1.30
Restructuring and other charges									$ 620	$ 9	$ 165
Costs related to separation transaction, after-tax	$ 28
Costs related to separation transaction, pre-tax	34
Gain on disposition of assets, after tax										81
Gain (loss) on disposition of assets, before tax									(7)	(10)	513
Gain (loss) on disposition of business									20	109	(57)
Payment for pension benefits, net of tax					$ 72
Payment for pension benefits					92				268	298	$ 310
Texarkana, Texas Rolling Mill
Diluted
Gain on disposition of assets, after tax	15				119				17
Gain (loss) on disposition of assets, before tax	$ 20								20	154
Gain (loss) on disposition of business					154
Eger
Diluted
Gain on disposition of assets, after tax					(39)
Gain (loss) on disposition of business					$ (43)				(43)	$ (43)
Impairment Of Disks
Diluted
Restructuring and other charges			$ 428						$ 428