Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			$ 25	$ 58	$ 59
Cash payments			(79)	(49)	(65)
Restructuring charges			630	124	65
Other			(542)	(108)	(1)
Restructuring reserve ending balance	$ 34		34	25	58
Restructuring and other charges			620	9	165
Gain (loss) on disposition of assets, before tax			(7)	(10)	513
Layoff costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			10	56	50
Cash payments			(74)	(47)	(59)
Restructuring charges			56	111	64
Other			39	(110)	1
Restructuring reserve ending balance	31		31	10	56
Restructuring and other charges			(10)
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			15	2	9
Cash payments			(5)	(2)	(6)
Restructuring charges			574	13	1
Other			(581)	2	(2)
Restructuring reserve ending balance	3		3	15	2
Restructuring and other charges			26	19	69
Reclassification of a stock awards reversal
Restructuring Reserve [Roll Forward]
Restructuring and other charges					13
Reversal of prior restructuring charges
Restructuring Reserve [Roll Forward]
Restructuring and other charges			10	19	11
Effects of foreign currency translation and other
Restructuring Reserve [Roll Forward]
Restructuring charges foreign currency translation					1
Reclassification of pension costs
Restructuring Reserve [Roll Forward]
Restructuring and other charges				119
Credit in post-retirement costs
Restructuring Reserve [Roll Forward]
Restructuring and other charges				28
Elimination Of Life Insurance Benefits
Restructuring Reserve [Roll Forward]
Restructuring and other charges			(58)
Other, Pension Settlement Cost
Restructuring Reserve [Roll Forward]
Restructuring and other charges			9
Impairment Of Disks
Restructuring Reserve [Roll Forward]
Restructuring and other charges		$ 428	428
Asset Impairment Associated With The Sale Of Business
Restructuring Reserve [Roll Forward]
Restructuring and other charges			112
Impairment For Trade Name Intangible Asset And Fixed Assets
Restructuring Reserve [Roll Forward]
Restructuring and other charges			25
Other Exit Cost Lease Termination Loss
Restructuring Reserve [Roll Forward]
Restructuring and other charges			12
Other Exit Costs, Other, Accelerated Depreciation
Restructuring Reserve [Roll Forward]
Restructuring and other charges			9
Impairment Of A Cost Method Investment
Restructuring Reserve [Roll Forward]
Restructuring and other charges			5
Other Miscellaneous Charges
Restructuring Reserve [Roll Forward]
Restructuring and other charges			1		$ 12
Other Exit Costs, Reclassification Of Lease Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring and other charges			(9)
Texarkana, Texas Rolling Mill
Restructuring Reserve [Roll Forward]
Gain (loss) on disposition of assets, before tax	$ 20		$ 20	$ 154