Restructuring and Other Charges - 2018 Actions (Details) $ in Millions		3 Months Ended	12 Months Ended
	Oct. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) position	Dec. 31, 2018 USD ($) position	Dec. 31, 2017 USD ($) position	Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 9	$ 165	$ 155
Restructuring and other charges after tax			9	143	114
Gain on disposition of assets, after tax			81
Gain (loss) on disposition of business, before tax			109	(57)	(3)
Gain (loss) on disposition of assets, before tax			(10)	$ 513	(11)
Number of employees associated with layoff costs | position				880
Cash payments for restructuring			49	$ 65	86
Engineered Products and Solutions
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | position				400
Corporate Segment
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | position				100
Pension Settlement Cost
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 96	96		2
Restructuring and other charges after tax			75		1
Pension Curtailment Charge
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			23
Restructuring and other charges after tax and noncontrolling interests			18
Postretirement Curtailment Benefit
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			28
Restructuring and other charges after tax			22
Restructuring Programs Layoffs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			20
Restructuring and other charges after tax			$ 17
Restructuring Programs Layoffs Two Thousand Eighteen
Restructuring Cost and Reserve [Line Items]
Approximate number of employees already laid off | position		110	110
Number of employees associated with layoff costs | position			125
Cash payments for restructuring			$ 9
Restructuring Programs Layoffs Two Thousand Eighteen | Engineered Products and Solutions
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | position			89
Restructuring Programs Layoffs Two Thousand Eighteen | Corporate Segment
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | position			36
Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 12
Restructuring and other charges after tax			9
Other Adjustments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			8	$ (11)	25
Restructuring and other charges after tax and noncontrolling interests			4	(8)
Restructuring and other charges after tax					12
Other Exit Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			19	69	57
Restructuring and other charges after tax			15	47	46
Cash payments for restructuring			2	$ 6	$ 13
Texarkana, Texas Rolling Mill And Cast House
Restructuring Cost and Reserve [Line Items]
Gain on disposition of assets, after tax			119
Gain (loss) on disposition of business, before tax	$ 154
Texarkana, Texas Rolling Mill
Restructuring Cost and Reserve [Line Items]
Gain on disposition of assets, after tax		$ 119
Gain (loss) on disposition of business, before tax		154
Gain (loss) on disposition of assets, before tax			154
Eger
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges after tax			39
Gain on disposition of assets, after tax		(39)
Gain (loss) on disposition of business, before tax		$ (43)	(43)
New York office | Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			6
Restructuring and other charges after tax			$ 4