Restructuring and Other Charges - 2015 Actions (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 divestiture
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 165	$ 155	$ 214
Restructuring and other charges after tax and noncontrolling interest	143	114	192
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	11	23	39
Divested Businesses
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges after tax and noncontrolling interest	41
Number of plant divestitures | divestiture				3
Divested Businesses | Global Rolled Products
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			136
Restructuring and other charges after tax and noncontrolling interest			134
Restructuring Programs Layoffs Two Thousand Fourteen
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			97
Restructuring and other charges after tax and noncontrolling interest			$ 70
Number of positions | employee			1,505
Restructuring Programs Layoffs Two Thousand Fourteen | Corporate
Restructuring Cost and Reserve [Line Items]
Number of positions | employee			400
Restructuring Programs Layoffs Two Thousand Fourteen | Global Rolled Products
Restructuring Cost and Reserve [Line Items]
Number of positions | employee			90
Restructuring Programs Layoffs Two Thousand Fourteen | Engineered Products and Solutions
Restructuring Cost and Reserve [Line Items]
Number of positions | employee			590
Restructuring Programs Layoffs Two Thousand Fourteen | Transportation and Construction Solutions
Restructuring Cost and Reserve [Line Items]
Number of positions | employee			425
Restructuring Programs Layoffs 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges for layoffs	5	55	$ 18
Shutdown and Curtailment Actions
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		37
Restructuring and other charges after tax and noncontrolling interest		24
Shutdown and Curtailment Actions | Australia
Restructuring Cost and Reserve [Line Items]
Gain on sale of land			18
Gain on sale of land after tax			13
Other Miscellaneous Charges
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	12	11	7
Restructuring and other charges after tax and noncontrolling interest		8	4
Other Adjustments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ (11)	25	8
Restructuring and other charges after tax and noncontrolling interest		$ 12	$ 3