Segment and Geographic Area Information - Schedule of Segment Operating Profit to Consolidated Net Income (Loss) Income Attributable to Arconic (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total segment operating profit			$ 1,581,000,000	$ 1,678,000,000	$ 1,622,000,000
Impairment of goodwill	$ 0		0	719,000,000	0
Restructuring and other charges			(9,000,000)	(165,000,000)	(155,000,000)
Operating income			1,325,000,000	480,000,000	954,000,000
Interest expense		$ (24,000,000)	(378,000,000)	(496,000,000)	(499,000,000)
Other (expense) income, net			(79,000,000)	486,000,000	(41,000,000)
Income from continuing operations before income taxes			868,000,000	470,000,000	414,000,000
Segment Reconciling Item
Segment Reporting Information [Line Items]
Impairment of goodwill			0	(719,000,000)	0
Restructuring and other charges			(9,000,000)	(165,000,000)	(155,000,000)
Corporate expense			(247,000,000)	(314,000,000)	(513,000,000)
Operating income			1,325,000,000	480,000,000	954,000,000
Interest expense			(378,000,000)	(496,000,000)	(499,000,000)
Other (expense) income, net			(79,000,000)	486,000,000	(41,000,000)
Income from continuing operations before income taxes			$ 868,000,000	$ 470,000,000	$ 414,000,000