Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total sales	$ 3,524	$ 3,236	$ 10,542	$ 9,689
Segment operating profit	389	377	1,221	1,282
Restructuring and other charges	17	14	27	111
Provision for depreciation and amortization	133	133	403	388
Operating Segments
Segment Reporting Information [Line Items]
Total sales	3,556	3,270	10,697	9,792
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	34	36	122	107
Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	3,522	3,234	10,575	9,685
Engineered Products and Solutions
Segment Reporting Information [Line Items]
Segment operating profit	238	239	671	736
Restructuring and other charges	15	10	25	24
Provision for depreciation and amortization	71	68	212	198
Engineered Products and Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,566	1,477	4,703	4,449
Engineered Products and Solutions | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	0	0	0	0
Engineered Products and Solutions | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,566	1,477	4,703	4,449
Global Rolled Products
Segment Reporting Information [Line Items]
Segment operating profit	74	64	309	333
Restructuring and other charges	2	2	2	76
Provision for depreciation and amortization	50	52	154	153
Global Rolled Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,460	1,270	4,365	3,860
Global Rolled Products | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	34	36	122	107
Global Rolled Products | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,426	1,234	4,243	3,753
Transportation and Construction Solutions
Segment Reporting Information [Line Items]
Segment operating profit	77	74	241	213
Restructuring and other charges	0	2	0	11
Provision for depreciation and amortization	12	13	37	37
Transportation and Construction Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales	530	523	1,629	1,483
Transportation and Construction Solutions | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	0	0	0	0
Transportation and Construction Solutions | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	$ 530	$ 523	$ 1,629	$ 1,483