Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total sales	$ 3,573	$ 3,261	$ 7,018	$ 6,453
Segment operating profit	432	454	832	905
Restructuring and other charges	10	31	10	97
Provision for depreciation and amortization	135	129	270	255
Operating Segments
Segment Reporting Information [Line Items]
Total sales	3,655	3,297	7,141	6,522
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	46	37	88	71
Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	3,609	3,260	7,053	6,451
Engineered Products and Solutions
Segment Reporting Information [Line Items]
Segment operating profit	212	250	433	497
Restructuring and other charges	9	8	10	14
Provision for depreciation and amortization	70	66	141	130
Engineered Products and Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,596	1,485	3,137	2,972
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	1,596	1,485	3,137	2,972
Global Rolled Products
Segment Reporting Information [Line Items]
Segment operating profit	123	133	235	269
Restructuring and other charges	1	17	0	74
Provision for depreciation and amortization	53	51	104	101
Global Rolled Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,497	1,308	2,905	2,590
Global Rolled Products | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales	46	37	88	71
Global Rolled Products | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Total sales	1,451	1,271	2,817	2,519
Transportation and Construction Solutions
Segment Reporting Information [Line Items]
Segment operating profit	97	71	164	139
Restructuring and other charges	0	6	0	9
Provision for depreciation and amortization	12	12	25	24
Transportation and Construction Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales	562	504	1,099	960
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	$ 562	$ 504	$ 1,099	$ 960