Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Sales:	$ 1,253	$ 1,818	$ 2,887	$ 3,570
Segment operating profit	200	360	539	673
Operating Segments
Segment Reporting Information [Line Items]
Sales:	1,253	1,822	2,885	3,578
Total sales	1,256	1,828	2,893	3,592
Segment operating profit	200	360	539	673
Restructuring and other charges (credits)	42	445	76	461
Provision for depreciation and amortization	66	69	131	140
Capital expenditures	30	90	67	206
Inter-segment sales
Segment Reporting Information [Line Items]
Sales:	(3)	(6)	(8)	(14)
Engine Products
Segment Reporting Information [Line Items]
Sales:	585	835	1,366	1,648
Segment operating profit	105	163	270	304
Restructuring and other charges (credits)	22	250	35	253
Provision for depreciation and amortization	31	35	61	69
Capital expenditures	14	55	33	126
Engine Products | Operating Segments
Segment Reporting Information [Line Items]
Sales:	585	835	1,366	1,648
Total sales	586	838	1,369	1,656
Engine Products | Inter-segment sales
Segment Reporting Information [Line Items]
Sales:	(1)	(3)	(3)	(8)
Fastening Systems
Segment Reporting Information [Line Items]
Sales:	326	399	711	794
Segment operating profit	70	99	166	195
Restructuring and other charges (credits)	24	1	26	6
Provision for depreciation and amortization	12	12	24	24
Capital expenditures	7	8	15	17
Fastening Systems | Operating Segments
Segment Reporting Information [Line Items]
Sales:	326	399	711	794
Total sales	326	399	711	794
Fastening Systems | Inter-segment sales
Segment Reporting Information [Line Items]
Sales:	0	0	0	0
Engineered Structures
Segment Reporting Information [Line Items]
Sales:	229	331	504	625
Segment operating profit	19	25	47	41
Restructuring and other charges (credits)	(5)	193	12	197
Provision for depreciation and amortization	14	14	27	31
Capital expenditures	5	7	8	18
Engineered Structures | Operating Segments
Segment Reporting Information [Line Items]
Sales:	229	331	504	625
Total sales	231	334	509	631
Engineered Structures | Inter-segment sales
Segment Reporting Information [Line Items]
Sales:	(2)	(3)	(5)	(6)
Forged Wheels
Segment Reporting Information [Line Items]
Sales:	113	257	304	511
Segment operating profit	6	73	56	133
Restructuring and other charges (credits)	1	1	3	5
Provision for depreciation and amortization	9	8	19	16
Capital expenditures	4	20	11	45
Forged Wheels | Operating Segments
Segment Reporting Information [Line Items]
Sales:	113	257	304	511
Total sales	113	257	304	511
Forged Wheels | Inter-segment sales
Segment Reporting Information [Line Items]
Sales:	$ 0	$ 0	$ 0	$ 0