Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales:	$ 1,134	$ 1,794	$ 4,021	$ 5,364
Segment operating profit	73	256	405	294
Restructuring and other charges	22	56	166	572
Provision for depreciation and amortization	68	70	212	224
Capital expenditures	36	127	220	532
Third-party sales
Segment Reporting Information [Line Items]
Sales:	1,134	1,794	4,019	5,372
Intersegment sales
Segment Reporting Information [Line Items]
Sales:	(2)	(5)	(10)	(19)
Operating Segments
Segment Reporting Information [Line Items]
Sales:	1,136	1,799	4,029	5,391
Segment operating profit	117	363	656	1,036
Restructuring and other charges	18	44	94	505
Provision for depreciation and amortization	66	66	197	206
Capital expenditures	33	61	100	267
Engine Products \| Third-party sales
Segment Reporting Information [Line Items]
Sales:	485	844	1,851	2,492
Engine Products \| Intersegment sales
Segment Reporting Information [Line Items]
Sales:	(1)	(1)	(4)	(9)
Engine Products \| Operating Segments
Segment Reporting Information [Line Items]
Sales:	486	845	1,855	2,501
Segment operating profit	39	161	309	465
Restructuring and other charges	9	43	44	296
Provision for depreciation and amortization	31	31	92	100
Capital expenditures	15	39	48	165
Fastening Systems \| Third-party sales
Segment Reporting Information [Line Items]
Sales:	271	391	982	1,185
Fastening Systems \| Intersegment sales
Segment Reporting Information [Line Items]
Sales:	0	0	0	0
Fastening Systems \| Operating Segments
Segment Reporting Information [Line Items]
Sales:	271	391	982	1,185
Segment operating profit	33	102	199	297
Restructuring and other charges	0	0	26	6
Provision for depreciation and amortization	12	12	36	36
Capital expenditures	9	7	24	24
Engineered Structures \| Third-party sales
Segment Reporting Information [Line Items]
Sales:	206	318	710	943
Engineered Structures \| Intersegment sales
Segment Reporting Information [Line Items]
Sales:	(1)	(4)	(6)	(10)
Engineered Structures \| Operating Segments
Segment Reporting Information [Line Items]
Sales:	207	322	716	953
Segment operating profit	10	40	57	81
Restructuring and other charges	9	1	21	198
Provision for depreciation and amortization	13	15	40	46
Capital expenditures	3	4	11	22
Forged Wheels \| Third-party sales
Segment Reporting Information [Line Items]
Sales:	172	241	476	752
Forged Wheels \| Intersegment sales
Segment Reporting Information [Line Items]
Sales:	0	0	0	0
Forged Wheels \| Operating Segments
Segment Reporting Information [Line Items]
Sales:	172	241	476	752
Segment operating profit	35	60	91	193
Restructuring and other charges	0	0	3	5
Provision for depreciation and amortization	10	8	29	24
Capital expenditures	$ 6	$ 11	$ 17	$ 56

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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