Segment and Geographic Area Information - Schedule of Operating Results of Arconic's Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total sales	$ 3,271	$ 3,236	$ 3,261	$ 3,192	$ 2,967	$ 3,138	$ 3,234	$ 3,055	$ 12,960	$ 12,394	$ 12,413
Depreciation and amortization									523	504	479
Adjusted EBITDA									2,144	2,063	1,894
Capital expenditures									543	689
Goodwill	4,202				4,817				4,202	4,817
Total assets	15,499				15,415				15,499	15,415
Operating Segments
Segment Reporting Information [Line Items]
Total sales									13,060	12,512	12,602
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment sales									148	118	125
Total sales									(148)	(118)	(125)
Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information Revenues From External Customers									12,912	12,394	12,477
Engineered Products and Solutions
Segment Reporting Information [Line Items]
Depreciation and amortization									268	255	233
Adjusted EBITDA									1,224	1,195	1,111
Capital expenditures									308	333
Goodwill	3,949				4,579				3,949	4,579
Total assets	10,252				10,542				10,252	10,542
Engineered Products and Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales									5,935	5,728	5,342
Engineered Products and Solutions | Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment sales									0	0	0
Engineered Products and Solutions | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information Revenues From External Customers									5,935	5,728	5,342
Global Rolled Products
Segment Reporting Information [Line Items]
Depreciation and amortization									205	201	203
Adjusted EBITDA									599	577	512
Capital expenditures									178	293
Goodwill	193				181				193	181
Total assets	4,179				3,891				4,179	3,891
Global Rolled Products | Operating Segments
Segment Reporting Information [Line Items]
Total sales									5,140	4,982	5,378
Global Rolled Products | Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment sales									148	118	125
Global Rolled Products | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information Revenues From External Customers									4,992	4,864	5,253
Transportation and Construction Solutions
Segment Reporting Information [Line Items]
Depreciation and amortization									50	48	43
Adjusted EBITDA									321	291	271
Capital expenditures									57	63
Goodwill	60				57				60	57
Total assets	$ 1,068				$ 982				1,068	982
Transportation and Construction Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total sales									1,985	1,802	1,882
Transportation and Construction Solutions | Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment sales									0	0	0
Transportation and Construction Solutions | Third-Party Sales | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information Revenues From External Customers									$ 1,985	$ 1,802	$ 1,882