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Segment and Geographic Area Information - Sales by Major Product Grouping (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Product Information [Line Items]
Consolidated sales	$ 2,967	$ 3,138	$ 3,234	$ 3,055	$ 2,991	$ 3,127	$ 3,204	$ 3,091	$ 12,394	$ 12,413	$ 12,542
Flat-Rolled Aluminum [Member]
Product Information [Line Items]
Consolidated sales									4,864	5,253	6,344
Investment Castings [Member]
Product Information [Line Items]
Consolidated sales									1,870	1,812	1,784
Alcoa Fastening Systems and Rings [Member]
Product Information [Line Items]
Consolidated sales									2,060	2,168	1,647
Architectural Aluminum Systems [Member]
Product Information [Line Items]
Consolidated sales									1,010	951	1,002
Aluminum Wheels [Member]
Product Information [Line Items]
Consolidated sales									689	790	786
Other Extruded and Forged Products [Member]
Product Information [Line Items]
Consolidated sales									1,495	1,332	1,019
Other [Member]
Product Information [Line Items]
Consolidated sales									$ 406	$ 107	$ (40)

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+ References

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- Definition

Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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