Proposed Separation Transaction - Additional Information (Detail) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)
Arconic Inc [Member]
Proposed Separation Transaction [Line Items]
Percentage of shares retained	19.90%	19.90%
Selling, General Administrative, and Other Expenses [Member]
Proposed Separation Transaction [Line Items]
Costs related to proposed transaction, pre-tax	$ 45	$ 63
Costs related to proposed transaction, after-tax	$ 37	$ 54

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant