Cash Flow Information - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Jul. 31, 2015	Mar. 31, 2015	Nov. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule Of Common Stock [Line Items]
Common stock conversion transaction value						$ 870	$ 610
Principal amount of convertible notes						$ 9,065	8,798	$ 1,250
Convertible notes due date						Jul. 25, 2019
Number of shares, option exercised						23,300,000
Business acquisition purchase price						$ (97)	2,385
Firth Rixson [Member]
Schedule Of Common Stock [Line Items]
Common stock shares issued for conversion transaction				36,523,010
Business acquisition purchase price							$ 2,995
Issuance of common stock			37,000,000				37,000,000
Common stock value							$ 610
RTI [Member]
Schedule Of Common Stock [Line Items]
Common stock conversion transaction value	$ 870	$ 870
Common stock shares issued for conversion transaction	87,000,000	87,397,414
5.25% Convertible Notes Due 2014 [Member]
Schedule Of Common Stock [Line Items]
Principal amount of convertible notes					$ 575		$ 575
Convertible notes, interest rate					5.25%		5.25%
Convertible notes due date					Mar. 15, 2014		Mar. 15, 2014
Number of shares, option exercised					89,000,000		89,000,000