Acquisitions and Divestitures - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended			0 Months Ended	1 Months Ended
	Jun. 25, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 25, 2014	Jun. 25, 2014 Firth Rixson [Member]	Aug. 31, 2014 Firth Rixson [Member]	Jun. 25, 2014 Firth Rixson [Member]
Business Acquisition [Line Items]
Business acquisition purchase price							$ 2,850
Cash paid for business acquisition							2,350
Value of common stock issued							500
Business acquisition potential earn-out									150
Common stock issued as part of acquisition	36,523,010						36,523,010
Business acquisition common stock issued, price per share						$ 13.69			$ 13.69
Business acquisition, unsecured bridge term loan									2,500
Interest expenses		126	108	351	341		13
Interest expenses, after tax							8
Percentage of acquisition of outstanding noncontrolling interest								30.00%
Acquisition of outstanding noncontrolling interest, amount paid								28
Difference between purchase price and carrying value of noncontrolling interest								$ 3