Stockholders' Equity - Schedule of Activity in Noncontrolling Interests (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Equity [Abstract]
Balance at September 30			$ 104	$ 122
Net income attributable to noncontrolling interests	$ 4	$ 1	8	5
Noncontrolling interest foreign currency translation adjustment	1	(1)	(2)	(3)
Noncontrolling interest dividends declared			(16)	(13)
Balance at March 31	$ 94	$ 111	$ 94	$ 111