Stockholders' Equity - Schedule of Activity in Noncontrolling Interests (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Balance at September 30			$ 98	$ 104
Net income (loss) attributable to noncontrolling interests, net of tax	$ 6	$ 4	10	8
Noncontrolling interest foreign currency translation adjustment	1	1	(3)	(2)
Noncontrolling interest dividends declared			(14)	(16)
Contribution from noncontrolling interest			2
Balance at March 31	$ 93	$ 94	$ 93	$ 94