Accumulated Other Comprehensive Income (Loss) - Components and Changes of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2016			$ (1,929)
Other comprehensive (loss) income before reclassifications, net of taxes			(44)
Amounts reclassified into income, net of taxes			50
Balance at June 30, 2017	$ (1,923)		(1,923)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2016			(1,011)
Other comprehensive (loss) income before reclassifications, net of taxes			(52)
Amounts reclassified into income, net of taxes			0
Balance at June 30, 2017	(1,064)		(1,064)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2016			(883)
Other comprehensive (loss) income before reclassifications, net of taxes			0
Amounts reclassified into income, net of taxes	15	$ 12	44	$ 36
Balance at June 30, 2017	(839)		(839)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2016			(35)
Other comprehensive (loss) income before reclassifications, net of taxes			8
Amounts reclassified into income, net of taxes	1	$ 3	7	$ 9
Balance at June 30, 2017	$ (20)		$ (20)