Accumulated Other Comprehensive Income (Loss) - (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2015			$ (1,738)
Other comprehensive income before reclassifications, net of taxes			61
Amounts reclassified into income, net of taxes			30
Balance at March 31, 2016	$ (1,647)		(1,647)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2015			(961)
Other comprehensive income before reclassifications, net of taxes			63
Amounts reclassified into income, net of taxes			0
Balance at March 31, 2016	(899)		(899)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2015			(741)
Other comprehensive income before reclassifications, net of taxes			0
Amounts reclassified into income, net of taxes	12	$ 11	24	$ 22
Balance at March 31, 2016	(717)		(717)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2015			(36)
Other comprehensive income before reclassifications, net of taxes			(2)
Amounts reclassified into income, net of taxes	3	$ 2	6	$ 3
Balance at March 31, 2016	$ (32)		$ (32)