Accumulated Other Comprehensive Income (Loss) - Components and Changes of Accumulated Other Comprehensive Income (Loss) (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2017 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2017	$ (1,723)
Other comprehensive loss before reclassifications, net of taxes	(36)
Amounts reclassified into income, net of taxes	18
Balance at December 31, 2017	(1,740)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2017	(1,001)
Other comprehensive loss before reclassifications, net of taxes	(36)
Amounts reclassified into income, net of taxes	0
Balance at December 31, 2017	(1,037)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2017	(703)
Other comprehensive loss before reclassifications, net of taxes	0
Amounts reclassified into income, net of taxes	17
Balance at December 31, 2017	(686)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at September 30, 2017	(18)
Other comprehensive loss before reclassifications, net of taxes	0
Amounts reclassified into income, net of taxes	1
Balance at December 31, 2017	$ (17)