Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) - Components and Changes of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	$ (2,088)	$ (2,548)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	34	115
Amounts reclassified into income, net of taxes	11	19
Accumulated other comprehensive income (loss), net of tax, ending balance	(2,043)	(2,414)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(1,292)	(1,416)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	41	64
Amounts reclassified into income, net of taxes	0	0
Accumulated other comprehensive income (loss), net of tax, ending balance	(1,251)	(1,352)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(784)	(1,040)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	24
Amounts reclassified into income, net of taxes	11	18
Accumulated other comprehensive income (loss), net of tax, ending balance	(774)	(998)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(10)	(91)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(7)	27
Amounts reclassified into income, net of taxes	0	2
Accumulated other comprehensive income (loss), net of tax, ending balance	$ (17)	$ (62)