CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 4,663	$ 4,257	$ 9,553	$ 8,436
Investment securities:
Net unrealized gain (loss)	(8)	36	50	51
Income tax effect	1	(8)	(11)	(11)
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	8	3	8	5
Income tax effect	(2)	0	(2)	(1)
Reclassification adjustments	3	3	6	4
Income tax effect	(1)	0	(2)	0
Derivative instruments:
Net unrealized gain (loss)	58	(75)	(19)	(191)
Income tax effect	(7)	17	9	31
Reclassification adjustments	(6)	6	33	(1)
Income tax effect	1	(3)	(8)	(7)
Foreign currency translation adjustments:
Translation adjustments	(357)	290	231	1,499
Income tax effect	(33)	0	24	0
Other comprehensive income (loss)	(343)	269	319	1,379
Comprehensive income	$ 4,320	$ 4,526	$ 9,872	$ 9,815