CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 4,577	$ 4,663	$ 9,696	$ 9,553
Investment securities:
Net unrealized gain (loss)	4	(8)	(20)	50
Income tax effect	(2)	1	4	(11)
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	6	8	6	8
Income tax effect	(1)	(2)	(1)	(2)
Reclassification adjustments	2	3	3	6
Income tax effect	0	(1)	0	(2)
Derivative instruments:
Net unrealized gain (loss)	(130)	58	38	(19)
Income tax effect	23	(7)	(2)	9
Reclassification adjustments	10	(6)	(32)	33
Income tax effect	(4)	1	3	(8)
Foreign currency translation adjustments:
Translation adjustments	459	(357)	(476)	231
Income tax effect	53	(33)	(42)	24
Other comprehensive income (loss)	420	(343)	(519)	319
Comprehensive income	$ 4,997	$ 4,320	$ 9,177	$ 9,872