CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 4,890	$ 4,179
Investment securities:
Net unrealized gain (loss)	58	15
Income tax effect	(12)	(3)
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	0	2
Income tax effect	0	(1)
Reclassification adjustments	3	1
Income tax effect	(1)	0
Derivative instruments:
Net unrealized gain (loss)	(77)	(116)
Income tax effect	16	14
Reclassification adjustments	39	(7)
Income tax effect	(9)	(4)
Foreign currency translation adjustments
Translation adjustments	588	1,209
Income tax effect	57	0
Other comprehensive income (loss)	662	1,110
Comprehensive income	$ 5,552	$ 5,289