CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 3,647	$ 3,026	$ 7,606	$ 6,152
Investment securities:
Net unrealized gain (loss)	(40)	(1)	(50)	(2)
Income tax effect	8	0	10	0
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	(2)	(2)	(1)	(3)
Income tax effect	0	1	0	2
Reclassification adjustments	1	3	2	6
Income tax effect	0	0	0	(1)
Derivative instruments:
Net unrealized gain (loss)	77	280	191	(17)
Income tax effect	(13)	(57)	(35)	6
Reclassification adjustments	(33)	5	(39)	(13)
Income tax effect	4	0	4	5
Foreign currency translation adjustments	(335)	(1,011)	(923)	35
Other comprehensive income (loss), net of tax	(333)	(782)	(841)	18
Comprehensive income	$ 3,314	$ 2,244	$ 6,765	$ 6,170