CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 2,373	$ 3,101	$ 8,729	$ 9,055
Investment securities:
Net unrealized gain (loss)	(3)	5	2	20
Income tax effect	1	(1)	0	(5)
Reclassification adjustments	(1)	1	(3)	1
Income tax effect	1	0	1	0
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	0	(1)	2	(8)
Income tax effect	0	0	(1)	1
Reclassification adjustments	9	2	15	2
Income tax effect	(2)	0	(3)	0
Derivative instruments:
Net unrealized gain (loss)	(106)	(68)	(247)	29
Income tax effect	23	14	54	(9)
Reclassification adjustments	(43)	(22)	(58)	(69)
Income tax effect	9	4	13	13
Foreign currency translation adjustments	277	262	621	(419)
Other comprehensive income (loss), net of tax	165	196	396	(444)
Comprehensive income	$ 2,538	$ 3,297	$ 9,125	$ 8,611