CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 3,101	$ 2,329	$ 9,055	$ 7,456
Investment securities:
Net unrealized gain (loss)	5	45	20	95
Income tax effect	(1)	(10)	(5)	(22)
Reclassification adjustments	1	(24)	1	(52)
Income tax effect	0	6	0	16
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	(1)	0	(8)	(2)
Income tax effect	0	0	1	1
Reclassification adjustments	2	4	2	4
Income tax effect	0	(1)	0	(1)
Derivative instruments:
Net unrealized gain (loss)	(68)	114	29	72
Income tax effect	14	(19)	(9)	(22)
Reclassification adjustments	(22)	10	(69)	45
Income tax effect	4	0	13	(5)
Foreign currency translation adjustments	262	(1,112)	(419)	(266)
Other comprehensive income (loss), net of tax	196	(987)	(444)	(137)
Comprehensive income	$ 3,297	$ 1,342	$ 8,611	$ 7,319