CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 3,272	$ 2,977
Investment securities:
Net unrealized gain (loss)	0	8
Income tax effect	0	(2)
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain (loss) and prior service credit (cost)	(1)	(7)
Income tax effect	0	1
Reclassification adjustments	4	0
Income tax effect	(1)	0
Derivative instruments:
Net unrealized gain (loss)	(188)	38
Income tax effect	39	(10)
Reclassification adjustments	(2)	(25)
Income tax effect	1	5
Foreign currency translation adjustments	483	(287)
Other comprehensive income (loss), net of tax	335	(279)
Comprehensive income	$ 3,607	$ 2,698