CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 1,941	$ 1,569
Investment securities, available-for-sale:
Net unrealized gain (loss)	34	(10)
Income tax effect	(16)	3
Reclassification adjustment for net gain realized in net income	0	(21)
Income tax effect	0	8
Defined benefit pension and other postretirement plans:
Net unrealized actuarial gain and prior service credit	56	6
Income tax effect	(21)	(1)
Amortization of actuarial loss and prior service credit realized in net income	(7)	(1)
Income tax effect	2	0
Derivative instruments classified as cash flow hedges:
Net unrealized gain	16	63
Income tax effect	(5)	(17)
Reclassification adjustment for net gain realized in net income	(48)	(6)
Income tax effect	14	2
Foreign currency translation adjustments	0	1
Other comprehensive income, net of tax	25	27
Comprehensive income	$ 1,966	$ 1,596