Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,141	$ 828	$ 3,162	$ 2,511
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	(11)	(38)	18	(2)
Change in unrealized net gains (losses) on cash flow hedges	8	13	30	(80)
Change in unrealized net gains (losses) on AFS securities	(375)	118	1,267	769
Other, net	1	0	(1)	2
Total OCI, net of tax	(377)	93	1,314	689
Total comprehensive income	764	921	4,476	3,200
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	(4)	(11)	5	0
Change in unrealized net gains (losses) on cash flow hedges	2	4	9	(25)
Change in unrealized net gains (losses) on AFS securities	(114)	37	389	237
Other, net	$ 0	$ (1)	$ 0	$ 0