Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 958	$ 885	$ 2,021	$ 1,683
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	14	19	29	36
Change in unrealized net gains (losses) on cash flow hedges	11	(59)	22	(93)
Change in unrealized net gains (losses) on AFS securities	(79)	342	1,642	651
Other, net	3	0	(2)	2
Total OCI, net of tax	(51)	302	1,691	596
Total comprehensive income	907	1,187	3,712	2,279
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	4	5	9	11
Change in unrealized net gains (losses) on cash flow hedges	4	(18)	7	(29)
Change in unrealized net gains (losses) on AFS securities	(24)	105	503	200
Other, net	$ 0	$ 1	$ 0	$ 1