Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 1,473	$ 1,063
OCI, net of tax:
Net change in net pension and postretirement costs	35	15
Net change in cash flow hedges	36	11
Net change in AFS securities	(2,304)	1,721
Other, net	1	(5)
Total OCI, net of tax	(2,232)	1,742
Total comprehensive income	(759)	2,805
Income Tax Effect of Items Included in OCI:
Net change in net pension and postretirement costs	11	5
Net change in cash flow hedges	11	3
Net change in AFS securities	(707)	527
Total income taxes related to OCI	$ (685)	$ 535