Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 3,237	$ 3,257	$ 2,415
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	42	(160)	(84)
Change in unrealized net gains (losses) on cash flow hedges	(70)	61	18
Change in unrealized net gains (losses) on AFS securities	880	(144)	(27)
Other, net	19	(5)	5
Total OCI, net of tax	871	(248)	(88)
Total comprehensive income	4,108	3,009	2,327
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	11	(50)	(15)
Change in unrealized net gains (losses) on cash flow hedges	(21)	20	7
Change in unrealized net gains (losses) on AFS securities	271	(45)	(27)
Other, net	$ 5	$ 1	$ 0