Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 3,257	$ 2,415	$ 2,442
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	(160)	(84)	(41)
Change in unrealized net gains (losses) on cash flow hedges	61	18	(9)
Change in unrealized net gains (losses) on AFS securities	(144)	(27)	(225)
Other, net	(5)	5	171
Total OCI	(248)	(88)	(104)
Total comprehensive income	3,009	2,327	2,338
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	(50)	(15)	(20)
Change in unrealized net gains (losses) on cash flow hedges	20	7	(4)
Change in unrealized net gains (losses) on AFS securities	(45)	(27)	(130)
Other, net	$ 1	$ 0	$ 99