Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 798	$ 791
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	17	14
Change in unrealized net gains (losses) on cash flow hedges	(34)	78
Change in unrealized net gains (losses) on AFS securities	309	(268)
Other, net	2	(2)
Total OCI	294	(178)
Total comprehensive income	1,092	613
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	6	4
Change in unrealized net gains (losses) on cash flow hedges	(11)	26
Change in unrealized net gains (losses) on AFS securities	95	(84)
Other, net	$ 0	$ 1