Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 839	$ 648	$ 2,452	$ 1,748
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	(12)	8	15	29
Change in unrealized net gains (losses) on cash flow hedges	20	9	124	(27)
Change in unrealized net gains (losses) on AFS securities	(155)	18	(522)	90
Other, net	1	2	(2)	4
Total OCI	(146)	37	(385)	96
Total comprehensive income	693	685	2,067	1,844
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	(5)	3	4	17
Change in unrealized net gains (losses) on cash flow hedges	6	5	40	(16)
Change in unrealized net gains (losses) on AFS securities	(48)	9	(163)	51
Other, net	$ 0	$ 0	$ 1	$ 0