Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 822	$ 674	$ 1,613	$ 1,100
OCI, net of tax:
Change in unrecognized net pension and postretirement costs	13	12	27	21
Change in unrealized net gains (losses) on cash flow hedges	26	(34)	104	(36)
Change in unrealized net gains (losses) on AFS securities	(99)	74	(367)	72
Other, net	(1)	0	(3)	2
Total OCI	(61)	52	(239)	59
Total comprehensive income	761	726	1,374	1,159
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	5	7	9	14
Change in unrealized net gains (losses) on cash flow hedges	8	(20)	34	(21)
Change in unrealized net gains (losses) on AFS securities	(31)	43	(115)	42
Other, net	$ 0	$ 0	$ 1	$ 0