Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 2,415	$ 2,442	$ 2,123
OCI, Net of Tax:
Change in unrecognized net pension and postretirement costs	(84)	(41)	(97)
Change in unrealized net gains (losses) on cash flow hedges	18	(9)	(29)
Change in unrealized net gains (losses) on AFS securities	(27)	(225)	(186)
Change in FDIC's share of unrealized gains/losses on AFS securities	0	169	38
Other, net	5	2	(3)
Total OCI	(88)	(104)	(277)
Total comprehensive income	2,327	2,338	1,846
Income Tax Effect of Items Included in OCI:
Change in unrecognized net pension and postretirement costs	(15)	(20)	(59)
Change in unrealized net gains (losses) on cash flow hedges	7	(4)	(18)
Change in unrealized net gains (losses) on AFS securities	(27)	(130)	(120)
Change in FDIC 's share of unrealized gains/losses on AFS securities	0	98	25
Other, net	$ 0	$ 1	$ 3