Parent Company (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Other	$ 32	$ 340	$ 65
Net cash provided (used) by operating activities	7,840	5,579	3,500
Investing Activities
Other	(1,684)	(1,220)	(817)
Net cash provided (used) by investing activities	(3,969)	(14,895)	(7,307)
Financing Activities
Net change in commercial paper	(100)	100
Preferred stock issuances			519
Acquisition of treasury stock	(2,877)	(2,447)	(2,062)
Preferred stock cash dividends paid	(236)	(236)	(209)
Common stock cash dividends paid	(1,601)	(1,266)	(1,061)
Net Increase (Decrease) In Cash And Due From Banks	359	370	814
Parent Company
Operating Activities
Net income attributable to common shareholders	5,301	5,338	3,903
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Equity in undistributed net earnings of subsidiaries	(2,307)	(1,974)	(971)
Return on investment in subsidiary		98
Other	155	194	143
Net cash provided (used) by operating activities	3,149	3,656	3,075
Investing Activities
Net change in loans and securities from affiliates	540	114	2,161
Net change in nonrestricted interest earning deposits	1,145	(1,116)	(1,607)
Net change in restricted interest-earning deposits			300
Other	2		266
Net cash provided (used) by investing activities	1,687	(1,002)	1,120
Financing Activities
Net change in other borrowed funds from affiliates	(29)	316	(124)
Net change in senior debt	498	1,325	(1,252)
Net change in subordinated debt	(553)	(580)	17
Net change in commercial paper	(100)	100
Preferred stock issuances			519
Common and treasury stock issuances	69	132	151
Acquisition of treasury stock	(2,877)	(2,447)	(2,062)
Preferred stock cash dividends paid	(236)	(236)	(209)
Common stock cash dividends paid	(1,603)	(1,264)	(1,060)
Net cash provided (used) by financing activities	(4,831)	(2,654)	(4,020)
Net Increase (Decrease) In Cash And Due From Banks	5	0	175
Cash and restricted deposits held at banking subsidiary at beginning of year	176	176	1
Cash and restricted deposits held at banking subsidiary at end of year	$ 181	$ 176	$ 176