Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Investment securities, Balance at beginning of period, net of tax		$ 65	$ (138)
Investment securities, Net unrealized holding gains arising during the period		286	229
Investment securities, Less: Provision for income taxes		68	54
Investment securities, Net unrealized holding gains arising during the period, net of tax		218	175
Investment securities, Net realized losses gains included in net securities losses		0	(8)
Investment securities, Less: Benefit for income taxes		0	(2)
Investment Securities, Reclassification adjustment for net securities losses included in net income, net of tax		0	(6)
Investment securities, Change in net unrealized gains on investment securities, net of tax		218	181
Investment securities, Balance at end of period, net of tax		283	43
Cash flow hedges, Balance at beginning of period, net of tax		34	0
Cash flow hedge: Net gains arising during the period		233	51
Cash flow hedges, Less: Provision for income tax		56	12
Change in net cash flow hedge gains arising during the period, net of tax		177	39
Net cash flow hedge gains (losses) included in interest and fees on loans		22	(1)
Cash flow hedges, Less: Provision for income tax		7	0
Cash flow hedges, reclassification adjustment for net cash flow hedge gains (losses) included in net income, net of tax		15	(1)
Cash flows hedges, Change in net gain on cash flow hedges		162	40
Cash flow hedges, Balance at end of period, net of tax	[1]	196	40
Benefit plans, Balance at beginning of period, net of tax		(334)	(471)
Benefit plans, Amortization of actuarial net loss		31	21
Benefit plans, Amortization of prior service credit		(14)	(13)
Benefit plans, Amounts recognized in other noninterest expenses		17	8
Benefit plans, Less: Provision for income taxes		4	2
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax		13	6
Benefit plans, Balance at end of period, net of tax		(321)	(465)
Total accumulated other comprehensive income (loss) at end of period, net of tax		$ 158	$ (382)	$ (235)

[1] The Corporation expects to reclassify $73 million of net gains, net of tax, from accumulated other comprehensive income to earnings over the next twelve months if interest yield curves and notional amounts remain at June 30, 2020 levels.