Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 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		323	109
Investment securities, Less: Provision for income taxes		76	25
Investment securities, Net unrealized holding gains arising during the period, net of tax		247	84
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		247	90
Investment securities, Balance at end of period, net of tax		312	(48)
Cash flow hedges, Balance at beginning of period, net of tax		34	0
Cash flow hedge: Net gains arising during the period		205	4
Cash flow hedges, Less: Provision for income tax		48	1
Change in net cash flow hedge gains arising during the period, net of tax		157	3
Net cash flow hedge losses included in interest and fees on loans		3	0
Cash flow hedges, Less: Provision for income tax		1	0
Cash flow hedges, reclassification adjustment for net cash flow hedge gains included in net income, net of tax		2	0
Cash flows hedges, Change in net gain on cash flow hedges		155	3
Cash flow hedges, Balance at end of period, net of tax	[1]	189	3
Benefit plans, Balance at beginning of period, net of tax		(334)	(471)
Benefit plans, Amortization of actuarial net loss		16	11
Benefit plans, Amortization of prior service credit		(7)	(7)
Benefit plans, Amounts recognized in other noninterest expenses		9	4
Benefit plans, Less: Provision for income taxes		2	1
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax		7	3
Benefit plans, Balance at end of period, net of tax		(327)	(468)
Total accumulated other comprehensive income (loss) at end of period, net of tax		$ 174	$ (513)	$ (235)

[1] The Corporation expects to reclassify $66 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 March 31, 2020 levels.