Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2020	Sep. 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		247	267
Investment securities, Less: Provision for income taxes		58	62
Investment securities, Net unrealized holding gains arising during the period, net of tax		189	205
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		189	211
Investment securities, Balance at end of period, net of tax		254	73
Cash flow hedges, Balance at beginning of period, net of tax		34	0
Cash flow hedge: Net gains arising during the period		232	69
Cash flow hedges, Less: Provision for income tax		56	16
Change in net cash flow hedge gains arising during the period, net of tax		176	53
Net cash flow hedge gains (losses) included in interest and fees on loans		46	(1)
Cash flow hedges, Less: Provision for income tax		12	0
Cash flow hedges, reclassification adjustment for net cash flow hedge gains (losses) included in net income, net of tax		34	(1)
Cash flows hedges, Change in net gain on cash flow hedges		142	54
Cash flow hedges, Balance at end of period, net of tax	[1]	176	54
Benefit plans, Balance at beginning of period, net of tax		(334)	(471)
Benefit plans, Amortization of actuarial net loss		47	30
Benefit plans, Amortization of prior service credit		(21)	(20)
Benefit plans, Amounts recognized in other noninterest expenses		26	10
Benefit plans, Less: Provision for income taxes		6	2
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax		20	8
Benefit plans, Balance at end of period, net of tax		(314)	(463)
Total accumulated other comprehensive income (loss) at end of period, net of tax		$ 116	$ (336)	$ (235)

[1] The Corporation expects to reclassify $72 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 September 30, 2020 levels.