Accumulated Other Comprehensive Loss (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Investment securities, Balance at beginning of period, net of tax		$ (138)	$ (101)
Cumulative effect of change in accounting principle		0	1
Investment securities, Net unrealized holding (losses) gains arising during the period		267	(254)
Investment securities, Less: (Benefit) provision for income taxes		62	(59)
Investment securities, Net unrealized holding (losses) gains arising during the period, net of tax		205	(195)
Investment securities, Net realized (losses) gains included in net securities (losses) gains		(8)	(20)
Investment securities, Less: Benefit for income taxes		(2)	(5)
Investment Securities, Reclassification adjustment for net securities (losses) gains included in net income, net of tax		(6)	(15)
Investment securities, Reclassification adjustment for net securities (losses) gains included in net income, net of tax		211	(180)
Investment securities, Balance at end of period, net of tax		73	(280)
Cash flow hedges, Balance at beginning of period, net of tax		0	0
Cash flow hedge: Net gains arising during the period		69	0
Cash flow hedges, Less: Provision for income tax		16	0
Change in net cash flow hedge gains arising during the period, net of tax		53	0
Net cash flow hedge losses included in interest and fees on loans		(1)	0
Cash flows hedges, Change in net gain on cash flow hedges		54	0
Cash flow hedges, Balance at end of period, net of tax	[1]	54	0
Benefit plans, Balance at beginning of period, net of tax		(471)	(350)
Benefit plans, Amortization of actuarial net loss		30	45
Benefit plans, Amortization of prior service credit		(20)	(20)
Benefit plans, Amounts recognized in other noninterest expense		10	25
Benefit plans, Less: Provision for income taxes		2	6
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax		8	19
Benefit plans, Balance at end of period, net of tax		(463)	(331)
Total accumulated other comprehensive loss at end of period, net of tax		$ (336)	$ (611)	$ (609)

[1] The Corporation expects to reclassify $12 million of net gains, net of tax, from accumulated other comprehensive loss to earnings over the next twelve months if interest yield curves and notional amounts remain at September 30, 2019 levels.