Accumulated Other Comprehensive Loss (Schedule Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Investment securities, Balance at beginning of period, net of tax	$ (101)	$ (33)
Cumulative effect of change in accounting principle	1	0
Investment securities, Net unrealized holding (losses) gains arising during the period	(254)	18
Investment securities, Less: (Benefit) provision for income taxes	(59)	7
Investment securities, Net unrealized holding (losses) gains arising during the period, net of tax	(195)	11
Less: Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	(20)	0
Less: Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Less: Benefit for income taxes	(5)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(15)	0
Less: Other Comprehensive income (Loss), Reclassification Adjustment From AOCI For Amortization Of Unrealized Gains (Losses) On Securities Transferred From Available-For-Sale To Held-To-Maturity, before tax	0	(3)
Less: Other Comprehensive income (Loss), Reclassification Adjustment From AOCI For Amortization Of Unrealized Gains (Losses) On Securities Transferred From Available-For-Sale To Held-To-Maturity, Less: Benefit for income taxes	0	(1)
Investment securities, Reclassification adjustment for net losses realized as a yield adjustment included in net income, net of tax	0	(2)
Investment securities, Change in net unrealized (losses) gains on investment securities, net of tax	(180)	13
Investment securities, Balance at end of period, net of tax	(280)	(20)
Benefit plans, Balance at beginning of period, net of tax	(350)	(350)
Benefit plans, Amortization of actuarial net loss	45	38
Benefit plans, Amortization of prior service credit	(20)	(20)
Benefit plans, Amounts recognized in other noninterest expense	25	18
Benefit plans, Less: Provision for income taxes	6	7
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax	19	11
Benefit plans, Balance at end of period, net of tax	(331)	(339)
Total accumulated other comprehensive loss at end of period, net of tax	$ (611)	$ (359)	$ (451)