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Stockholders' Equity and Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start $ (964) $ (749) $ (550)
Other comprehensive income (loss), net of tax 874 (215) (66)
Reclassification of the Tax Reform related revaluation of deferred tax items within accumulated other comprehensive income     (133)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End (90) (964) (749)
Accumulated Net Unrealized Loss on Held To Maturity Securities [Member]      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start (27) (33) (33)
Other comprehensive income (loss), net of tax 5 6 6
Reclassification of the Tax Reform related revaluation of deferred tax items within accumulated other comprehensive income     (6)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End (22) (27) (33)
Accumulated Net Unrealized Securities Available For Sale Gain (Loss) [Member]      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start (397) (153) (106)
Other comprehensive income (loss), net of tax 602 (244) (12)
Reclassification of the Tax Reform related revaluation of deferred tax items within accumulated other comprehensive income     (35)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End 205 (397) (153)
Accumulated Net Gain (Loss) from Derivative Instruments Designated as Cash Flow Hedges [Member]      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start (63) (51) 11
Other comprehensive income (loss), net of tax 385 (12) (51)
Reclassification of the Tax Reform related revaluation of deferred tax items within accumulated other comprehensive income     (11)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End 322 (63) (51)
Accumulated Defined Benefit Pension Plans Adjustment [Member]      
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]      
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start (477) (512) (422)
Other comprehensive income (loss), net of tax (118) 35 (9)
Reclassification of the Tax Reform related revaluation of deferred tax items within accumulated other comprehensive income     (81)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End $ (595) $ (477) $ (512)