Debt And Shareholders' Equity (Schedule Of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	$ 40	$ (41)
Income Tax Expense (Benefit)	61	70
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	127	(128)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1	0
Beginning balance	(250)	(139)
Other comprehensive income (loss)	128	(128)
Ending balance	(122)	(267)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	2	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	0	0
Other Comprehensive Income (Loss), Tax	42	(42)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	122	(126)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Beginning balance	(228)	(114)
Other comprehensive income (loss)	122	(126)
Ending balance	(106)	(240)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	5	(2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1	0
Beginning balance	(1)	(2)
Other comprehensive income (loss)	6	(2)
Ending balance	5	(4)
Accumulated Defined Benefit Plans Adjustment [Member]
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Beginning balance	(21)	(23)
Other comprehensive income (loss)	0	0
Ending balance	(21)	(23)
Interest Rate Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Debt And Shareholders' Equity [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(1)	0
Reclassification from AOCI, Current Period, Tax	(1)	0
Income Tax Expense (Benefit)	$ 0	$ 0