Debt And Shareholders' Equity (Schedule Of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax			$ 45	$ 40
Interest income expense, net, after tax	$ 154	$ 91	283	169
Income Tax Expense (Benefit)	80	60	124	102
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			75	81
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)	(3)
Beginning balance			(122)	(55)
Other comprehensive income (loss)	62	35	73	78
Ending balance	(49)	23	(49)	23
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax			0	8
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax			0	1
Other Comprehensive Income (Loss), Tax			45	49
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			73	65
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Beginning balance			(93)	(18)
Other comprehensive income (loss)			73	65
Ending balance	(20)	47	(20)	47
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			2	17
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)	(3)
Beginning balance			2	1
Other comprehensive income (loss)			0	14
Ending balance	2	15	2	15
Accumulated Defined Benefit Plans Adjustment [Member]
Debt And Shareholders' Equity [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0	(1)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Beginning balance			(31)	(38)
Other comprehensive income (loss)			0	(1)
Ending balance	(31)	(39)	(31)	(39)
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	3	3	6
Interest income expense, net, after tax	1	2	2	3
Income Tax Expense (Benefit)	$ 0	$ 1	$ 1	$ 3