Derivative Financial Instruments (Notional Amounts, Balance Sheet Location And Estimated Fair Values Of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Contractual Notional Amount	$ 1,653	$ 2,048
Total derivative assets	10	3
Amounts netted	(10)	(1)
Net derivative assets	0	2
Total derivative liabilities	(21)	(21)
Amounts netted	10	1
Net derivative liabilities	(11)	(20)
Hedging Instrument [Member]
Derivative [Line Items]
Contractual Notional Amount	1,200	1,235
Hedging Instrument [Member] | Other Assets/Other Liabilities [Member]
Derivative [Line Items]
Contractual Notional Amount		1,660
Total derivative assets		2
Total derivative liabilities		(14)
Hedging Instrument [Member] | Other Assets/Other Liabilities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual Notional Amount	1,200	1,235
Total derivative assets	0	2
Total derivative liabilities	(19)	(5)
Hedging Instrument [Member] | Other Assets/Other Liabilities [Member] | Forward Contracts [Member]
Derivative [Line Items]
Contractual Notional Amount		425
Total derivative assets		0
Total derivative liabilities		(9)
Non-Hedging Instrument [Member]
Derivative [Line Items]
Contractual Notional Amount	453	388
Total derivative assets	10	1
Total derivative liabilities	(2)	(7)
Non-Hedging Instrument [Member] | Other Assets/Other Liabilities [Member] | Options [Member]
Derivative [Line Items]
Contractual Notional Amount		100
Total derivative assets		0
Total derivative liabilities		0
Non-Hedging Instrument [Member] | Equity Securities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual Notional Amount	179	171
Total derivative assets	7	1
Total derivative liabilities	(1)	(5)
Non-Hedging Instrument [Member] | Equity Securities [Member] | Futures [Member]
Derivative [Line Items]
Contractual Notional Amount	274	117
Total derivative assets	3	0
Total derivative liabilities	$ (1)	$ (2)