Derivative Financial Instruments (Notional Amounts, Balance Sheet Location And Estimated Fair Values Of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Total derivative assets	$ 23	$ 16
Amounts netted	(1)	(14)
Net derivative assets	22	2
Total derivative liabilities	(1)	(17)
Derivative, Notional Amount	1,335	1,879
Amounts netted	1	14
Net derivative liabilities	0	(3)
Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,200	1,200
Hedging Instruments [Member] | Other Assets/Other Liabilities | Interest Rate Swaps [Member]
Derivative [Line Items]
Total derivative assets	22	7
Total derivative liabilities	(1)	(11)
Derivative, Notional Amount	1,200	1,200
Non-Hedging Instruments [Member]
Derivative [Line Items]
Total derivative assets	1	9
Total derivative liabilities	0	(6)
Derivative, Notional Amount	135	679
Non-Hedging Instruments [Member] | Other Assets/Other Liabilities | Options [Member]
Derivative [Line Items]
Total derivative assets		0
Total derivative liabilities		0
Derivative, Notional Amount		100
Non-Hedging Instruments [Member] | Equity Securities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Total derivative assets	0	4
Total derivative liabilities	0	(1)
Derivative, Notional Amount	1	164
Non-Hedging Instruments [Member] | Equity Securities [Member] | Futures [Member]
Derivative [Line Items]
Total derivative assets	1	5
Total derivative liabilities	0	(5)
Derivative, Notional Amount	$ 134	$ 415