Derivative Financial Instruments (Notional Amounts, Balance Sheet Location And Estimated Fair Values Of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Notional Amount	$ 785	$ 1,335
Total derivative assets	43	23
Amounts netted	0	(1)
Net derivative assets	43	22
Total derivative liabilities	(5)	(1)
Amounts netted	0	1
Net derivative liabilities	(5)	0
Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	575	1,200
Hedging Instruments [Member] | Other Assets/Other Liabilities | Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	575	1,200
Total derivative assets	37	22
Total derivative liabilities	0	(1)
Non-Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	210	135
Total derivative assets	6	1
Total derivative liabilities	(5)	0
Non-Hedging Instruments [Member] | Equity Securities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	27	1
Total derivative assets	0	0
Total derivative liabilities	0	0
Non-Hedging Instruments [Member] | Equity Securities [Member] | Futures [Member]
Derivative [Line Items]
Derivative, Notional Amount	183	134
Total derivative assets	6	1
Total derivative liabilities	$ (5)	$ 0