Investments (Rollforward Of Total Amount Of Credit-Related OTTI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Investment Income [Line Items]
Interest income	$ 74	$ 88	$ 235	$ 279
Taxable
Net Investment Income [Line Items]
Interest income	63	77	203	245
Nontaxable
Net Investment Income [Line Items]
Interest income	11	11	32	34
Held-to-maturity
Net Investment Income [Line Items]
Interest income	5	6	15	18
Held-to-maturity | Taxable
Net Investment Income [Line Items]
Interest income	2	3	7	7
Held-to-maturity | Nontaxable
Net Investment Income [Line Items]
Interest income	3	3	8	11
Available-for-sale
Net Investment Income [Line Items]
Interest income	67	81	215	257
Available-for-sale | Taxable
Net Investment Income [Line Items]
Interest income	61	74	196	238
Available-for-sale | Nontaxable
Net Investment Income [Line Items]
Interest income	6	7	19	19
Trading
Net Investment Income [Line Items]
Interest income	2	1	5	4
Trading | Taxable
Net Investment Income [Line Items]
Interest income	0	0	0	0
Trading | Nontaxable
Net Investment Income [Line Items]
Interest income	$ 2	$ 1	$ 5	$ 4