Investments (Rollforward of Total Amount of Credit-Related OTTI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net Investment Income [Line Items]
Interest income	$ 78	$ 74	$ 223	$ 235
Taxable
Net Investment Income [Line Items]
Interest income	67	63	190	203
Nontaxable
Net Investment Income [Line Items]
Interest income	11	11	33	32
Held-to-maturity
Net Investment Income [Line Items]
Interest income	4	5	12	15
Held-to-maturity | Taxable
Net Investment Income [Line Items]
Interest income	3	2	8	7
Held-to-maturity | Nontaxable
Net Investment Income [Line Items]
Interest income	1	3	4	8
Available-for-sale
Net Investment Income [Line Items]
Interest income	72	67	204	215
Available-for-sale | Taxable
Net Investment Income [Line Items]
Interest income	64	61	182	196
Available-for-sale | Nontaxable
Net Investment Income [Line Items]
Interest income	8	6	22	19
Trading
Net Investment Income [Line Items]
Interest income	2	2	7	5
Trading | Taxable
Net Investment Income [Line Items]
Interest income	0	0	0	0
Trading | Nontaxable
Net Investment Income [Line Items]
Interest income	$ 2	$ 2	$ 7	$ 5