Investments (Rollforward of Total Amount of Credit-Related OTTI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net Investment Income [Line Items]
Interest income	$ 74	$ 80	$ 145	$ 161
Taxable
Net Investment Income [Line Items]
Interest income	63	70	123	140
Nontaxable
Net Investment Income [Line Items]
Interest income	11	10	22	21
Held-to-maturity
Net Investment Income [Line Items]
Interest income	3	5	8	10
Held-to-maturity | Taxable
Net Investment Income [Line Items]
Interest income	2	3	5	5
Held-to-maturity | Nontaxable
Net Investment Income [Line Items]
Interest income	1	2	3	5
Available-for-sale
Net Investment Income [Line Items]
Interest income	68	74	132	148
Available-for-sale | Taxable
Net Investment Income [Line Items]
Interest income	61	67	118	135
Available-for-sale | Nontaxable
Net Investment Income [Line Items]
Interest income	7	7	14	13
Trading
Net Investment Income [Line Items]
Interest income	3	1	5	3
Trading | Taxable
Net Investment Income [Line Items]
Interest income	0	0	0	0
Trading | Nontaxable
Net Investment Income [Line Items]
Interest income	$ 3	$ 1	$ 5	$ 3