Investments (Tax and Nontaxable Income by Investment Type) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Investment Income [Line Items]
Interest income	$ 311	$ 304	$ 362
Taxable
Net Investment Income [Line Items]
Interest income	266	262	318
Nontaxable
Net Investment Income [Line Items]
Interest income	45	42	44
Held-to-maturity
Net Investment Income [Line Items]
Interest income	15	20	22
Held-to-maturity | Taxable
Net Investment Income [Line Items]
Interest income	10	10	9
Held-to-maturity | Nontaxable
Net Investment Income [Line Items]
Interest income	5	10	13
Available-for-sale
Net Investment Income [Line Items]
Interest income	285	277	333
Available-for-sale | Taxable
Net Investment Income [Line Items]
Interest income	256	252	308
Available-for-sale | Nontaxable
Net Investment Income [Line Items]
Interest income	29	25	25
Trading
Net Investment Income [Line Items]
Interest income	11	7	7
Trading | Taxable
Net Investment Income [Line Items]
Interest income	0	0	1
Trading | Nontaxable
Net Investment Income [Line Items]
Interest income	$ 11	$ 7	$ 6