Investments (Net Investment Income) (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]
Gross investment income	$ 1,014	$ 954	$ 2,636	$ 2,762
Less: Investment expenses	37	50	128	152
Net investment income	977	904	2,508	2,610
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	665	654	1,990	1,962
Equity securities
Net Investment Income [Line Items]
Gross investment income	1	1	4	6
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	163	172	495	505
Policy loans
Net Investment Income [Line Items]
Gross investment income	9	12	23	34
Limited partnerships and LLCs
Net Investment Income [Line Items]
Gross investment income	156	80	48	175
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Gross investment income	6	25	38	52
Other
Net Investment Income [Line Items]
Gross investment income	$ 14	$ 10	$ 38	$ 28