Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities AFS by Sector) (Details) $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Total number of securities in an unrealized loss position for less than 12 months	686	2,988
Total number of securities in an unrealized loss position for 12 months or greater	297	1,022
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	$ 1,931	$ 10,450
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	43	465
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	320	2,290
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	22	194
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	14	359
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	0	7
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	0	1,355
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	0	103
RMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	802	1,550
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	6	21
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	346	2,567
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	4	99
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	577	3,916
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	12	199
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	510	746
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	55	107
CMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	552	2,264
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	7	52
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	171	800
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	2	34
State and political subdivision
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	120	346
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	2	7
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	8	158
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	0	8
ABS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	358	1,407
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	2	21
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	676	70
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	9	1
Foreign government
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	65	520
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	2	25
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	0	132
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	0	6
Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months	4,419	20,812
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	74	797
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater	2,031	8,118
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	$ 92	$ 552