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	720	3,027
Total number of securities in an unrealized loss position for 12 months or greater	302	1,028
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.	$ 2,017	$ 10,584
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	44	470
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	326	2,328
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	23	199
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months.	576	3,982
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	12	203
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	561	774
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	62	113
RMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months.	857	1,627
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	8	26
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	386	2,611
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	4	101
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.	40	412
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	2	8
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	0	1,543
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	0	104
CMBS
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value of securities in an unrealized loss position for less than 12 months.	559	2,317
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	7	53
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	171	803
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.	143	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.	362	1,422
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	521
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	2	26
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.	4,619	21,211
Gross Unrealized Losses of securities in an unrealized loss position for less than 12 months	79	814
Estimated Fair Value of securities in an unrealized loss position for 12 months or greater.	2,128	8,419
Gross Unrealized Losses of securities in an unrealized loss position for 12 months or greater	$ 100	$ 566