Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities Available-For-Sale) (Details) $ in Millions	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Total number of securities in an unrealized loss position less than 12 months	6,667	2,153
Total number of securities in an unrealized loss position equal or greater than 12 months	947	1,411
Fixed Maturity Securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	$ 72,420	$ 24,806
Less than 12 months Gross Unrealized Loss	6,572	578
Equal to or Greater than 12 Months Estimated Fair Value	7,749	15,700
Equal to or Greater than 12 Months Gross Unrealized Loss	1,135	1,069
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	22,055	3,817
Less than 12 months Gross Unrealized Loss	2,136	107
Equal to or Greater than 12 Months Estimated Fair Value	655	2,226
Equal to or Greater than 12 Months Gross Unrealized Loss	174	198
Foreign government
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	5,813	3,295
Less than 12 months Gross Unrealized Loss	335	149
Equal to or Greater than 12 Months Estimated Fair Value	1,347	1,490
Equal to or Greater than 12 Months Gross Unrealized Loss	194	172
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	21,922	3,188
Less than 12 months Gross Unrealized Loss	2,401	133
Equal to or Greater than 12 Months Estimated Fair Value	2,103	5,873
Equal to or Greater than 12 Months Gross Unrealized Loss	364	584
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	1,103	5,391
Less than 12 months Gross Unrealized Loss	8	97
Equal to or Greater than 12 Months Estimated Fair Value	37	196
Equal to or Greater than 12 Months Gross Unrealized Loss	0	9
RMBS
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	5,617	2,341
Less than 12 months Gross Unrealized Loss	390	25
Equal to or Greater than 12 Months Estimated Fair Value	227	584
Equal to or Greater than 12 Months Gross Unrealized Loss	20	14
ABS
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	9,866	3,692
Less than 12 months Gross Unrealized Loss	757	22
Equal to or Greater than 12 Months Estimated Fair Value	2,995	4,843
Equal to or Greater than 12 Months Gross Unrealized Loss	323	66
Municipals
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	1,351	1,156
Less than 12 months Gross Unrealized Loss	60	29
Equal to or Greater than 12 Months Estimated Fair Value	1	1
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
CMBS
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	4,693	1,926
Less than 12 months Gross Unrealized Loss	485	16
Equal to or Greater than 12 Months Estimated Fair Value	384	487
Equal to or Greater than 12 Months Gross Unrealized Loss	60	26
Investment Grade
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	63,072	22,838
Less than 12 months Gross Unrealized Loss	5,080	437
Equal to or Greater than 12 Months Estimated Fair Value	6,970	13,813
Equal to or Greater than 12 Months Gross Unrealized Loss	919	821
Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Estimated Fair Value	9,348	1,968
Less than 12 months Gross Unrealized Loss	1,492	141
Equal to or Greater than 12 Months Estimated Fair Value	779	1,887
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 216	$ 248