Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities Available-For-Sale) (Details) $ in Millions	Dec. 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	2,177	2,153
Total number of securities in an unrealized loss position equal or greater than 12 months	690	1,411
Fixed Maturity Securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	$ 27,727	$ 24,806
Less than 12 months, Gross Unrealized Loss	1,031	578
Equal to or Greater than 12 Months, Estimated Fair Value	6,236	15,700
Equal to or Greater than 12 Months ,Gross Unrealized Loss	401	1,069
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	4,338	3,817
Less than 12 months, Gross Unrealized Loss	196	107
Equal to or Greater than 12 Months, Estimated Fair Value	506	2,226
Equal to or Greater than 12 Months ,Gross Unrealized Loss	50	198
Foreign government
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	6,795	3,295
Less than 12 months, Gross Unrealized Loss	305	149
Equal to or Greater than 12 Months, Estimated Fair Value	836	1,490
Equal to or Greater than 12 Months ,Gross Unrealized Loss	100	172
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	4,856	3,188
Less than 12 months, Gross Unrealized Loss	321	133
Equal to or Greater than 12 Months, Estimated Fair Value	1,255	5,873
Equal to or Greater than 12 Months ,Gross Unrealized Loss	147	584
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	4,619	5,391
Less than 12 months, Gross Unrealized Loss	87	97
Equal to or Greater than 12 Months, Estimated Fair Value	33	196
Equal to or Greater than 12 Months ,Gross Unrealized Loss	2	9
RMBS
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	1,531	2,341
Less than 12 months, Gross Unrealized Loss	27	25
Equal to or Greater than 12 Months, Estimated Fair Value	152	584
Equal to or Greater than 12 Months ,Gross Unrealized Loss	14	14
ABS
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	3,428	3,692
Less than 12 months, Gross Unrealized Loss	26	22
Equal to or Greater than 12 Months, Estimated Fair Value	2,842	4,843
Equal to or Greater than 12 Months ,Gross Unrealized Loss	49	66
Municipals
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	273	1,156
Less than 12 months, Gross Unrealized Loss	6	29
Equal to or Greater than 12 Months, Estimated Fair Value	0	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	1,887	1,926
Less than 12 months, Gross Unrealized Loss	63	16
Equal to or Greater than 12 Months, Estimated Fair Value	612	487
Equal to or Greater than 12 Months ,Gross Unrealized Loss	39	26
Investment Grade
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	24,572	22,838
Less than 12 months, Gross Unrealized Loss	829	437
Equal to or Greater than 12 Months, Estimated Fair Value	5,841	13,813
Equal to or Greater than 12 Months ,Gross Unrealized Loss	350	821
Below Investment Grade
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	3,155	1,968
Less than 12 months, Gross Unrealized Loss	202	141
Equal to or Greater than 12 Months, Estimated Fair Value	395	1,887
Equal to or Greater than 12 Months ,Gross Unrealized Loss	$ 51	$ 248

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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