Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities by Sector) (Details) $ in Millions	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	$ 12,018	$ 3,323
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	$ 725	$ 83
Fixed maturity securities in continuous unrealized loss position, less than 12 months, number of securities	1,697	665
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	$ 1,085	$ 1,221
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 53	$ 60
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, number of securities	292	241
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	$ 6,426	$ 1,726
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	419	57
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	310	181
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	11	13
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	1,614	243
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	88	7
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	289	345
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	35	37
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	985	236
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	132	6
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	0	0
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	0	0
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	834	180
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	16	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	56	22
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	2	1
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	860	331
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	31	7
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	85	44
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	3	2
State and political subdivision
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	590	46
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	26	0
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	0	0
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	0	0
ABS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	538	506
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	3	3
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	345	629
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	2	7
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	171	55
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	10	1
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	0	0
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 0	$ 0

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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