Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities by Sector) (Details) $ in Millions	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	$ 3,323	$ 4,419
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	$ 83	$ 74
Fixed maturity securities in continuous unrealized loss position, less than 12 months, number of securities	665	686
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	$ 1,221	$ 2,031
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 60	$ 92
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, number of securities	241	297
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	$ 1,726	$ 1,931
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	57	43
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	181	320
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	13	22
Foreign Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	243	577
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	7	12
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	345	510
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	37	55
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	236	14
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	6	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
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	180	802
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	2	6
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	22	346
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	1	4
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	331	552
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	7	7
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	44	171
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	2	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	46	120
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	0	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	0	8
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	506	358
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	3	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	629	676
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	7	9
Foreign Government
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	55	65
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	1	2
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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