Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities by Sector) (Details) $ in Millions	Sep. 30, 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	$ 5,468	$ 4,419
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	$ 179	$ 74
Fixed maturity securities in continuous unrealized loss position, less than 12 months, number of securities	1,052	686
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	$ 1,256	$ 2,031
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 100	$ 92
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, number of securities	244	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	$ 2,965	$ 1,931
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	111	43
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	185	320
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	21	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	849	577
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	36	12
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	403	510
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	64	55
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	419	802
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	9	6
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	12	346
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	0	4
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	0	14
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	0	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
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	342	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	60	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	104	120
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	2	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	667	358
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	8	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	590	676
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	13	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	122	65
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	6	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	6	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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