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	$ 5,530	$ 4,619
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	$ 181	$ 79
Fixed maturity securities in continuous unrealized loss position, less than 12 months, number of securities	1,069	720
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	$ 1,305	$ 2,128
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 109	$ 100
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, number of securities	248	302
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	$ 2,993	$ 2,017
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	112	44
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	188	326
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	21	23
Foreign Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	862	576
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	37	12
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	451	561
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	73	62
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	420	857
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	9	8
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	11	386
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	40
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	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	344	559
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	59	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	123	143
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	362
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	121	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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