Investments (Continuous Gross Unrealized Losses for Fixed Maturity Securities by Sector) (Details) $ in Millions	Mar. 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	$ 16,545	$ 4,419
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	$ 1,313	$ 74
Fixed maturity securities in continuous unrealized loss position, less than 12 months, number of securities	2,843	686
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	$ 1,463	$ 2,031
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 237	$ 92
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, number of securities	272	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	$ 8,459	$ 1,931
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	736	43
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	272	320
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	55	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	3,726	577
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	316	12
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	503	510
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	112	55
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities in continuous unrealized loss position, less than 12 months, estimated fair value	977	802
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	49	6
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	19	346
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	2	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	73	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	1,531	552
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	76	7
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	143	171
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	94	120
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	4	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	1,192	358
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	92	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	522	676
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	64	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	493	65
Fixed maturity securities in continuous unrealized loss position, less than 12 months, gross unrealized losses	40	2
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, estimated fair value	4	0
Fixed maturity securities in continuous unrealized loss position, 12 months or greater, gross unrealized losses	$ 1	$ 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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