Investments - Investments - Available-for-Sale Securities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	$ 39,640		$ 40,078
Allowance for credit losses, fixed maturity, AFS	(32)		0
Gross Unrealized Gains, fixed maturities, available-for-sale	2,867		2,125
Gross Unrealized Losses, fixed maturities, available-for-sale	(275)		(55)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	42,200		42,148
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			4
ABS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,387		1,461
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	30		18
Gross Unrealized Losses, fixed maturities, available-for-sale	(1)		(3)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	1,416		1,476
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
CLOs
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	2,246		2,186
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	0		5
Gross Unrealized Losses, fixed maturities, available-for-sale	(59)		(8)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	2,187		2,183
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	4,067		4,210
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	208		141
Gross Unrealized Losses, fixed maturities, available-for-sale	(64)		(13)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	4,211		4,338
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			4
Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	17,283		16,435
Allowance for credit losses, fixed maturity, AFS	(32)	$ (12)	0
Gross Unrealized Gains, fixed maturities, available-for-sale	1,441		986
Gross Unrealized Losses, fixed maturities, available-for-sale	(129)		(25)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	18,563		17,396
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
Foreign Govt./Govt. Agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	906		1,057
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	70		66
Gross Unrealized Losses, fixed maturities, available-for-sale	(4)		0
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	972		1,123
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
Municipal
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	8,604		8,763
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	804		737
Gross Unrealized Losses, fixed maturities, available-for-sale	(14)		(2)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	9,394		9,498
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
RMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	3,750		4,775
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	149		97
Gross Unrealized Losses, fixed maturities, available-for-sale	(4)		(3)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	3,895		4,869
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			0
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,397		1,191
Allowance for credit losses, fixed maturity, AFS	0
Gross Unrealized Gains, fixed maturities, available-for-sale	165		75
Gross Unrealized Losses, fixed maturities, available-for-sale	0		(1)
Fixed maturities, available-for-sale, at fair value (amortized cost of $54,478 and $53,805)	$ 1,562		1,265
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities			$ 0

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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