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Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	$ 45,297			$ 44,524
Fixed maturities, available for sale, allowance for expected credit losses	54	$ 61		0
Available for sale (AFS) fixed maturities	48,193			46,505
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	45,297			44,524
Fixed maturities, available for sale, allowance for expected credit losses	54			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	3,204			2,069
Fixed maturities, Available for sale, Gross Unrealized, Losses	(254)			(88)
Available for sale (AFS) fixed maturities	48,193			46,505
Total fixed maturities \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	2,950			1,981
U.S. Government and government agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	211			199
Fixed maturities, available for sale, allowance for expected credit losses	0			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	13			10
Fixed maturities, Available for sale, Gross Unrealized, Losses	0			0
Available for sale (AFS) fixed maturities	224			209
U.S. Government and government agencies \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	13			10
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	6,150			6,604
Fixed maturities, available for sale, allowance for expected credit losses	0			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	575			363
Fixed maturities, Available for sale, Gross Unrealized, Losses	(3)			(4)
Available for sale (AFS) fixed maturities	6,722			6,963
States, municipalities and political subdivisions \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	572			359
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	187			170
Fixed maturities, available for sale, allowance for expected credit losses	0			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	8			3
Fixed maturities, Available for sale, Gross Unrealized, Losses	0			(1)
Available for sale (AFS) fixed maturities	195			172
Foreign government \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	8			2
Residential MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	2,882			2,900
Fixed maturities, available for sale, allowance for expected credit losses	3			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	264			265
Fixed maturities, Available for sale, Gross Unrealized, Losses	(6)			(5)
Available for sale (AFS) fixed maturities	3,137			3,160
Residential MBS \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	258			260
Commercial MBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	814			896
Fixed maturities, available for sale, allowance for expected credit losses	0			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	44			31
Fixed maturities, Available for sale, Gross Unrealized, Losses	(2)			0
Available for sale (AFS) fixed maturities	856			927
Commercial MBS \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	42			31
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	4,643			4,307
Fixed maturities, available for sale, allowance for expected credit losses	20			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	25			10
Fixed maturities, Available for sale, Gross Unrealized, Losses	(41)			(37)
Collateralized loan obligations \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	(16)			(27)
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	7,405			6,992
Fixed maturities, available for sale, allowance for expected credit losses	16			0
Fixed maturities, Available for sale, Gross Unrealized, Gains	154			156
Fixed maturities, Available for sale, Gross Unrealized, Losses	(124)			(20)
Available for sale (AFS) fixed maturities	7,419			7,128
Other asset-backed securities \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	30			136
Corporate and other
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available for sale, amortized cost	23,005			22,456
Fixed maturities, available for sale, allowance for expected credit losses	15	$ 22	$ 0	0
Fixed maturities, Available for sale, Gross Unrealized, Gains	2,121			1,231
Fixed maturities, Available for sale, Gross Unrealized, Losses	(78)			(21)
Available for sale (AFS) fixed maturities	25,033			23,666
Corporate and other \| Debt Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	2,043			1,210
Managed by third parties \| Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Available for sale (AFS) fixed maturities	$ 4,607			$ 4,280