Derivative Instruments Derivative Instruments (Credit Derivatives) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	$ 3,921	$ 3,053
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	131	63
Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	3,921	3,053
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	131	63
NAIC 1
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	49	50
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 1 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 1 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	49	50
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 2
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 2 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 2 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 3
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	3,342	3,003
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	76	63
NAIC 3 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 3 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	3,342	3,003
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	76	63
NAIC 4
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 4 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 4 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 5
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 5 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 5 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 6
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	530	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	55	0
NAIC 6 | Single Name
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	0	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	0	0
NAIC 6 | Credit Default Index
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	530	0
Credit Risk Derivatives, at Fair Value, Asset Net (Liability)	$ 55	$ 0