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Investments (Fixed Maturity Securities Pledged And Received As Collateral) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items] |  |
Document Period End Date | Mar. 31, 2021 |
Collateral Fixed Maturity Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | $ 131 | $ 148
Available-for-sale Securities | 139 | 162
Collateral Received Fixed Maturity Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities | 1,751 | 1,784
Reported Value Measurement [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Assets Held-in-trust | 27,893 | 27,675
Estimate of Fair Value Measurement [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Assets Held-in-trust | $ 29,954 | $ 31,179

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