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Schedule I - Summary Of Investments (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
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SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost | $ 3,575 |
Investments | 3,792 | $ 3,937
Other Investments and Securities, at Cost | 388 |
Other Investments | 478 | $ 391
U.S. Government Obligations [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities | 156 |
Short-term Investments [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 737 |
Available-for-sale Securities | 737 |
U S Government Obligations [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost | 157 |
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 194 |
Available-for-sale Securities | 215 |
Fixed Income Securities [Member] | Corporate Debt Securities [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 1,396 |
Available-for-sale Securities | 1,430 |
Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 44 |
Available-for-sale Securities | 44 |
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 200 |
Available-for-sale Securities | 248 |
Fixed Income Securities [Member] | Collateralized Mortgage Backed Securities [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 49 |
Available-for-sale Securities | 50 |
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 147 |
Available-for-sale Securities | 146 |
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 263 |
Available-for-sale Securities | 287 |
Fair Value Measurement [Domain] |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Investments | 3,807 |
Other Investments | $ 493 |

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