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Additional Information - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Allowance for reinsurance recoverables [Line Items] |  |  |
Commitments to fund limited partnerships | $ 897 |  |
Retirement and employee savings plan expense | 39 | $ 37 | $ 45
Allowance for reinsurance recoverables |  |  |
Allowance for reinsurance recoverables [Line Items] |  |  |
Aggregate allowance for losses on reinsurance recoverables | 18 | 18 |
Net expense reduction against the allowance for losses on reinsurance recoverables |  | $ (2) |
Reinsurance recoverable write-offs |  |  | 2
Maximum | Allowance for reinsurance recoverables |  |  |
Allowance for reinsurance recoverables [Line Items] |  |  |
Net expense reduction against the allowance for losses on reinsurance recoverables | $ (1) |  | $ (1)

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