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Claim and Claim Adjustment Expense Reserves (Impact of Loss Portfolio Transfer on the Consolidated Statement of Operations) (Details) - Loss Portfolio Transfer - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Net A&EP adverse development before consideration of LPT | $ 60 | $ 200 | $ 150
Retroactive reinsurance benefit recognized | (68) | (107) | (85)
Pretax impact of A&EP reserve development and the LPT | $ (8) | $ 93 | $ 65

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