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Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Total |  | $ 546 |  | $ 583 |
Collections for Cases |  | (56) |  | (124) |
Accretion of Recoveries |  | 26 |  | 11 |
Changes in Discount Rates |  | (14) |  | 3 |
Changes in Assumptions |  | 1,091 |  | 68 |
Changes in LAE Recoveries |  | (8) |  | (1) |
Other | [1] | (2) |  | 6 |
Gross Reserve ending balance, Total |  | 1,583 |  | 546 |
Insurance Loss Recoverable [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Insurance loss recoverable |  | 511 |  | 504 |
Collections for Cases |  | (56) |  | (124) |
Accretion of Recoveries |  | 25 |  | 10 |
Changes in Discount Rates |  | (13) |  | 2 |
Changes in Assumptions |  | 1,099 | [2] | 113 |
Changes in LAE Recoveries |  | 0 |  | 0 |
Other | [1] | (2) |  | 6 |
Gross Reserve ending balance, Insurance loss recoverable |  | 1,564 |  | 511 |
Recoveries On Unpaid Losses [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance,Recoveries on unpaid losses |  | 35 | [3] | 79 | [4]
Collections for Cases |  | 0 |  | 0 |
Accretion of Recoveries | [3] | 1 |  | 1 | [4]
Changes in Discount Rates | [3] | (1) |  | 1 | [4]
Changes in Assumptions | [3] | (8) |  | (45) | [4]
Changes in LAE Recoveries | [3] | (8) |  | (1) | [4]
Other |  | 0 |  | 0 | [1],[4]
Gross Reserve ending balance, Recoveries on unpaid losses | [3] | $ 19 |  | $ 35 |
[1] | Primarily changes in amount and timing of collections.
[2] | Includes amounts which have been paid and are expected to be recovered in the future.
[3] | As of December 31, 2018 and December 31, 2017, excludes Puerto Rico recoveries, which have been netted against reserves.
[4] | Excludes Zohar II recoveries, which have been netted against reserves.

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