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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, 2017 | Dec. 31, 2016
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Insurance loss recoverable |  | $ 504 |  | $ 577 | [1]
Gross Reserve beginning balance, Total |  | 583 |  | 677 |
Collections for Cases with Recoveries |  | (124) |  | (69) |
Accretion of Recoveries |  | 11 |  | 6 |
Changes in Discount Rates |  | 3 |  | (14) |
Changes in Assumptions |  | 68 |  | 52 |
Changes in LAE Recoveries |  | (1) |  | 3 |
Other | [2] | 6 |  | (72) |
Gross Reserve ending balance, Insurance loss recoverable |  | 511 |  | 504 |
Gross Reserve ending balance, Total |  | 546 |  | 583 |
Insurance Loss Recoverable [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Insurance loss recoverable |  | 504 |  | 577 |
Collections for Cases with Recoveries |  | (124) |  | (69) |
Accretion of Recoveries |  | 10 |  | 5 |
Changes in Discount Rates |  | 2 |  | (17) |
Changes in Assumptions |  | 113 | [3] | 86 |
Changes in LAE Recoveries |  | 0 |  | (6) |
Other | [2] | 6 |  | (72) |
Gross Reserve ending balance, Insurance loss recoverable |  | 511 |  | 504 |
Recoveries On Unpaid Losses [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance,Recoveries on unpaid losses |  | 79 | [1] | 100 |
Collections for Cases with Recoveries |  | 0 |  | 0 |
Accretion of Recoveries |  | 1 | [4] | 1 | [1]
Changes in Discount Rates | [1] | 1 |  | 3 |
Changes in Assumptions | [1] | (45) |  | (34) |
Changes in LAE Recoveries | [1] | (1) |  | 9 |
Other |  | 0 |  | 0 | [2]
Gross Reserve ending balance, Recoveries on unpaid losses | [1] | $ 35 |  | $ 79 |
[1] | As of December 31, 2017 and December 31, 2016, excludes Puerto Rico recoveries, and as of December 31, 2016, the Zohar II recoveries, which have been netted against reserves.
[2] | Primarily changes in amount and timing of collections.
[3] | Includes amounts which have been paid and are expected to be recovered in the future.
[4] | As of December 31, 2017 and December 31, 2016, excludes Puerto Rico recoveries, and as of December 31, 2016, the Zohar II recoveries, which have been netted against reserves.

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