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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, 2016 | Dec. 31, 2015
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Total |  | $ 677 |  | $ 680 |
Collections for Cases with Recoveries |  | (69) |  | (74) |
Accretion of Recoveries |  | 6 |  | 10 |
Changes in Discount Rates |  | (14) |  | (1) |
Changes in Assumptions |  | 52 |  | 94 |
Changes in LAE Recoveries |  | 3 |  | 5 |
Other |  | (72) | [1] | (37) | [2]
Gross Reserve ending balance, Total |  | 583 |  | 677 |
Insurance Loss Recoverable [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance, Insurance loss recoverable |  | 577 |  | 533 |
Collections for Cases with Recoveries |  | (69) |  | (74) |
Accretion of Recoveries |  | 5 |  | 8 |
Changes in Discount Rates |  | (17) |  | 1 |
Changes in Assumptions |  | 86 |  | 140 |
Changes in LAE Recoveries |  | (6) |  | 6 |
Other | [2] | (72) |  | (37) |
Gross Reserve ending balance, Insurance loss recoverable |  | 504 |  | 577 |
Recoveries On Unpaid Losses [Member] |  |  |  |  |
Loss And Loss Adjustment Expense Recoveries [Line Items] |  |  |  |  |
Gross Reserve beginning balance,Recoveries on unpaid losses |  | 100 |  | 147 |
Collections for Cases with Recoveries | [3] | 0 |  | 0 |
Accretion of Recoveries | [3] | 1 |  | 2 |
Changes in Discount Rates | [3] | 3 |  | (2) |
Changes in Assumptions | [3] | (34) |  | (46) |
Changes in LAE Recoveries | [3] | 9 |  | (1) |
Other | [2],[3] | 0 |  | 0 |
Gross Reserve ending balance, Recoveries on unpaid losses |  | $ 79 |  | $ 100 |
[1] | Primarily changes in amount and timing of payments.
[2] | Primarily changes in amount and timing of collections.
[3] | Excludes Puerto Rico and Zohar II recoveries, which have been netted against reserves.

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