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Business Developments And Risks And Uncertainties (Narrative) (Detail) $ / shares in Units, $ in Millions |  | 3 Months Ended
--- | --- | ---
Apr. 13, 2018 $ / shares shares | Mar. 31, 2018 USD ($) segments
Business Acquisition [Line Items] |  |
Number of operating segments | segments |  | 3
Puerto Rico [Member] |  |
Business Acquisition [Line Items] |  |
Claims payments | $ |  | $ 69
SubsequentEvent [Member] |  |
Business Acquisition [Line Items] |  |
Warrants outstanding | 9,940,000 |
Warrant exercise price | $ / shares | $ 9.59 |
Treasury shares issued for warrants exercised | 1,200,000 |

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