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Basis of Presentation and Significant Accounting Policies FX gain (loss) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Foreign Currency Transaction Gain (Loss), before Tax |  | $ 21,116 | $ (39,128) | $ (17,010)
Successor [Member] |  |  |  |
Foreign Currency Transaction Gain (Loss), before Tax | $ (4,769) | 30,179 | 5,816 |
Lossandlossreserves [Member] |  |  |  |
Foreign Currency Transaction Gain (Loss), before Tax |  | 28,939 | (77,578) | (24,838)
Gain (Loss) on Investments [Member] |  |  |  |
Foreign Currency Transaction Gain (Loss), before Tax |  | (4,769) | 30,179 | 5,816
Premiums Receivable [Member] |  |  |  |
Foreign Currency Transaction Gain (Loss), before Tax | $ (1,904) | 8,003 | (2,555) |
Unrealized Gains Or Losses On Credit Derivative Contracts [Member] |  |  |  |
Foreign Currency Transaction Gain (Loss), before Tax |  | $ (1,150) | $ 32 | $ 3,981

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- Definition Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30700-110894 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30690-110894 + Details
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