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Schedule I - Summary Of Investments (Details) - Successor [Member] - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Summary of Investments, Other than Investments in Related Parties, Cost | $ 5,668,507 |
Investments | 5,740,791 | $ 6,500,215
Available-for-sale Securities, Amortized Cost Basis | 5,271,818 | 5,931,045
Available-for-sale Securities | 5,309,161 | 6,049,908
Other Investments and Securities, at Cost | 396,689 |
Other Investments | 431,630 | 450,307
Corporate Debt Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities | 2,914,145 | 2,622,566
U.S. Government Obligations [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities | 185,127 |
Short-term Investments [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 557,476 | 430,827
Available-for-sale Securities | 557,270 | 430,788
U S Government Obligations [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Summary of Investments, Other than Investments in Related Parties, Cost | 186,619 |
Fixed Income Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 4,614,623 | 5,435,385
Available-for-sale Securities | 4,652,172 | 5,554,215
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 845,778 | 376,064
Available-for-sale Securities | 779,834 | 374,368
Fixed Income Securities [Member] | Corporate Debt Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 858,774 | 1,803,136
Available-for-sale Securities | 860,075 | 1,802,165
Fixed Income Securities [Member] | Foreign Government Debt Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 26,245 | 41,932
Available-for-sale Securities | 26,543 | 43,135
Fixed Income Securities [Member] | U.S. Agency Obligations [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis |  | 4,063
Available-for-sale Securities |  | 4,060
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 2,214,512 | 2,284,425
Available-for-sale Securities | 2,251,333 | 2,351,595
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 50,754 | 113,650
Available-for-sale Securities | 51,037 | 113,923
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 531,660 | 778,383
Available-for-sale Securities | $ 597,942 | $ 828,783

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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562 + Details
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