Schedule I - Summary Of Investments (Details) - Successor [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
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

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Amount of investments classified as other.

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