Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 01, 2013	Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items]
Common Stock Voting Restrictions				10.00%
Common Stock, Par or Stated Value Per Share						$ 0.01
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Preferred stock, shares authorized						20,000,000
Preferred Stock, Par or Stated Value Per Share						$ 0.01
Common stock, shares issued						45,000,000
Junior surplus note of Ambac Assurance Segregated Account					$ 350,000
Common Stock Transfer Restrictions				5.00%
Common Stock Additional Transfer Restrictions				5.00%
Minimum [Member] | Furniture and Fixtures [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum [Member] | Furniture and Fixtures [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Successor [Member]
Finite-Lived Intangible Assets [Line Items]
Obligations under investment agreements	$ 0	$ 82,358
Income Taxes Paid	40,334	21,437	$ 16,969
Decrease in long-term debt as a result of an exchange for investment securities	55,426	0	0
Goodwill, Impairment Loss	$ 0	$ 0	$ 514,511
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01			$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares issued					45,000,000
Warrant Exercised During Period Shares	0	136	740
Successor [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Debt Instrument, Interest Rate, Basis for Effective Rate		.0094
Long-term Debt [Member] | Successor [Member]
Finite-Lived Intangible Assets [Line Items]
Interest Paid	$ 39,112	$ 4,537	$ 1,847
Accounting Standards Update 2018-02 [Domain] | Successor [Member]
Finite-Lived Intangible Assets [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0
Accounting Standards Update 2018-02 [Domain] | AOCI Attributable to Parent [Member] | Successor [Member]
Finite-Lived Intangible Assets [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(6,588)
Accounting Standards Update 2018-02 [Domain] | Retained Earnings [Member] | Successor [Member]
Finite-Lived Intangible Assets [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 6,588