Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014	Aug. 03, 2018	May 01, 2013	Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items]
Operating Lease, Liability	$ 29	$ 29	$ 15
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			0
Income Taxes Paid		$ 21	$ 35	$ 40
AMPS Exchange Carrying Value of Surplus Notes Issued							$ 187
Decrease in long-term debt as a result of an exchange for investment securities				$ 55
Common Stock Voting Restrictions						10.00%
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01						$ 0.01
Entity Incorporation, Date of Incorporation		Apr. 29, 1991
Preferred stock, shares authorized	20,000,000	20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01
Common stock, shares issued	45,571,743	45,571,743	45,365,170
Warrant Exercised During Period Shares	0			194	0
Junior surplus note of Ambac Assurance Segregated Account								$ 350
Common Stock Transfer Restrictions						5.00%
Common Stock Additional Transfer Restrictions						5.00%
Non Cash Impact of Rehabilitation Exit Transaction			$ 1,919
Cash and cash equivalents	$ 24	$ 24	63	$ 624
Restricted Cash	55	55	19
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	81	$ 81	83	625	$ 96
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
Long-term Debt [Member]
Finite-Lived Intangible Assets [Line Items]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		$ 143	232	39
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Finite-Lived Intangible Assets [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			(3)
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Finite-Lived Intangible Assets [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			3
Variable Interest Entity, Primary Beneficiary [Member]
Finite-Lived Intangible Assets [Line Items]
Restricted Cash	$ 2	$ 2	$ 1	$ 1