Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Jul. 01, 2019	Jun. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Operating Lease, Liability	$ 30	$ 30
Income Taxes Paid		$ 11
Common Stock, Par or Stated Value Per Share	$ 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	45,865,081	45,865,081
Warrant Exercised During Period Shares		34
Cash and cash equivalents	$ 20	$ 20
Restricted Cash	13	13
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	35	35
UK Income Tax Rate			19.00%	17.00%
Restricted Cash	$ 13	$ 13
Weighted average period of future premiums		8 years 3 months 18 days
Estimated Future Premium Payments Weighted Average Discounted Rate	2.20%	2.20%
Business Combination, Redeemable Noncontrolling Percentage	20.00%	20.00%
Xchange
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	14 years
Restricted Cash	$ 4	$ 4
Restricted Cash	$ 4	$ 4
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		$ 107
Variable Interest Entity, Primary Beneficiary [Member]
Estimated Future Premium Payments Weighted Average Discounted Rate	2.40%	2.40%