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Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions |  | 3 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Apr. 29, 1991 | Dec. 31, 2021 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2015 | Jun. 30, 2020 | Jul. 01, 2019 | Dec. 31, 2018 | Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |  |
Operating Lease, Liability |  | $ 28 | $ 28 | $ 30 |  |  |  |  |  |
Income Taxes Paid |  |  | $ 15 | $ 11 | $ 21 |  |  |  |  |
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 | 20,000,000 | 20,000,000 |  |  |  |  |  |
Preferred Stock, Par or Stated Value Per Share |  | $ 0.01 | $ 0.01 |  |  |  |  |  |  | $ 0.01
Common stock, shares issued |  | 46,477,068 | 46,477,068 | 45,865,081 |  |  |  |  |  |
Warrant Exercised During Period Shares |  |  | 132 | 34 | 0 |  |  |  |  |
Common Stock Transfer Restrictions | 5.00% |  |  |  |  |  |  |  |  |
Common Stock Additional Transfer Restrictions |  |  |  |  |  | 5.00% |  |  |  |
Cash and cash equivalents |  | $ 17 | $ 17 | $ 20 | $ 24 |  |  |  |  |
Restricted Cash |  | 5 | 5 | 13 | 55 |  |  |  |  |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents |  | 23 | 23 | 35 | 81 |  |  |  | $ 83 |
UK Income Tax Rate |  |  |  |  |  |  | 17.00% | 19.00% |  |
Restricted Cash |  | $ 5 | $ 5 | $ 13 | 55 |  |  |  |  |
Weighted average period of future premiums |  |  | 8 years | 8 years 3 months 18 days |  |  |  |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate |  | 2.20% | 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 |  | $ 5 | $ 5 | $ 4 |  |  |  |  |  |
Restricted Cash |  | 5 | $ 5 | 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 |  |  | $ 80 | 107 | 143 |  |  |  |  |
Fixed Income Securities [Member] |  |  |  |  |  |  |  |  |  |
Investment income due and accrued |  | 10 | 10 | 10 |  |  |  |  |  |
Investment income due and accrued |  | 10 | 10 | 10 |  |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |  |  |
Restricted Cash |  | 2 | 2 | 2 | 2 |  |  |  |  |
Restricted Cash |  | $ 2 | $ 2 | $ 2 | $ 2 |  |  |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate |  | 3.00% | 3.00% | 2.40% |  |  |  |  |  |

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