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Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Details) - USD ($) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2022
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | $ 1 | $ 0 | $ 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 31 | 31 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 27 | 53 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 636 | 400 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 63 | 53 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 90 | 106 |
Fixed maturity securities, at fair value | 1,923 |  |
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Period Increase (Decrease) | 1 |  |
Short-term Investments [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 14 | 86 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 12 | 78 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 2 | 8 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Fixed maturity securities, at fair value | 367 | 507 |
Fixed Income Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 1,147 | 1,183 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 1 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 31 | 31 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 513 | 791 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 27 | 53 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 634 | 392 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 63 | 53 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 90 | 106 |
Fixed maturity securities, at fair value | 1,494 | 1,395 |
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 17 | 28 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 1 | 21 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 1 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 17 | 7 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 2 | 1 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 2 | 2 |
Fixed maturity securities, at fair value | 57 | 43 |
Fixed Income Securities [Member] | Corporate Debt Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 630 | 559 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 1 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 237 | 280 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 7 | 21 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 393 | 279 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 47 | 42 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 54 | 63 |
Fixed maturity securities, at fair value | 679 | 598 |
Fixed Income Securities [Member] | Foreign Obligations [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 72 | 73 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 19 | 27 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 1 | 2 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 53 | 47 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 7 | 7 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 8 | 9 |
Fixed maturity securities, at fair value | 79 | 76 |
Fixed Income Securities [Member] | US Government Debt Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 57 | 58 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 19 | 40 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 1 | 3 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 38 | 19 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 2 | 1 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 4 |
Fixed maturity securities, at fair value | 63 | 65 |
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 132 | 132 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 1 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 26 | 28 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 120 | 132 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 14 | 19 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 12 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 2 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 16 | 19 |
Fixed maturity securities, at fair value | 240 | 238 |
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 125 | 126 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 10 | 90 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 3 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 115 | 36 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 3 | 1 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 3 | 4 |
Fixed maturity securities, at fair value | 137 | 137 |
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 111 | 203 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 3 | 2 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 105 | 198 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 4 | 4 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 6 | 5 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 1 | 1 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 5 | 5 |
Fixed maturity securities, at fair value | 223 | 224 |
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 3 | 3 |
Debt Securities, Available-for-sale, Allowance for Credit Loss |  | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 3 | 3 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Fixed Income Securities [Member] | Collateralized Mortgage Backed Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Fixed maturity securities, at fair value | 15 | 15 |
Fixed Income Investments And Other Investments [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 1 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 31 | 31 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 90 | 106 |
Fixed maturity securities, at fair value | 1,862 | 1,902 |
Collateral Pledged [Member] | Fixed Income Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Fixed maturity securities, at fair value | 61 | 64 |
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Fixed maturity securities, at fair value | 61 | 64 |
Asset Pledged as Collateral [Member] | Fixed Income Securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | $ 0 | $ 0 |

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
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