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Employee Benefit Plans - Narrative (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Employee benefit plans [Line Items] |  |  |
Recognized contribution expense | $ 16,000,000 | $ 20,000,000 | $ 20,000,000
Sound Point Agreement | Disposal Group, Held-for-Sale, Not Discontinued Operations |  |  |
Employee benefit plans [Line Items] |  |  |
Postretirement plan benefit obligation | $ 8,000,000 |  |
U.S. |  |  |
Employee benefit plans [Line Items] |  |  |
Number of years of service to become fully vested | 1 year |  |
401 (k) Plan | U.S. |  |  |
Employee benefit plans [Line Items] |  |  |
Percentage by which employer contribution matches up to 6% of participant's compensation | 100.00% |  |
Maximum percentage of participant's compensation eligible for employer contribution match | 7.00% | 7.00% | 7.00%
Core contribution made by the company as a percentage of participant's compensation | 7.00% | 7.00% | 7.00%
Nonqualified Supplemental Executive Retirement Plan | U.S. |  |  |
Employee benefit plans [Line Items] |  |  |
Percentage by which employer contribution matches up to 6% of participant's compensation | 100.00% |  |
Maximum percentage of participant's compensation eligible for employer contribution match | 6.00% |  |
Core contribution made by the company as a percentage of participant's compensation | 6.00% |  |
Restricted Stock Units (RSUs) |  |  |
Employee benefit plans [Line Items] |  |  |
Unrecognized compensation expense | $ 15,000,000 |  |
Expected weighted-average remaining service period for recognition of unrecognized compensation cost (in years) | 1 year 8 months 12 days |  |
Total fair value of awards delivered | $ 18,000,000 | $ 12,000,000 | $ 12,000,000
Granted (in dollars per share) | $ 61.26 | $ 56.46 | $ 44.08
Restricted Stock Units (RSUs) | Minimum |  |  |
Employee benefit plans [Line Items] |  |  |
Vesting period of awards (in years) | 3 years |  |
Restricted Stock Units (RSUs) | Maximum |  |  |
Employee benefit plans [Line Items] |  |  |
Vesting period of awards (in years) | 4 years |  |
Performance Restricted Stock Units |  |  |
Employee benefit plans [Line Items] |  |  |
Vesting period of awards (in years) | 3 years |  |
Unrecognized compensation expense | $ 13,000,000 |  |
Expected weighted-average remaining service period for recognition of unrecognized compensation cost (in years) | 1 year 8 months 12 days |  |
Total fair value of awards delivered | $ 11,000,000 | $ 8,000,000 | $ 9,000,000
Granted (in dollars per share) | $ 71.34 | $ 62.89 | $ 52.04
Number of shares issued per right (in shares) | 2 |  |
Performance Restricted Stock Units, Tied to Relative TSR |  |  |
Employee benefit plans [Line Items] |  |  |
Granted (in dollars per share) | $ 38.96 |  |
Number of shares issued per right (in shares) | 2.5 |  |
Restricted Stock Awards |  |  |
Employee benefit plans [Line Items] |  |  |
Unrecognized compensation expense | $ 700,000 |  |
Expected weighted-average remaining service period for recognition of unrecognized compensation cost (in years) | 3 months 18 days |  |
Granted (in dollars per share) | $ 52.26 | $ 59.47 | $ 51.34
Total fair value of awards vested | $ 2,200,000 | $ 2,300,000 | $ 1,900,000
Assured Guaranty Ltd. 2004 Long-Term Incentive Plan |  |  |
Employee benefit plans [Line Items] |  |  |
Maximum number of common shares that may be delivered (in shares) | 18,670,000 |  |
Assured Guaranty Ltd. 2004 Long-Term Incentive Plan | Stock Options |  |  |
Employee benefit plans [Line Items] |  |  |
Number of common shares available for grant (in shares) | 7,841,664 |  |
Employee Stock Purchase Plan | Employee Stock |  |  |
Employee benefit plans [Line Items] |  |  |
Number of common shares available for grant (in shares) | 367,838 |  |
Value of shares that can be purchased as a percentage of participant's compensation | 10.00% |  |
Value of shares that can be purchased | $ 25,000 |  |
Purchase price of shares as a percentage of the fair market value of the stock | 85.00% |  |
Capital shares reserved for future issuance (in shares) | 1,200,000 |  |

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