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v3.25.3

Marketable Securities Held in Trusts - Continuous Loss Position (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | $ 103.6 |  | $ 103.6 |  | $ 136.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (4.4) |  | (4.4) |  | (8.4)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 32.4 |  | 32.4 |  | 436.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0.2 |  | 0.2 |  | 10.2
Corporate debt securities |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 55.2 |  | 55.2 |  | 81.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (3.1) |  | (3.1) |  | (6.1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 8.7 |  | 8.7 |  | 53.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0.0 |  | 0.0 |  | 0.7
Municipal bonds |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 48.4 |  | 48.4 |  | 55.6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (1.3) |  | (1.3) |  | (2.3)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 14.3 |  | 14.3 |  | 102.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0.2 |  | 0.2 |  | 1.7
U.S. government bonds |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 9.4 |  | 9.4 |  | 280.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0.0 |  | 0.0 |  | $ 7.8
Debt securities |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Debt Securities, Available-for-sale, Realized Loss | 0.8 | $ 1.2 | 8.6 | $ 10.4 |
Debt Securities, Available-for-sale, Realized Gain | $ 0.6 | $ 6.4 | $ 1.3 | $ 17.2 |

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