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v3.23.3

Marketable Securities Held in Trusts - Continuous Loss Position (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | $ 215.7 |  | $ 215.7 |  | $ 135.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (21.0) |  | (21.0) |  | (15.8)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 426.5 |  | 426.5 |  | 475.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 14.3 |  | 14.3 |  | 12.9
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 | 124.4 |  | 124.4 |  | 72.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (13.5) |  | (13.5) |  | (10.6)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 62.1 |  | 62.1 |  | 105.6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 1.9 |  | 1.9 |  | 6.5
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 | 91.3 |  | 91.3 |  | 61.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (7.5) |  | (7.5) |  | (5.1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 102.1 |  | 102.1 |  | 104.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 3.3 |  | 3.3 |  | 2.9
U.S. government 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 | 0.0 |  | 0.0 |  | 0.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0.0 |  | 0.0 |  | (0.1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 262.3 |  | 262.3 |  | 264.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 9.1 |  | 9.1 |  | $ 3.5
Debt securities |  |  |  |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss |  |  |  |  |
Debt Securities, Available-for-sale, Realized Loss | $ 5.7 | $ 1.0 | $ 20.9 | $ 26.8 |

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