Marketable Securities Held in Trusts - Continuous Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 432.1	$ 337.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6.3	0.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	52.3	88.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2.9)	(3.9)
Corporate debt securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	89.6	17.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1.1	0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	33.0	48.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2.2)	(2.7)
Municipal bonds
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	37.7	14.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.3	0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	19.3	40.2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(0.7)	(1.2)
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	304.8	306.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 4.9	$ 0.5

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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