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Financial Instruments - Schedule Of Available-For-Sale Investments With Unrealized Losses (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]    
Unrealized losses less than 12 months, fair value $ 2,922.5 $ 132.5
Unrealized losses less than 12 months (24.5) (0.1)
Unrealized losses 12 months or greater, fair value 520.1 2,595.1
Unrealized losses 12 months or greater (9.2) (60.4)
Total Fair Value 3,442.6 2,727.6
Total Unrealized Losses (33.7) (60.5)
U.S. treasuries    
Schedule of Available-for-sale Securities [Line Items]    
Unrealized losses less than 12 months, fair value 2,744.4 48.5
Unrealized losses less than 12 months (23.3) 0.0
Unrealized losses 12 months or greater, fair value 190.1 1,112.9
Unrealized losses 12 months or greater (4.2) (25.4)
Total Fair Value 2,934.5 1,161.4
Total Unrealized Losses (27.5) (25.4)
Corporate debt securities    
Schedule of Available-for-sale Securities [Line Items]    
Unrealized losses less than 12 months, fair value 0.0 54.2
Unrealized losses less than 12 months 0.0 (0.1)
Unrealized losses 12 months or greater, fair value 218.7 1,219.2
Unrealized losses 12 months or greater (3.7) (25.8)
Total Fair Value 218.7 1,273.4
Total Unrealized Losses (3.7) (25.9)
U.S. government agencies    
Schedule of Available-for-sale Securities [Line Items]    
Unrealized losses less than 12 months, fair value 178.1 29.8
Unrealized losses less than 12 months (1.2) 0.0
Unrealized losses 12 months or greater, fair value 106.7 185.6
Unrealized losses 12 months or greater (1.2) (7.3)
Total Fair Value 284.8 215.4
Total Unrealized Losses (2.4) (7.3)
Municipal securities    
Schedule of Available-for-sale Securities [Line Items]    
Unrealized losses less than 12 months, fair value 0.0 0.0
Unrealized losses less than 12 months 0.0 0.0
Unrealized losses 12 months or greater, fair value 4.6 77.4
Unrealized losses 12 months or greater (0.1) (1.9)
Total Fair Value 4.6 77.4
Total Unrealized Losses $ (0.1) $ (1.9)