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Available-for-Sale Debt Securities - Schedule of Fair Value of Available-For-Sale Debt Securities (Details) - USD ($)
$ in Millions
Sep. 30, 2024
Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost, Current $ 877.4 $ 781.7
Unrealized Gain, Current 1.6 0.3
Unrealized Loss, Current (0.1) (1.5)
Fair Value, Current 878.9 780.5
Amortized Cost, Noncurrent 637.1 684.6
Unrealized Gain, Noncurrent 7.0 3.4
Unrealized Loss, Noncurrent (0.2) (0.5)
Fair Value, Noncurrent 643.9 687.5
Commercial paper    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost, Current 37.3 53.5
Unrealized Gain, Current 0.0 0.0
Unrealized Loss, Current 0.0 0.0
Fair Value, Current 37.3 53.5
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost, Current 531.4 382.1
Unrealized Gain, Current 1.0 0.1
Unrealized Loss, Current (0.1) (1.0)
Fair Value, Current 532.3 381.2
Amortized Cost, Noncurrent 488.9 483.5
Unrealized Gain, Noncurrent 6.2 2.9
Unrealized Loss, Noncurrent (0.1) (0.4)
Fair Value, Noncurrent 495.0 486.0
Securities of government-sponsored entities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost, Current 308.7 346.1
Unrealized Gain, Current 0.6 0.2
Unrealized Loss, Current 0.0 (0.5)
Fair Value, Current 309.3 345.8
Amortized Cost, Noncurrent 148.2 201.1
Unrealized Gain, Noncurrent 0.8 0.5
Unrealized Loss, Noncurrent (0.1) (0.1)
Fair Value, Noncurrent $ 148.9 $ 201.5