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FINANCIAL INSTRUMENTS - Available-for-Sale Debt Securities in a Continuous Unrealized Loss Position (Details) - USD ($)
$ in Millions
Sep. 30, 2024
Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value $ 1,160.8 $ 132.5
Unrealized losses less than 12 months, gross unrealized losses (1.4) (0.1)
Unrealized losses more than 12 months, fair value 788.6 2,595.1
Unrealized losses more than 12 months, gross unrealized losses (13.2) (60.4)
Total unrealized losses, fair value 1,949.4 2,727.6
Total unrealized losses, gross unrealized losses (14.6) (60.5)
U.S. treasuries    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 1,093.8 48.5
Unrealized losses less than 12 months, gross unrealized losses (1.3) 0.0
Unrealized losses more than 12 months, fair value 305.2 1,112.9
Unrealized losses more than 12 months, gross unrealized losses (5.7) (25.4)
Total unrealized losses, fair value 1,399.0 1,161.4
Total unrealized losses, gross unrealized losses (7.0) (25.4)
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 35.3 54.2
Unrealized losses less than 12 months, gross unrealized losses 0.0 (0.1)
Unrealized losses more than 12 months, fair value 324.6 1,219.2
Unrealized losses more than 12 months, gross unrealized losses (5.1) (25.8)
Total unrealized losses, fair value 359.9 1,273.4
Total unrealized losses, gross unrealized losses (5.1) (25.9)
U.S. government agencies    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 31.7 29.8
Unrealized losses less than 12 months, gross unrealized losses (0.1) 0.0
Unrealized losses more than 12 months, fair value 144.1 185.6
Unrealized losses more than 12 months, gross unrealized losses (2.3) (7.3)
Total unrealized losses, fair value 175.8 215.4
Total unrealized losses, gross unrealized losses (2.4) (7.3)
Municipal securities    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 0.0 0.0
Unrealized losses less than 12 months, gross unrealized losses 0.0 0.0
Unrealized losses more than 12 months, fair value 14.7 77.4
Unrealized losses more than 12 months, gross unrealized losses (0.1) (1.9)
Total unrealized losses, fair value 14.7 77.4
Total unrealized losses, gross unrealized losses $ (0.1) $ (1.9)