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FINANCIAL INSTRUMENTS - Available-for-Sale Debt Securities in a Continuous Unrealized Loss Position (Details) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value $ 1,323.5 $ 132.5
Unrealized losses less than 12 months, gross unrealized losses (7.9) (0.1)
Unrealized losses more than 12 months, fair value 1,783.1 2,595.1
Unrealized losses more than 12 months, gross unrealized losses (42.9) (60.4)
Total unrealized losses, fair value 3,106.6 2,727.6
Total unrealized losses, gross unrealized losses (50.8) (60.5)
U.S. treasuries    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 1,214.8 48.5
Unrealized losses less than 12 months, gross unrealized losses (7.5) 0.0
Unrealized losses more than 12 months, fair value 705.5 1,112.9
Unrealized losses more than 12 months, gross unrealized losses (18.0) (25.4)
Total unrealized losses, fair value 1,920.3 1,161.4
Total unrealized losses, gross unrealized losses (25.5) (25.4)
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 16.0 54.2
Unrealized losses less than 12 months, gross unrealized losses 0.0 (0.1)
Unrealized losses more than 12 months, fair value 828.8 1,219.2
Unrealized losses more than 12 months, gross unrealized losses (17.6) (25.8)
Total unrealized losses, fair value 844.8 1,273.4
Total unrealized losses, gross unrealized losses (17.6) (25.9)
U.S. government agencies    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 92.7 29.8
Unrealized losses less than 12 months, gross unrealized losses (0.4) 0.0
Unrealized losses more than 12 months, fair value 179.4 185.6
Unrealized losses more than 12 months, gross unrealized losses (6.1) (7.3)
Total unrealized losses, fair value 272.1 215.4
Total unrealized losses, gross unrealized losses (6.5) (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 69.4 77.4
Unrealized losses more than 12 months, gross unrealized losses (1.2) (1.9)
Total unrealized losses, fair value 69.4 77.4
Total unrealized losses, gross unrealized losses $ (1.2) $ (1.9)