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FINANCIAL INSTRUMENTS - Available-for-Sale Debt Securities in a Continuous Unrealized Loss Position (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value $ 405.9 $ 2,922.5
Unrealized losses less than 12 months, gross unrealized losses (0.7) (24.5)
Unrealized losses more than 12 months, fair value 834.2 520.1
Unrealized losses more than 12 months, gross unrealized losses (3.7) (9.2)
Total unrealized losses, fair value 1,240.1 3,442.6
Total unrealized losses, gross unrealized losses (4.4) (33.7)
U.S. treasuries    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 405.9 2,744.4
Unrealized losses less than 12 months, gross unrealized losses (0.7) (23.3)
Unrealized losses more than 12 months, fair value 730.7 190.1
Unrealized losses more than 12 months, gross unrealized losses (2.3) (4.2)
Total unrealized losses, fair value 1,136.6 2,934.5
Total unrealized losses, gross unrealized losses (3.0) (27.5)
Corporate debt 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 73.1 218.7
Unrealized losses more than 12 months, gross unrealized losses (1.2) (3.7)
Total unrealized losses, fair value 73.1 218.7
Total unrealized losses, gross unrealized losses (1.2) (3.7)
U.S. government agencies    
Debt Securities, Available-for-sale [Line Items]    
Unrealized losses less than 12 months, fair value 0.0 178.1
Unrealized losses less than 12 months, gross unrealized losses 0.0 (1.2)
Unrealized losses more than 12 months, fair value 29.0 106.7
Unrealized losses more than 12 months, gross unrealized losses (0.2) (1.2)
Total unrealized losses, fair value 29.0 284.8
Total unrealized losses, gross unrealized losses (0.2) (2.4)
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 1.4 4.6
Unrealized losses more than 12 months, gross unrealized losses 0.0 (0.1)
Total unrealized losses, fair value 1.4 4.6
Total unrealized losses, gross unrealized losses $ 0.0 $ (0.1)