v3.20.4
CORPORATE BORROWINGS AND FINANCE LEASE OBLIGATIONS - Senior Unsecured Convertible Notes (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jul. 31, 2020
Sep. 14, 2018
CORPORATE BORROWINGS AND CAPITAL AND FINANCING LEASE OBLIGATIONS          
Discount $ 338.7 $ (69.1)      
Debt issuance costs (42.1) (88.8)      
Derivative liability   0.5      
Amortization of net discount (premium) on corporate borrowings to interest expense (22.0) 11.3 $ 0.2    
Amortization of debt issuance costs 14.2 15.8 16.0    
2.95% Senior Secured Convertible Notes due 2024          
CORPORATE BORROWINGS AND CAPITAL AND FINANCING LEASE OBLIGATIONS          
Principal balance 600.0       $ 600.0
Discount (61.5) (73.7)      
Debt issuance costs (9.5)        
Change fair value of derivative (89.4) 23.5 $ 66.4    
Reclassification to Additional Paid-in Capital (89.9)        
Carrying value 529.0        
Convertible Notes due 2026          
CORPORATE BORROWINGS AND CAPITAL AND FINANCING LEASE OBLIGATIONS          
Principal balance       $ 600.0  
Derivative liability         90.4
Convertible Notes          
CORPORATE BORROWINGS AND CAPITAL AND FINANCING LEASE OBLIGATIONS          
Principal balance   600.0     600.0
Discount   (73.7)     (86.7)
Debt issuance costs   (11.2)     (13.0)
Derivative liability   0.5     24.0
Amortization of net discount (premium) on corporate borrowings to interest expense 12.2 13.0      
Amortization of debt issuance costs 1.7 1.8      
Change fair value of derivative 89.4 (23.5)      
Carrying value   515.6     $ 524.3
Increase to Expense (Income) $ 103.3 $ (8.7)