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ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - OCI and tax effects (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Pre-Tax Amount      
Realized gain (loss) on foreign currency transactions $ (0.9) $ 1.9 $ 0.5
Other comprehensive income (loss), before tax (66.8) 64.6 (34.0)
Tax (Expense) Benefit      
Realized gain (loss) on foreign currency transactions, net of tax 0.5    
Other comprehensive income (loss), tax (0.2) 0.2 2.4
Net-of-Tax Amount      
Realized gain (loss) on foreign currency transactions reclassified into investment expense (income), net of tax (0.4) 1.9 0.5
Other comprehensive income (loss) (67.0) 64.8 (31.6)
Foreign Currency      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period (78.9) 66.8 (18.3)
Tax (Expense) Benefit      
Unrealized foreign currency translation adjustment arising during the period, tax   0.2 1.8
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax (78.9) 67.0 (16.5)
Realized gain (loss) on foreign currency transactions reclassified into investment expense (income), net of tax (0.4)    
Realized net (gain) loss reclassified into equity in earnings of non-consolidated entities, net of tax   1.9  
Pension and Other Benefit Adjustments, Net Gain or Loss      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period 13.0 (4.1) (16.1)
Tax (Expense) Benefit      
Unrealized foreign currency translation adjustment arising during the period, tax (0.7)   0.6
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax $ 12.3 $ (4.1) (15.5)
Unrealized Loss from Equity Method Investees' Cash Flow Hedge      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period     (0.1)
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax     $ (0.1)