v3.10.0.1
ACCUMULATED OTHER COMPREHENSIVE INCOME - OCI and tax effects (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Sep. 30, 2018
Sep. 30, 2017
Pre-Tax Amount                
Unrealized net holding gain (loss) arising during the period $ 0.2             $ 0.9
Amortization of net (gain) loss reclassified into general and administrative: other, before tax               (0.5)
Other comprehensive income (loss), before tax (8.0)     $ 37.9     $ (104.8) 119.2
Tax (Expense) Benefit                
Unrealized net holding gain (loss) arising during the period, tax (0.1)             (0.4)
Other comprehensive income (loss), tax 0.5     (4.2)     0.9 (10.9)
Net-of-Tax Amount                
Unrealized net holding gain (loss) arising during the period, net of tax 0.1              
Realized loss on foreign currency transactions, net of tax             1.0  
Amortization of net (gain) loss reclassified into general and administrative: other, net of tax               (0.5)
Realized net (gain) loss reclassified into investment income, net of tax               (0.1)
Other comprehensive income (loss), net of tax (7.5) $ (107.0) $ 10.5 33.7 $ 76.5 $ (1.9) (103.9) 108.3
Foreign Currency                
Pre-Tax Amount                
Unrealized net holding gain (loss) arising during the period (5.7)     39.0     (101.7) 120.4
Realized net (gain) loss reclassified into investment expense (income)             1.0  
Tax (Expense) Benefit                
Unrealized net holding gain (loss) arising during the period, tax       (4.6)     0.1 (11.1)
Net-of-Tax Amount                
Unrealized net holding gain (loss) arising during the period, net of tax (5.7)     34.4     (101.6) 109.3
Realized loss on foreign currency transactions, net of tax             1.0  
Reclassification adjustment for net gain (loss) realized in net earnings, net of tax             1.0  
Other comprehensive income (loss), net of tax             (100.6)  
Pension and Other Benefit Adjustments, Net Gain or Loss                
Pre-Tax Amount                
Unrealized net holding gain (loss) arising during the period             (1.5)  
Tax (Expense) Benefit                
Unrealized net holding gain (loss) arising during the period, tax             0.2  
Net-of-Tax Amount                
Unrealized net holding gain (loss) arising during the period, net of tax             (1.3)  
Unrealized Gains on Marketable Securities (Recorded in Investment income)                
Pre-Tax Amount                
Unrealized net holding gain (loss) arising during the period       0.4        
Realized net (gain) loss reclassified into investment expense (income)               (0.1)
Tax (Expense) Benefit                
Unrealized net holding gain (loss) arising during the period, tax       0.2        
Net-of-Tax Amount                
Unrealized net holding gain (loss) arising during the period, net of tax       0.2       0.5
Realized net (gain) loss reclassified into investment income, net of tax               (0.1)
Unrealized Gain from Equity Method Investees' Cash Flow Hedge                
Pre-Tax Amount                
Unrealized net holding gain (loss) arising during the period       (0.1)     0.2  
Net-of-Tax Amount                
Unrealized net holding gain (loss) arising during the period, net of tax       (0.1)     0.2  
Reclassification adjustment for net gain (loss) realized in net earnings, net of tax             (2.2)  
Other comprehensive income (loss), net of tax             (2.0)  
Realized Net Loss from Non-Consolidated Entities' Cash Flow Hedge                
Pre-Tax Amount                
Reclassification adjustment for net gain (loss) realized in net earnings (2.5)     (1.6)     (2.8) (1.5)
Tax (Expense) Benefit                
Reclassification adjustment for net gain (loss) realized in net earnings, tax 0.6     0.6     0.6 0.6
Net-of-Tax Amount                
Reclassification adjustment for net gain (loss) realized in net earnings, net of tax $ (1.9)     $ (1.0)     $ (2.2) $ (0.9)