Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation) (Details)

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FAIR VALUE MEASUREMENTS (Fair Value, Assets and Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance $ 93.5 $ 59.2 $ 49.5 $ 30.1
Total gains        
Included in earnings 158.6 51.0 202.8 84.6
Settlements (77.5) (40.0) (77.7) (44.5)
Ending balance - June 30 174.6 70.2 174.6 70.2
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date 80.6 17.8 125.1 51.0
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance 0.0 0.0 (1.7) 0.0
Total losses        
Included in earnings (3.7) (20.2) (4.3) (20.2)
Settlements 0.7 0.0 3.0 0.0
Ending balance - June 30 (3.0) (20.2) (3.0) (20.2)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ (3.0) $ (20.2) $ (3.0) $ (20.2)