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, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance $ 106.7 $ 93.5 $ 91.4 $ 49.5
Included in earnings 74.3 158.6 89.6 202.8
Settlements (62.9) (77.5) (62.9) (77.7)
Ending balance - June 30 118.1 174.6 118.1 174.6
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date 73.0 80.6 88.3 125.1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning balance (9.8) 0.0 0.0 (1.7)
Included in earnings 4.5 (3.7) (5.3) (4.3)
Settlements 5.3 0.7 5.3 3.0
Ending balance - June 30 0.0 (3.0) 0.0 (3.0)
Total losses for the period included in earnings attributable to the change in unrealized losses on liabilities still held at the reporting date $ 0.0 $ (3.0) $ 0.0 $ (3.0)