NON-TRADED INVESTMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Variable Interest Entity [Line Items]
Assets	$ 20,809.7	$ 20,496.2	$ 20,864.3
VIEs
Variable Interest Entity [Line Items]
Assets	199.8		225.4
Liabilities	$ 155.2		$ 162.4