LONG-TERM INCENTIVE COMPENSATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Long-term incentive compensation expense
Total long-term incentive compensation	$ 76.8	$ 51.3	$ 63.1
Restricted Stock Awards
Long-term incentive compensation expense
Total long-term incentive compensation	35.1	27.0	21.0
Restricted Stock Awards | Intech Investment Management LLC | Key employees
Long-term incentive compensation expense
Total long-term incentive compensation	1.0	1.7	2.4
Mutual Fund Share Awards
Long-term incentive compensation expense
Total long-term incentive compensation	25.3	32.4	38.3
Profits Interest And Other
Long-term incentive compensation expense
Total long-term incentive compensation	16.2		0.7
Long-term incentive compensation benefit		(8.5)
Employee stock options
Long-term incentive compensation expense
Total long-term incentive compensation	$ 0.2	$ 0.4	$ 3.1