FAIR VALUE MEASUREMENTS (Details 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jul. 01, 2015	Dec. 31, 2014
Changes in fair value
Distributions			$ (1.0)	$ (0.9)
Purchase of redeemable noncontrolling interests in INTECH			(0.4)	(0.9)
Foreign currency translation losses		$ (0.7)	(0.4)	(1.7)
Change in fair value			0.3	1.6
Level 3 | INTECH founding member ownership interests | Fair Value, Measurements, Recurring
Changes in fair value
Balance at the beginning of the year, Liability Value	$ 7.2	4.6	5.4	7.3
Distributions	(0.1)	(0.2)	(0.7)	(0.7)
Current earnings	0.1	0.1	0.4	0.4
Purchase of redeemable noncontrolling interests in INTECH				(0.6)
Amortization of INTECH appreciation rights	0.8		2.7
Change in fair value	(0.5)	0.3	(0.3)	(1.6)
Balance at the end of the year, Liability Value	7.5	$ 4.8	7.5	$ 4.8
VelocityShares | Fair Value, Measurements, Recurring
Changes in fair value
Issuance	21.8		21.8			$ 17.9
VelocityShares | Level 3 | Fair Value, Measurements, Recurring
Changes in fair value
Balance at the beginning of the year, Liability Value	18.5		17.9
Change in fair value	3.3		3.9
Balance at the end of the year, Liability Value	21.8		21.8
Kapstream
Changes in fair value
Issuance	5.6		5.6		$ 6.0
Kapstream | Fair Value, Measurements, Recurring
Changes in fair value
Issuance	5.6		5.6
Kapstream | Level 3 | Fair Value, Measurements, Recurring
Changes in fair value
Issuance	6.0		6.0
Foreign currency translation losses	(0.5)		(0.5)
Change in fair value	0.1		0.1
Balance at the end of the year, Liability Value	$ 5.6		$ 5.6