MARKETABLE SECURITIES - Trading Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net gains (losses) on trading securities	$ 0.1	$ (0.5)	$ 0.6	$ 1.6
Fair Value, Inputs, Level 1 [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities classified as level 1	$ 10.3		$ 10.3		$ 14.2