INVESTMENTS IN VARIABLE INTEREST ENTITIES (NARRATIVE) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) entity	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Variable Interest Entity [Line Items]
Gain (loss) on dissolution of variable interest entities	$ (7.3)	$ 11.3	$ 0.0
Repayments of investment borrowings related to variable interest entities, amounts due in 2017	16.8
Repayments of investment borrowings related to variable interest entities, amounts due in 2018	0.7
Repayments of investment borrowings related to variable interest entities, amounts due in 2019	0.8
Repayments of investment borrowings related to variable interest entities, amounts due in 2020	0.2
Repayments of investment borrowings related to variable interest entities, amounts due in 2022	150.2
Repayments of investment borrowings related to variable interest entities, amounts due in 2024	381.8
Repayments of investment borrowings related to variable interest entities, amounts due in 2026	326.9
Repayments of investment borrowings related to variable interest entities, amounts due in 2027	276.3
Repayments of investment borrowings related to variable interest entities, amounts due in 2028	539.9
Variable interest entity amortized cost securities held	1,708.6
Variable interest entity, gross unrealized gains fixed maturity securities	19.5
Variable interest entity gross unrealized losses fixed maturity securities	(3.8)
Variable interest entity, estimated fair value of securities held	1,724.3
Variable interest entities net realized gain (loss) on investments	(20.4)	(6.4)	(2.2)
Variable interest entities, net losses from the sales of fixed maturities	(11.9)	(1.3)
Writedowns of investments for other than temporary declines in fair value recognized through net income	$ (1.2)	(16.4)
Number of VIEs in default | entity	0
Investments held by VIEs and sold	$ 192.2	46.1	38.7
Variable interest entity, gross investment losses from sale	20.3	1.8	$ 2.4
Less than twelve months [Member]
Variable Interest Entity [Line Items]
Fair value investments held by variable interest entity that had been in an unrealized loss position	93.8	1,178.7
Gross unrealized gain (loss) on investments held by VIEs	(0.9)	(23.9)
Greater than twelve months [Member]
Variable Interest Entity [Line Items]
Fair value investments held by variable interest entity that had been in an unrealized loss position	143.9	294.3
Gross unrealized gain (loss) on investments held by VIEs	$ (2.9)	$ (22.3)