INVESTMENTS IN VARIABLE INTEREST ENTITIES (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2012 VIEs	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Variable Interest Entity [Line Items]
Investments held by variable interest entities		$ 814.3	$ 496.3
Cash and cash equivalents held by variable interest entities		54.2	74.4
Borrowings related to variable interest entities		767.0	519.9
Number of Variable Interest Entities Liquidated	1
Variable interest entity amortized cost securities held		809.3
Variable interest entity, gross unrealized gains fixed maturity securities		6.6
Variable interest entity gross unrealized losses fixed maturity securities		(1.6)
Variable interest entities net realized gain (loss) on investments		(0.4)	(1.3)	(3.7)
Variable Interest Entities Net Gains Losses From Sale Of Fixed Maturity Investments		0.4	3.0	(0.4)
Total other-than-temporary impairment losses on investments held by variable interest entities		(0.8)	(4.3)	(3.3)
Variable Interest Entities, Investments Sold		34.9	27.5
Variable Interest Entity, Available For Sale Securities, Gross Investment Losses From Sale, Before Tax		0.3	2.7
Investments held in limited partnerships		28.4
Unfunded committments to limited partnerships		40.5
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments held by variable interest entities		814.3	496.3
Notes receivable of VIEs held by insurance subsidiaries		(78.5)	(45.3)
Cash and cash equivalents held by variable interest entities		54.2	74.4
Accrued investment income		1.8	1.7
Income tax assets, net		0.7	5.4
Other assets		9.6	7.7
Total assets		802.1	540.2
Other liabilities		36.6	30.2
Borrowings related to variable interest entities		767.0	519.9
Notes payable of VIEs held by insurance subsidiaries		0	0
Total liabilities		803.6	550.1
VIEs [Member]
Variable Interest Entity [Line Items]
Investments held by variable interest entities		814.3	496.3
Notes receivable of VIEs held by insurance subsidiaries		0	0
Cash and cash equivalents held by variable interest entities		54.2	74.4
Accrued investment income		1.8	1.7
Income tax assets, net		3.3	6.8
Other assets		9.6	7.7
Total assets		883.2	586.9
Other liabilities		39.9	30.3
Borrowings related to variable interest entities		767.0	519.9
Notes payable of VIEs held by insurance subsidiaries		82.5	49.3
Total liabilities		889.4	599.5
Eliminations [Member]
Variable Interest Entity [Line Items]
Investments held by variable interest entities		0	0
Notes receivable of VIEs held by insurance subsidiaries		(78.5)	(45.3)
Cash and cash equivalents held by variable interest entities		0	0
Accrued investment income		0	0
Income tax assets, net		(2.6)	(1.4)
Other assets		0	0
Total assets		(81.1)	(46.7)
Other liabilities		(3.3)	(0.1)
Borrowings related to variable interest entities		0	0
Notes payable of VIEs held by insurance subsidiaries		(82.5)	(49.3)
Total liabilities		(85.8)	(49.4)
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		114.1	349.9
Gross unrealized losses on investments held by variable interest entity		0.7	6.0
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		59.1	33.0
Gross unrealized losses on investments held by variable interest entity		$ 0.9	$ 1.7