Schedule of Level 3 Financial Assets (Details) (Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
U.S. government and agency
Level 3 Financial Assets:
Balance, beginning of period	$ 25.9	[1]	$ 31.7	[1]
Purchases	44.3	[1]	3.2	[1]
Sales	(4.3)	[1]	(6.7)	[1]
Transfers into Level 3	0	[1]	0	[1]
Transfers out of Level 3	0	[1]	0	[1]
Realized & unrealized gains (losses) included in income	0	[1],[2]	0	[1],[2]
Unrealized gains (losses) included in OCI	(7.1)	[1]	(2.3)	[1]
Total	58.8	[1]	25.9	[1]
State and political subdivision
Level 3 Financial Assets:
Balance, beginning of period	116.1		48.7
Purchases	47.8		41.9
Sales	(1.5)		(0.8)
Transfers into Level 3	0		12.9
Transfers out of Level 3	0		0
Realized & unrealized gains (losses) included in income	0	[2]	0	[2]
Unrealized gains (losses) included in OCI	(28.6)		13.4
Total	133.8		116.1
Foreign government
Level 3 Financial Assets:
Balance, beginning of period	8.0		3.1
Purchases	0		3.5
Sales	0		0
Transfers into Level 3	1.6		0
Transfers out of Level 3	(6.1)		0
Realized & unrealized gains (losses) included in income	0	[2]	0	[2]
Unrealized gains (losses) included in OCI	(0.2)		1.4
Total	3.3		8.0
Corporate
Level 3 Financial Assets:
Balance, beginning of period	801.5		513.8
Purchases	364.8		297.1
Sales	(12.8)		(16.2)
Transfers into Level 3	41.6		21.0
Transfers out of Level 3	(10.9)		(14.2)
Realized & unrealized gains (losses) included in income	0	[2]	0	[2]
Unrealized gains (losses) included in OCI	(81.9)		0
Total	1,102.3		801.5
CMBS
Level 3 Financial Assets:
Balance, beginning of period	19.3		35.4
Purchases	19.3		0
Sales	(0.7)		(0.6)
Transfers into Level 3	0		1.1
Transfers out of Level 3	(1.5)		(17.1)
Realized & unrealized gains (losses) included in income	(0.2)	[2]	0	[2]
Unrealized gains (losses) included in OCI	(4.3)		0.5
Total	31.9		19.3
RMBS
Level 3 Financial Assets:
Balance, beginning of period	222.6		268.0
Purchases	1.3		1.6
Sales	(28.9)		(38.9)
Transfers into Level 3	5.1		0
Transfers out of Level 3	0		0
Realized & unrealized gains (losses) included in income	(0.4)	[2]	2.0	[2]
Unrealized gains (losses) included in OCI	(23.8)		(10.1)
Total	175.9		222.6
CDO/CLO
Level 3 Financial Assets:
Balance, beginning of period	56.8		62.5
Purchases	36.6		2.8
Sales	(6.6)		(5.3)
Transfers into Level 3	0		0
Transfers out of Level 3	0		0
Realized & unrealized gains (losses) included in income	(0.3)	[2]	(0.3)	[2]
Unrealized gains (losses) included in OCI	(15.6)		(2.9)
Total	70.9		56.8
Other asset-backed
Level 3 Financial Assets:
Balance, beginning of period	80.1		81.2
Purchases	13.4		9.5
Sales	(6.0)		(7.6)
Transfers into Level 3	0		0
Transfers out of Level 3	0		(1.8)
Realized & unrealized gains (losses) included in income	0	[2]	0	[2]
Unrealized gains (losses) included in OCI	(5.2)		(1.2)
Total	82.3		80.1
Total available-for-sale debt securities
Level 3 Financial Assets:
Balance, beginning of period	1,330.3		1,044.4
Purchases	527.5		359.6
Sales	(60.8)		(76.1)
Transfers into Level 3	48.3		35.0
Transfers out of Level 3	(18.5)		(33.1)
Realized & unrealized gains (losses) included in income	(0.9)	[2]	1.7	[2]
Unrealized gains (losses) included in OCI	(166.7)		(1.2)
Total	1,659.2		1,330.3
Related party reinsurance derivative asset
Level 3 Financial Assets:
Balance, beginning of period	0		3.5
Purchases	0		0
Sales	0		0
Transfers into Level 3	0		0
Transfers out of Level 3	0		0
Realized & unrealized gains (losses) included in income	0	[2]	(3.5)	[2]
Unrealized gains (losses) included in OCI	0		0
Total	0		0
Fair value investments
Level 3 Financial Assets:
Balance, beginning of period	22.7		27.5
Purchases	21.1		5.7
Sales	(3.8)		(11.5)
Transfers into Level 3	0		0
Transfers out of Level 3	0		0
Realized & unrealized gains (losses) included in income	(4.4)	[2]	1.0	[2]
Unrealized gains (losses) included in OCI	0		0
Total	35.6		22.7
Total assets
Level 3 Financial Assets:
Balance, beginning of period	1,353.0		1,075.4
Purchases	548.6		365.3
Sales	(64.6)		(87.6)
Transfers into Level 3	48.3		35.0
Transfers out of Level 3	(18.5)		(33.1)
Realized & unrealized gains (losses) included in income	(5.3)	[2]	(0.8)	[2]
Unrealized gains (losses) included in OCI	(166.7)		(1.2)
Total	$ 1,694.8		$ 1,353.0

[1] Includes securities whose underlying collateral is an obligation of a U.S. government entity.

[2] Reflected in realized investment gains and losses for all assets except fair value investments which are included in net investment income.