Fair Value Measurements - Level 3 Financial Instruments (Details) (Assets measured on recurring basis, Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Separate Accounts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Equity securities, available-for-sale, beginning balance	$ 17.9		$ 2.2		$ 13.1	[1]	$ 16.3	[1]
Total Realized/Unrealized Gains (Losses) Included in Net Income	0.1		(0.1)		0.1	[1]	(0.1)	[1]
Total Realized/Unrealized Gains (Losses) Included in OCI	0		0		0	[1]	0	[1]
Purchases	0.1		21.1		5.9	[1]	21.3	[1]
Issuances	0		0		0	[1]	0	[1]
Sales	2.2		3.3		3.2	[1]	9.9	[1]
Settlements	0		0		0	[1]	0	[1]
Transfers in to Level 3	0		0		0	[1],[2]	2.2	[1],[2]
Transfers out of Level 3	0	[1],[2]	0		0	[1],[2]	(9.9)	[1],[2]
Fair Value, Equity securities, available-for-sale, ending balance	15.9	[1]	19.9	[1]	15.9	[1]	19.9	[1]
Change in Unrealized Gains (Losses) Included in Earnings	0		(0.1)		0	[1],[3]	0.2	[1],[3]
Stabilizer (Investment Only) and MCG Contracts
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Derivatives, beginning balance	(18.0)		(78.0)		0	[4]	(102.0)	[4]
Total Realized/Unrealized Gains (Losses) Included in Net Income	(12.8)		51.7		(29.6)	[4]	77.2	[4]
Total Realized/Unrealized Gains (Losses) Included in OCI	0		0		0	[4]	0	[4]
Purchases	0		0		0	[4]	0	[4]
Issues	(1.2)		(1.7)		(2.4)	[4]	(3.2)	[4]
Sales	0		0		0	[4]	0	[4]
Settlements	0		0		0	[4]	0	[4]
Transfers in to Level 3	0		0		0	[2],[4]	0	[2],[4]
Transfers out of Level 3	0	[2],[4]	0		0	[2],[4]	0	[2],[4]
Fair Value, Derivatives, ending balance	(32.0)	[4]	(28.0)	[4]	(32.0)	[4]	(28.0)	[4]
Change in Unrealized Gains (Losses) Included in Earnings	0		0		0	[3],[4]	0	[3],[4]
Embedded Derivative Fixed Indexed Annuity [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Derivatives, beginning balance	(24.3)		(21.6)		(23.1)	[4]	(20.4)	[4]
Total Realized/Unrealized Gains (Losses) Included in Net Income	(1.4)		0.5		(2.4)	[4]	(0.7)	[4]
Total Realized/Unrealized Gains (Losses) Included in OCI	0		0		0	[4]	0	[4]
Purchases	0		0		0	[4]	0	[4]
Issues	0		0		(0.2)	[4]	0	[4]
Sales	0		0		0	[4]	0	[4]
Settlements	0		0		0	[4]	0	[4]
Transfers in to Level 3	0		0		0	[2],[4]	0	[2],[4]
Transfers out of Level 3	0	[2],[4]	0		0	[2],[4]	0	[2],[4]
Fair Value, Derivatives, ending balance	(25.7)	[4]	(21.1)	[4]	(25.7)	[4]	(21.1)	[4]
Change in Unrealized Gains (Losses) Included in Earnings	0		0		0	[3],[4]	0	[3],[4]
U.S. government agencies and authorities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	2.5		0		5.1		0
Total Realized/Unrealized Gains (Losses) Included in Net Income	0		0		0		0
Total Realized/Unrealized Gains (Losses) Included in OCI	0		0		0		0
Purchases	0		0		0		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	0		0		0		0
Transfers in to Level 3	0		0		0		0
Transfers out of Level 3	(2.5)	[2]	0	[2]	(5.1)		0
Fair Value, Fixed maturities, including securities pledged, ending balance	0		0		0		0
Change in Unrealized Gains (Losses) Included in Earnings	0		0		0		0
U.S. corporate, state and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	183.4		167.6		145.3		154.6
Total Realized/Unrealized Gains (Losses) Included in Net Income	(0.1)		(0.1)		(0.1)		(0.2)
Total Realized/Unrealized Gains (Losses) Included in OCI	0.4		(1.9)		2.8		(1.0)
Purchases	43.1		0		81.3		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	(0.9)		(0.8)		(2.9)		(2.4)
Transfers in to Level 3	45.5		0		45.0	[2]	17.6	[2]
Transfers out of Level 3	0	[2]	(24.9)		0	[2]	(28.7)	[2]
Fair Value, Fixed maturities, including securities pledged, ending balance	271.4		139.9		271.4		139.9
Change in Unrealized Gains (Losses) Included in Earnings	(0.1)		(0.1)		(0.1)	[3]	(0.2)	[3]
Foreign securities government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	34.8		25.7		42.8		24.6
Total Realized/Unrealized Gains (Losses) Included in Net Income	0		0		0		0
Total Realized/Unrealized Gains (Losses) Included in OCI	(0.6)		(0.4)		1.9		0.7
Purchases	56.3		0		56.3		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	0		(6.6)		0		(6.6)
Transfers in to Level 3	68.4		0		66.8	[2]	0	[2]
Transfers out of Level 3	(13.3)	[2]	0		(22.2)	[2]	0	[2]
Fair Value, Fixed maturities, including securities pledged, ending balance	145.6		18.7		145.6		18.7
Change in Unrealized Gains (Losses) Included in Earnings	0		0		0	[3]	0	[3]
Residential mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	23.1		18.4		23.7		9.1
Total Realized/Unrealized Gains (Losses) Included in Net Income	(0.7)		(0.4)		(1.1)		(0.8)
Total Realized/Unrealized Gains (Losses) Included in OCI	0.1		0.3		0.1		0.1
Purchases	0.3		18.6		0.3		22.4
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	0		0		0		0
Transfers in to Level 3	0		0		0	[2]	0	[2]
Transfers out of Level 3	(1.6)	[2]	(6.1)		(1.8)	[2]	0	[2]
Fair Value, Fixed maturities, including securities pledged, ending balance	21.2		30.8		21.2		30.8
Change in Unrealized Gains (Losses) Included in Earnings	(0.7)		(0.4)		(1.1)	[3]	(0.7)	[3]
Commercial mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	14.0		0		0		0
Total Realized/Unrealized Gains (Losses) Included in Net Income	0		0		0		0
Total Realized/Unrealized Gains (Losses) Included in OCI	0		0		0		0
Purchases	0		0		0		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	0		0		0		0
Transfers in to Level 3	0		0		0		0
Transfers out of Level 3	(14.0)		0		0		0
Fair Value, Fixed maturities, including securities pledged, ending balance	0		0		0		0
Change in Unrealized Gains (Losses) Included in Earnings	0		0				0
Other asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	11.1		27.4		17.7		33.2
Total Realized/Unrealized Gains (Losses) Included in Net Income	0		0.6		0.7		1.7
Total Realized/Unrealized Gains (Losses) Included in OCI	0		(0.1)		(0.5)		(0.3)
Purchases	0		0		0		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	(0.2)		(3.2)		(7.1)		(9.9)
Transfers in to Level 3	0		0		0	[2]	0	[2]
Transfers out of Level 3	(8.5)	[2]	0		(8.4)	[2]	0	[2]
Fair Value, Fixed maturities, including securities pledged, ending balance	2.4		24.7		2.4		24.7
Change in Unrealized Gains (Losses) Included in Earnings	0		0.3		0	[3]	0.4	[3]
Fixed maturities, available-for-sale, including securities pledged
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Fixed maturities, including securities pledged, beginning balance	268.9		239.1		234.6		221.5
Total Realized/Unrealized Gains (Losses) Included in Net Income	(0.8)		0.1		(0.5)		0.7
Total Realized/Unrealized Gains (Losses) Included in OCI	(0.1)		(2.1)		4.3		(0.5)
Purchases	99.7		18.6		137.9		22.4
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	(1.1)		(10.6)		(10.0)		(18.9)
Transfers in to Level 3	113.9		0		111.8	[2]	17.6	[2]
Transfers out of Level 3	(39.9)	[2]	(31.0)		(37.5)	[2]	(28.7)	[2]
Fair Value, Fixed maturities, including securities pledged, ending balance	440.6		214.1		440.6		214.1
Change in Unrealized Gains (Losses) Included in Earnings	(0.8)		(0.2)		(1.2)	[3]	(0.5)	[3]
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Equity securities, available-for-sale, beginning balance	37.2		35.8		35.9		17.0
Total Realized/Unrealized Gains (Losses) Included in Net Income	0		(0.1)		0		(0.1)
Total Realized/Unrealized Gains (Losses) Included in OCI	0		1.2		1.3		2.2
Purchases	0		0		0		0
Issuances	0		0		0		0
Sales	0		0		0		0
Settlements	0		0		0		0
Transfers in to Level 3	0		0		0	[2]	34.5	[2]
Transfers out of Level 3	0	[2]	0		0	[2]	(16.7)	[2]
Fair Value, Equity securities, available-for-sale, ending balance	37.2		36.9		37.2		36.9
Change in Unrealized Gains (Losses) Included in Earnings	$ 0		$ 0		$ 0	[3]	$ 0	[3]

[1] The investment income and realized gains (losses) and change in unrealized gains (losses) included in net income (loss) for separate account assets are offset by an equal amount for separate account liabilities, which result in a net zero impact on net income (loss) for the Company.

[2] The Company’s policy is to recognize transfers in and transfers out as of the beginning of the reporting period.

[3] For financial instruments still held as of June 30, amounts are included in Net investment income and Other net realized capital gains (losses) in the Condensed Consolidated Statements of Operations.

[4] All gains and losses on Level 3 are classified as realized gains (losses) for the purpose of this disclosure because it is impracticable to track realized and unrealized gains (losses) separately on a contract-by-contract basis. These amounts are included in Other net realized capital gains (losses) in the Condensed Consolidated Statements of Operations.