Fair Value Measurements Level 3 Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, liabilities	$ (3,842.8)
Total realized/unrealized gains (losses) included in Net income	517.3	[1]
Total realized/unrealized gains (losses) included in OCI	0
Purchases	0
Issuances	(59.6)
Sales	0
Settlements	35.4
Transfers Into Level 3	0	[2]
Transfers out of Level 3	0	[2]
Fair Value, ending balance, liabilities	(3,349.7)				(3,349.7)
Change in unrealized gains (losses) included in earnings on liabilities	0	[3]
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, liabilities			(1,837.0)		(3,512.1)		(1,655.7)
Total realized/unrealized gains (losses) included in Net income			(861.4)	[1]	227.1	[1]	(977.0)	[1]
Total realized/unrealized gains (losses) included in OCI			0		0		0
Purchases					0
Issuances					(183.0)
Purchases and Issuances			(60.3)				(207.7)
Sales					0
Settlements					118.3
Sales and Settlements			28.9				110.6
Transfers Into Level 3			0	[2]	0	[2]	0	[2]
Transfers out of Level 3			0	[2]	0	[2]	0	[2]
Fair Value, ending balance, liabilities	(3,349.7)		(2,729.8)		(3,349.7)		(2,729.8)
Change in unrealized gains (losses) included in earnings on liabilities			0	[3]	0	[3]	0	[3]
Level 3 | Fixed Indexed Annuities (FIA)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, liabilities	(1,384.2)		(1,310.2)		(1,282.2)		(1,165.5)
Total realized/unrealized gains (losses) included in Net income	(38.9)		136.6		(170.3)		(18.2)
Total realized/unrealized gains (losses) included in OCI	0		0		0		0
Purchases	0				0
Issuances	(15.9)				(69.2)
Purchases and Issuances			(21.4)				(91.4)
Sales	0				0
Settlements	35.4				118.1
Sales and Settlements			28.6				108.7
Transfers Into Level 3	0	[2]	0	[2]	0	[2]	0	[2]
Transfers out of Level 3	0	[2]	0	[2]	0	[2]	0	[2]
Fair Value, ending balance, liabilities	(1,403.6)		(1,166.4)		(1,403.6)		(1,166.4)
Change in unrealized gains (losses) included in earnings on liabilities	0	[3]	0	[3]	0	[3]	0	[3]
Level 3 | GMAB / GMWB / GMWBL
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, liabilities	(2,458.6)		(526.8)		(2,229.9)		(490.2)
Total realized/unrealized gains (losses) included in Net income	556.2		(998.0)		397.4		(958.8)
Total realized/unrealized gains (losses) included in OCI	0		0		0		0
Purchases	0				0
Issuances	(43.7)				(113.8)
Purchases and Issuances			(38.9)				(116.3)
Sales	0				0
Settlements	0				0.2
Sales and Settlements			0.3				1.9
Transfers Into Level 3	0	[2]	0	[2]	0	[2]	0	[2]
Transfers out of Level 3	0	[2]	0	[2]	0	[2]	0	[2]
Fair Value, ending balance, liabilities	(1,946.1)		(1,563.4)		(1,946.1)		(1,563.4)
Change in unrealized gains (losses) included in earnings on liabilities	0	[3]	0	[3]	0	[3]	0	[3]
U.S. corporate, state and municipalities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, assets, including securities pledged	102.4		122.4		124.5		40.1
Total realized/unrealized gains (losses) included in Net income	0.6		0		0.7		0
Total realized/unrealized gains (losses) included in OCI	(2.7)		(0.4)		(1.5)		(1.4)
Purchases	18.8				2.4
Issuances	0				0
Purchases and Issuances			0				0
Sales	0				0
Settlements	(4.0)				(0.1)
Sales and Settlements			(3.4)				(25.9)
Transfers in to Level 3	17.0	[2]	0	[2]	36.3	[2]	105.8	[2]
Transfers out of Level 3	0	[2]	0	[2]	(30.2)	[2]	0	[2]
Fair Value, ending balance, assets, including securities pledged	132.1		118.6		132.1		118.6
Change in unrealized gains (losses) included in earnings on assets	0.6	[3]	0	[3]	0.6	[3]	0	[3]
Foreign | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, assets, including securities pledged	15.2		27.3		56.9		9.8
Total realized/unrealized gains (losses) included in Net income	0		0.1		0.6		0.3
Total realized/unrealized gains (losses) included in OCI	0.2		(0.6)		(0.4)		(3.8)
Purchases	0				0
Issuances	0				0
Purchases and Issuances			0				0
Sales	0				(4.1)
Settlements	(1.5)				(4.2)
Sales and Settlements			(1.9)				(10.8)
Transfers in to Level 3	8.4	[2]	15.5	[2]	8.3	[2]	44.3	[2]
Transfers out of Level 3	0	[2]	(4.2)	[2]	(34.8)	[2]	(3.6)	[2]
Fair Value, ending balance, assets, including securities pledged	22.3		36.2		22.3		36.2
Change in unrealized gains (losses) included in earnings on assets	0	[3]	0	[3]	0	[3]	0	[3]
Residential mortgage-backed securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, assets, including securities pledged	21.7		19.6		60.7		198.6
Total realized/unrealized gains (losses) included in Net income	2.5		0.2		(0.5)		(1.1)
Total realized/unrealized gains (losses) included in OCI	(0.7)		(0.1)		(1.1)		0.7
Purchases	0				0.1
Issuances	0				0
Purchases and Issuances			0				2.9
Sales	0				0
Settlements	(0.1)				(0.9)
Sales and Settlements			(0.3)				(2.5)
Transfers in to Level 3	0.5	[2]	0	[2]	0	[2]	0	[2]
Transfers out of Level 3	0	[2]	0	[2]	(34.4)	[2]	(179.2)	[2]
Fair Value, ending balance, assets, including securities pledged	23.9		19.4		23.9		19.4
Change in unrealized gains (losses) included in earnings on assets	2.5	[3]	0.2	[3]	(0.9)	[3]	(1.1)	[3]
Other asset-backed securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, assets, including securities pledged	67.6		178.4		72.8		644.8
Total realized/unrealized gains (losses) included in Net income	1.9		(8.5)		4.9		(77.1)
Total realized/unrealized gains (losses) included in OCI	1.9		3.5		2.7		61.9
Purchases	0				0
Issuances	0				0
Purchases and Issuances			0				0
Sales	0				(9.3)
Settlements	(1.3)				(3.4)
Sales and Settlements			(66.7)				(232.1)
Transfers in to Level 3	14.5	[2]	0	[2]	16.9	[2]	1.2	[2]
Transfers out of Level 3	0	[2]	(15.4)	[2]	0	[2]	(307.4)	[2]
Fair Value, ending balance, assets, including securities pledged	84.6		91.3		84.6		91.3
Change in unrealized gains (losses) included in earnings on assets	1.9	[3]	(9.7)	[3]	4.6	[3]	(11.5)	[3]
Fixed maturities, available-for-sale, including securities pledged | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, assets, including securities pledged	206.9		347.7		314.9		893.3
Total realized/unrealized gains (losses) included in Net income	5.0		(8.2)		5.7		(77.9)
Total realized/unrealized gains (losses) included in OCI	(1.3)		2.4		(0.3)		57.4
Purchases	18.8				2.5
Issuances	0				0
Purchases and Issuances			0				2.9
Sales	0				(13.4)
Settlements	(6.9)				(8.6)
Sales and Settlements			(72.3)				(271.3)
Transfers in to Level 3	40.4	[2]	15.5	[2]	61.5	[2]	151.3	[2]
Transfers out of Level 3	0	[2]	(19.6)	[2]	(99.4)	[2]	(490.2)	[2]
Fair Value, ending balance, assets, including securities pledged	262.9		265.5		262.9		265.5
Change in unrealized gains (losses) included in earnings on assets	5.0	[3]	(9.5)	[3]	4.3	[3]	(12.6)	[3]
Equity securities, available-for-sale | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance, assets	16.8		16.2		16.3		13.5
Total realized/unrealized gains (losses) included in Net income	(0.1)		0		(0.1)		0.1
Total realized/unrealized gains (losses) included in OCI	0		0		(0.1)		(0.1)
Purchases	0				2.3
Issuances	0				0
Purchases and Issuances			0.1				4.2
Sales	(0.7)				(2.4)
Settlements	0				0
Sales and Settlements			0				(0.1)
Transfers in to Level 3	0	[2]	0	[2]	0	[2]	0	[2]
Transfers out of Level 3	0	[2]	0	[2]	0	[2]	(1.3)	[2]
Fair value, ending balance, assets	16.0		16.3		16.0		16.3
Change in unrealized gains (losses) included in earnings on assets	0	[3]	0	[3]	0	[3]	0	[3]
Derivatives | Level 3
Fair Value, Assets (Liabilities) Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, derivatives, net	9.6		87.4		(4.3)		76.5
Total realized/unrealized gains (losses) included in Net income, derivatives, net	23.7		(17.2)		14.8		(0.9)
Total realized/unrealized gains (losses) included in OCI, derivatives, net	0		0		0		0
Purchases, derivatives, net	4.3				13.9
Issuances, derivatives, net	0				0
Purchases and Issuances, derivatives, net			0				0
Sales, derivatives, net	0				0
Settlements, derivatives, net	(6.8)				7.9
Sales and Settlements, derivatives, net			(35.5)				(40.9)
Transfers in to Level 3, derivatives, net	0	[2]	0	[2]	0	[2]	0	[2]
Transfers out of Level 3, derivatives, net	0	[2]	0	[2]	1.5	[2]	0	[2]
Fair Value, ending balance, derivatives, net	30.8		34.7		30.8		34.7
Change in unrealized gains (losses) included in earnings on assets (liabilities)	$ 19.8	[3]	$ (35.7)	[3]	$ 13.0	[3]	$ (18.8)	[3]

[1] All gains and losses on Level 3 liabilities 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 Statements of Operations.

[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 Statements of Operations.