Business, Basis of Presentation and Significant Accounting Polices Accounting Changes (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		Dec. 31, 2011
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs, Value of business acquired and Sales inducements to contract owners	$ 3,734.8			$ 3,734.8			$ 4,396.5
Deferred income taxes	52.3			52.3			(38.6)
Future policy benefits and claims reserves	27,394.3			27,394.3			29,708.3
Accumulated other comprehensive income (loss)	438.0	265.7		438.0	265.7		245.1
Retained earnings (deficit)	(2,133.7)			(2,133.7)			(2,083.1)
Other net realized capital gains (losses)	(208.9)	1,151.3		(1,061.0)	851.9
Net amortization of deferred policy acquisition costs and value of business acquired	238.5	(695.9)		284.6	(566.6)
Income tax expense (benefit)	45.6	(100.0)		(27.4)	(94.5)
Net income (loss)	192.2	122.3		(50.6)	236.4
Other assets	377.2			377.2			394.6
Other income	7.3	12.8		27.6	46.4
Fee income	196.8	210.1		609.8	658.5
Interest credited and other benefits to contract owners	(173.5)	2,340.0		304.8	2,890.1
Operating expenses	106.3	108.4		332.0	333.3
Other expense	4.4	10.6		20.9	27.2
Before Change in Method
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs, Value of business acquired and Sales inducements to contract owners	2,785.9			2,785.9			3,974.9
Deferred income taxes	233.6			233.6			418.9
Future policy benefits and claims reserves	25,927.3			25,927.3			27,970.2
Accumulated other comprehensive income (loss)	631.4			631.4			435.2
Retained earnings (deficit)	(1,990.4)			(1,990.4)			(1,423.3)
Other net realized capital gains (losses)	(694.3)	2,012.7		(1,332.0)	1,828.9
Net amortization of deferred policy acquisition costs and value of business acquired	652.4	(242.3)		515.7	(131.7)
Income tax expense (benefit)	20.6	23.1		(41.5)	41.6
Net income (loss)	145.4	350.9		(76.8)	489.3
Other assets							385.8
Other income		0.4			0.8
Fee income		261.4			820.4
Interest credited and other benefits to contract owners		2,437.8			3,167.7
Operating expenses	106.6	105.8		332.4	325.6
Other expense		10.4			26.7
Effect of Changes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other net realized capital gains (losses)		(861.4)			(977.0)
Other income		12.4			45.6
Fee income		(51.3)			(161.9)
Interest credited and other benefits to contract owners		(900.4)			(1,100.0)
Effect of GMWBL Change | Effect of Changes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs, Value of business acquired and Sales inducements to contract owners	948.9			948.9			1,037.6
Deferred income taxes	(181.4)			(181.4)			(245.1)
Future policy benefits and claims reserves	1,467.0			1,467.0			1,738.1
Accumulated other comprehensive income (loss)	(196.3)			(196.3)			(288.9)
Retained earnings (deficit)	(140.5)			(140.5)			(166.4)
Other net realized capital gains (losses)	485.4	0		271.0	0
Net amortization of deferred policy acquisition costs and value of business acquired	(413.9)	(548.6)		(231.1)	(498.2)
Income tax expense (benefit)	25.0	(88.9)		14.0	(111.2)
Net income (loss)	46.5	(165.1)		25.9	(206.5)
Other assets							0
Other income		0			0
Fee income		0			0
Interest credited and other benefits to contract owners		802.6			815.9
Operating expenses	0	0		0	0
Other expense		0			0
Effect of Pension Change | Effect of Changes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs, Value of business acquired and Sales inducements to contract owners	0			0			0
Deferred income taxes	0.1			0.1			0
Future policy benefits and claims reserves	0			0			0
Accumulated other comprehensive income (loss)	2.9			2.9			3.2
Retained earnings (deficit)	(2.8)			(2.8)			(3.2)
Other net realized capital gains (losses)	0	0		0	0
Net amortization of deferred policy acquisition costs and value of business acquired	0	0		0	0
Income tax expense (benefit)	0	0.1		0.1	0.2
Net income (loss)	0.3	0		0.3	0.1
Other assets							0
Other income		0			0
Fee income		0			0
Interest credited and other benefits to contract owners		0			0
Operating expenses	(0.3)	(0.2)		(0.4)	(0.4)
Other expense		0			0
Other Changes | Effect of Changes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs, Value of business acquired and Sales inducements to contract owners							(616.0)	[1]
Deferred income taxes							(212.4)	[1]
Future policy benefits and claims reserves							0	[1]
Accumulated other comprehensive income (loss)							95.6	[1]
Retained earnings (deficit)							(490.2)	[1]
Other net realized capital gains (losses)		(861.4)	[1]		(977.0)	[1]
Net amortization of deferred policy acquisition costs and value of business acquired		95.0	[1]		63.3	[1]
Income tax expense (benefit)		(34.3)	[1]		(25.1)	[1]
Net income (loss)		(63.5)	[1]		(46.5)	[1]
Other assets							8.8	[1]
Other income		12.4	[1]		45.6	[1]
Fee income		(51.3)	[1]		(161.9)	[1]
Interest credited and other benefits to contract owners		(900.4)	[1]		(1,093.5)	[1]
Operating expenses		2.8	[1]		8.1	[1]
Other expense		$ 0.2	[1]		$ 0.5	[1]

[1] See reclassifications in Basis of Presentation above and Adoption of New Pronouncements below.