DAC and VOBA - Value of Business Acquired (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended						36 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2012 Minimum	Dec. 31, 2012 Maximum
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	$ 593.6		$ 864.2		$ 981.2
Deferrals of commissions and expenses	8.1		8.5		17.6
Amortization:
Amortization	(152.6)		(125.1)		(16.0)
Interest accrued	62.5	[1]	70.5	[1]	67.8	[1]
Net amortization included in the Consolidated Statements of Operations	(90.1)		(54.6)		51.8
Change in unrealized capital gains/losses on availabe-for-sale securities	(130.2)		(224.5)		(186.4)
Ending balance	381.4		593.6		864.2
Value of Business Acquired (VOBA), Interest Accrued Percentage							5.00%	7.00%
Estimated amount of VOBA amortization expense, net of interest, 2013	66.0
Estimated amount of VOBA amortization expense, net of interest, 2014	50.7
Estimated amount of VOBA amortization expense, net of interest, 2015	45.4
Estimated amount of VOBA amortization expense, net of interest, 2016	42.3
Estimated amount of VOBA amortization expense, net of interest, 2017	$ 34.9

[1] Interest accrued at 5.0% and 7.0% during 2012, 2011 and 2010