Schedule of Net Unrealized Gain on Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Change in Components of Net Unrealized Gain on Securities
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ (1,425.1)	$ 564.0	$ (1,703.6)	$ 366.8
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	6,803.9		7,221.5
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(2,144.3)		(2,561.9)
Balance, End of Period, Net of Tax	4,659.6		4,659.6
Other Investments
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	72.5		92.8
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(15.4)		(35.7)
Balance, End of Period, Net of Tax	57.1		57.1
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	(61.2)		(67.0)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	17.4		23.2
Balance, End of Period, Net of Tax	(43.8)		(43.8)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	(5,979.7)		(6,277.5)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	1,481.6		1,779.4
Balance, End of Period, Net of Tax	(4,498.1)		(4,498.1)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	353.9		351.5
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(70.3)		(67.9)
Balance, End of Period, Net of Tax	283.6		283.6
Deferred Income Tax Charges
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	(397.0)		(447.8)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	234.2		285.0
Balance, End of Period, Net of Tax	(162.8)		(162.8)
Net Unrealized Gain on Securities
Change in Components of Net Unrealized Gain on Securities
Balance, Beginning of Period, Net of Tax	792.4		873.5
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(496.8)		(577.9)
Balance, End of Period, Net of Tax	$ 295.6		$ 295.6