Derivative Financial Instruments Net Realized Gains and Losses (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
Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	$ (307.6)	$ 832.1	$ (1,259.4)	$ 440.3
Other net realized capital gains (losses) | Interest rate contracts | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	(27.1)	1,054.3	275.4	1,173.7
Other net realized capital gains (losses) | Foreign exchange contracts | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	(38.1)	56.5	(10.1)	(7.5)
Other net realized capital gains (losses) | Equity contracts | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	(709.1)	798.1	(1,661.6)	488.0
Other net realized capital gains (losses) | Credit contracts | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	0.9	(11.4)	0.5	(6.5)
Fixed maturities | Other net realized capital gains (losses) | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	(3.0)	8.8	(3.9)	9.0
Within retail annuity products | Other net realized capital gains (losses) | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	517.3	(861.4)	227.1	(977.0)
Within reinsurance agreement | Interest credited and other benefits to contract owners | Non-Qualifying for hedge accounting
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	(48.5)	(213.1)	(86.8)	(239.4)
Cash Flow Hedging | Other net realized capital gains (losses) | Interest rate contracts | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	0	0.3	0	0
Fair Value Hedging | Other net realized capital gains (losses) | Interest rate contracts | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Net realized gains (losses) on derivatives	$ 0	$ 0	$ 0	$ 0