Investments (Rollforwards of Cumulative Amounts Related to Credit Loss Portion of OTTI Losses) (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Investments
Credit losses, beginning of period	$ 16.3	$ 21.4	$ 16.7	$ 20.0
Credit losses for which an OTTI was not previously recognized		0.1		0.3
Additional credit losses on securities for which an OTTI was previously recognized		0.6	0.2	2.2
Reductions for securities sold or matured during the period	(0.7)	(2.6)	(1.3)	(3.0)
Reduction for securities reclassified as intend to sell	(0.8)		(0.8)
Credit losses, end of period	$ 14.8	$ 19.5	$ 14.8	$ 19.5

OTTI Credit Losses Recognized In Earnings Additions Additional Credit Losses

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OTTI Credit Losses Recognized In Earnings Additions No Previous Impairment

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OTTI Credit Losses Recognized In Earnings On Debt Securities

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OTTI Credit Losses Recognized In Earnings Reductions Securities Sold

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Reduction for Securities Reclassified As Intend To Sell As Intend To Sell

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