Investments Net Investment Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Gain (Loss) on Investments [Line Items]
Gross investment income	$ 86.4		$ 94.9		$ 173.4		$ 188.0
Investment Income, Investment Expense	1.3	[1]	1.7	[1]	2.5	[1]	3.3
Net investment income	85.0		93.1		170.9		184.6
Net realized gains (losses)	14.3		(1.9)		16.2		2.2
Realized Investment Gains (Losses)	22.0		(2.9)	[2]	24.9		3.5	[2]
Income taxes (credits)(b)	7.7	[3]	(1.0)	[2],[3]	8.7	[3]	1.2	[2]
Interest expense incurred on funds held	0.5		0.5		1.0		0.9
Fixed Maturity Securities [Member]
Gain (Loss) on Investments [Line Items]
Fixed maturity securities, gross realized gains	16.9		3.9		18.6		11.6
Fixed maturity securities, gross realized losses	0		(0.3)		0		(1.4)
Net realized gains (losses)	16.9		3.6		18.6		10.1
Changes in unrealized investment gains (losses) on, fixed maturity securities	45.7		88.0		41.1		57.7
Less: Deferred income taxes (credits)	15.9		30.7		14.3		20.2
Net changes in unrealized investment gains (losses)	29.8		57.2		26.8		37.5
Equity securities & other long-term investments [Member]
Gain (Loss) on Investments [Line Items]
Realized Investment Gains (Losses)	5.0		(6.6)		6.3		(6.6)
Changes in unrealized investment gains (losses) on, fixed maturity securities	(17.1)		(38.5)		44.9		(43.6)
Less: Deferred income taxes (credits)	(5.9)		(13.4)		15.6		(15.3)
Net changes in unrealized investment gains (losses)	(11.1)		(25.0)		29.2		(28.2)
Fixed Maturity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross investment income	81.9		90.6		164.8		179.7
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross investment income	2.6		2.5		5.1		4.9
Short-term Investments [Member]
Gain (Loss) on Investments [Line Items]
Gross investment income	0.4		0.3		1.0		0.8
Investments [Member]
Gain (Loss) on Investments [Line Items]
Gross investment income	$ 1.3		$ 1.3		$ 2.4		$ 2.4

[1] (a)Investment expenses consist of personnel costs and investment management and custody service fees, as well as interest incurred on funds held of $.5 for both quarters ended June 30, 2012 and 2011, and $1.0 and $.9 for the six months ended June 30, 2012 and 2011, respectively.(b

[2] (c) 2011 segment information for General Insurance and RFIG Run-off Business has been reclassified to conform to the 2012 presentation.

[3] (b)Reflects primarily the combination of fully taxable realized investment gains or losses and judgments about the recoverability of deferred tax assets.