Business Segments - Earned Premiums by Product Line (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Life	$ 99.7	$ 100.0	$ 199.1	$ 199.5
Premiums Earned, Net, Accident and Health	41.5	40.1	82.7	80.0
Earned Premiums	548.1	578.1	1,094.1	1,159.6
Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty	397.0	426.9	792.6	857.5
Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty	286.2	316.9	573.3	639.1
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty	75.7	74.5	149.8	148.6
Other Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty	35.1	35.5	69.5	69.8
Commercial Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty	$ 9.9	$ 11.1	$ 19.7	$ 22.6