Business Segments - Earned Premiums by Product Line (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
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Life	$ 98.6	$ 99.1	$ 196.5	$ 197.6
Earned Premiums, Accident and Health	40.3	41.4	80.5	82.9
Earned Premiums, Total	512.8	529.8	1,022.7	1,059.0
Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	360.8	378.8	720.5	757.8
Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	244.6	265.6	490.3	533.3
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	82.1	78.7	162.5	155.8
Other Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	34.1	34.5	67.7	68.7
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	$ 13.1	$ 10.5	$ 25.2	$ 20.7