Business Segments - Earned Premiums by Product Line (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Life	$ 98.4	$ 98.4	$ 294.9	$ 296.0
Earned Premiums, Accident and Health	40.7	41.3	121.2	124.2
Earned Premiums, Total	507.5	527.3	1,530.2	1,586.3
Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	354.9	376.6	1,075.4	1,134.4
Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	239.1	261.3	729.4	794.6
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	82.3	80.8	244.8	236.6
Other Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	33.5	34.5	101.2	103.2
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	$ 13.5	$ 11.0	$ 38.7	$ 31.7