Business Segments - Earned Premiums by Product Line (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Life	$ 97.9	$ 98.5
Earned Premiums, Accident and Health	40.2	41.5
Earned Premiums, Total	509.9	529.2
Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	359.7	379.0
Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	245.7	267.7
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	80.4	77.1
Other Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	33.6	34.2
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	$ 12.1	$ 10.2