Business Segments - Earned Premiums by Product Line (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Life	$ 95.8	$ 95.5	$ 285.7	$ 279.5
Earned Premiums, Accident and Health	37.6	36.2	111.2	108.7
Total Earned Premiums	558.9	536.7	1,658.6	1,468.1
Personal Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	313.8	288.5	927.4	730.9
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	68.5	72.1	204.2	216.3
Other Personal Property and Casualty Insurance [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	29.9	30.7	89.9	92.0
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	$ 13.3	$ 13.7	$ 40.2	$ 40.7