Business Segments - Earned Premiums by Product Line (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Life	$ 95.5	$ 96.0	$ 189.9	$ 184.0
Earned Premiums, Accident and Health	36.7	35.7	73.6	72.5
Earned Premiums, Total	553.7	500.1	1,099.7	931.4
Personal Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	310.3	252.6	613.6	442.4
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	67.6	71.6	135.7	144.2
Other Personal Property and Casualty Insurance [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	30.2	30.7	60.0	61.3
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Earned Premiums, Property and Casualty	$ 13.4	$ 13.5	$ 26.9	$ 27.0