Business Segments - Earned Premiums by Product Line (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Life									$ 393.4	$ 395.1	$ 396.7
Premiums Earned, Net, Accident and Health									165.2	166.3	161.9
Earned Premiums	520.8	527.3	529.8	529.2	536.5	543.0	548.1	546.0	2,107.1	2,173.6	2,289.4
Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty									1,505.0	1,572.2	1,687.2
Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty									1,050.1	1,129.4	1,249.5
Homeowners [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty									318.0	304.1	298.7
Other Personal Lines [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty									136.9	138.7	139.0
Commercial Automobile [Member]
Entity-Wide Information, Revenue from External Customer [Line Items]
Premiums Earned, Net, Property and Casualty									$ 43.5	$ 40.0	$ 43.6