Investment Securities (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Investments holding table
Fixed maturity investments, at fair value	$ 1,474.1	$ 1,886.2
Fixed maturity investments
Investments holding table
Cost or amortized Cost	1,800.6	1,956.1
Gross unrealized gains	52.3	51.0
Gross unrealized loss	(1.5)	(9.0)
Net foreign currency gains (losses)		(0.1)
Fixed maturity investments, at fair value	1,851.4	1,998.0
Runoff assets reclassified to assets held for sale	377.3
AutoOne assets reclassified to assets held for sale		111.8
U.S. Government and agency obligations
Investments holding table
Cost or amortized Cost	204.4	213.6
Gross unrealized gains	0.8	1.8
Fixed maturity investments, at fair value	205.2	215.4
Debt securities issued by corporations
Investments holding table
Cost or amortized Cost	606.6	725.8
Gross unrealized gains	32.6	34.9
Gross unrealized loss	(1.2)	(1.9)
Net foreign currency gains (losses)		(0.1)
Fixed maturity investments, at fair value	638.0	758.7
Municipal obligations
Investments holding table
Cost or amortized Cost	3.3	2.2
Fixed maturity investments, at fair value	3.3	2.2
Asset-backed securities
Investments holding table
Cost or amortized Cost	902.0	928.5
Gross unrealized gains	12.3	10.6
Gross unrealized loss	(0.4)	(0.8)
Fixed maturity investments, at fair value	913.9	938.3
Foreign government obligations
Investments holding table
Cost or amortized Cost	6.0	7.7
Gross unrealized gains	0.6	0.5
Gross unrealized loss	0.1	(0.1)
Fixed maturity investments, at fair value	6.7	8.1
Preferred stocks
Investments holding table
Cost or amortized Cost	78.3	78.3
Gross unrealized gains	6.0	3.2
Gross unrealized loss		(6.2)
Fixed maturity investments, at fair value	84.3	75.3
Common Equity securities
Investments holding table
Cost or amortized Cost	252.3	240.6
Gross unrealized gains	44.2	30.3
Gross unrealized loss	(1.2)	(4.4)
Fixed maturity investments, at fair value	295.3	266.5
Convertible fixed maturity investments
Investments holding table
Cost or amortized Cost	71.1	76.3
Gross unrealized gains	4.4	4.4
Gross unrealized loss	(2.9)	(0.9)
Fixed maturity investments, at fair value	72.6	79.8
Other investments
Investments holding table
Cost or amortized Cost	122.4	124.6
Gross unrealized gains	37.0	37.8
Gross unrealized loss	(2.5)	(7.3)
Fixed maturity investments, at fair value	$ 156.9	$ 155.1