Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2010	Dec. 31, 2009
Consolidated Balance Sheets
Fixed maturities, amortized cost	$ 4,598.8	$ 4,520.3
Equity securities, cost	$ 120.7	$ 57.3
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	20.0	20.0
Preferred stock, issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300.0	300.0
Common stock, shares issued	60.5	60.5
Treasury stock, shares	15.6	13.0