Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fixed maturities, available-for-sale, amortized cost	$ 1,815.5	$ 1,804.0
Equity securities, available-for-sale, cost	231.4	196.6
Other invested assets, available-for-sale, cost	50.4	49.5
Losses and loss expenses payable, affiliates	443.3	438.0
Unearned premiums, affiliates	103.0	78.4
Notes payable, affiliates	$ 15.5	$ 15.5
Common stock, shares authorized (shares)	100.0	100.0
Common stock, shares issued (shares)	47.7	47.5
Common stock, stated value per share (usd per share)	$ 2.50	$ 2.50
Treasury stock (shares)	6.8	6.8
Class A Preferred Stock [Member]
Preferred stock, no par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	2.5	2.5
Preferred stock, shares issued (shares)	0	0
Class B Preferred Stock [Member]
Preferred stock, no par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	2.5	2.5
Preferred stock, shares issued (shares)	0	0
Common Stock [Member]
Common stock, no par value (usd per share)	$ 0	$ 0