Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fixed maturities, available-for-sale, amortized cost	$ 1,991.5	$ 1,972.9
Equity securities, available-for-sale, cost	274.5	265.2
Other invested assets, available-for-sale, cost	57.1	56.9
Deferred policy acquisitions costs from affiliates	50.2	49.3
Losses and loss expenses payable, affiliates	554.3	532.4
Unearned premiums, affiliates	212.1	214.2
Notes payable, affiliates	15.2	15.2
Net Postretirement and Pension Benefits	(54.6)	(56.0)
Net Other Liabilities from Affiliates	$ 7.1	$ (8.4)
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized (shares)	100,000,000	100,000,000
Common stock, shares issued (shares)	48,200,000	48,100,000
Common stock, stated value per share (usd per share)	$ 2.5	$ 2.5
Treasury stock (shares)	6,800,000	6,800,000
Net Accumulated Other Comprehensive Income	$ (55.6)	$ (56.7)
Class A Preferred Stock [Member]
Preferred stock, no par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	2,500,000	2,500,000
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)	2,500,000	2,500,000
Preferred stock, shares issued (shares)	0	0