Condensed Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Document Period End Date	Mar. 31, 2017
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost $2,104.7 and $2,095.9, respectively)	$ 2,123.5	$ 2,109.3
Equity securities, available-for-sale, at fair value (cost $321.3 and $323.1, respectively)	395.6	382.8
Other invested assets, available-for-sale, at fair value (cost $25.5 and $25.5, respectively)	48.1	45.1
Other invested assets	5.4	5.4
Notes receivable from affiliate	70.0	70.0
Total investments	2,642.6	2,612.6
Cash and cash equivalents	44.8	51.1
Accrued investment income and other assets	46.6	40.0
Deferred policy acquisition costs (affiliated net assumed $47.6 and $50.7, respectively)	124.0	129.8
Reinsurance recoverable on losses and loss expenses payable	4.8	3.6
Prepaid reinsurance premiums	6.0	6.1
Due from affiliate	1.1	0.0
Current federal income taxes	6.8	6.7
Net deferred federal income taxes	94.9	102.1
Property and equipment, at cost	7.3	7.4
Total assets	2,978.9	2,959.4
Liabilities and Stockholders’ Equity
Losses and loss expenses payable (affiliated net assumed $646.8 and $630.9, respectively)	1,217.3	1,181.6
Unearned premiums (affiliated net assumed $222.2 and $220.9, respectively)	606.5	617.8
Notes payable (affiliates $15.2 and $15.2, respectively)	122.1	122.1
Postretirement and pension benefits (affiliated net ceded $38.3 and $40.1, respectively)	71.2	74.4
Due to Affiliate	0.0	2.4
Other liabilities (affiliated net assumed $16.5 and $11.0, respectively)	60.7	69.8
Total liabilities	2,077.8	2,068.1
Stockholders’ equity:
Common stock, without par value. Authorized 100.0 shares; 48.8 and 48.6 shares issued, respectively, at stated value of $2.50 per share	121.9	121.6
Treasury stock, 6.9 and 6.8 shares, respectively, at cost	(116.7)	(116.5)
Additional paid-in capital	162.6	159.9
Accumulated other comprehensive income (affiliated net ceded $52.8 and $53.7, respectively)	47.9	32.5
Retained earnings	685.4	693.8
Total stockholders’ equity	901.1	891.3
Total liabilities and stockholders’ equity	2,978.9	2,959.4
Class A Preferred Stock [Member]
Stockholders’ equity:
Preferred stock value	0.0	0.0
Class B Preferred Stock [Member]
Stockholders’ equity:
Preferred stock value	$ 0.0	$ 0.0