Condensed Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Document Period End Date	Mar. 31, 2018
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost $2,199.0 and $2,173.1, respectively)	$ 2,181.6	$ 2,192.8
Equity securities	350.2	365.3
Other invested assets	55.5	56.0
Other invested assets, at cost	5.6	5.6
Notes receivable from affiliate	70.0	70.0
Total investments	2,662.9	2,689.7
Cash and cash equivalents	60.9	91.5
Accrued investment income and other assets	40.4	36.5
Deferred policy acquisition costs (affiliated net assumed $55.5 and $57.2, respectively)	105.1
Reinsurance recoverable on losses and loss expenses payable	2.1	3.1
Prepaid reinsurance premiums	6.4	6.4
Current federal income taxes	5.7	4.8
Net deferred federal income taxes	66.6
Property and equipment, at cost	7.2	7.3
Total assets	2,957.3	3,008.4
Liabilities and Stockholders’ Equity
Losses and loss expenses payable (affiliated net assumed $677.6 and $711.4, respectively)	1,247.6	1,255.6
Unearned premiums (affiliated net assumed $157.3 and $187.9, respectively)	589.2	611.8
Notes payable (affiliates $15.2 and $15.2, respectively)	122.1	122.1
Pension and postretirement benefits (affiliated net ceded $34.5 and $34.8, respectively)	63.6	64.5
Due to Affiliate	11.8	2.7
Other liabilities (affiliated net assumed $17.6 and $15.5, respectively)	73.9	76.7
Total liabilities	2,108.2	2,133.4
Stockholders’ equity:
Common stock, without par value. Authorized 100.0 shares; 49.5 and 49.2 shares issued, respectively, at stated value of $2.50 per share	123.8	123.0
Treasury stock, 6.8 and 6.8 shares, respectively, at cost	(116.9)	(116.8)
Additional paid-in capital	180.3	171.8
Accumulated other comprehensive (loss) income (affiliated net ceded $51.0 and $50.7, respectively)	(48.8)	36.7
Retained earnings	710.7
Total stockholders’ equity	849.1
Total liabilities and stockholders’ equity	2,957.3
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