Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Condensed Consolidated Balance Sheets
Available-for-sale, amortized cost	$ 1,646,411	$ 1,596,227
Equity securities available-for-sale, cost	182,002	187,573
Premiums and reinsurance balances receivable, allowances for uncollectible amounts	16,935	15,981
Reinsurance balances recoverable on unpaid losses and settlement expenses, allowances for uncollectible amounts	10,014	10,699
Property and equipment, accumulated depreciation	$ 47,676	$ 41,999
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	67,078,569	66,874,911
Common stock, shares outstanding (in shares)	44,148,355	43,944,697
Treasury stock, shares (in shares)	22,930,214	22,930,214