Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Condensed Consolidated Balance Sheets
Available-for-sale, amortized cost	$ 1,745,648	$ 1,646,411
Equity securities, cost	210,119	182,002
Premiums and reinsurance balances receivable, allowances for uncollectible amounts	17,076	16,935
Reinsurance balances recoverable on unpaid losses and settlement expenses, allowances for uncollectible amounts	9,827	10,014
Property and equipment, accumulated depreciation	$ 52,418	$ 47,676
Common stock, par value (in dollars per share)	$ 0.01	$ 1.00
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	67,414,868	67,078,569
Common stock, shares outstanding (in shares)	44,484,654	44,148,355
Treasury stock, shares (in shares)	22,930,214	22,930,214