Schedule II - Condensed Financial Information of Registrant (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investments:
Short-term investments	$ 68,924	$ 46,944
Cost or Amortized Cost/Fixed-maturity securities-held to maturity, at amortized cost	583,287	646,048
Fixed-maturity securities - available-for-sale, at fair value	149,139	100,742
Equity securities - available-for-sale, at fair value	6,766	12,240
Total investments	808,116	805,974
Cash and cash equivalents	92,676	45,536	60,966	63,188
Deferred income taxes	29,521	30,048
Property and equipment, net of allowance	7,711	7,628
Other assets	10,809	11,254
Total assets	1,220,946	1,143,973
Liabilities:
Accounts payable and other liabilities	25,649	23,721
Payable for securities purchased	276	616
Subordinated debt securities		25,780
Total liabilities	839,724	794,536
Shareholders' equity (net of Treasury stock of $22,370 at December 31, 2012 and December 31, 2011	381,222	349,437	328,721
Total liabilities and shareholders' equity	1,220,946	1,143,973
Parent Company [Member]
Investments:
Short-term investments	11,161	25,564
Cost or Amortized Cost/Fixed-maturity securities-held to maturity, at amortized cost	678	701
Fixed-maturity securities - available-for-sale, at fair value	1,018	2,933
Equity securities - available-for-sale, at fair value		780
Investment in subsidiaries	330,825	321,727
Total investments	343,682	351,705
Cash and cash equivalents	31,792	14,887	19,830	4,488
Deferred income taxes	1,312	1,458
Notes receivable from subsidiaries	1,235	5,501
Property and equipment, net of allowance	2,214	2,018
Other assets	987	860
Total assets	381,222	376,429
Liabilities:
Accounts payable and other liabilities		596
Payable for securities purchased		616
Subordinated debt securities		25,780
Total liabilities		26,992
Shareholders' equity (net of Treasury stock of $22,370 at December 31, 2012 and December 31, 2011	381,222	349,437
Total liabilities and shareholders' equity	$ 381,222	$ 376,429