Schedule II. Condensed Financial Information of Registrant - Condensed Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Short-term investments	$ 84,422	$ 68,924
Amortized Cost	536,583	583,287
Fixed-maturity securities-available-for-sale, at fair value	237,877	149,139
Other investments	10,591
Total investments	878,775	808,116
Cash and cash equivalents	123,077	92,676	45,536	60,966
Deferred income taxes	33,645	29,521
Property and equipment, net	7,549	7,711
Other assets	8,637	10,809
Total assets	1,329,001	1,220,946
Liabilities:
Accounts payable and other liabilities	26,940	25,649
Total liabilities	912,187	839,724
Shareholders' equity (net of Treasury stock of $22,370 at December 31, 2013 and 2012)	416,814	381,222	349,437	328,721
Total liabilities and shareholders' equity	1,329,001	1,220,946
Parent Company [Member]
Assets
Short-term investments	248	11,161
Amortized Cost		678
Fixed-maturity securities-available-for-sale, at fair value	965	1,018
Other investments	10,591
Investment in subsidiaries	352,193	330,825
Total investments	363,997	343,682
Cash and cash equivalents	47,726	31,792	14,887	19,830
Deferred income taxes	1,383	1,312
Notes receivable from subsidiaries	1,805	1,235
Property and equipment, net	2,181	2,214
Other assets	556	987
Total assets	417,648	381,222
Liabilities:
Accounts payable and other liabilities	834
Total liabilities	834
Shareholders' equity (net of Treasury stock of $22,370 at December 31, 2013 and 2012)	416,814	381,222
Total liabilities and shareholders' equity	$ 417,648	$ 381,222