Schedule II. Condensed Financial Information of Registrant - Condensed Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Net investment income	$ 6,763	$ 6,947	$ 6,649	$ 6,670	$ 6,698	$ 6,801	$ 6,605	$ 6,914	$ 27,029	$ 27,018	$ 26,340
Fee and other income									534	562	1,080
Total revenues	94,309	88,003	87,511	86,512	85,583	80,374	76,637	78,654	356,335	321,248	280,663
Expenses
Interest expense										566	1,311
Total expenses									297,131	284,105	253,306
Income tax expense (benefit)									15,567	7,790	3,176
Net income	17,443	9,699	7,644	8,851	9,226	7,121	3,445	9,561	43,637	29,353	24,181
Parent Company [Member]
Revenues
Net investment income									1,051	571	478
Fee and other income									5,453	4,765	9,710
Total revenues									6,504	5,336	10,188
Expenses
Other operating costs									6,504	4,770	4,827
Interest expense										566	1,311
Total expenses									6,504	5,336	6,138
Income (loss) before income taxes and equity in earnings of subsidiaries											4,050
Income tax expense (benefit)									6	(9)	1,213
Gain (loss) before equity in earnings of subsidiaries									(6)	9	2,837
Equity in net income of subsidiaries									43,643	29,344	21,344
Net income									$ 43,637	$ 29,353	$ 24,181