Investments - Gross Unrealized Gains and Losses and Cost or Amortized Cost and Fair Value of Investments Classified as Available-for-sale (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Cost or Amortized Cost	$ 283,582	$ 263,891
Gross Unrealized Gains	5,114	2,914
Gross Unrealized Losses	(6,005)	(9,035)
Fair Value	282,691	257,770
Total Fixed Maturity [Member]
Investment [Line Items]
Cost or Amortized Cost	270,135	244,409
Gross Unrealized Gains	4,033	1,936
Gross Unrealized Losses	(5,979)	(8,468)
Fair Value	268,189	237,877
Other Investments [Member]
Investment [Line Items]
Cost or Amortized Cost	10,000	10,000
Gross Unrealized Gains	820	591
Fair Value	10,820	10,591
States and political subdivisions [Member]
Investment [Line Items]
Cost or Amortized Cost	153,335	154,024
Gross Unrealized Gains	3,530	1,491
Gross Unrealized Losses	(2,790)	(5,140)
Fair Value	154,075	150,375
Corporate bonds [Member]
Investment [Line Items]
Cost or Amortized Cost	106,789	80,344
Gross Unrealized Gains	503	445
Gross Unrealized Losses	(198)	(361)
Fair Value	107,094	80,428
U.S. agency-based mortgage-backed securities [Member]
Investment [Line Items]
Cost or Amortized Cost	10,011	10,041
Gross Unrealized Losses	(2,991)	(2,967)
Fair Value	7,020	7,074
Equity securities [Member]
Investment [Line Items]
Cost or Amortized Cost	3,447	9,482
Gross Unrealized Gains	261	387
Gross Unrealized Losses	(26)	(567)
Fair Value	$ 3,682	$ 9,302