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	Dec. 31, 2013	Dec. 31, 2012
Investment [Line Items]
Cost or Amortized Cost	$ 263,891	$ 151,514
Gross Unrealized Gains	2,914	6,101
Gross Unrealized Losses	(9,035)	(1,710)
Fair Value	257,770	155,905
Other Investments [Member]
Investment [Line Items]
Cost or Amortized Cost	10,000
Gross Unrealized Gains	591
Fair Value	10,591
States and political subdivisions [Member]
Investment [Line Items]
Cost or Amortized Cost	154,024	93,362
Gross Unrealized Gains	1,491	5,022
Gross Unrealized Losses	(5,140)	(142)
Fair Value	150,375	98,242
Corporate bonds [Member]
Investment [Line Items]
Cost or Amortized Cost	80,344	39,211
Gross Unrealized Gains	445	623
Gross Unrealized Losses	(361)	(24)
Fair Value	80,428	39,810
U.S. agency-based mortgage-backed securities [Member]
Investment [Line Items]
Cost or Amortized Cost	10,041	11,941
Gross Unrealized Gains		5
Gross Unrealized Losses	(2,967)	(859)
Fair Value	7,074	11,087
Total Fixed Maturity [Member]
Investment [Line Items]
Cost or Amortized Cost	244,409	144,514
Gross Unrealized Gains	1,936	5,650
Gross Unrealized Losses	(8,468)	(1,025)
Fair Value	237,877	149,139
Equity securities [Member]
Investment [Line Items]
Cost or Amortized Cost	9,482	7,000
Gross Unrealized Gains	387	451
Gross Unrealized Losses	(567)	(685)
Fair Value	$ 9,302	$ 6,766