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	Jun. 30, 2014	Dec. 31, 2013
Investment [Line Items]
Cost or Amortized Cost	$ 295,686	$ 263,891
Gross Unrealized Gains	8,052	2,914
Gross Unrealized Losses	(4,053)	(9,035)
Fair Value	299,685	257,770
Total fixed maturity [Member]
Investment [Line Items]
Cost or Amortized Cost	282,240	244,409
Gross Unrealized Gains	6,420	1,936
Gross Unrealized Losses	(4,047)	(8,468)
Fair Value	284,613	237,877
Other investments [Member]
Investment [Line Items]
Cost or Amortized Cost	10,000	10,000
Gross Unrealized Gains	1,092	591
Fair Value	11,092	10,591
States and political subdivisions [Member]
Investment [Line Items]
Cost or Amortized Cost	151,140	154,024
Gross Unrealized Gains	5,711	1,491
Gross Unrealized Losses	(1,759)	(5,140)
Fair Value	155,092	150,375
Corporate bonds [Member]
Investment [Line Items]
Cost or Amortized Cost	121,088	80,344
Gross Unrealized Gains	708	445
Gross Unrealized Losses	(33)	(361)
Fair Value	121,763	80,428
U.S. agency-based mortgage-backed securities [Member]
Investment [Line Items]
Cost or Amortized Cost	10,012	10,041
Gross Unrealized Gains	1
Gross Unrealized Losses	(2,255)	(2,967)
Fair Value	7,758	7,074
Equity securities [Member]
Investment [Line Items]
Cost or Amortized Cost	3,446	9,482
Gross Unrealized Gains	540	387
Gross Unrealized Losses	(6)	(567)
Fair Value	$ 3,980	$ 9,302