Investments - Summary of Fixed Maturities and Equity Securities with Unrealized Losses (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 172,366	$ 58,694
Less Than 12 Months, Unrealized Losses	4,063	1,421
More Than 12 Months, Fair Value	8,851	13,670
More Than 12 Months, Unrealized Losses	304	173
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	23,866	6,821
Less Than 12 Months, Unrealized Losses	265	18
More Than 12 Months, Fair Value		937
More Than 12 Months, Unrealized Losses		1
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	54,722	4,146
Less Than 12 Months, Unrealized Losses	1,842	15
More Than 12 Months, Fair Value		1,309
More Than 12 Months, Unrealized Losses		4
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	33,096	26,854
Less Than 12 Months, Unrealized Losses	718	500
More Than 12 Months, Fair Value	2,215	2,398
More Than 12 Months, Unrealized Losses	176	36
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	50,284	13,361
Less Than 12 Months, Unrealized Losses	458	72
More Than 12 Months, Fair Value	6,636	9,026
More Than 12 Months, Unrealized Losses	128	132
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	10,398	7,512
Less Than 12 Months, Unrealized Losses	$ 780	$ 816