Investments - Summary of Fixed Maturities and Equity Securities with Unrealized Losses (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 23,578	$ 213,632
Less Than 12 Months, Unrealized Losses	825	3,798
More Than 12 Months, Fair Value	8,913	18,862
More Than 12 Months, Unrealized Losses	617	1,126
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		10,168
Less Than 12 Months, Unrealized Losses		51
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	1,572	19,437
Less Than 12 Months, Unrealized Losses	1	483
More Than 12 Months, Fair Value	986
More Than 12 Months, Unrealized Losses	20
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	16,039	69,482
Less Than 12 Months, Unrealized Losses	167	1,615
More Than 12 Months, Fair Value	6,302	11,324
More Than 12 Months, Unrealized Losses	587	958
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	2,931	105,300
Less Than 12 Months, Unrealized Losses	5	876
More Than 12 Months, Fair Value	1,530	7,538
More Than 12 Months, Unrealized Losses	5	168
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	3,036	9,245
Less Than 12 Months, Unrealized Losses	652	$ 773
More Than 12 Months, Fair Value	95
More Than 12 Months, Unrealized Losses	$ 5