Fair Values of Financial Instruments - Summary of Carrying Values and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	$ 662,276	$ 664,371
Fixed maturity securities-held-to-maturity	645,164	639,631
Fixed maturity securities-available-for-sale	380,022	331,242
Equity securities	31	28
Short-term investments	7,718	33,684
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	645,164	639,631
Fixed maturity securities-available-for-sale	380,022	331,242
Equity securities	31	28
Cash and cash equivalents	69,481	90,956
Short-term investments	7,718	33,684
Other investments	12,217	11,748
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	662,276	664,371
Fixed maturity securities-available-for-sale	380,022	331,242
Equity securities	31	28
Cash and cash equivalents	69,481	90,956
Short-term investments	7,718	33,684
Other investments	$ 12,217	$ 11,748