Investment Securities - Summary of Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investment income (loss):
Amortization of premium or discount on fixed-maturity securities	$ (144)	$ (429)	$ (323)	$ (958)
Investment income on fixed-maturity securities	326	907	739	2,009
Interest income on cash and equivalents	62	5	119	7
Realized net gain from sale of investments	81	388	267	415
Unrealized (losses) on trading securities held at period end	(197)	(434)	(273)	(368)
Net investment income	$ 128	$ 437	$ 529	$ 1,105