Investment Securities - Summary of Net Investment Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investment income (loss):
Amortization of premium or discount on fixed-maturity securities	$ (392)	$ (631)	$ (1,350)	$ (1,715)
Investment income on fixed-maturity securities	740	1,621	2,748	5,258
Interest income on cash and equivalents	2	2	9	11
Realized net gain (loss) from sale of investments	19	(767)	435	(754)
Unrealized (losses) gains on trading securities held at period end	(283)	565	(651)	(4,022)
Net investment income (loss)	$ 86	$ 790	$ 1,191	$ (1,222)