Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Fixed-Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Amortized Cost, 2016	$ 63,020
Amortized Cost, 2017-2019	24,884
Total fixed-maturity securities, Amortized Cost	87,904	$ 99,088
Estimated Fair Value, 2016	63,034
Estimated Fair Value, 2017-2019	25,005
Total fixed-maturity securities, Estimated Fair Value	$ 88,039	$ 99,055