Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Fixed-Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Amortized Cost, 2015	$ 73,442
Amortized Cost, 2016-2019	32,444
Total fixed-maturity securities, Amortized Cost	105,886	$ 60,202
Estimated Fair Value, 2015	73,464
Estimated Fair Value, 2016-2019	32,541
Total fixed-maturity securities, Estimated Fair Value	$ 106,005	$ 60,641