Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 20,005	$ 5,551
Due after one year through five years	13,893	22,757
Due after five years	233	330
Amortized Cost, Total	34,131	28,638
Fair Value
Due in one year or less	19,969	5,554
Due after one year through five years	13,843	22,708
Due after five years	242	340
Fair Value, Total	$ 34,054	$ 28,602