Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 20,993	$ 5,551
Due after one year through five years	10,572	22,757
Due after five years	330	330
Amortized Cost, Total	31,895	28,638
Fair Value
Due in one year or less	20,940	5,554
Due after one year through five years	10,533	22,708
Due after five years	343	340
Fair Value, Total	$ 31,816	$ 28,602