Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 2,880	$ 4,768
Due after one year through five years	17,594	17,584
Due after five years	0	0
Amortized Cost, Total	20,474	22,352
Fair Value
Due in one year or less	2,868	4,743
Due after one year through five years	17,529	17,394
Due after five years	0	0
Fair Value, Total	$ 20,397	$ 22,137