Investments - Schedule of Investments in Fixed Maturity Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Single Maturity Date	$ 7,600	$ 8,100
Cost	20,474	22,352
Gross Unrealized Gains	57	7
Gross Unrealized Losses	(134)	(222)
Fair Value	20,397	22,137
U.S. Treasury securities, obligations of U.S. Government agencies and Municipalities
Schedule of Available-for-sale Securities [Line Items]
Cost	20,241	21,729
Gross Unrealized Gains	51	7
Gross Unrealized Losses	(134)	(222)
Fair Value	20,158	21,514
Corporate debt
Schedule of Available-for-sale Securities [Line Items]
Cost	233	623
Gross Unrealized Gains	6	0
Gross Unrealized Losses	0	0
Fair Value	$ 239	$ 623