Investments - Schedule of Investments in Fixed Maturity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Single Maturity Date	$ 9,200	$ 9,500
Cost	31,895	28,638
Gross Unrealized Gains	19	24
Gross Unrealized Losses	(98)	(60)
Fair Value	31,816	28,602
U.S. Treasury securities, obligations of U.S. Government agencies and Municipals
Schedule of Available-for-sale Securities [Line Items]
Cost	30,063	26,280
Gross Unrealized Gains	3	11
Gross Unrealized Losses	(98)	(59)
Fair Value	29,968	26,232
Corporate debt
Schedule of Available-for-sale Securities [Line Items]
Cost	1,832	2,358
Gross Unrealized Gains	16	13
Gross Unrealized Losses	0	(1)
Fair Value	$ 1,848	$ 2,370