Investments - Schedule of Investments in Fixed Maturity Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale, Maturity and Collection of Investments	$ 17,923	$ 9,644	$ 18,890
Cost	22,352	31,042
Gross Unrealized Gains	7	12
Gross Unrealized Losses	(222)	(206)
Fair Value	22,137	30,848
Payments to Acquire Investments	9,284	$ 10,665	$ 25,872
Short-term Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 4,800