Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	$ 186,713	$ 133,630
Other comprehensive income (loss) before reclassifications	(238)	187
Amount reclassified from accumulated other comprehensive income	0	0
Net current period other comprehensive income (loss)	(238)	187
Balance, Value	160,474	114,522
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	170	(114)
Net current period other comprehensive income (loss)	(238)	187
Balance, Value	$ (68)	$ 73