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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	$ 230,459	$ 249,001	$ 160,474	$ 186,713	$ 249,001	$ 186,713
Amount reclassified from accumulated other comprehensive income			(60)		(39)	(60)
Net current period other comprehensive income (loss)	(17)	(61)	703	(238)
Balance, Value	203,466	230,459	140,928	160,474	203,466	140,928
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	12	73	(68)	170	73	170
Other comprehensive income (loss) before reclassifications					(39)	525
Amount reclassified from accumulated other comprehensive income					(39)	(60)
Net current period other comprehensive income (loss)	(17)	(61)	703	(238)	(78)	465
Balance, Value	$ (5)	$ 12	$ 635	$ (68)	$ (5)	$ 635