Changes in Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	$ 649,958
Other comprehensive loss before reclassifications	(494)
Ending Balance, Amount	660,973
Cumulative Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	(610)
Other comprehensive loss before reclassifications	(1,077)
Ending Balance, Amount	(1,687)
Unrealized Gain on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	274
Other comprehensive loss before reclassifications	583
Ending Balance, Amount	857
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	(336)
Ending Balance, Amount	$ (830)