Changes in Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	$ 762,655
Other comprehensive loss before reclassifications	(2,729)
Ending Balance, Amount	774,714
Cumulative Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	4,180
Other comprehensive loss before reclassifications	(2,489)
Ending Balance, Amount	1,691
Unrealized Gain on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	423
Other comprehensive loss before reclassifications	(240)
Ending Balance, Amount	183
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance, Amount	4,603
Ending Balance, Amount	$ 1,874