Stockholders' Equity - Summary of Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ 607,595	$ 541,387	$ 417,019
Other comprehensive income (loss)	174	(442)	377
Ending Balance	643,515	607,595	541,387
Unrealized gain (loss) on investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	0	0	(1)
Other comprehensive income (loss)	0	0	1
Ending Balance	0	0	0
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(446)	(4)	(380)
Other comprehensive income (loss)	174	(442)	376
Ending Balance	(272)	(446)	(4)
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(446)	(4)	(381)
Other comprehensive income (loss)	174	(442)	377
Ending Balance	$ (272)	$ (446)	$ (4)