Accumulated Other Comprehensive Income (Loss) - Summary of Components of AOCI (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Beginning	$ 288,172	$ 332,732	$ 348,275
Other comprehensive income (loss)	(900)	1,800	(1,600)
Income tax (expense) benefit		(500)	300
Total other comprehensive income (loss)	(925)	1,281	(1,352)
Balance, Ending	275,980	288,172	332,732
Foreign Currency Translation
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Beginning	(500)	(400)	(100)
Other comprehensive income (loss)	(900)	(100)	(300)
Total other comprehensive income (loss)	(900)	(100)	(300)
Balance, Ending	(1,400)	(500)	(400)
Marketable Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Beginning	400	(1,000)
Other comprehensive income (loss)		1,900	(1,300)
Income tax (expense) benefit		(500)	300
Total other comprehensive income (loss)		1,400	(1,000)
Balance, Ending	400	400	(1,000)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Beginning	(131)	(1,412)	(60)
Balance, Ending	$ (1,056)	$ (131)	$ (1,412)