Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash balance included foreign bank balance	$ 123,499	$ 67,502
Gross realized gains on sale of debt securities	1,581	669	$ 929
Gross realized losses on sale of debt securities	$ 129	$ 168	$ 100