Organization and Description of Business - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents	$ 245,364	$ 223,117
Restricted cash included in other long-term assets	315	380
Total cash, cash equivalents, and restricted cash	$ 245,679	$ 223,497	$ 247,299	$ 35,685