Description of the Business and Basis of Presentation - Summary of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 488,416	$ 39,946
Restricted cash, included in other current assets	$ 1,455	$ 979
Restricted cash, current, asset, statement of financial position [extensible list]	us-gaap:OtherAssetsCurrent	us-gaap:OtherAssetsCurrent
Total cash, cash equivalents and restricted cash	$ 489,871	$ 40,925	$ 52,590	$ 35,007