Reconciliation of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents presented in the consolidated balance sheets	$ 268,345	$ 50,443
Restricted cash		2,505
Cash, cash equivalents and restricted cash presented in the consolidated statements of cash flows	$ 268,345	$ 52,948	$ 39,620	$ 103,172