Supplemental Cash Flow Information of the Company - Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	$ 348,417	$ 731,991	$ 849,009	$ 60,044
Restricted cash	13,042	91,139	16,300	16,300
Cash and cash equivalents and restricted cash	$ 361,459	$ 823,130	$ 865,309	$ 76,344