Restricted Cash - Reconciliation of Cash and Cash Equivalents, and Restricted Cash to the Total of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 7,883	$ 13,841	$ 8,237	$ 6,482
Restricted cash	[1]	34,419	68,146
Total of cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows		$ 42,302	$ 81,987	$ 8,237	$ 6,482

[1] Under a contract with a customer that commenced in the fourth quarter of fiscal year 2020, the Company received advance payments to be used to pay providers of services to the customer, a separate third-party. The advanced payments are treated as restricted cash as the Company is required under the contract to distribute the advanced funds to the third-party providers of services or return the advanced funds to the customer. Because the Company receives the advance payments from the customer, which must be refunded to the customer or remitted to a third party, the cash receipts are treated as borrowings and recorded in restricted cash and accrued expenses and other current