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		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 13,841	$ 6,482	$ 11,694	$ 11,809
Restricted cash - current	[1]	68,146			11,191
Restricted cash - non-current				1,292	1,266
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows		$ 81,987	$ 6,482	$ 12,986	$ 24,266

[1] Restricted cash – current at the beginning of the year ended December 31, 2018 represents amounts held in an escrow account for the acquisition of The Future Customer (“TFC”).