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, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 5,804	$ 11,809	$ 6,485	$ 6,042
Restricted cash - current	[1]		11,191
Restricted cash - non-current		1,286	1,266	1,251	1,843
Total of cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows		$ 7,090	$ 24,266	$ 7,736	$ 7,885

[1] Restricted cash – current as of December 31, 2017 represents amount held in an escrow account for the acquisition of The Future Customer. See Note 12 – Business Combinations.