Restricted Cash - Reconciliation of Cash and Cash Equivalents, and Restricted Cash to the Total Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents		$ 11,809	$ 6,042	$ 7,747	$ 12,122
Restricted cash - current	[1]	11,191
Restricted cash - non-current		1,266	1,843	1,362	1,478
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows		$ 24,266	$ 7,885	$ 9,109	$ 13,600

[1] Restricted cash – current for the year ended December 31, 2017 represents amounts held in an escrow account for a future acquisition. See Note 19 – Subsequent Events.