Consolidated Statements of Cash Flow (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Statement Of Cash Flows [Abstract]
Cash	$ 33	$ 207	$ 279
Restricted cash included in other long-term assets	$ 6,158
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Total cash and restricted cash	$ 6,191	$ 207	$ 279	$ 75