Accounts Receivable and Other Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 32,970	$ 38,433
Less: allowance for doubtful accounts	(150)	(55)
Accounts receivable, net	32,820	38,378
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance for doubtful accounts, beginning of the year	55	103	$ 124
Charged to costs and expenses	153	(34)	(17)
Less: write-offs, net of recoveries	(58)	(14)	(4)
Remaining allowance, end of the year	150	55	$ 103
Other receivables	$ 3,421	$ 4,161