Trade Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Trade receivables	$ 42,804	$ 45,628
Allowance for doubtful accounts	(119)	(170)
Total trade receivable	42,685	45,458
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, January 1	170	918	$ 108
Charges to bad debt expense	311	289	786
Recoveries (write-offs), net	(362)	(1,037)	24
Balance, December 31	$ 119	$ 170	$ 918