Accounts Receivable and Contract Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Accounts Receivable and Contract Assets [Abstract]
Accounts receivable - customers	$ 4,482	$ 4,661
Other receivables	182	191
Accounts receivable	4,664	4,852
Less allowance for doubtful accounts	(343)	(305)
Accounts receivable, net	4,321	4,547
Unbilled revenue	2,517	$ 2,459
Change in accounts receivable - customers	(179)
Change in other receivables	(9)
Change in accounts receivable	(188)
Change in allowance for doubtful accounts	(38)
Change in accounts receivable, net	(226)
Change in unbilled revenue	$ 58