Inventories (Allowance) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Inventory Valuation Reserves [Roll Forward]
Balance, beginning of period	$ 1,642	$ 1,065	$ 1,382	$ 757
Provisions for excess and obsolete inventories	(206)	112	54	420
Inventories written off	(243)	0	(243)	0
Balance, end of period	$ 1,193	$ 1,177	$ 1,193	$ 1,177