Inventories (Allowance) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Inventory Valuation Reserves [Roll Forward]
Balance, beginning of period	$ 1,442	$ 894	$ 1,382	$ 757
Provisions for excess and obsolete inventories	200	171	260	308
Inventories written off	0	0	0	0
Balance, end of period	$ 1,642	$ 1,065	$ 1,642	$ 1,065