Organization and Significant Accounting Policies - Excess and Obsolete Inventory Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Excess and Obsolete Inventory Reserve [Roll Forward]
Excess and obsolete inventory reserve, beginning balance	$ 825	$ 0
Provision charged to expense	228	825
Write-offs / Recoveries		0
Excess and obsolete inventory reserve, ending balance	$ 1,053	$ 825