Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounting Policies [Abstract]
Stock-based compensation expense	$ 162	$ 73
Useful life of demonstration assets	2 years
Demonstration assets	$ 2,100		$ 2,200
Amortization expense for demonstration assets	$ 400	$ 500