Stock Based Compensation - Stock Compensation Expense, Restricted Stock Units (Details) - RSUs - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	$ 382	$ 407
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	38	35
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	54	39
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	9	8
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	$ 281	$ 325