Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Stock-Based Compensation [Abstract]

Classification of Stock-Based Compensation Expense

The following table presents the classification of stock-based compensation expense recognized for the periods below:

	Three months ended June 30,				Six months ended June 30,
(in thousands)	2019		2018		2019		2018
Selling, general and administrative expense	$	309	$	555	$	635	$	1,006
Research and development expense		30		51		66		101
Total stock-based compensation expense	$	339	$	606	$	701	$	1,107