Net Loss Per Common Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Securities Excluded from Computation of Diluted Loss Per Share

Securities excluded from the calculation of diluted loss per share are shown in the chart below:

	Years Ended December 31,
(in thousands)	2017		2016		2015
Outstanding options to purchase common stock		1,616		1,903		1,921
Conversion of the Convertible Notes		—		1,216		2,500