Income Taxes (Details 5) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 41,688	$ 31,336
Research tax credits (expiring through 2025)	168	168
Alternative minimum tax credits (available without expiration)	0	86
State | Tennessee (expiring in 2032)
Operating Loss Carryforwards [Line Items]
Net operating losses	659	529
State | New Jersey (expiring in 2037)
Operating Loss Carryforwards [Line Items]
Net operating losses	4,320	1,764
State | Illinois (expiring in 2037)
Operating Loss Carryforwards [Line Items]
Net operating losses	389	222
State | Alabama (expiring in 2032)
Operating Loss Carryforwards [Line Items]
Net operating losses	24	0
Foreign
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 255	$ 232