Summary of Significant Accounting Policies - Significant Customers and Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Allowance for doubtful accounts receivable	$ 0.2	$ 0.2
Customer Concentration Risk | Sales Revenue, Services, Net
Concentration Risk [Line Items]
Concentration risk percentage	100.00%	100.00%
Increase (decrease) in concentration risk percentage	0.00%
Customer Concentration Risk | Sales Revenue, Services, Net | U.S. Department of Defense
Concentration Risk [Line Items]
Concentration risk percentage	46.30%	69.00%
Increase (decrease) in concentration risk percentage	(22.70%)
Customer Concentration Risk | Sales Revenue, Services, Net | Incuron, LLC
Concentration Risk [Line Items]
Concentration risk percentage	53.70%	31.00%
Increase (decrease) in concentration risk percentage	22.70%
Customer Concentration Risk | Accounts Receivable
Concentration Risk [Line Items]
Credit term	30 days