License Agreements and Grants - National Institute of Health Grant (Details) - National Institute of Health Grant - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		35 Months Ended
	Feb. 28, 2015	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and Development Arrangement, Contract to Perform for Others, Proposed Period	5 years
Total grant funding	$ 5,000	$ 60	$ 3
Research and Development Arrangement, Contract to Perform for Others, Invoiced				$ 885