Research Collaboration and License Agreement (Details) - Research Collaboration and License Agreement - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2018	Sep. 30, 2017	Mar. 31, 2016
Collaboration and License Agreement
Term	10 years
PTG-300
Collaboration and License Agreement
Upfront payment to the former collaboration partner				$ 250,000
Additional payment obligation to the former collaboration partner			$ 250,000
Potential obligation to former collaboration partner for development and commercialization of product	$ 128,500,000
PTG-300 | Forecast
Collaboration and License Agreement
Additional payment obligation to the former collaboration partner		$ 500,000