Nature of the Business (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Nature of the Business
Shares sold	$ 6,164,000
Sales price (in dollars per share)	$ 14.00	$ 14.00
Net proceeds	$ 77,800,000
Convertible preferred stock converted into shares	15,109,950
Shares that warrant can purchase	7,614	7,614
Accumulated deficit	$ (91,886,000)	$ (91,886,000)	$ (57,525,000)
Revenue		$ 0