Warrants (Details) - USD ($)		1 Months Ended	12 Months Ended
	Dec. 12, 2016	Nov. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 12, 2016
Warrants to Purchase Common Stock
Total fair value of warrants			$ 11,868,000	$ 6,365,000
Share-based Compensation			1,658,000	1,608,000
Balance at beginning of the period			11,868,000	6,365,000
Issuance of 5-year preferred stock warrants with financing - July 2017				351,000
Change in fair value of preferred stock warrants			(1,632,000)	5,152,000
Reclassification into equity upon initial public offering			(10,236,000)
Balance at end of the period				11,868,000
Performance Award
Warrants to Purchase Common Stock
Minimum gross proceeds for meeting performance requirement		$ 25,000,000
Warrants potentially issued for meeting performance requirement		234,860
Number of warrants issued	234,860
Warrants exercise price					$ 14.50
Total fair value of warrants	$ 661,000				$ 661,000
Vesting period	5 years
Share-based Compensation			$ 132,000	$ 132,000
Balance at end of the period	$ 661,000