Commitments and Contingencies - License Agreement (Details) $ in Thousands		5 Months Ended	12 Months Ended
	Jun. 22, 2017 USD ($) trading_days payment	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Jul. 31, 2017 USD ($)
License Agreement
Other Commitments [Line Items]
Upfront payments | payment	2
Percent of upfront payments which may be paid by issuing common stock	50.00%
Percent of average share price	75.00%
Threshold trading days | trading_days	20
Maximum additional product milestone payments	$ 1,800
Maximum additional commercialization milestone payments	$ 5,000
Termination advance notice period	30 days
Rent expense		$ 150	$ 350	$ 200
Supply Agreement
Other Commitments [Line Items]
Other commitment, period	20 years
Material cure period	60 days