Annual report pursuant to Section 13 and 15(d)

Nature of Operations and Basis of Presentation - Additional Information (Details)

Nature of Operations and Basis of Presentation - Additional Information (Details)					3 Months Ended								12 Months Ended
	Jan. 21, 2020 USD ($) Debtinstrument shares	Jun. 26, 2018 USD ($) $ / shares shares	May 30, 2018 USD ($) $ / shares shares	May 15, 2018 $ / shares	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 16, 2019 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse share split				0.0636
Share consolidation basis nominal value per share \| $ / shares				$ 0.01571
Share consolidation basis, Renominalisation value per share \| $ / shares				$ 0.01
Net proceeds from issuance of stock after deducting underwriting discounts,commissions and offering cost		$ 2,400,000	$ 71,800,000											$ 74,153,000
Net losses					$ 23,641,000	$ 31,271,000	$ 27,638,000	$ 20,580,000	$ 24,258,000	$ 24,905,000	$ 15,747,000	$ 12,146,000	$ 103,130,000	77,056,000	$ 29,406,000
Accumulated deficit					$ 234,923,000				$ 131,793,000				$ 234,923,000	$ 131,793,000
Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate initial offering price of securities authorized to issue																$ 150,000,000
IPO
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of shares issued \| shares		200,000	6,150,000
Offering price per share \| $ / shares		$ 13.00	$ 13.00
Subsequent Event \| Private Placement \| Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	$ 51,600,000
Debt instrument interest rate	6.50%
Debt instrument price per unit	$ 1,000
Subsequent Event \| Private Placement \| RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	$ 100,000
Number of debt instruments within each notes \| Debtinstrument	50
Debt instrument, aggregate potential payment capped value	$ 160,000
Debt instrument, aggregate potential payment capped rate	4,000 times
Subsequent Event \| Private Placement \| RLNs \| Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument, percentage of net revenue from domestic sale for potential aggregate payments	15.00%
Subsequent Event \| Private Placement \| RLNs \| Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument, percentage of net revenue from domestic sale for potential aggregate payments	20.00%
Subsequent Event \| Private Placement \| Securities
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument price per unit	$ 1,000
Debt instrument, shares embedded within each unit, shares \| shares	1,000
Debt instrument, shares embedded within each unit, value	$ 1,000
Proceeds from sale of securities	$ 46,700,000