Nature of Business and Basis of Presentation - Schedule of Error Corrections (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accumulated deficit		$ 507,408	$ 320,443	$ 171,962	$ 162,316
Deemed dividends on preferred stock and amortization of beneficial conversion feature			(5,208)	(9,742)
Gain on redemption of preferred stock	$ 9,100	0	9,075	0
Redemption of Series A Preferred Stock			(21,348)
Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accumulated deficit		520,278	340,291	194,687	191,308
Deemed dividends on preferred stock and amortization of beneficial conversion feature			(5,208)	(9,742)
Gain on redemption of preferred stock			9,075
Redemption of Series A Preferred Stock			(21,348)
Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accumulated deficit		(11,357)	(19,363)	(23,079)	(29,071)
Series A Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deemed dividends on preferred stock and amortization of beneficial conversion feature			5,208	9,742
Redeemable preferred stock		$ 0	0	32,615	22,873
Redemption of Series A Preferred Stock			(37,823)
Series A Redeemable Convertible Preferred Stock | Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Gain on redemption of preferred stock	$ 21,300
Previously Reported | Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accumulated deficit			372,186	230,030	216,104
Deemed dividends on preferred stock and amortization of beneficial conversion feature			419	805
Previously Reported | Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accumulated deficit			(51,258)	(58,422)	$ (53,867)
Deemed dividends on preferred stock and amortization of beneficial conversion feature			(5,627)	(10,547)
Gain on redemption of preferred stock			9,075
Previously Reported | Series A Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deemed dividends on preferred stock and amortization of beneficial conversion feature			8,406
Gain on redemption of preferred stock			9,075
Redeemable preferred stock				$ 32,615
Redemption of Series A Preferred Stock			(50,096)
Restatement Adjustment | Series A Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deemed dividends on preferred stock and amortization of beneficial conversion feature			18,150
Gain on redemption of preferred stock			(18,150)
Reclassification | Series A Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deemed dividends on preferred stock and amortization of beneficial conversion feature			(21,348)
Gain on redemption of preferred stock			9,075
Redemption of Series A Preferred Stock			$ 12,273