Stock Warrants - Additional Information (Details) - USD ($)				1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 15, 2018	Oct. 10, 2018	Oct. 10, 2014	Nov. 18, 2016	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Oct. 31, 2018	Dec. 26, 2017
Equity, Class of Treasury Stock [Line Items]
Proceeds from Issuance or Sale of Equity	$ 18,600,000
Warrants Not Settleable in Cash, Fair Value Disclosure											$ 9,000
Proceeds from Issuance of Common Stock									$ 12,200,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	13,672,173
Fair Value Adjustment of Warrants					$ 0	$ (783,000)	$ 0	$ (3,438,000)	$ (4,083,000)
Conversion of Stock, Shares Converted							7,900
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 1.38									$ 1.38
Class A [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Issued During Period, Shares, New Issues	2,520,000
Class B [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Issued During Period, Shares, New Issues	15,723
Preferred Stock Conversion Price Per Share	$ 1.15
Series B Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	13,672,173
Stock Issued During Period, Value, Issued for Services	$ 1,000
Preferred Stock, Par or Stated Value Per Share	$ 1,000				$ 1,000		$ 1,000		$ 1,000
Conversion of Stock, Shares Converted	13,672,173
IPO [Member]
Equity, Class of Treasury Stock [Line Items]
Warrants Not Settleable in Cash, Fair Value Disclosure				$ 15,700,000	$ 100,000	624,000	$ 100,000	624,000
Stock Issued During Period, Shares, New Issues				714,286
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				1,428,571
Fair Value Adjustment of Warrants						714,000		3,000,000
Sale of Stock, Price Per Share			$ 1.47	$ 35.00
IPO [Member] | Series A [Member]
Equity, Class of Treasury Stock [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights				50.05
IPO [Member] | Series B [Member]
Equity, Class of Treasury Stock [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 60.20
Underwritten Public Offering [Member] | October 2018 Warrants [Member]
Equity, Class of Treasury Stock [Line Items]
Warrant Term	5 years
Over-Allotment Option [Member]
Equity, Class of Treasury Stock [Line Items]
Issuance Of Warrants To Purchase Of Common Stock	1,807,826
Stock Issued During Period, Shares, New Issues	2,428,825	2,428,825
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	2,428,825	2,428,825
Series A Warrants [Member]
Equity, Class of Treasury Stock [Line Items]
Proceeds from Issuance of Common Stock			$ 19,100,000
Sale of Stock, Number of Shares Issued in Transaction			14,059,616
Issuance Of Warrants To Purchase Of Common Stock			0.50
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number			61.25
Share Based Compensation Arrangement By Share Based Payment Award Warrants Vested and Expected To Vest Outstanding Number			200,852
Fair Value of Warrant Liability					$ 0	21,000	$ 0	21,000
Fair Value Adjustment of Warrants			$ 7,400,000			$ 69,000		$ 395,000
Warrant [Member]
Equity, Class of Treasury Stock [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Warrants Exercisable Number											714
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	13,672,173