Fair Value Measurements - Schedule of Common Stock and the risk-free interest rate (Detail) - Second Tranche Warrants [Member]	Jun. 30, 2018	Jun. 25, 2018
Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input	85.40	81.00
Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input	2.10	2.10
Measurement Input, Expected Term (in years) [Member]
Warrants and Rights Outstanding, Measurement Input	0.5	0.5
Measurement Input, Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input	0	0
Measurement Input, Share Price [Member]
Warrants and Rights Outstanding, Measurement Input	2.08	2.00
Probability of Issuance [Member]
Warrants and Rights Outstanding, Measurement Input	100	100