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Fair Value Measurements - Additional Information (Detail) - USD ($)
12 Months Ended
Jun. 30, 2018
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2017
Jun. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Warrant exercise price $ 1.23 $ 1.23   $ 2.50 $ 2.50
Transaction costs allocated to second tranche liability and additional advance warrant liability $ 326,000        
Second Tranche Warrants [Member]          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Warrant exercise price     $ 1.43