Stockholders' Equity - Stock-Based Compensation Expense - Additional Information (Detail) - USD ($)	9 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class of Stock [Line Items]
Unrecognized compensation expense	$ 2,400,000
Unrecognized compensation expense weighted average period	1 year 5 months 1 day
General and Administrative Expense [Member]
Class of Stock [Line Items]
Increase in stock-based compensation expense attributable to option modification to extend exercise period of vested stock options, net of non-vested option forfeitures		$ 274,000
Decrease in stock-based compensation expense attributable to stock option forfeitures, net of option modification to extend exercise period of vested stock options		117,000
Research and Development Expense [Member] | U.K. [Member]
Class of Stock [Line Items]
Decrease in stock-based compensation expense attributable to stock option forfeitures, net of option modification to extend exercise period of vested stock options		$ 35,000