Stock-Based Compensation - Stock-Based Compensation Expense - Additional Information (Detail)	12 Months Ended
	Jun. 30, 2017 USD ($)
Class of Stock [Line Items]
Unrecognized compensation expense	$ 4,200,000
Unrecognized compensation expense weighted average period	2 years 15 days
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	104,000
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