Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions			1 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended	47 Months Ended
	Sep. 10, 2014	Nov. 06, 2012	Jul. 31, 2016	Apr. 30, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2013	Sep. 30, 2016
Accounting Policies [Abstract]
Company milestone-based grant	$ 12.6	$ 8.3
Fund received for research and development activities		$ 2.6
Milestone payments received	$ 10.6		$ 2.8	$ 2.4				$ 2.5
Company grant revenue					$ 0.0	$ 1.0	$ 2.7		$ 20.9
Prior period reclassification adjustment						$ 0.3	$ 0.4
Valuation allowances and reserves					$ 1.8