Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions			1 Months Ended		3 Months Ended		12 Months Ended	47 Months Ended
	Sep. 10, 2014	Nov. 06, 2012	Jul. 31, 2016	Apr. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2013	Sep. 30, 2016
Revenue Recognition, Milestone Method [Line Items]
Valuation Allowances and Reserves, Balance					$ 1.8
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	$ 1.7		$ 20.9