Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			9 Months Ended
	Feb. 17, 2015	Feb. 03, 2015	Sep. 30, 2015
License Agreement
Class of Stock [Line Items]
Issuance of common stock in licensing agreement (in shares)			11,722,163
J.P. Morgan Securities Inc.
Class of Stock [Line Items]
Issuance of common stock in public offering (in shares)	1,500,000	10,000,000
Issuance & sale of common stock in public offering price per share		$ 8.75
Option granted, exercisable period		30 days
Sale of stock price per share		$ 8.225
Net proceeds from issuance of common stock	$ 94.3