Common Stock - Additional Information (Detail) - USD ($)	Sep. 30, 2015	May. 31, 2015
Equity [Abstract]
Shelf registration, maximum aggregate offering price		$ 200,000,000
Shelf registration, maximum common stock shares authorized		2,500,000.0
At-the-market sales agreement, maximum common stock shares authorized value		$ 75,000,000
Sale of securities	$ 0