Financings - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Feb. 17, 2015	Feb. 09, 2015	Feb. 03, 2015	Oct. 29, 2013	Oct. 23, 2013
Class of Stock [Line Items]
Sale of stock price per share				$ 3.50
J.P. Morgan Securities Inc.
Class of Stock [Line Items]
Stock issued during period	1,500,000	10,000,000	10,000,000	2,145,000	14,300,000
Issuance & sale of common stock in public offering price per share			$ 8.75		$ 3.50
Option granted, exercisable period			30 days		30 days
Sale of stock price per share			$ 8.225		$ 3.29
Net proceeds from issuance of common stock	$ 94.3
Option to purchase common stock			1,500,000		2,145,000
Net proceeds from issuance of common stock				$ 53.9