Controlled Equity Offering and Public Offering of Common Stock - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	0 Months Ended
	Apr. 30, 2014	Mar. 31, 2015	Feb. 20, 2015	Apr. 14, 2014
Stockholders Equity Common Stock [Line Items]
Common stock to be sold, shares				12,500,000
Public offering price	$ 4.00			$ 4.00
Expected aggregate gross proceeds				$ 50,000,000
Value of stock to be purchased by existing stockholders				10,000,000
Over-allotment option, shares to be issued to underwriters				1,875,000
Shares issued from option exercise by underwriters	1,610,000
Additional proceeds from exercise of option by underwriters	6,400,000
Proceeds from issuance of common stock, net of issuance costs	52,400,000	1,783,000
Issuance costs of Issuance of common shares	4,000,000
Aggregate maximum value of designated securities to be sold	$ 100,000,000
Cantor Fitzgerald & Co. [Member]
Stockholders Equity Common Stock [Line Items]
Sale of common stock in an at-the-market offering			25,000,000
Percentage of commission paid			3.00%