Controlled Equity Offering and Public Offering of Common Stock - Additional Information (Detail) - USD ($)				1 Months Ended	6 Months Ended
	Jul. 10, 2015	Jun. 11, 2015	Feb. 20, 2015	Apr. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Apr. 14, 2014
Stockholders Equity Common Stock [Line Items]
Common stock to be sold, shares		16,666,667					12,500,000
Public offering price		$ 3.00		$ 4.00			$ 4.00
Expected aggregate gross proceeds		$ 50,000,000					$ 50,000,000
Over-allotment option, shares to be issued to underwriters		2,500,000					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		$ 46,400,000		52,400,000	$ 52,533,000	$ 52,506,000
Issuance costs of Issuance of common shares				4,000,000	4,000,000
Aggregate maximum value of designated securities to be sold				$ 100,000,000	$ 100,000,000
Value of stock to be purchased by existing stockholders							$ 10,000,000
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%
Subsequent Event [Member]
Stockholders Equity Common Stock [Line Items]
Public offering price	$ 3.00
Shares issued from option exercise by underwriters	2,075,000
Additional proceeds from exercise of option by underwriters	$ 6,200,000
Proceeds from issuance of common stock, net of issuance costs	$ 5,800,000