Common Stock - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Mar. 30, 2014
Class of Stock [Line Items]
Proceeds from issuance of common stock			$ 4,532,000	$ 28,178,000
At Market Agreement
Class of Stock [Line Items]
Aggregate offering price						$ 30,000,000
Commission to sales agent as a percentage of gross proceeds						3.00%
Shares of common stock issued		1,279,416			217,622
Price of common stock per share					$ 5.49
Gross proceeds from sale of common stock					$ 1,196,000
Commissions					36,000
Proceeds from issuance of common stock	$ 0	$ 4,532,000			$ 1,159,000