Common Stock - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended			12 Months Ended
	Aug. 16, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 At Market Agreement	Dec. 31, 2013 At Market Agreement	Oct. 25, 2013 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	500,000			2,674,500	99,942
Price of common stock per share					$ 9.02
Gross proceeds from sale of common stock					944,000
Initial legal and accounting costs					82,000
Commissions					29,000
Proceeds from issuance of common stock		28,238,000	3,000,000	28,238,000	833,000
Proceeds from sale of common stock	3,000,000
Warrants issued	0
Stock issuance costs	0
Proceeds from exercise of common stock warrants and options		$ 2,187,000	$ 3,189,000