Stockholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended				12 Months Ended
	Apr. 30, 2014	Nov. 30, 2012	Feb. 29, 2012	Jan. 31, 2012	Dec. 31, 2014	Dec. 31, 2012
Equity [Abstract]
Sale of common stock, preferred stock, debt securities and warrants					$ 145,900,000
Maximum value of common stock issuable under agreement	25,000,000	50,000,000
Number of shares of common stock sold under the sales agreement					3,291,521
Gross proceeds from the sales agreement					4,067,751
Sale of stock compensation percentage on gross proceeds under agreement	2.50%	2.50%
Number of shares of common stock sold in public offering				13,333,334
Common stock, public offering price			$ 3.75	$ 3.75
Net proceeds from offering				$ 48,700,000	$ 3,923,000	$ 48,709,000
Number of common stock issued on partial exercise of underwriters' overallotment option			576,358