Stockholders' Equity - Summary of Warrant Activity (Detail) (Warrants [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Warrants [Member]
Class of Warrant or Right [Line Items]
Balance outstanding, Beginning, Number of Warrants	978,830	1,369,321
Warrants issued, Number of Warrants		44,088
Warrants exercised, Number of Warrants		(137)
Warrants expired, Number of Warrants	(105,494)	(434,579)
Warrants cancelled, Number of Warrants	0	0
Balance outstanding, Ending, Number of Warrants	873,336	978,830	1,369,321
Balance outstanding, Beginning, Weighted Average Exercise Price	$ 19.82	$ 19.00
Warrants exercisable at December 31, 2014, Number of Warrants	873,336
Warrants issued, Weighted Average Exercise Price		$ 2.28
Warrants exercised, Weighted Average Exercise Price		$ 5.60
Warrants expired, Weighted Average Exercise Price	$ 32.68	$ 15.72
Warrants cancelled, Weighted Average Exercise Price	$ 0	$ 0
Balance outstanding, Ending, Weighted Average Exercise Price	$ 17.79	$ 19.82	$ 19.00
Warrants exercisable at December 31, 2014, Weighted Average Exercise Price	$ 17.79
Balance outstanding, Weighted Average Remaining Contractual Life (in years)	1 year	1 year 10 months 24 days	2 years 1 month 6 days
Warrants exercisable at December 31, 2014, Weighted Average Remaining Contractual Life (in years)	1 year