Debt - Activity Related to Secured Promissory Note (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 October 2012 Junior secured promissory notes [Member]	Sep. 30, 2013 October 2012 Junior secured promissory notes [Member] Principal [Member]	Sep. 30, 2013 October 2012 Junior secured promissory notes [Member] Debt discount related to issuance of common stock warrants [Member]	Sep. 30, 2013 October 2012 Junior secured promissory notes [Member] Discount related to the $3,750,000 Notes [Member]	Sep. 30, 2013 April 2012 Senior secured promissory note [Member]	Sep. 30, 2013 April 2012 Senior secured promissory note [Member] Principal [Member]	Sep. 30, 2013 April 2012 Senior secured promissory note [Member] Discount related to Series C Warrant [Member]	Sep. 30, 2013 April 2012 Senior secured promissory note [Member] Discount related to financing costs [Member]
Debt Instrument [Line Items]
DEBT, BEGINNING BALANCE	$ 12,438	$ 16,338	$ 7,242	$ 7,500	$ (258)		$ 8,374	$ 9,139	$ (251)	$ (514)
AMORTIZATION OF DEBT DISCOUNT			153		95	58	765		251	514
PRINCIPAL PAYMENTS							(9,139)	(9,139)
DEBT, ENDING BALANCE	12,438	16,338	11,941	12,450	(276)	(233)
ADDITIONS			$ 4,546	$ 4,950	$ (113)	$ (291)