Organization And Description of Business - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended					9 Months Ended	1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Patient	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Jun. 20, 2006	Sep. 30, 2013 Facility Loan Agreement	Nov. 22, 2013 Subsequent Event	Oct. 31, 2013 Subsequent Event
Organization And Description Of Business [Line Items]
Number of patients			1,000
Accumulated deficit	$ (344,928,000)		$ (344,928,000)		$ (329,480,000)
Net income (loss)	(1,307,000)	(511,000)	(6,159,000)	(8,465,000)
Cash flows from operating activities			(4,921,000)	(10,913,000)
Cash and cash equivalents	32,080,000	8,106,000	32,080,000	8,106,000	7,726,000	8,021,000
Working capital (deficit)	29,900,000		29,900,000		(9,900,000)
Gross proceeds from sale of stock			26,800,000							2,900,000
Facility loan, drawn			4,853,000					5,000,000
Maximum borrowing capacity							30,000,000	10,000,000
Net proceeds from sale of stock			28,900,000
Stock issued for cancellation of debt			16,900,000
Gross proceeds from sale of stock			$ 23,975,000						$ 3,000,000