Reconciliation of Liabilities Measured at Fair Value Using Significant Observable Inputs (Level 3) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012
Warrants and Rights Outstanding [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 345,000
Issuance of common stock warrants	20,959,000
Changes in fair value	3,611,000
Ending Balance	24,915,000
Embedded Derivative Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	845,000
Issuance of common stock warrants	0
Changes in fair value	(166,000)
Ending Balance	$ 679,000