Warrant Exercise (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		115 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013
Class of Warrant or Right [Line Items]
Liability Reclassed to Equity		$ 42
Cash Received	101	140	13,180
Equity Warrants
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised	49,315	68,494
Liability Warrants
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised		31,712
Common Stock Issued
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised	49,315	76,515
Cash exercises
Class of Warrant or Right [Line Items]
Cash Received	101	140
Cash exercises | Equity Warrants
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised	49,315	68,494
Cash exercises | Common Stock Issued
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised	49,315	68,494
Cashless Exercise
Class of Warrant or Right [Line Items]
Liability Reclassed to Equity		$ 42
Cashless Exercise | Liability Warrants
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised		31,712
Cashless Exercise | Common Stock Issued
Class of Warrant or Right [Line Items]
Number Of Warrants Exercised		8,021