Assumptions Used In Binomial Valuation Model and Black-Scholes Valuation Model (Detail)	Dec. 31, 2012 Y	Dec. 31, 2009 Y	Feb. 23, 2007 Y	May 03, 2006	Dec. 31, 2005 Y	Dec. 31, 2004 Y	Dec. 22, 2004 Y	Dec. 31, 2012 Monte Carlo Option Pricing Model	Dec. 31, 2011 Monte Carlo Option Pricing Model	Dec. 31, 2012 Monte Carlo Option Pricing Model Minimum Y	Dec. 31, 2011 Monte Carlo Option Pricing Model Minimum Y	Dec. 31, 2011 Monte Carlo Option Pricing Model Maximum Y	Dec. 31, 2010 Black Scholes Option Pricing Model	Dec. 31, 2008 Black Scholes Option Pricing Model Y	Dec. 31, 2010 Black Scholes Option Pricing Model Minimum Y	Dec. 31, 2010 Black Scholes Option Pricing Model Maximum Y
Class of Warrant or Right [Line Items]
Risk-free interest rate	3.93%	2.14%	4.71%	5.01%	4.39%	3.93%	3.93%			0.25%	0.05%	0.35%		1.55%	0.42%	1.48%
Expected life in years	7	5	5		5	7	7			1.94	0.42	2.92		3.42	1.42	3.92
Expected volatility	134.00%	105.00%	93.00%	100.00%	109.00%	134.00%	134.00%			70.00%	64.00%	80.00%		102.00%	75.00%	116.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%				0.00%	0.00%