Reconciliation of the Federal Statutory Corporate Income Tax Rate to the Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of Provision of Income Taxes [Line Items]
Statutory federal income tax rate	(35.00%)	35.00%	(35.00%)
State income tax rate, net of federal benefit	(4.00%)	5.00%	(6.00%)
Revaluation of warrant liability	13.00%	8.00%	3.00%
Other permanent differences		1.00%	1.00%
Change in valuation allowance	26.00%	(49.00%)	37.00%
Effective tax rate	0.00%	0.00%	0.00%