Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Net operating loss carryforwards	$ 42,715,000	$ 18,283,000
Net Operating loss Carryforwards resulting from excess tax deduction	4,100,000
Increase (decrease) in valuation allowance	47,600,000
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	111,500,000
Net operating loss carryforwards, expiration date	Expiring in varying amounts through 2031
Research and Development Credit
Income Taxes [Line Items]
Net operating loss carryforwards	20,000,000
Net operating loss carryforwards, expiration date	Expiring in varying amounts through 2031
Net Operating Loss Carryforwards
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets	(11,200,000)
General Business Credits
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets	$ (636,000)