Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Net operating loss carryforwards	$ 66,209,000	$ 42,715,000
Research and development credit carryforwards	25,058,000	18,388,000
Net Operating loss Carryforwards resulting from excess tax deduction	4,200,000
Increase (decrease) in valuation allowance	26,300,000
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	197,000,000
Net operating loss carryforwards, expiration date	2032
Research and Development Credit
Income Taxes [Line Items]
Net operating loss carryforwards, expiration date	2032
Research and development credit carryforwards	25,000,000
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)