Income Taxes - Schedule of Reconciliation of Statutory Federal Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Federal tax provision at statutory rate	35.00%	35.00%	35.00%
State taxes (net of Federal benefit)	1.43%	10.81%	2.27%
Change in tax reserve	(2.31%)	(0.06%)	(0.94%)
Orphan drug credit		0.25%	(0.70%)
Stock-based compensation	(0.25%)	1.50%	0.06%
Non-deductible officer compensation	(1.79%)	(1.86%)	0.20%
Change in valuation allowance	(52.09%)	(45.48%)	(29.94%)
Research and development credits	19.37%		7.05%
Net proceeds from stockholder securities law settlement			(2.43%)
Other	0.37%	(0.19%)	(0.53%)
Benefit (provision) for taxes	(0.27%)	(0.03%)	10.04%