Income Taxes - Summary of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Net operating loss carryforward	$ 22,952,000	$ 31,338,000
Capitalized research and development expenses	6,055,000	10,402,000
License fees	277,000	325,000
Stock-based compensation expense	2,264,000	2,264,000
Other	547,000	737,000
Gross deferred tax assets	32,095,000	45,066,000
Valuation allowance	(32,095,000)	(45,066,000)
Net deferred tax assets