Accounting for Stock-Based Compensation - Employee and Non-Employee Share Based Compensation Expense Allocation (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 743,444	$ 660,566
Research and Development Expenses [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	191,945	206,879
General and Administrative Expenses [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total stock-based compensation expense	$ 551,499	$ 453,687