Other Current Assets - Additional Information (Detail) (USD $)	Dec. 31, 2013	Sep. 24, 2013	Dec. 31, 2012	Nov. 30, 2012	Dec. 31, 2013 Other Current Assets	Dec. 31, 2013 Other Long-term Assets	Jan. 31, 2013 $1.5 Million Purchase Agreement with Lincoln Park	Dec. 31, 2012 $1.5 Million Purchase Agreement with Lincoln Park	Dec. 31, 2013 $1.5 Million Purchase Agreement with Lincoln Park Other Long-term Assets	Dec. 31, 2013 Licensing fee if Merck is unable to advance directly to Phase III trials of Tcelna	Dec. 31, 2013 Licensing fee if Merck is unable to advance directly to Phase III trials of Tcelna $1.5 Million Purchase Agreement with Lincoln Park	Dec. 31, 2013 Licensing fee if Merck is unable to advance directly to Phase III trials of Tcelna $15 Million Purchase Agreement with Lincoln Park	Dec. 31, 2012 Options to purchase an aggregate of 20,600 shares $1.5 Million Purchase Agreement with Lincoln Park	Dec. 31, 2012 Options to purchase an aggregate of 20,600 shares $15 Million Purchase Agreement with Lincoln Park	Dec. 31, 2013 ATM Agreement Third Party	Dec. 31, 2012 ATM Agreement Third Party	Dec. 31, 2013 Purchase Agreements	Dec. 31, 2012 Purchase Agreements	Dec. 31, 2013 Purchase Agreements Other Current Assets	Dec. 31, 2012 Purchase Agreements Other Current Assets	Dec. 31, 2013 Purchase Agreements Options to purchase an aggregate of 20,600 shares	Dec. 31, 2012 Purchase Agreements Options to purchase an aggregate of 20,600 shares
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Purchase agreement, aggregate shares opexa has right to sell				$ 16,500,000			$ 1,500,000	$ 1,500,000	$ 15,000,000	$ 1,500,000	$ 1,500,000	$ 1,500,000	$ 15,000,000	$ 15,000,000			$ 1,500,000				$ 15,000,000	$ 15,000,000
Deferred financing cost	134,518		341,166		44,069	74,030										101,972		79,732	134,518	159,462
Deferred financing cost, non current		$ 86,231	$ 211,479														$ 103,636
Termination of ATM Agreement															2013-12