Equity - Additional Information (Detail) (USD $)	1 Months Ended					9 Months Ended	128 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended				1 Months Ended
	Sep. 24, 2013	Jun. 30, 2013	Feb. 11, 2013	Jan. 23, 2013	Jan. 29, 2013	Sep. 30, 2013	Sep. 30, 2013	Feb. 28, 2013 Common Stock	Sep. 30, 2013 Common Stock	Aug. 13, 2013 Public Offering	Feb. 28, 2013 ATM Agreement	Sep. 30, 2013 $1.5 Million Purchase Agreement with Lincoln Park	Jan. 31, 2013 $1.5 Million Purchase Agreement with Lincoln Park	Jan. 31, 2013 $1.5 Million Purchase Agreement with Lincoln Park Common Stock
Equity Note [Line Items]
Common shares issued		123,231				900,000				12,000,000	167,618			125,000
Purchase agreement, aggregate shares opexa has right to sell						$ 16,500,000	$ 16,500,000					$ 1,500,000	$ 1,500,000
Net proceeds from shares sold											536,417			142,400
Common stock issued as fee														975
Common shares issued, note conversion	1,714,697							365,263	2,079,960
Common shares issued			1,083,334
Warrants settlement ratio			Each unit consisting of one share of common stock and a warrant to purchase half (0.5) a share of common stock
Share issue to private offering, price per share			$ 3.00			$ 1.50				$ 1.50
Proceeds from issuance of common stocks and warrants, net			3,250,002			21,319,153	70,772,950
Warrant term			4 years	5 years	5 years
Warrant exercise price			$ 3.00	$ 1.24	$ 1.21
Commission rate on gross proceed for common stock sold			6.00%
Gross proceeds from shares of common stock sold						1,350,000				18,000,000
Amount netted against additional paid in capital as stock offering costs						$ 2,256,549