Equity - Additional Information (Detail) (USD $)	1 Months Ended							12 Months Ended		131 Months Ended		1 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended			1 Months Ended			1 Months Ended	12 Months Ended					1 Months Ended		12 Months Ended		1 Months Ended
	Dec. 23, 2013	Sep. 30, 2013	Sep. 24, 2013	Feb. 11, 2013	Jan. 23, 2013	Jan. 31, 2013	Jul. 25, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Nov. 30, 2012	Nov. 08, 2013 Senior management	Dec. 31, 2013 Senior management	Dec. 31, 2012 Notes Which Mature On July Two Thousand Twelve	Feb. 28, 2013 Common Stock	Dec. 31, 2013 Common Stock	Dec. 31, 2010 Common Stock	Dec. 31, 2004 Common Stock	Aug. 13, 2013 Public Offering	Nov. 30, 2012 Purchase Agreements Agreement	Dec. 31, 2013 Purchase Agreements	Jul. 01, 2013 Accrued Interest	Dec. 31, 2013 Accrued Interest	Dec. 31, 2012 Accrued Interest	Dec. 31, 2012 Accrued Interest Notes Which Mature On July Two Thousand Twelve	Dec. 31, 2013 Accrued Interest Common Stock	Dec. 31, 2012 Accrued Interest Common Stock	Feb. 28, 2013 ATM Agreement	Nov. 30, 2012 $1.5 Million Purchase Agreement with Lincoln Park	Dec. 31, 2012 $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]
Purchase agreement, aggregate shares opexa has right to sell											$ 16,500,000										$ 1,500,000									$ 1,500,000	$ 1,500,000
Number of purchase agreements entered																				2
Common shares issued	4,738,000	900,000												163,224					12,000,000			123,231			185,683	123,231	163,224	167,618	56,507	265,000		125,000
Common shares issued, value																						188,543	188,543	185,683		1,232	1,632		149,131
Proceeds from issuance of common stocks, warrants and options	8,054,600			3,250,002				28,484,878	381,309	77,938,675																				333,970
Common stock issued as fee																														2,610		975
Net proceeds from shares sold																												536,417				142,400
Common shares issued, note conversion			1,714,697												365,263	2,079,960	690,045	15,187
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	$ 1.70	$ 1.50		$ 3.00															$ 1.50
Warrant term				4 years	5 years	5 years	5 years
Warrant exercise price				$ 3.00	$ 1.24	$ 1.21	$ 5.00
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
Restricted common stock shares issued												78,571
Restricted common stock shares issued, aggregate fair value												147,713
Stock issued for services								69,899		2,131,642			69,899
Amount netted against additional paid in capital as stock offering costs								$ 2,985,319