Business Overview and Summary of Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended		131 Months Ended			12 Months Ended	1 Months Ended
	Dec. 14, 2012	Jun. 30, 2006	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2013 Opexa Hong Kong	Dec. 31, 2013 Employee Stock Based Compensation	Aug. 31, 2009 Technology License Agreement	Dec. 31, 2013 Option and License Agreement	Feb. 04, 2013 Option and License Agreement	Dec. 31, 2013 Option and License Agreement Licensing fee if Merck is unable to advance directly to Phase III trials of Tcelna
Description Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Proceeds from up front cash payment									$ 3,000,000	$ 5,000,000	$ 5,000,000
Proceed from technology transfer milestone fee									500,000
Reverse stock split ratio	0.25	0.10
Common Shares outstanding before reverse split	23,600,000
Common stock, shares outstanding	5,900,000		27,546,058	6,249,369	27,546,058
Cash and cash equivalents			23,644,542	592,004	23,644,542	7,109,215	10,805
Licensing milestone										25,000,000		15,000,000
Option and License Agreement, deferred revenue										5,000,000
Share-based awards, vesting period								3 years
Research and development expense			$ 9,181,090	$ 6,318,476	$ 85,678,441