Options and Warrants - Additional Information (Detail) (USD $)	1 Months Ended				12 Months Ended
	Feb. 11, 2013	Jan. 23, 2013	Jan. 31, 2013	Jul. 25, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted					427,072	411,938	76,157	38,138	193,583	160,100	73,475
Number of Shares, Forfeited and canceled					89,243	30,241	18,750	98,168	85,605	31,617	4,336
Number of common stock to be issued upon exercise of warrant	541,668		187,500	1,436,121
Exercise price				$ 2.56
Warrants term				5 years
Warrants issued to purchase common stock		243,750	243,750
Warrant exercise price	$ 3.00	$ 1.24	$ 1.21	$ 5.00
Warrant term	4 years	5 years	5 years	5 years
Warrant redemption price per share		$ 0.01	$ 0.01
Terms for warrant redeem		Opexa can redeem the warrants at $0.01 per share if the Company's common stock closes at or above $10.00 per share for 20 consecutive trading days.	Opexa can redeem the warrants at $0.01 per underlying share of common stock if the common stock closes at or above $10.00 per share for 20 consecutive trading days.	Opexa can redeem the warrants at $0.01 per share if its common stock closes at or above $10.00 per share for 20 consecutive trading days.
Restricted cash			$ 500,000		$ 0	$ 1,000,000
Aggregate intrinsic value of the outstanding options					49,851	13,846
2010 Plan | Amended and Restated 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, common stock shares reserved for issuance, increased amount					3,000,000
Share based compensation, common stock shares reserved for issuance					3,625,000
Stock Incentive Plan 2004
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, common stock shares for issuance					575,000
Remaining shares available under the Amended and Restated 2010 Plan					513,220
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant exercise price				$ 2.56
Warrants Attached to Debt
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount rate		0.76%
Expected life		5 years
Expected volatility rate		191.00%
Expected dividends		0
Estimated fair value of warrants		195,969
Common Stock Warrants issued to Release a Claim on Cash
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount rate			0.90%
Expected life			5 years
Expected volatility rate			191.00%
Estimated fair value of warrants			219,553
Employee Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						107,832
Stock option, term						10 years
Vesting period						3 years
Fair value of stock granted during period						$ 381,020
Expected dividends						0
Number of Shares, Forfeited and canceled					78,171	4,678
Stock-based compensation expense					766,875	549,150
Unamortized stock-based compensation expense					894,821	1,142,135
Employee Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, Granted						$ 1.80
Discount rate						1.40%
Expected life						5 years 3 months
Expected volatility rate						180.00%
Employee Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, Granted						$ 3.80
Discount rate						1.98%
Expected life						7 years
Expected volatility rate						183.00%
Employee Option | Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted					338,500
Stock option, term					10 years
Vesting period					3 years
Expected dividends					0
Fair value of stock granted during period					659,601
Employee Option | Employees | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, Granted					$ 1.45
Discount rate					1.73%
Expected life					5 years 3 months
Expected volatility rate					191.83%
Employee Option | Employees | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, Granted					$ 2.34
Discount rate					2.78%
Expected life					6 years
Expected volatility rate					203.69%
Senior management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						254,756
Weighted average exercise price, Granted						$ 3.80
Stock option, term						10 years
Vesting period						3 years
Fair value of stock granted during period						$ 964,715
Discount rate						1.98%
Expected life						10 years
Expected volatility rate						183.00%
Expected dividends						0
Aggregate number of shares commenced vesting during period						82,009
Acting Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						18,750
Weighted average exercise price, Granted						$ 2.04
Stock option, term						10 years
Fair value of stock granted during period						$ 37,096
Discount rate						1.80%
Expected life						5 years 3 months
Expected volatility rate						185.00%
Expected dividends						0
Shares immediately vesting, percent						33.00%
Shares vesting till year end, percent						33.00%
Shares vesting next year, percent						33.00%
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						30,600
Weighted average exercise price, Granted						$ 3.76
Fair value of stock granted during period						$ 111,428
Discount rate						2.03%
Expected life						5 years 3 months
Expected volatility rate						186.00%
Expected dividends						0
Director | Options to purchase an aggregate of 10,000 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						10,000
Stock option, term						10 years
Shares immediately vesting, percent						50.00%
Stock options vesting percentage, remaining of period						50.00%
Director | Options to purchase an aggregate of 20,600 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted						20,600
Stock option, term						10 years
Shares immediately vesting, percent						50.00%
Stock options vesting percentage, remaining of period						50.00%
Stock Option Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Forfeited and canceled						25,563
Directors and Consultants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense					143,212	141,576
Unamortized stock-based compensation expense					4,190	14,770
Non Employee Director Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted					88,572
Weighted average exercise price, Granted					$ 1.75
Fair value of stock granted during period					$ 151,867
Discount rate					1.73%
Expected life					5 years 3 months
Expected volatility rate					201.21%
Expected dividends					0
Non Employee Director Stock Option | Options to purchase an aggregate of 20,000 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted					20,000
Stock option, term					10 years
Stock options vesting percentage, immediately from date of grant					50.00%
Non Employee Director Stock Option | Options to purchase an aggregate of 20,000 shares | Vest After One Year From Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting percentage, remaining of period					50.00%
Non Employee Director Stock Option | Options to purchase an aggregate of 68,572 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted					68,572
Stock options vesting percentage, immediately from date of grant					50.00%
Non Employee Director Stock Option | Options to purchase an aggregate of 68,572 shares | Vest at 12/31/2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting percentage, remaining of period					50.00%
Non Employee Director Stock Option | Options to purchase an aggregate of 68,572 shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, term					10 years
Non-Employee Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Forfeited and canceled					11,072
Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares were forfeited					1,482,892	464,584
Aggregate intrinsic value of the outstanding Warrant					$ 255,750	$ 57,891