Exercise price of the warrants.

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The estimated amount of dividends to be paid to holders of the underlying shares (expected dividends) over the option's term. Dividends are taken into account because payment of dividends to shareholders reduces the fair value of the underlying shares, and option holders generally do not receive dividends.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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Stock-Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended				3 Months Ended
	Feb. 28, 2013	Feb. 11, 2013	Jan. 23, 2013	Jan. 29, 2013	Mar. 31, 2013	Jan. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, common stock shares issued and outstanding					903,289		824,620
Option expense recognized					$ 191,634
Unamortized stock compensation expense					1,126,780
Number of Shares, Granted					125,000
Number of Shares, Forfeited and canceled					46,331
Warrant term	4 years	4 years	5 years	5 years
Warrants issued to purchase common stock					187,500	243,750
Warrant exercise price	$ 3.00	$ 3.00	$ 1.24	$ 1.21
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.	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.
Number of common stock to be issued upon exercise of warrant	541,668			187,500
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued to purchase common stock			243,750
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
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, term					10 years
Employee Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, term					10 years
Number of Shares, Granted					125,000
Weighted average exercise price, Granted					$ 2.34
Vesting period					3 years
Fair value of stock granted during period					285,226
Discount rate					1.87%
Expected life					5 years 3 months
Expected volatility rate					194.00%
Expected dividends					$ 0
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, common stock shares authorized					625,000
Share based compensation, common stock shares issued and outstanding					903,289