Date of reincorporation.

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- Definition

Number of shares of parent company common stock exchanged for each share of common stock issued in connection with merger.

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No definition available.

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- Definition

Organization, consolidation and presentation of financial statement.

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No definition available.

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- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

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No definition available.

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- Definition

With respect to a business combination completed during the period, this element provides a description of the business, other than the name, which may include the industry, size, products and other important information.

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- Definition

Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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- Definition

Face amount or stated value per share of common stock.

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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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- Definition

The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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No definition available.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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No definition available.

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Face amount per share of no-par value preferred stock nonredeemable or redeemable solely at the option of the issuer.

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- Definition

Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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- Definition

Per share or per unit amount of equity securities issued.

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No definition available.

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- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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- Definition

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

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Nature of Operations and Basis of Presentation - Additional Information (Details)			12 Months Ended
	Sep. 19, 2017 $ / shares shares	Sep. 18, 2017 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	May 15, 2018 $ / shares	May 14, 2018 $ / shares
Organization Consolidation and Presentation of Financial Statement [Line Items]
Common stock, shares outstanding \| shares	6,500,000		10,087,363	7,497,433
Aggregate common stock issued and sold prior to merger \| $			$ 42,622,700	$ 21,506,842
Shares issued price per share	$ 9.47
Preferred stock, no par value				$ 0		$ 0
Preferred stock, par value			$ 0.0001
Common stock, par value			$ 0.0001	$ 0.01		$ 0.01
Private Acer
Organization Consolidation and Presentation of Financial Statement [Line Items]
Percentage of outstanding common stock owned by acquirer's shareholders	89.00%
Percentage of outstanding common stock owned by registrant's shareholders	11.00%
Private Acer
Organization Consolidation and Presentation of Financial Statement [Line Items]
Shares issued in exchange of common stock upon merger \| shares	1
Aggregate common stock issued and sold prior to merger \| $		$ 15,700,000
Shares issued price per share		$ 9.47
Private Acer \| Convertible Promissory Notes
Organization Consolidation and Presentation of Financial Statement [Line Items]
Debt conversion, outstanding principal and accrued interest \| $		$ 5,700,000
Merger of Private Acer with Opexa Merger Sub Incorporation
Organization Consolidation and Presentation of Financial Statement [Line Items]
Business combination date of completion	Sep. 19, 2017
Business combination date of agreement	Jun. 30, 2017
Reverse stock split ratio	0.09656678989
Delaware Reincorporation and Subsidiary Merger
Organization Consolidation and Presentation of Financial Statement [Line Items]
Merger incorporation description			On May 15, 2018, the Company changed its state of incorporation from the State of Texas to the State of Delaware pursuant to a plan of conversion, dated May 15, 2018. As a result of this reincorporation, the par value of the Company’s preferred stock was changed from no par value to $0.0001 and the par value of the Company’s common stock was reduced to $0.0001 from $0.01.
Date Of Reincorporation			May 15, 2018
Preferred stock, par value					$ 0.0001
Common stock, par value					$ 0.0001