Significant Accounting Policies (Policies)	6 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation – The Company has prepared the accompanying condensed consolidated financial statements pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to these rules and regulations. These condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and footnotes related thereto for the year ended December 31, 2018, included in the Company’s Annual Report on Form 10 -K filed with the SEC on February 6, 2019 ( the “Annual Report”). Except as noted below, there have been no material changes to the Company’s significant accounting policies described in Note 2 to the consolidated financial statements included in the Annual Report. In the opinion of management, the unaudited condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the Company’s financial position and the results of its operations and cash flows. The results of operations for such interim periods are not necessarily indicative of the results to be expected for the full year.
Consolidation, Policy [Policy Text Block]	Basis of Consolidation – The condensed consolidated financial statements include the financial statements of Vaxart, Inc. and its subsidiaries. All significant transactions and balances between Vaxart, Inc. and its subsidiaries have been eliminated in consolidation.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates – The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and disclosure of contingent assets and liabilities in the financial statements and accompanying notes. Actual results and outcomes could differ from these estimates and assumptions.
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentration of Credit Risk – Financial instruments that potentially subject the Company to significant concentrations of credit risk consist principally of cash, cash equivalents, short-term investments and accounts receivable. The Company places its cash, cash equivalents and short-term investments at financial institutions that management believes are of high credit quality. The Company is exposed to credit risk in the event of default by the financial institutions holding the cash and cash equivalents to the extent such amounts are in excess of the federally insured limits. The Company has not experienced any losses on its deposits since inception. The primary focus of the Company’s investment strategy is to preserve capital and meet liquidity requirements. The Company’s investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. The Company generally requires no collateral from its customers.
Lessee, Leases [Policy Text Block]	L eases – Effective January 1, 2019, the Company records operating leases as right-of-use assets and operating lease liabilities in its condensed consolidated balance sheets for all operating leases with terms exceeding one year. Right-of-use assets represent the right to use an underlying asset for the lease term, including extension options considered reasonably certain to be exercised, and operating lease liabilities to make lease payments. Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term. To the extent that lease agreements do not provide an implicit rate, the Company uses its incremental borrowing rate based on information available at the lease commencement date to determine the present value of lease payments. The expense for operating lease payments is recognized on a straight-line basis over the lease term and is included in operating expenses in the Company’s statement of operations and comprehensive loss.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent ly Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016 - 02 Leases (Topic 842 ) , which replaced most current lease guidance when it became effective. This standard update was designed to increase transparency and improve comparability by requiring entities to recognize assets and liabilities on the balance sheet for all leases, with certain exceptions. The new standard states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying asset for the lease term. Leases are classified as either finance or operating, with classification affecting the pattern of expense recognition in the statements of operations. The Company adopted the new guidance effective January 1, 2019, using the modified retrospective method, and used the effective date method of adoption, as permitted by ASU 2018 - 11, Leases (Topic 842 ): Ta rgeted Improvements , which the FASB issued in July 2018, clarified by ASU 2019 - 01, Leases (Topic 842 ): Codification Improvements , which the FASB issued in March 2019, which reduces the disclosure requirements on transition. The Company has elected the short-term lease recognition exemption for all classes of assets, which means that it will not recognize right-of-use assets or lease liabilities for leases with a duration of one year or less. Further, the Company has elected to use all of the practical expedients available on transition, whereby it has not reassessed under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. The adoption of this standard had a material effect on the Company’s condensed consolidated balance sheets, the most significant effects being the recognition of new right-of-use assets and lease liabilities. The Company recognized lease liabilities of $1,229,000, $783,000 of which was current, and right-of-use assets of $953,000 based on the present value of the remaining minimum rental payments for existing operating leases, derecognized liabilities related to deferred rent and lease loss accrual of $249,000, $111,000 of which was current, and recognized an increase of $27,000 to accumulated deficit on adoption of the new accounting policy. The increase in accumulated deficit arose because the right-of-use asset impairment charge that would have been recorded in the three months ended December 31, 2018, under Topic 842 exceeded the lease loss accrual, net of accretion, that was recorded. This impact aside, the adoption had no effect on the Company’s statements of operations or cash flows, other than on related disclosures. Recent Accounting Pronouncements The Company has reviewed all newly-issued accounting pronouncements and concluded that they either are not applicable to the Company’s operations or no material effect is expected on its condensed consolidated financial statements as a result of future adoption.