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Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 28, 2025
Jun. 30, 2024
Cover [Abstract]      
Document Type 10-K/A    
Amendment Flag true    
Document Period End Date Dec. 31, 2024    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Trading Symbol ADTN    
Entity Registrant Name ADTRAN Holdings, Inc.    
Entity Central Index Key 0000926282    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Accelerated Filer    
Entity Shell Company false    
Entity Emerging Growth Company false    
Entity Small Business false    
Document Financial Statement Error Correction [Flag] true    
Document Financial Statement Restatement Recovery Analysis [Flag] true    
ICFR Auditor Attestation Flag true    
Entity Common Stock, Shares Outstanding   79,860,033  
Entity Public Float     $ 410,464,716
Entity Interactive Data Current Yes    
Entity File Number 000-41446    
Entity Tax Identification Number 87-2164282    
Entity Address, Address Line One 901 Explorer Boulevard    
Entity Address, City or Town Huntsville    
Entity Address, State or Province AL    
Entity Address, Postal Zip Code 35806-2807    
City Area Code 256    
Local Phone Number 963-8000    
Entity Incorporation, State or Country Code DE    
Document Annual Report true    
Document Transition Report false    
Title of 12(b) Security Common Stock, Par Value $0.01    
Security Exchange Name NASDAQ    
Documents Incorporated by Reference

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive Proxy Statement on Schedule 14A for the registrant's 2025 Annual Meeting of Stockholders filed with the Securities and Exchange Commission on March 31, 2025 are incorporated herein by reference into Part III of this report to the extent described in Part III.

    
Auditor Opinion [Text Block]

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated balance sheets of ADTRAN Holdings, Inc. and its subsidiaries (the “Company”) as of December 31, 2024 and 2023, and the related consolidated statements of loss, of comprehensive (loss) income, of changes in equity and of cash flows for each of the three years in the period ended December 31, 2024, including the related notes and financial statement schedule listed in the accompanying index (collectively referred to as the “consolidated financial statements”). We also have audited the Company's internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company did not maintain, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO because material weaknesses in internal control over financial reporting existed as of that date related to the Company not (i) designing and maintaining effective controls in response to the risks of material misstatement; (ii) designing and maintaining effective controls over financial statement preparation, presentation and disclosure commensurate with its financial reporting requirements; and (iii) designing and maintaining effective controls to address the initial application of complex accounting standards and accounting of non-routine, unusual or complex events and transactions.

A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of the annual or interim financial statements will not be prevented or detected on a timely basis. The material weaknesses referred to above are described in Management's Report on Internal Control over Financial Reporting appearing under Item 9A. We considered these material weaknesses in determining the nature, timing, and extent of audit tests applied in our audit of the 2024 consolidated financial statements, and our opinion regarding the effectiveness of the Company’s internal control over financial reporting does not affect our opinion on those consolidated financial statements.

Restatement of Previously Issued Financial Statements and Management’s Conclusion Regarding Internal Control over Financial Reporting

As discussed in Note 1 to the consolidated financial statements, the Company has restated its 2024 and 2023 financial statements and financial statement schedule to correct errors.

Management and we previously concluded that the Company did not maintain effective internal control over financial reporting as of December 31, 2024 because of the material weaknesses related to the Company not (i) designing and maintaining effective controls in response to the risks of material misstatement; (ii) designing and maintaining effective controls over financial statement preparation, presentation and disclosure commensurate with its financial reporting requirements; and (iii) designing and maintaining effective controls to address the initial application of complex accounting standards and accounting of non-routine, unusual or complex events and transactions. However, management has subsequently determined that material weaknesses in internal control over financial reporting existed as of December 31, 2024 related to the Company not (i) designing and maintaining effective controls relating to communicating accurate information internally and with those charged with governance and (ii) designing and maintaining effective controls over an inventory suspense account. Accordingly, management’s report and our opinion on the effectiveness of internal control over financial reporting have been restated to include these additional material weaknesses.

    
Auditor Name PricewaterhouseCoopers LLP    
Auditor Firm ID 238    
Auditor Location Birmingham, Alabama    
Amendment Description ADTRAN Holdings, Inc. (“ADTRAN,” the “Company,” “we,” “us” or “our”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment No. 1” or "Form 10-K/A") to amend and restate certain portions of the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 filed with the U.S. Securities and Exchange Commission (the “SEC”) on March 3, 2025 (the “Original Filing”). Financial information of Fiscal 2023 and the 2024 Interim Periods (each as defined below) is also restated within this Amendment No. 1. As previously disclosed in the Company’s Current Report on Form 8-K furnished to the SEC on April 16, 2025 (the “Form 8-K”), the Company’s majority-owned subsidiary, Adtran Networks SE (“Networks”), published an ad hoc notification in Germany on April 15, 2025 (the “Ad Hoc Notification”), disclosing that, in the course of finalizing Networks’ statutory financial statements for its fiscal year ended December 31, 2024, Networks identified an adjustment to inventory resulting in an increase to costs of goods sold, which resulted in a €5.7 million increase in the amount of Networks’ 2024 loss from that which was previously published in Networks’ preliminary financial results on February 27, 2025. The Form 8-K disclosed that the Company was in the process of assessing the impact of the adjustment to Networks’ 2024 financial results (the “Adjustment”) on the Company’s historical consolidated financial statements. Subsequently, as disclosed in the Company’s preliminary earnings release dated May 7, 2025 (the “Preliminary Earnings Release”), the Company determined that the Adjustment to Networks’ 2024 financial results caused the Company’s financial statements for the year ended December 31, 2024 and the interim fiscal periods therein, and the year ended December 31, 2023, to be adjusted, as described in the Preliminary Earnings Release, which was attached as an exhibit to a Current Report on Form 8-K furnished by the Company to the SEC on May 8, 2025. On May 13, 2025, the Audit Committee of the Board of Directors (the “Audit Committee”) of the Company concluded, after considering the recommendations of management, that the Company’s (i) audited consolidated financial statements as of and for the years ended December 31, 2024 (“Fiscal 2024”) and December 31, 2023 (“Fiscal 2023”) included in the Original Filing and (ii) unaudited condensed consolidated financial statements as of and for the interim periods ended March 31, 2024, June 30, 2024 and September 30, 2024 (the “2024 Interim Periods”) included in the Company’s Quarterly Reports filed with the SEC on May 10, 2024, August 9, 2024, and November 12, 2024, respectively (such 2024 Interim Periods, collectively with Fiscal 2024 and the 2024 Interim Periods, the “Affected Periods”), as well as the relevant portions of any communications which describe or are based on such financial statements, should no longer be relied upon. In addition to the corrections to reflect the impact of the Adjustment on its financial statements, the Company has also corrected other immaterial errors in connection with the restatement of the financial statements with respect to each of the Affected Periods. A summary description of the significant errors in the Company's Consolidated Financial Statements for the Affected Periods are as follows:•Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) is entitled to receive from us an Annual Recurring Compensation payment of €0.52 per share. The Company erroneously accrued this liability every quarter at €0.59 per share, overstating the associated accrual, the net income attributable to non-controlling interest and the net loss attributable to ADTRAN Holdings, Inc. for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. •For the periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024 the Company remeasured the redeemable non-controlling interest each quarter-end at the current exchange rate of euros to U.S. Dollar. The Company treated the redeemable non-controlling interest as a monetary mezzanine equity instrument but should have treated it as a non-monetary mezzanine equity instrument not subject to remeasurement. •For the year ended December 31, 2023 through the year ended December 31, 2024, the Company understated cost of revenue and overstated inventory in the Company's Adtran Networks subsidiary due to a system error. In addition, there were adjustments in the Company's U.S and Australian subsidiaries related to inventory reserves that were understated.•For the year ended December 31, 2023 through the year ended December 31, 2024, the Company understated goodwill and overstated income tax receivable. The understatement was attributable to corrections to goodwill and deferred income tax associated with goodwill for an internal divestiture of a wholly owned subsidiary required by statutory laws in Europe.In addition to the misstatements identified above, the Company has corrected other immaterial errors. These other errors are quantitatively and qualitatively immaterial, individually and in the aggregate. However, the Company has corrected these other errors as part of the correction for the significant errors described above.For additional information on the restated consolidated financial statements for Fiscal 2024 and Fiscal 2023, see Note 1, Summary Of Significant Accounting Policies, of the Notes to Consolidated Financial Statements in this Amendment No. 1. For additional information on the unaudited restated quarterly financial information for the 2024 Interim Periods, see Note 22, Restatement of Quarterly Financial Information (Unaudited), of the Notes to Consolidated Financial Statements in this Amendment No. 1.Furthermore, in connection with the identification of the Adjustment, the Audit Committee has overseen an internal investigation into the circumstances surrounding the Adjustment and its impact on the Company’s historical financial statements. Based on the findings of the internal investigation, which is substantially complete, it has been determined that the underlying error giving rise to the Adjustment were not properly addressed in the Company’s previously filed financial statements as of and for Fiscal 2024 and Fiscal 2023 and was not communicated to the Audit Committee or the independent auditors prior to the filing of the initial 2024 Annual Report on Form 10-K. As described in Item 9A of this Amendment No. 1, the Company is taking remedial actions to address the material weaknesses in its internal controls associated with these findings.As a result of the above described errors and the identification of additional material weaknesses (described further in Part II, Item 9A), the Company is filing this Amendment No. 1 to (i) restate the disclosure on the effectiveness of the Company’s disclosure controls and procedures and restate management’s report on internal control over financial reporting in Part II, Item 9A of the Original Filing to reflect the additional material weaknesses, (ii) restate the Company’s consolidated financial statements to reflect the correction of the errors described above, including with respect to each of the Affected Periods, and to correct certain disclosure related to the appraisal proceedings in connection with the Domination and Profit and Loss Transfer Agreement ("DPLTA"), (iii) update seven risk factors related to the Company’s credit facility, material weaknesses, restatements, inventory levels, indebtedness, impairment charges, and the DPLTA, (iv) restate Part II, Item 7, MD&A, of the Original Filing solely to reflect the restated financial statements for Fiscal 2024 and Fiscal 2023 and to correct certain disclosure related to the DPLTA appraisal proceedings, (v) reissue the Report of the Independent Registered Public Accounting Firm, which appears in Part II, Item 8 of the Original Filing, and (vi) amend Part IV – Item 15 Exhibits and Financial Statement Schedules of the Original Filing to include currently dated certifications from the Company’s Chief Executive Officer and Chief Financial Officer as required by Section 302 and 906 of the Sarbanes-Oxley Act of 2002, as well as a corrected version of Exhibit 10.1(z), the Form of Restricted Stock Unit Agreement under the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan, and to fix certain immaterial errors.This Amendment No. 1 sets forth the Original Filing, as amended, in its entirety; however, there were no changes to any parts of the Original Filing other than the sections referenced in the immediately preceding paragraph. Moreover, pursuant to Rule 12b-15 promulgated by the SEC under the Securities Exchange Act of 1934, as amended, the Company has included the entire text of Part I, Item 1A, as well as Part II, Items 7, 8 and 9A and Part IV, Item 15, of the Original Filing in this Amendment No. 1. There have been no changes to the text of Part I, Item 1A or Part II, Items 7, 8 and 9A other than the changes stated in the immediately preceding paragraph. Other than as described above and through the inclusion with this Amendment No. 1 of new certifications by management, a new consent of PricewaterhouseCoopers LLP, an updated Exhibit 10.1(z), and a new signature page, this Amendment No. 1 speaks only as of the date of the Original Filing and does not amend, supplement, or update any information contained in the Original Filing to give effect to any subsequent events (including with respect to the cover page of the Original Filing, which has been updated only to present this filing as Amendment No. 1 and to update the reference to documents incorporated by reference into the Original Filing). Accordingly, this Amendment No. 1 should be read in conjunction with the Original Filing and the Company's reports (including any amendments thereto) filed with the SEC subsequent to the Original Filing.