| Document and Entity Information - USD ($) | 12 Months Ended | ||
| Dec. 31, 2018 | Feb. 15, 2019 | Jun. 30, 2018 | |
| Document And Entity Information [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | true | ||
| Document Period End Date | Dec. 31, 2018 | ||
| Document Fiscal Year Focus | 2018 | ||
| Document Fiscal Period Focus | FY | ||
| Trading Symbol | ADTN | ||
| Entity Registrant Name | ADTRAN INC | ||
| Entity Central Index Key | 0000926282 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity Well-known Seasoned Issuer | Yes | ||
| Entity Current Reporting Status | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Emerging Growth Company | false | ||
| Entity Small Business | false | ||
| Entity Shell Company | false | ||
| Entity Common Stock Shares Outstanding | 47,777,043 | ||
| Entity Public Float | $ 704,932,782 | ||
| Amendment Description | ADTRAN, Inc. (“ADTRAN,” the “Company,” “we,” “us” or “our”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment No. 1”) to amend and restate certain portions of the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 28, 2019 (the “Original Filing”) as a result of the identification of the material weaknesses described below. Specifically, the Company is filing this Amendment No. 1 to (i) revise the disclosure on the effectiveness of our 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 management’s conclusion that our internal control over financial reporting and disclosure controls and procedures were not effective at December 31, 2018, and (ii) reissue the Report of the Independent Registered Public Accounting Firm of PricewaterhouseCoopers LLP (“PwC”) regarding the effectiveness of our internal control over financial reporting, which appears in Part II, Item 8 of the Original Filing. Pursuant to Rule 12b-15 promulgated under the Securities Exchange Act of 1934, as amended, we have included the entire text of Part II, Item 8 and Part II, Item 9A of the Original Filing in this Amendment No. 1. There have been no changes to the text of Part II, Item 8 or Part II, Item 9A other than the changes stated in the immediately preceding paragraph. Furthermore, there have been no changes to the XBRL data filed in Exhibit 101 of the Original Filing. Other than as described above and through the inclusion with this Amendment No. 1 of new certifications by management, a new consent of PwC, and related amendments to the list of exhibits contained in Part IV, Item 15 of the Original Filing, 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 delete 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 our reports filed with the SEC subsequent to the Original Filing. This Amendment No. 1 does not change our consolidated financial statements as set forth in the Original Filing. |
