| Document and Entity Information | Aug. 30, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | ADTRAN INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000926282 |
| Document Type | 8-K |
| Document Period End Date | Aug. 30, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 000-24612 |
| Entity Tax Identification Number | 63-0918200 |
| 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 |
| Written Communications | true |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, Par Value $0.01 |
| Trading Symbol | ADTN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
