Commitments and Contingencies	12 Months Ended
Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 16 – Commitments and Contingencies Securities Class Action Lawsuit On October 17, 2019, a purported stockholder class action lawsuit, captioned Burbridge v. ADTRAN, Inc. et al., Docket No. 19-cv-09619, was filed in the United States District Court for the Southern District of New York against the Company, two of its current executive officers and one of its former executive officers. The complaint alleges violations of federal securities laws and seeks unspecified compensatory damages on behalf of purported purchasers of ADTRAN securities between February 28, 2019 and October 9, 2019. The lawsuit claims that the defendants made materially false and misleading statements regarding, and/or failed to disclose material adverse facts about, the Company’s business, operations and prospects, specifically relating to the Company’s internal control over financial reporting, excess and obsolete inventory reserves, financial results and shipments to a Latin American customer. Investors in ADTRAN securities had until December 16, 2019 to move the court to serve as lead plaintiff in this action. On December 16, 2019, two purported investors in ADTRAN securities filed motions seeking to be appointed lead plaintiff in the case. On January 6, 2020, the United States District Court for the Southern District of New York granted Defendants’ unopposed request to transfer the case to the United States District Court for the Northern District of Alabama, where the case is now pending as Burbridge v. ADTRAN, Inc. et al., Docket No. 5:20-cv-00050-LCB. On January 27, 2020, the two prospective lead plaintiff movants filed a stipulation among plaintiffs seeking to be appointed as co-lead plaintiffs in the case. We disagree with the claims made in the complaint and intend to vigorously defend against this lawsuit. At this time, we are unable to predict the outcome of or estimate the possible loss or range of loss, if any, associated with this lawsuit. Other Legal Matters In addition to the litigation described above, from time to time we are subject to or otherwise involved in various lawsuits, claims, investigations and legal proceedings that arise out of or are incidental to the conduct of our business (collectively, “Legal Matters”), including those relating to employment matters, patent rights, regulatory compliance matters, stockholder claims, and contractual and other commercial disputes. Such Legal Matters, even if not meritorious, could result in the expenditure of significant financial and managerial resources. Additionally, an unfavorable outcome in a legal matter, including in a patent dispute, could require the Company to pay damages, entitle claimants to other relief, such as royalties, or could prevent the Company from selling some of its products in certain jurisdictions. While the Company cannot predict with certainty the results of the Legal Matters in which it is currently involved, the Company does not expect that the ultimate outcome of such Legal Matters will individually or in the aggregate have a material adverse effect on its business, results of operations, financial condition or cash flows. Investment Commitment We have committed to invest up to an aggregate of $7.9 million in two private equity funds, of which $7.7 million has been applied to these commitments as of December 31, 2019. Performance Bonds Certain contracts, customers and/or jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of December 31, 2019, we had commitments related to these bonds totaling $9.3 million which expire at various dates through August 2024. As of December 31, 2018, we had commitments related to these bonds totaling $6.5 million. Although the triggering events vary from contract to contract, in general we would only be liable for the amount of these guarantees in the event of default in our under each contract, the probability of which we believe is remote.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Note 16 – Commitments and Contingencies

Securities Class Action Lawsuit

On October 17, 2019, a purported stockholder class action lawsuit, captioned Burbridge v. ADTRAN, Inc. et al., Docket No. 19-cv-09619, was filed in the United States District Court for the Southern District of New York against the Company, two of its current executive officers and one of its former executive officers. The complaint alleges violations of federal securities laws and seeks unspecified compensatory damages on behalf of purported purchasers of ADTRAN securities between February 28, 2019 and October 9, 2019. The lawsuit claims that the defendants made materially false and misleading statements regarding, and/or failed to disclose material adverse facts about, the Company’s business, operations and prospects, specifically relating to the Company’s internal control over financial reporting, excess and obsolete inventory reserves, financial results and shipments to a Latin American customer. Investors in ADTRAN securities had until December 16, 2019 to move the court to serve as lead plaintiff in this action.

On December 16, 2019, two purported investors in ADTRAN securities filed motions seeking to be appointed lead plaintiff in the case. On January 6, 2020, the United States District Court for the Southern District of New York granted Defendants’ unopposed request to transfer the case to the United States District Court for the Northern District of Alabama, where the case is now pending as Burbridge v. ADTRAN, Inc. et al., Docket No. 5:20-cv-00050-LCB. On January 27, 2020, the two prospective lead plaintiff movants filed a stipulation among plaintiffs seeking to be appointed as co-lead plaintiffs in the case.

We disagree with the claims made in the complaint and intend to vigorously defend against this lawsuit. At this time, we are unable to predict the outcome of or estimate the possible loss or range of loss, if any, associated with this lawsuit.

Other Legal Matters

In addition to the litigation described above, from time to time we are subject to or otherwise involved in various lawsuits, claims, investigations and legal proceedings that arise out of or are incidental to the conduct of our business (collectively, “Legal Matters”), including those relating to employment matters, patent rights, regulatory compliance matters, stockholder claims, and contractual and other commercial disputes. Such Legal Matters, even if not meritorious, could result in the expenditure of significant financial and managerial resources. Additionally, an unfavorable outcome in a legal matter, including in a patent dispute, could require the Company to pay damages, entitle claimants to other relief, such as royalties, or could prevent the Company from selling some of its products in certain jurisdictions. While the Company cannot predict with certainty the results of the Legal Matters in which it is currently involved, the Company does not expect that the ultimate outcome of such Legal Matters will individually or in the aggregate have a material adverse effect on its business, results of operations, financial condition or cash flows.

Investment Commitment

We have committed to invest up to an aggregate of $7.9 million in two private equity funds, of which $7.7 million has been applied to these commitments as of December 31, 2019.

Performance Bonds

Certain contracts, customers and/or jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of December 31, 2019, we had commitments related to these bonds totaling $9.3 million which expire at various dates through August 2024. As of December 31, 2018, we had commitments related to these bonds totaling $6.5 million. Although the triggering events vary from contract to contract, in general we would only be liable for the amount of these guarantees in the event of default in our under each contract, the probability of which we believe is remote.