Commitments and Contingencies	9 Months Ended
Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	17. 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 from a Latin American customer. Investors in ADTRAN securities have until December 16, 2019 to move the court to serve as lead plaintiff in this action. 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 as of September 30, 2019.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

17. 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 from a Latin American customer. Investors in ADTRAN securities have until December 16, 2019 to move the court to serve as lead plaintiff in this action. 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 as of September 30, 2019.