Subsequent Events	12 Months Ended
Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Note 18 – Subsequent Events On January 23, 2019, the Board declared a quarterly cash dividend of $0.09 per common share to be paid to shareholders of record at the close of business on February 7, 2019. The quarterly dividend payment was $4.3 million and was paid on February 21, 2019. In July 2003, our Board of Directors elected to begin declaring quarterly dividends on our common stock considering the tax treatment of dividends and adequate levels of Company liquidity. During the first quarter and as of February 26, 2019, we have repurchased 13,000 shares of our common stock through open market purchases at an average cost of $14.06 per share. We currently have the authority to purchase an additional 2.5 million shares of our common stock under the current plan approved by the Board of Directors. In February 2019, $1.0 million of an outstanding investment loan due to ADTRAN was replaced with a secured loan in that amount. The remaining balance of this investment loan was converted to participating preferred shares of the respective company. In February 2019, we announced the restructuring of our workforce in Germany, which includes the closure of the office location in Munich, Germany accompanied by relocation or severance benefits for the affected employees and a voluntary early retirement offering to certain other employees. The restructuring is expected to be completed in the fourth quarter of 2019. ADTRAN does not have sufficient information currently on which to estimate the liability associated with this restructuring, including costs associated with employee severance and relocation. On February 25, 2019, one the Company’s customers filed for voluntary Chapter 11 bankruptcy as a result of a court ruling resulting in a substantial legal judgment against the customer. In 2018, this customer accounted for less than 5% of the Company’s revenue. As of December 31, 2018, the Company had $2.6 million related to product and services revenue and $0.3 million related to a leased equipment arrangement included in accounts receivable on the Consolidated Balance Sheet that was due from this customer. As of December 31, 2018, the Company had $9.4 million included in other receivables related to a leased equipment arrangement on its Consolidated Balance Sheet that was due from this customer. Since December 31, 2018, and through the date of this filing, all $2.6 million of the outstanding products and services accounts receivable and $0.1 million of the outstanding accounts receivable related to leased equipment have been collected. Additionally, $1.7 million of the outstanding other receivables related to leased equipment have been collected. Therefore, there is potential risk of uncollectibility up to $7.8 million on the remaining outstanding receivable balances as of December 31 2018. The Company has evaluated the collectibility of the remaining receivable balances with the best available and applicable information as of the date of this filing and the impact was not material to the consolidated financial statements as of December 31, 2018. The Company will continue to evaluate the collectibility of the remaining accounts receivable balances in subsequent reporting periods. Additionally, it is uncertain at this time the impact this voluntary bankruptcy filing might have on the Company’s operating income prospectively; however, the Company believes it will not have a significant impact on the Company’s liquidity and capital resources.

Subsequent Events

12 Months Ended

Dec. 31, 2018

Note 18 – Subsequent Events

On January 23, 2019, the Board declared a quarterly cash dividend of $0.09 per common share to be paid to shareholders of record at the close of business on February 7, 2019. The quarterly dividend payment was $4.3 million and was paid on February 21, 2019. In July 2003, our Board of Directors elected to begin declaring quarterly dividends on our common stock considering the tax treatment of dividends and adequate levels of Company liquidity.

During the first quarter and as of February 26, 2019, we have repurchased 13,000 shares of our common stock through open market purchases at an average cost of $14.06 per share. We currently have the authority to purchase an additional 2.5 million shares of our common stock under the current plan approved by the Board of Directors.

In February 2019, $1.0 million of an outstanding investment loan due to ADTRAN was replaced with a secured loan in that amount. The remaining balance of this investment loan was converted to participating preferred shares of the respective company.

In February 2019, we announced the restructuring of our workforce in Germany, which includes the closure of the office location in Munich, Germany accompanied by relocation or severance benefits for the affected employees and a voluntary early retirement offering to certain other employees. The restructuring is expected to be completed in the fourth quarter of 2019. ADTRAN does not have sufficient information currently on which to estimate the liability associated with this restructuring, including costs associated with employee severance and relocation.

On February 25, 2019, one the Company’s customers filed for voluntary Chapter 11 bankruptcy as a result of a court ruling resulting in a substantial legal judgment against the customer. In 2018, this customer accounted for less than 5% of the Company’s revenue. As of December 31, 2018, the Company had $2.6 million related to product and services revenue and $0.3 million related to a leased equipment arrangement included in accounts receivable on the Consolidated Balance Sheet that was due from this customer. As of December 31, 2018, the Company had $9.4 million included in other receivables related to a leased equipment arrangement on its Consolidated Balance Sheet that was due from this customer. Since December 31, 2018, and through the date of this filing, all $2.6 million of the outstanding products and services accounts receivable and $0.1 million of the outstanding accounts receivable related to leased equipment have been collected. Additionally, $1.7 million of the outstanding other receivables related to leased equipment have been collected. Therefore, there is potential risk of uncollectibility up to $7.8 million on the remaining outstanding receivable balances as of December 31 2018. The Company has evaluated the collectibility of the remaining receivable balances with the best available and applicable information as of the date of this filing and the impact was not material to the consolidated financial statements as of December 31, 2018. The Company will continue to evaluate the collectibility of the remaining accounts receivable balances in subsequent reporting periods. Additionally, it is uncertain at this time the impact this voluntary bankruptcy filing might have on the Company’s operating income prospectively; however, the Company believes it will not have a significant impact on the Company’s liquidity and capital resources.