Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN^®, Inc. and its subsidiaries (ADTRAN) have been prepared pursuant to the rules and regulations for reporting on Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles for complete financial statements are not included herein. The December 31, 2014 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States. In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2014, filed on February 24, 2015 with the SEC. Changes in Classifications We reclassified $2.3 million from other receivables to accounts receivable at December 31, 2014 to conform to the current period presentation. Out of Period Adjustment In connection with the preparation of our Condensed Consolidated Financial Statements, we recorded corrections of certain out of period, immaterial misstatements that occurred in prior periods, the most significant of which resulted in an increase in Other Expense of $1.3 million in the first quarter of 2015. The aggregate impact of the corrections was a $0.8 million reduction to pre-tax income for the nine months ended September 30, 2015 and is not expected to be material to the current year annual results. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), which supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. In August 2015, the FASB issued ASU 2015-14, which deferred the effective date of ASU 2014-09 to fiscal years beginning after December 31, 2017, and interim periods within those fiscal years. ASU 2014-09 allows for either full retrospective or modified retrospective adoption. We are currently evaluating the transition method that will be elected and the impact that the adoption of ASU 2014-09 will have on our financial position, results of operations and cash flows. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015-05), which provides guidance on accounting for fees paid by a customer in a cloud computing arrangement. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 is effective for annual reporting periods beginning after December 15, 2015, including interim periods within that reporting period. Early adoption is permitted. The amendments may be applied either prospectively to all arrangements entered into or materially modified after the effective date or retrospectively. We do not believe the adoption of ASU 2015-05 will have a material impact on our financial position, results of operations and cash flows. In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11). Currently, Topic 330, Inventory, requires an entity to measure inventory at the lower of cost or market. Market could be replacement cost, net realizable value, or net realizable value less an approximately normal profit margin. ASU 2015-11 does not apply to inventory that is measured using last-in, first-out (LIFO) or the retail inventory method. The amendments apply to all other inventory, which includes inventory that is measured using first-in, first-out (FIFO) or average cost. ASU 2015-11 requires an entity to measure in scope inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. The amendments should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We do not believe the adoption of ASU 2015-05 will have a material impact on our financial position, results of operations and cash flows.

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying unaudited consolidated financial statements of ADTRAN^®, Inc. and its subsidiaries (ADTRAN) have been prepared pursuant to the rules and regulations for reporting on Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles for complete financial statements are not included herein. The December 31, 2014 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.

In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2014, filed on February 24, 2015 with the SEC.

Changes in Classifications

We reclassified $2.3 million from other receivables to accounts receivable at December 31, 2014 to conform to the current period presentation.

Out of Period Adjustment

In connection with the preparation of our Condensed Consolidated Financial Statements, we recorded corrections of certain out of period, immaterial misstatements that occurred in prior periods, the most significant of which resulted in an increase in Other Expense of $1.3 million in the first quarter of 2015. The aggregate impact of the corrections was a $0.8 million reduction to pre-tax income for the nine months ended September 30, 2015 and is not expected to be material to the current year annual results.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), which supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. In August 2015, the FASB issued ASU 2015-14, which deferred the effective date of ASU 2014-09 to fiscal years beginning after December 31, 2017, and interim periods within those fiscal years. ASU 2014-09 allows for either full retrospective or modified retrospective adoption. We are currently evaluating the transition method that will be elected and the impact that the adoption of ASU 2014-09 will have on our financial position, results of operations and cash flows.

In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015-05), which provides guidance on accounting for fees paid by a customer in a cloud computing arrangement. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 is effective for annual reporting periods beginning after December 15, 2015, including interim periods within that reporting period. Early adoption is permitted. The amendments may be applied either prospectively to all arrangements entered into or materially modified after the effective date or retrospectively. We do not believe the adoption of ASU 2015-05 will have a material impact on our financial position, results of operations and cash flows.

In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11). Currently, Topic 330, Inventory, requires an entity to measure inventory at the lower of cost or market. Market could be replacement cost, net realizable value, or net realizable value less an approximately normal profit margin. ASU 2015-11 does not apply to inventory that is measured using last-in, first-out (LIFO) or the retail inventory method. The amendments apply to all other inventory, which includes inventory that is measured using first-in, first-out (FIFO) or average cost. ASU 2015-11 requires an entity to measure in scope inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. The amendments should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We do not believe the adoption of ASU 2015-05 will have a material impact on our financial position, results of operations and cash flows.