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, 2012 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 for a fair presentation of these interim statements have been included 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, 2012, filed on February 28, 2013 with the SEC.

Changes in Classifications

Certain changes in classifications have been made to the prior period balances in other comprehensive income to conform to the current period’s presentation as a result of our adoption of Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Comprehensive Income.

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 allowance for doubtful accounts, obsolete and excess inventory reserves, warranty reserves, customer rebates, allowance for sales returns, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated working capital adjustments under negotiation related to the Nokia Siemens Networks Broadband Access business acquisition, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.

Recent Accounting Pronouncements

During the six months ended June 30, 2013, we adopted the following accounting standard, which had no material effect on our consolidated results of operations or financial condition:

In February 2013, the FASB issued Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU 2013-02). ASU 2013-02 requires entities to provide information about the amounts reclassified out of accumulated other comprehensive income by component either on the face of the financial statements or in the footnotes. ASU 2013-02 does not change the current requirements for reporting net income or other comprehensive income in the financial statements. This update is effective prospectively for reporting periods beginning after December 15, 2012. We adopted this amendment during the first quarter of 2013, and we have provided the disclosures required for the periods ended June 30, 2013 and 2012 in Note 10 of Notes to Consolidated Financial Statements.

On May 4, 2012, we acquired the Nokia Siemens Networks Broadband Access business (NSN BBA business). This acquisition provides us with an established customer base in key markets and complementary, market-focused products and was accounted for as a business combination. We have included the financial results of the NSN BBA business in our consolidated financial statements since the date of acquisition. These revenues are included in the Carrier Networks division in the Broadband Access subcategory.

We received a cash payment of $7.5 million from NSN and recorded a bargain purchase gain of $1.8 million, net of income taxes, in the second quarter of 2012, subject to customary working capital adjustments between the parties as defined in the purchase agreement. As of June 30, 2013, the parties were in the process of resolving the working capital adjustments. We adjusted the purchase price allocation during the fourth quarter of 2012 to record additional estimated liabilities and an estimated receivable from NSN related to working capital adjustments under negotiation. The bargain purchase gain of $1.8 million represents the excess of the consideration exchanged over the fair value of the assets acquired and liabilities assumed. We have assessed the recognition and measurements of the assets acquired and liabilities assumed based on historical and pro forma data for future periods and have concluded that our valuation procedures and resulting measures were appropriate.

The allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date is as follows:

The fair value of the customer relationships acquired was calculated using a discounted cash flow method (excess earnings) and is being amortized using a declining balance method derived from projected customer revenue over an average estimated useful life of 13 years. The fair value of the developed technology acquired was calculated using a discounted cash flow method (relief from royalty) and is being amortized using the straight-line method over an estimated useful life of five years.

The following supplemental pro forma information presents the financial results of the acquired NSN BBA business for the three and six months ended June 30, 2012. The pro forma results for the period January 1, 2012 to May 4, 2012 are not included in our consolidated financial statements.

This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2012, nor are they indicative of any future results.

For the three and six months ended June 30, 2013, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $0.7 and $1.6 million related to this acquisition.

Our effective tax rate decreased from 35.6% in the six months ended June 30, 2012 to 33.2% in the six months ended June 30, 2013. The decrease in the effective tax rate between the two periods is primarily attributable to the net effect of recording the benefit for the research tax credit for the 2012 tax year in January 2013 pursuant to the American Taxpayer Relief Act of 2012, the inclusion of the benefit of the estimated 2013 research tax credit in the estimated annual effective rate for 2013, and foreign subsidiary losses for which no tax benefits are recorded.

As a result of our acquisition of the NSN BBA business, we assumed a defined benefit obligation of $17.0 million as of May 4, 2012. We established a Contribution Trust Arrangement (CTA) to hold the pension assets, and NSN transferred assets to us equal to the defined benefit obligation.

The following table summarizes the components of net periodic pension cost for the three and six months ended June 30, 2013 and the period May 4, 2012 to June 30, 2012:

The following table summarizes the stock-based compensation expense related to stock options, restricted stock units (RSUs) and restricted stock for the three and six months ended June 30, 2013 and 2012, which was recognized as follows:

The fair value of our stock options was estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate.

There were no options granted during the three and six months ended June 30, 2013 or 2012.

The fair value of our RSUs is calculated using a Monte Carlo Simulation valuation method. There were no RSU grants during the three and six months ended June 30, 2013 or 2012.

The fair value of restricted stock is equal to the closing price of our stock on the date of grant. There were no restricted stock grants during the three and six months ended June 30, 2013 or 2012.

Stock-based compensation expense recognized in our Consolidated Statements of Income for the three and six months ended June 30, 2013 and 2012 is based on options, RSUs and restricted stock ultimately expected to vest, and has been reduced for estimated forfeitures. Estimated forfeitures for stock options were based upon historical experience and approximate 1.6% annually. We estimated a 0% forfeiture rate for our RSUs and restricted stock due to the limited number of recipients and historical experience for these awards.

As of June 30, 2013, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $14.3 million, which is expected to be recognized over an average remaining recognition period of 2.2 years.

The following table is a summary of our stock options outstanding as of December 31, 2012 and June 30, 2013 and the changes that occurred during the six months ended June 30, 2013:

The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between ADTRAN’s closing stock price on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on June 30, 2013. The aggregate intrinsic value will change based on the fair market value of ADTRAN’s stock.

The total pre-tax intrinsic value of options exercised during the three and six month period ended June 30, 2013 was $0.2 million.

The following table is a summary of our RSUs and restricted stock outstanding as of December 31, 2012 and June 30, 2013 and the changes that occurred during the six months ended June 30, 2013:

At June 30, 2013, we held the following securities and investments, recorded at either fair value or cost.

At December 31, 2012, we held the following securities and investments, recorded at either fair value or cost.

As of June 30, 2013, our corporate bonds and municipal fixed-rate bonds had the following contractual maturities:

Our investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5% of the market value of our total investment portfolio.

At June 30, 2013, we held a $48.3 million restricted certificate of deposit, which is carried at cost. This investment serves as a collateral deposit against the principal amount outstanding under loans made to ADTRAN pursuant to an Alabama State Industrial Development Authority revenue bond (the Bond). At June 30, 2013, the estimated fair value of the Bond was approximately $46.3 million, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of A-. For more information on the Bond, see “Debt” under “Liquidity and Capital Resources” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in Item 2 of Part I of this report.

We review our investment portfolio for potential “other-than-temporary” declines in value on an individual investment basis. We assess, on a quarterly basis, significant declines in value which may be considered other-than-temporary and, if necessary, recognize and record the appropriate charge to write-down the carrying value of such investments. In making this assessment, we take into consideration qualitative and quantitative information, including but not limited to the following: the magnitude and duration of historical declines in market prices, credit rating activity, assessments of liquidity, public filings, and statements made by the issuer. We generally begin our identification of potential other-than-temporary impairments by reviewing any security with a fair value that has declined from its original or adjusted cost basis by 25% or more for six or more consecutive months. We then evaluate the individual security based on the previously identified factors to determine the amount of the write-down, if any. As a result of our review, we recorded an other-than-temporary impairment charge of $4 thousand during the six months ended June 30, 2013 related to one marketable security. For the six months ended June 30, 2012, we recorded an other-than-temporary impairment charge of $33 thousand related to eight marketable equity securities.

Realized gains and losses on sales of securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our investments.

As of June 30, 2013 and 2012, gross unrealized losses related to individual securities in a continuous loss position for 12 months or longer were not significant.

We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 – Values based on unadjusted, quoted prices in active markets for identical assets or liabilities; Level 2 – Values based on inputs other than quoted prices included within Level 1 that are directly or indirectly observable for the asset or liability; Level 3 – Values based on unobservable inputs for the asset or liability. These inputs include information supplied by investees.

The fair value of our Level 2 securities is calculated using a weighted average market price for each security. Market prices are obtained from a variety of industry standard data providers, security master files from large financial institutions, and other third-party sources. These multiple market prices are used as inputs into a distribution-curve-based algorithm to determine the daily market value of each security.

Our municipal variable rate demand notes have a structure that implies a standard expected market price. The frequent interest rate resets make it reasonable to expect the price to stay at par. These securities are priced at the expected market price.

We have certain international customers who are billed in their local currency. Changes in the monetary exchange rates may adversely affect our results of operations and financial condition. When appropriate, we enter into various derivative transactions to enhance our ability to manage the volatility relating to these typical business exposures. We do not hold or issue derivative instruments for trading or other speculative purposes. Our derivative instruments are recorded in the Consolidated Balance Sheets at their fair values. Our derivative instruments do not qualify for hedge accounting, and accordingly, all changes in the fair value of the instruments are recognized as other income (expense) in the Consolidated Statements of Income. The maximum time frame for our derivatives is currently less than twelve months. Our derivative instruments are not subject to master netting arrangements and are not offset in the Consolidated Balance Sheets.

As of June 30, 2013, we had forward contracts and swaps outstanding with notional amounts totaling €20.7 million ($26.9 million) and €0.3 million ($0.4 million), respectively, which mature through 2013.

The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2013 were as follows:

The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and six months ended June 30, 2013 were as follows:

At June 30, 2013 and December 31, 2012, inventory consisted of the following:

We establish reserves for estimated excess, obsolete, or unmarketable inventory equal to the difference between the cost of the inventory and the estimated fair value of the inventory based upon assumptions about future demand and market conditions. At June 30, 2013 and December 31, 2012, raw materials reserves totaled $14.9 million and $9.9 million, respectively, and finished goods inventory reserves totaled $3.7 million and $2.1 million, respectively.

The change in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the six months ended June 30, 2013 is as follows:

We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If we determine that the two-step quantitative test is necessary, then we compare the fair value of the reporting unit to which the goodwill is assigned to the reporting unit’s carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, then the amount of the impairment loss is measured. There were no impairment losses recorded during the six months ended June 30, 2013 or 2012.

Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangibles acquired in conjunction with our acquisition of Objectworld Communications Corporation on September 15, 2009, Bluesocket, Inc. on August 4, 2011, and the NSN BBA business on May 4, 2012.

The following table presents our intangible assets as of June 30, 2013 and December 31, 2012:

Amortization expense, all of which relates to business acquisitions, was $0.6 million and $0.5 million for the three months ended June 30, 2013 and 2012, respectively, and $1.2 million and $0.8 million for the six months ended June 30, 2013 and 2012, respectively.

As of June 30, 2013, the estimated future amortization expense of our intangible assets is as follows:

A summary of the changes in stockholders’ equity for the six months ended June 30, 2013 is as follows:

Stock Repurchase Program

Since 1997, our Board of Directors has approved multiple share repurchase programs that have authorized open market repurchase transactions of up to 35 million shares of our common stock. On May 1, 2013, our Board of Directors authorized the repurchase of an additional 5.0 million shares of our common stock, which commenced upon completion of the repurchase plan announced on October 11, 2011. This new authorization is being implemented through open market or private purchases from time to time as conditions warrant.

During the six months ended June 30, 2013, we repurchased 4.2 million shares of our common stock at an average price of $21.49 per share. We currently have the authority to purchase an additional 4.9 million shares of our common stock under the current plan approved by the Board of Directors.

Stock Option Exercises

We issued 45 thousand shares of treasury stock during the six months ended June 30, 2013 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $23.46. We received proceeds totaling $0.8 million from the exercise of these stock options during the six months ended June 30, 2013.

Dividend Payments

During the six months ended June 30, 2013, we paid cash dividends as follows (in thousands except per share amount):

Other Comprehensive Income

Other comprehensive income consists of unrealized gains (losses) on available-for-sale securities, reclassification adjustments for amounts included in net income related to impairments of available-for-sale securities and realized gains (losses) on available-for-sale securities, defined benefit plan adjustments and foreign currency translation adjustments.

The following tables present changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2013 and 2012: