ADTRAN (ADTN) 10-Q 5 Aug 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 22, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
Trading Symbol	ADTN
Entity Registrant Name	ADTRAN INC
Entity Central Index Key	926,282
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		48,398,992

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 70,914	$ 84,550
Short-term investments	50,867	34,396
Accounts receivable, less allowance for doubtful accounts of $19 at June 30, 2016 and December 31, 2015	89,386	71,917
Other receivables	11,676	19,321
Income tax receivable, net	2,405
Inventory, net	86,936	91,533
Prepaid expenses and other current assets	13,563	10,145
Deferred tax assets, net	18,488	18,924
Total Current Assets	344,235	330,786
Property, plant and equipment, net	74,115	73,233
Deferred tax assets, net	19,127	18,091
Goodwill	3,492	3,492
Other assets	9,340	9,276
Long-term investments	186,249	198,026
Total Assets	636,558	632,904
Current Liabilities
Accounts payable	59,211	48,668
Unearned revenue	15,982	16,615
Accrued expenses	12,126	12,108
Accrued wages and benefits	15,702	12,857
Income tax payable, net		2,395
Total Current Liabilities	103,021	92,643
Non-current unearned revenue	6,437	7,965
Other non-current liabilities	25,476	24,236
Bonds payable	27,900	27,900
Total Liabilities	162,834	152,744
Commitments and contingencies (see Note 13)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 48,712 shares outstanding at June 30, 2016 and 79,652 shares issued and 49,558 shares outstanding at December 31, 2015	797	797
Additional paid-in capital	249,851	246,879
Accumulated other comprehensive loss	(8,695)	(8,969)
Retained earnings	912,536	906,772
Less treasury stock at cost: 30,940 and 30,094 shares at June 30, 2016 and December 31, 2015, respectively	(680,765)	(665,319)
Total Stockholders’ Equity	473,724	480,160
Total Liabilities and Stockholders’ Equity	$ 636,558	$ 632,904

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 19	$ 19
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,652,000	79,652,000
Common stock, shares outstanding	48,712,000	49,558,000
Treasury stock, shares	30,940,000	30,094,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Sales
Products	$ 138,549	$ 144,098	$ 262,432	$ 273,603
Services	24,152	16,040	42,473	29,370
Total Sales	162,701	160,138	304,905	302,973
Cost of sales
Products	67,844	84,210	131,917	155,770
Services	15,902	7,682	28,239	13,394
Total Cost of Sales	83,746	91,892	160,156	169,164
Gross Profit	78,955	68,246	144,749	133,809
Selling, general and administrative expenses	32,866	32,123	63,651	63,187
Research and development expenses	31,277	35,479	60,765	68,015
Operating Income	14,812	644	20,333	2,607
Interest and dividend income	927	908	1,782	1,841
Interest expense	(142)	(149)	(287)	(297)
Net realized investment gain	1,110	3,255	2,838	6,370
Other expense, net	(251)	(547)	(132)	(900)
Income before provision for income taxes	16,456	4,111	24,534	9,621
Provision for income taxes	(6,228)	(1,567)	(9,292)	(3,760)
Net Income	$ 10,228	$ 2,544	$ 15,242	$ 5,861
Weighted average shares outstanding – basic	48,831	51,822	49,026	52,607
Weighted average shares outstanding – diluted	49,048	51,917	49,218	52,742
Earnings per common share – basic	$ 0.21	$ 0.05	$ 0.31	$ 0.11
Earnings per common share – diluted	0.21	0.05	0.31	0.11
Dividend per share	$ 0.09	$ 0.09	$ 0.18	$ 0.18

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 10,228	$ 2,544	$ 15,242	$ 5,861
Other Comprehensive Income (Loss), net of tax:
Net unrealized losses on available-for-sale securities	(165)	(1,783)	(420)	(2,286)
Defined benefit plan adjustments	22	72	67	140
Foreign currency translation	(601)	872	627	(2,446)
Other Comprehensive Income (Loss), net of tax	(744)	(839)	274	(4,592)
Comprehensive Income, net of tax	$ 9,484	$ 1,705	$ 15,516	$ 1,269

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 15,242	$ 5,861
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,689	7,256
Amortization of net premium on available-for-sale investments	376	1,578
Net realized investment gain	(2,838)	(6,370)
Net loss on disposal of property, plant and equipment	5	160
Stock-based compensation expense	3,109	3,114
Deferred income taxes	(354)	(1,743)
Tax benefit from stock option exercises		(23)
Excess tax benefits from stock-based compensation arrangements		38
Changes in operating assets and liabilities:
Accounts receivable, net	(17,192)	(2,003)
Other receivables	7,876	(119)
Inventory	4,938	(14,254)
Prepaid expenses and other assets	(4,263)	(1,433)
Accounts payable	10,354	30,938
Accrued expenses and other liabilities	1,474	2,175
Income tax payable/receivable, net	(4,799)	(3,961)
Net cash provided by operating activities	20,617	21,214
Cash flows from investing activities:
Purchases of property, plant and equipment	(6,679)	(5,392)
Proceeds from disposals of property, plant and equipment		8
Proceeds from sales and maturities of available-for-sale investments	109,993	120,422
Purchases of available-for-sale investments	(112,903)	(62,626)
Net cash provided by (used in) investing activities	(9,589)	52,412
Cash flows from financing activities:
Proceeds from stock option exercises	541	833
Purchases of treasury stock	(16,579)	(49,307)
Dividend payments	(8,860)	(9,509)
Excess tax benefits from stock-based compensation arrangements		(38)
Net cash used in financing activities	(24,898)	(58,021)
Net increase (decrease) in cash and cash equivalents	(13,870)	15,605
Effect of exchange rate changes	234	(1,829)
Cash and cash equivalents, beginning of period	84,550	73,439
Cash and cash equivalents, end of period	70,914	87,215
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 554	$ 270

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2016
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 ® 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, 2015, filed on February 24, 2016 with the SEC. 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 (Topic 606) Revenue Recognition with early adoption permitted for reporting periods beginning after December 15, 2016. Subsequently, the FASB issued ASUs in 2016 containing implementation guidance related to ASU 2014-09, including: ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which is intended to improve the operability and understandability of the implementation guidance on principal versus agent considerations; ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which is intended to clarify two aspects of Topic 606: identifying performance obligations and the licensing implementation guidance; and ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which contains certain provisions and practical expedients in response to identified implementation issues. In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory Inventory In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting During the first quarter of 2016, we adopted the following accounting standards, which had no material effect on our financial position, results of operations or 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

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	2. INCOME TAXES Our effective tax rate decreased from 39.1% in the six months ended June 30, 2015 to 37.9% in the six months ended June 30, 2016. The decrease in the effective tax rate between the two periods is primarily attributable to the research and development tax credit being made permanent.

Pension Benefit Plan

Pension Benefit Plan	6 Months Ended
	Jun. 30, 2016
Compensation And Retirement Disclosure [Abstract]
Pension Benefit Plan	3. PENSION BENEFIT PLAN We maintain a defined benefit pension plan covering employees in certain foreign countries. The following table summarizes the components of net periodic pension cost for the three and six months ended June 30, 2016 and 2015: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2016 2015 2016 2015 Service cost $ 310 $ 324 $ 607 $ 664 Interest cost 184 152 360 311 Expected return on plan assets (271 ) (250 ) (530 ) (511 ) Amortization of actuarial losses 45 100 88 205 Net periodic pension cost $ 268 $ 326 $ 525 $ 669

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	4. STOCK-BASED COMPENSATION 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, 2016 and 2015, which was recognized as follows: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2016 2015 2016 2015 Stock-based compensation expense included in cost of sales $ 95 $ 53 $ 194 $ 143 Selling, general and administrative expense 788 723 1,557 1,414 Research and development expense 668 699 1,358 1,557 Stock-based compensation expense included in operating expenses 1,456 1,422 2,915 2,971 Total stock-based compensation expense 1,551 1,475 3,109 3,114 Tax benefit for expense associated with non-qualified options (213 ) (222 ) (425 ) (402 ) Total stock-based compensation expense, net of tax $ 1,338 $ 1,253 $ 2,684 $ 2,712 The fair value of our stock options is 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 months ended June 30, 2015. The weighted-average assumptions and value of options granted for the three and six months ended June 30, 2016 and the six months ended June 30, 2015 are as follows: Three and Six Months Ended Six Months Ended June 30, June 30, 2016 2015 Expected volatility 34.74 % 38.75 % Risk-free interest rate 1.33 % 1.46 % Expected dividend yield 1.91 % 1.60 % Expected life (in years) 6.26 6.47 Weighted-average estimated value $ 5.42 $ 7.63 The fair value of our RSUs is calculated using a Monte Carlo Simulation valuation method. No RSUs were granted or vested during the three and six months ended June 30, 2016 and 2015. Twelve thousand RSUs were forfeited during the six months ended June 30, 2015. The fair value of restricted stock is equal to the closing price of our stock on the date of grant. Two thousand shares of restricted stock were granted during the six months ended June 30, 2016. Two thousand shares of restricted stock vested during the three and six months ended June 30, 2015. Stock-based compensation expense recognized in our Consolidated Statements of Income for the three and six months ended June 30, 2016 and 2015 is based on options, RSUs and restricted stock ultimately expected to vest, and has been reduced for estimated forfeitures. Estimated forfeitures for stock options are based upon historical experience and approximate 3.7% 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, 2016, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $11.5 million, which is expected to be recognized over an average remaining recognition period of 2.4 years. The following table is a summary of our stock options outstanding as of December 31, 2015 and June 30, 2016 and the changes that occurred during the six months ended June 30, 2016: (In thousands, except per share amounts) Number of Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Options outstanding, December 31, 2015 7,108 $ 21.97 6.42 $ 3,284 Options granted 1 $ 18.83 Options exercised (33 ) $ 16.58 Options forfeited (42 ) $ 17.88 Options expired (54 ) $ 25.65 Options outstanding, June 30, 2016 6,980 $ 22.00 5.93 $ 6,522 Options vested and expected to vest, June 30, 2016 6,865 $ 22.09 5.88 $ 6,260 Options exercisable, June 30, 2016 4,420 $ 24.35 4.44 $ 2,298 The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between the closing price of our stock 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, 2016. The aggregate intrinsic value will change based on the fair market value of our stock. The total pre-tax intrinsic value of options exercised during the three and six months ended June 30, 2016 was $0.1 million.

Investments

Investments	6 Months Ended
	Jun. 30, 2016
Investments Debt And Equity Securities [Abstract]
Investments	5. INVESTMENTS At June 30, 2016, we held the following securities and investments, recorded at either fair value or cost. Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 11,516 $ 1,628 $ (49 ) $ 13,095 Corporate bonds 54,044 149 (61 ) 54,132 Municipal fixed-rate bonds 16,889 59 - 16,948 Asset-backed bonds 23,526 53 (6 ) 23,573 Mortgage/Agency-backed bonds 19,214 44 (39 ) 19,219 U.S. Government bonds 33,498 308 - 33,806 Variable rate demand notes 11,740 - - 11,740 Marketable equity securities 32,948 1,901 (1,478 ) 33,371 Available-for-sale securities held at fair value $ 203,375 $ 4,142 $ (1,633 ) $ 205,884 Restricted investment held at cost 30,000 Other investments held at cost 1,232 Total carrying value of available-for-sale investments $ 237,116 At December 31, 2015, we held the following securities and investments, recorded at either fair value or cost. Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 11,325 $ 1,575 $ (66 ) $ 12,834 Corporate bonds 58,328 20 (734 ) 57,614 Municipal fixed-rate bonds 26,414 28 (18 ) 26,424 Asset-backed bonds 19,281 2 (44 ) 19,239 Mortgage/Agency-backed bonds 15,463 1 (91 ) 15,373 U.S. Government bonds 35,646 - (248 ) 35,398 Marketable equity securities 31,643 4,301 (1,693 ) 34,251 Available-for-sale securities held at fair value $ 198,100 $ 5,927 $ (2,894 ) $ 201,133 Restricted investment held at cost 30,000 Other investments held at cost 1,289 Total carrying value of available-for-sale investments $ 232,422 As of June 30, 2016, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, and U.S. government bonds had the following contractual maturities: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset- backed bonds Mortgage / Agency- backed bonds U.S. Government bonds Less than one year $ 20,729 $ 10,473 $ - $ 4,972 $ 2,953 One to two years 24,884 4,488 822 2,569 7,481 Two to three years 6,099 1,536 9,077 2,058 11,344 Three to five years 2,420 451 10,991 - 12,028 Five to ten years - - 2,506 1,036 - More than ten years - - 177 8,584 - Total $ 54,132 $ 16,948 $ 23,573 $ 19,219 $ 33,806 Actual maturities may differ from contractual maturities because some borrowers have the right to call or prepay obligations with or without call or prepayment penalties. 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, 2016, we held a $30.0 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), which totaled $28.9 million at June 30, 2016 and December 31, 2015. At June 30, 2016, the estimated fair value of the Bond using a level 2 valuation technique was approximately $29.4 million, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of AAA. We have the right to set-off the balance of the Bond with the collateral deposit in order to reduce the balance of the indebtedness. The Bond matures on January 1, 2020, and bears interest at the rate of 2% per annum. In conjunction with this program, we are eligible to receive certain economic incentives from the state of Alabama that reduce the amount of payroll withholdings we are required to remit to the state for those employment positions that qualify under this program. We are required to make payments in the amounts necessary to pay the interest on the amounts currently outstanding. It is our intent to make annual principal payments in addition to the interest amounts that are due. 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. For the three and six months ended June 30, 2016 and 2015, other-than-temporary impairment charges were not significant. 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. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Gross realized gains $ 1,517 $ 3,459 $ 3,881 $ 6,604 Gross realized losses $ (407 ) $ (204 ) $ (1,043 ) $ (234 ) As of June 30, 2016 and 2015, 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 for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at June 30, 2016 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,915 $ 1,915 $ - $ - Commercial Paper 15,996 - 15,996 - Cash equivalents 17,911 1,915 15,996 - Available-for-sale securities Deferred compensation plan assets 13,095 13,095 - - Available-for-sale debt securities Corporate bonds 54,132 - 54,132 - Municipal fixed-rate bonds 16,948 - 16,948 - Asset-backed bonds 23,573 - 23,573 - Mortgage/Agency-backed bonds 19,219 - 19,219 - U.S. Government bonds 33,806 33,806 - - Variable rate demand notes 11,740 - 11,740 - Available-for-sale marketable equity securities Marketable equity securities – technology industry 4,386 4,386 - - Marketable equity securities – other 28,985 28,985 - - Available-for-sale securities 205,884 80,272 125,612 - Total $ 223,795 $ 82,187 $ 141,608 $ - Fair Value Measurements at December 31, 2015 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,271 $ 1,271 $ - $ - Commercial Paper 11,696 - 11,696 - Cash equivalents 12,967 1,271 11,696 - Available-for-sale securities Deferred compensation plan assets 12,834 12,834 - - Available-for-sale debt securities Corporate bonds 57,614 - 57,614 - Municipal fixed-rate bonds 26,424 - 26,424 - Asset-backed bonds 19,239 - 19,239 - Mortgage/Agency-backed bonds 15,373 - 15,373 - U.S. Government bonds 35,398 35,398 - - Available-for-sale marketable equity securities Marketable equity securities – technology industry 5,384 5,384 - - Marketable equity securities – other 28,867 28,867 - - Available-for-sale securities 201,133 82,483 118,650 - Total $ 214,100 $ 83,754 $ 130,346 $ - 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 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.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	6 Months Ended
	Jun. 30, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	6. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES We have certain customers and suppliers who are invoiced or pay in a non-functional currency. Changes in the monetary exchange rates may adversely affect our results of operations and financial condition, as these are remeasured to the functional currency through profit and loss. 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 contractual period 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, 2016, we had forward contracts outstanding with notional amounts totaling €6.0 million ($6.7 million), which mature in the third quarter of 2016. The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2016 and December 31, 2015 were as follows: (In thousands) Balance Sheet Location June 30, 2016 December 31, 2015 Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – asset derivatives Other receivables $ 188 $ - 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, 2016 and 2015 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2016 2015 2016 2015 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ 237 $ (1,299 ) $ 190 $ 177

Inventory

Inventory	6 Months Ended
	Jun. 30, 2016
Inventory Disclosure [Abstract]
Inventory	7. INVENTORY At June 30, 2016 and December 31, 2015, inventory consisted of the following: June 30, December 31, (In thousands) 2016 2015 Raw materials $ 35,761 $ 34,223 Work in process 2,322 2,893 Finished goods 48,853 54,417 Total $ 86,936 $ 91,533 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, 2016 and December 31, 2015, raw materials reserves totaled $18.0 million and $17.5 million, respectively, and finished goods inventory reserves totaled $9.8 million and $9.2 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	8. GOODWILL AND INTANGIBLE ASSETS Goodwill, all of which relates to our acquisition of Bluesocket, Inc., was $3.5 million at June 30, 2016 and December 31, 2015, and was previously recorded in our Enterprise Networks reportable segment. As a result of our new reporting structure, which is discussed further in Note 11, we reallocated goodwill from our Enterprise Networks reportable segment to our two, new reportable segments – Network Solutions and Services & Support. As a result, goodwill of $3.1 million and $0.4 million was reallocated to our Network Solutions and Services & Support reportable segments, respectively. 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. We have elected to first assess the qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step impairment test. If we determine that it is more likely than not that its fair value is less than its carrying amount, then the two-step impairment test will be performed. Based on the results of our qualitative assessment in 2015, we concluded that it was not necessary to perform the two-step impairment test. There have been no impairment losses recognized since the acquisition in 2011. Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangibles acquired in conjunction with our acquisitions 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, 2016 and December 31, 2015: (In thousands) June 30, 2016 December 31, 2015 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 5,925 $ (2,966 ) $ 2,959 $ 5,828 $ (2,627 ) $ 3,201 Developed technology 5,778 (4,767 ) 1,011 5,720 (4,329 ) 1,391 Intellectual property 2,340 (2,021 ) 319 2,340 (1,854 ) 486 Trade names 270 (270 ) - 270 (265 ) 5 Total $ 14,313 $ (10,024 ) $ 4,289 $ 14,158 $ (9,075 ) $ 5,083 Amortization expense, all of which relates to business acquisitions, was $0.4 million and $0.5 million for the three months ended June 30, 2016 and 2015, respectively, and $0.9 million and $1.0 million for the six months ended June 30, 2016 and 2015, respectively. As of June 30, 2016, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2016 $ 807 2017 1,162 2018 702 2019 308 2020 285 Thereafter 1,025 Total $ 4,289

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2016
Equity [Abstract]
Stockholders' Equity	9. STOCKHOLDERS’ EQUITY A summary of the changes in stockholders’ equity for the six months ended June 30, 2016 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2015 $ 480,160 Net income 15,242 Dividend payments (8,860 ) Dividends accrued for unvested restricted stock units (26 ) Net unrealized losses on available-for-sale securities (net of tax) (420 ) Defined benefit plan adjustments 67 Foreign currency translation adjustment 627 Proceeds from stock option exercises 541 Purchase of treasury stock (16,579 ) Income tax effect of stock compensation arrangements (137 ) Stock-based compensation expense 3,109 Balance, June 30, 2016 $ 473,724 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 50.0 million shares of our common stock, which will be implemented through open market or private purchases from time to time as conditions warrant. During the six months ended June 30, 2016, we repurchased 0.9 million shares of our common stock at an average price of $18.48 per share. As of June 30, 2016, we have the authority to purchase an additional 4.9 million shares of our common stock under the current plans approved by the Board of Directors. Stock Option Exercises We issued 33 thousand shares of treasury stock during the six months ended June 30, 2016 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $18.97. We received proceeds totaling $0.5 million from the exercise of these stock options during the six months ended June 30, 2016. Dividend Payments During the six months ended June 30, 2016, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid February 4, 2016 February 18, 2016 $ 0.09 $ 4,453 April 28, 2016 May 12, 2016 $ 0.09 $ 4,407 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, realized gains (losses) on available-for-sale securities, and amortization of actuarial gains (losses) related to our defined benefit plan, 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, 2016 and 2015: Three Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,677 $ (3,850 ) $ (5,778 ) $ (7,951 ) Other comprehensive income (loss) before reclassifications 481 - (601 ) (120 ) Amounts reclassified from accumulated other comprehensive income (646 ) 22 - (624 ) Net current period other comprehensive income (loss) (165 ) 22 (601 ) (744 ) Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) Three Months Ended June 30, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 8,461 $ (5,689 ) $ (6,600 ) $ (3,828 ) Other comprehensive income (loss) before reclassifications 177 - 872 1,049 Amounts reclassified from accumulated other comprehensive income (1,960 ) 72 - (1,888 ) Net current period other comprehensive income (loss) (1,783 ) 72 872 (839 ) Ending balance $ 6,678 $ (5,617 ) $ (5,728 ) $ (4,667 ) The following tables present changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2016 and 2015: Six Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 1,239 - 627 1,866 Amounts reclassified from accumulated other comprehensive income (1,659 ) 67 - (1,592 ) Net current period other comprehensive income (loss) (420 ) 67 627 274 Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) Six Months Ended June 30, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 8,964 $ (5,757 ) $ (3,282 ) $ (75 ) Other comprehensive income (loss) before reclassifications 1,537 - (2,446 ) (909 ) Amounts reclassified from accumulated other comprehensive income (3,823 ) 140 - (3,683 ) Net current period other comprehensive income (loss) (2,286 ) 140 (2,446 ) (4,592 ) Ending balance $ 6,678 $ (5,617 ) $ (5,728 ) $ (4,667 ) The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2016 and 2015: (In thousands) Three Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,354 Net realized investment gain Impairment expense (295 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (33 ) (1) Total reclassifications for the period, before tax 1,026 Tax (expense) benefit (402 ) Total reclassifications for the period, net of tax $ 624 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 30, 2015 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,264 Net realized investment gain Impairment expense (51 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (105 ) (1) Total reclassifications for the period, before tax 3,108 Tax (expense) benefit (1,220 ) Total reclassifications for the period, net of tax $ 1,888 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2016 and 2015: (In thousands) Six Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,115 Net realized investment gain Impairment expense (395 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,622 Tax (expense) benefit (1,030 ) Total reclassifications for the period, net of tax $ 1,592 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 30, 2015 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 6,340 Net realized investment gain Impairment expense (73 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (203 ) (1) Total reclassifications for the period, before tax 6,064 Tax (expense) benefit (2,381 ) Total reclassifications for the period, net of tax $ 3,683 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2016 and 2015: Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 789 $ (308 ) $ 481 $ 290 $ (113 ) $ 177 Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,059 ) 413 (646 ) (3,213 ) 1,253 (1,960 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 33 (11 ) 22 105 (33 ) 72 Foreign currency translation adjustment (601 ) - (601 ) 872 - 872 Total Other Comprehensive Income (Loss) $ (838 ) $ 94 $ (744 ) $ (1,946 ) $ 1,107 $ (839 ) The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2016 and 2015: Six Months Ended June 30, 2016 Six Months Ended June 30, 2015 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 2,031 $ (792 ) $ 1,239 $ 2,520 $ (983 ) $ 1,537 Reclassification adjustment for amounts related to available-for-sale investments included in net income (2,720 ) 1,061 (1,659 ) (6,267 ) 2,444 (3,823 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 98 (31 ) 67 203 (63 ) 140 Foreign currency translation adjustment 627 - 627 (2,446 ) - (2,446 ) Total Other Comprehensive Income (Loss) $ 36 $ 238 $ 274 $ (5,990 ) $ 1,398 $ (4,592 )

Earnings per Share

Earnings per Share	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Earnings per Share	10. EARNINGS PER SHARE A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2016 and 2015 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2016 2015 2016 2015 Numerator Net income $ 10,228 $ 2,544 $ 15,242 $ 5,861 Denominator Weighted average number of shares – basic 48,831 51,822 49,026 52,607 Effect of dilutive securities Stock options 161 72 138 122 Restricted stock and restricted stock units 56 23 54 13 Weighted average number of shares – diluted 49,048 51,917 49,218 52,742 Net income per share – basic $ 0.21 $ 0.05 $ 0.31 $ 0.11 Net income per share – diluted $ 0.21 $ 0.05 $ 0.31 $ 0.11 Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 5.6 million and 6.1 million for the three months ended June 30, 2016 and 2015, respectively, and 5.8 million and 5.7 million for the six months ended June 30, 2016 and 2015, respectively.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Segment Information	11. SEGMENT INFORMATION In 2015, we began a realignment of our organizational structure to better match our market opportunities, technological development initiatives, and improve efficiencies. During the first quarter of 2016, our chief operating decision maker requested changes in the information that he regularly reviews for purposes of allocating resources and assessing performance. As a result, beginning with the quarter ended March 31, 2016, we began reporting our financial performance based on two, new reportable segments – Network Solutions and Services & Support. Network Solutions includes hardware products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes our suite of ProCloud ® We evaluate the performance of our new segments based on gross profit; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net realized investment gain/loss, other income/expense and provision for taxes are reported on a company-wide, functional basis only. Historical financial information by reportable segment and category, as discussed below, has been recast to conform to our new reporting structure. There are no inter-segment revenues. The following table presents information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2016 and 2015. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2016 June 30, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 138,549 $ 70,705 $ 144,098 $ 59,888 Services & Support 24,152 8,250 16,040 8,358 Total $ 162,701 $ 78,955 $ 160,138 $ 68,246 Six Months Ended June 30, 2016 June 30, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 262,432 $ 130,515 $ 273,603 $ 117,833 Services & Support 42,473 14,234 29,370 15,976 Total $ 304,905 $ 144,749 $ 302,973 $ 133,809 Sales by Category In addition to our new reporting segments, we will also report revenue for the following three categories – Access & Aggregation, Customer Devices, Traditional & Other Products. Access & Aggregation generally includes software and hardware based products and services that communication service providers (CSPs) use to aggregate and/or originate network access technologies. The portfolio of ADTRAN solutions within this category includes a wide array of modular or fixed physical form factors designed to deliver the best technology and economic fit for our customers based on the target subscriber density and environmental conditions. The Access & Aggregation category includes product and service families such as: · Total Access ® · hiX 5600 Series fiber aggregation and Fiber to the Node (FTTN) Multi-Service Access Nodes (MSAN) · Fiber to the Distribution Point (FTTdp) Optical Network Units (ONU) · Optical Line Terminals (OLT) · Optical Networking Edge (ONE) aggregation · Distribution Point Units (DPUs) · IP Digital Subscriber Line Access Multiplexers (DSLAMs) · Cabinet and Outside-Plant (OSP) enclosures and services · Network Management and Cloud based software platforms and applications · Pluggable optical transceivers (i.e., SFP, SFP+, XFP, QSFP), cables and other miscellaneous materials · Other products and services that are generally applicable to Access & Aggregation Customer Devices generally includes the products and services that provide end users access to the CSP network. The Customer Devices portfolio includes a comprehensive array of service provider and enterprise hardware and software products and services. The Customer Devices category includes products and services such as: · Broadband customer premise solutions, including Passive Optical Network (PON) and point-to-point Ethernet Optical Network Terminals (ONTs) · Residential and business gateways · Wi-Fi access points and associated powering and switching infrastructure · enterprise Session Border Controllers (eSBC) · Branch office and access routers · Carrier Ethernet services termination devices · VoIP media gateways · ProServices ® · Planning, engineering, program management, maintenance, installation and commissioning services to implement the customer devices solutions into consumer, small business and enterprise locations · Other products and services that are generally applicable to customer devices Traditional & Other Products generally includes a mix of prior generation technologies’ products and services, as well as other products and services that do not fit within the Access & Aggregation or Customer Devices categories. The Traditional & Other Products category includes products and services such as: · Time Division Multiplexed (TDM) and Asynchronous Transfer Mode (ATM) based aggregation systems and customer devices · HDSL, ADSL and other mature technologies used to deliver business and residential services over the CSP access and customer networks · Other products and services that do not fit within the Access & Aggregation and Customer Devices categories The table below presents sales information by category for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Access & Aggregation $ 102,232 $ 112,732 $ 196,087 $ 205,583 Customer Devices 40,876 30,042 73,229 61,746 Traditional & Other Products 19,593 17,364 35,589 35,644 Total $ 162,701 $ 160,138 $ 304,905 $ 302,973

Liability for Warranty Returns

Liability for Warranty Returns	6 Months Ended
	Jun. 30, 2016
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	12. LIABILITY FOR WARRANTY RETURNS Our products generally include warranties of 90 days to ten years for product defects. We accrue for warranty returns at the time revenue is recognized based on our estimate of the cost to repair or replace the defective products. We engage in extensive product quality programs and processes, including actively monitoring and evaluating the quality of our component suppliers. Our products continue to become more complex in both size and functionality as many of our product offerings migrate from line card applications to total systems. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage, and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $8.9 million and $8.7 million at June 30, 2016 and December 31, 2015, respectively. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets. A summary of warranty expense and write-off activity for the three and six months ended June 30, 2016 and 2015 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Balance at beginning of period $ 9,042 $ 8,684 $ 8,739 $ 8,415 Plus:Amounts charged to cost and expenses 1,431 667 2,329 1,128 Less:Deductions (1,538 ) (418 ) (2,133 ) (610 ) Balance at end of period $ 8,935 $ 8,933 $ 8,935 $ 8,933

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. COMMITMENTS AND CONTINGENCIES In the ordinary course of business, we may be subject to various legal proceedings and claims, including employment disputes, patent claims, disputes over contract agreements and other commercial disputes. In some cases, claimants seek damages or other relief, such as royalty payments related to patents, which, if granted, could require significant expenditures. Although the outcome of any claim or litigation can never be certain, it is our opinion that the outcome of all contingencies of which we are currently aware will not materially affect our business, operations, financial condition or cash flows. We have committed to invest up to an aggregate of $7.9 million in two private equity funds, and we have contributed $8.4 million as of June 30, 2016, of which $7.7 million has been applied to these commitments.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	14. SUBSEQUENT EVENTS On July 12, 2016, we announced that our Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to stockholders of record at the close of business on July 28, 2016. The payment date will be August 11, 2016. The quarterly dividend payment will be approximately $4.3 million. 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 third quarter and as of August 5, 2016, we have repurchased 0.3 million shares of our common stock through open market purchases at an average cost of $17.99 per share. We currently have the authority to purchase an additional 4.6 million shares of our common stock under the current plan approved by the Board of Directors.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN ® 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, 2015, filed on February 24, 2016 with the SEC.
Use of Estimates	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	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition with early adoption permitted for reporting periods beginning after December 15, 2016. Subsequently, the FASB issued ASUs in 2016 containing implementation guidance related to ASU 2014-09, including: ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , which is intended to improve the operability and understandability of the implementation guidance on principal versus agent considerations; ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which is intended to clarify two aspects of Topic 606: identifying performance obligations and the licensing implementation guidance; and ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which contains certain provisions and practical expedients in response to identified implementation issues. In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory Inventory In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting During the first quarter of 2016, we adopted the following accounting standards, which had no material effect on our financial position, results of operations or 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

Pension Benefit Plan (Tables)

Pension Benefit Plan (Tables)	6 Months Ended
	Jun. 30, 2016
Compensation And Retirement Disclosure [Abstract]
Summarization of Components of Net Periodic Pension Cost	The following table summarizes the components of net periodic pension cost for the three and six months ended June 30, 2016 and 2015: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2016 2015 2016 2015 Service cost $ 310 $ 324 $ 607 $ 664 Interest cost 184 152 360 311 Expected return on plan assets (271 ) (250 ) (530 ) (511 ) Amortization of actuarial losses 45 100 88 205 Net periodic pension cost $ 268 $ 326 $ 525 $ 669

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense Related to Stock Options, Restricted Stock Units (RSUs) and Restricted Stock	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, 2016 and 2015, which was recognized as follows: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2016 2015 2016 2015 Stock-based compensation expense included in cost of sales $ 95 $ 53 $ 194 $ 143 Selling, general and administrative expense 788 723 1,557 1,414 Research and development expense 668 699 1,358 1,557 Stock-based compensation expense included in operating expenses 1,456 1,422 2,915 2,971 Total stock-based compensation expense 1,551 1,475 3,109 3,114 Tax benefit for expense associated with non-qualified options (213 ) (222 ) (425 ) (402 ) Total stock-based compensation expense, net of tax $ 1,338 $ 1,253 $ 2,684 $ 2,712
Summary of Weighted-Average Assumptions and Value of Options Granted	There were no options granted during the three months ended June 30, 2015. The weighted-average assumptions and value of options granted for the three and six months ended June 30, 2016 and the six months ended June 30, 2015 are as follows: Three and Six Months Ended Six Months Ended June 30, June 30, 2016 2015 Expected volatility 34.74 % 38.75 % Risk-free interest rate 1.33 % 1.46 % Expected dividend yield 1.91 % 1.60 % Expected life (in years) 6.26 6.47 Weighted-average estimated value $ 5.42 $ 7.63
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2015 and June 30, 2016 and the changes that occurred during the six months ended June 30, 2016: (In thousands, except per share amounts) Number of Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Options outstanding, December 31, 2015 7,108 $ 21.97 6.42 $ 3,284 Options granted 1 $ 18.83 Options exercised (33 ) $ 16.58 Options forfeited (42 ) $ 17.88 Options expired (54 ) $ 25.65 Options outstanding, June 30, 2016 6,980 $ 22.00 5.93 $ 6,522 Options vested and expected to vest, June 30, 2016 6,865 $ 22.09 5.88 $ 6,260 Options exercisable, June 30, 2016 4,420 $ 24.35 4.44 $ 2,298

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2016
Investments Debt And Equity Securities [Abstract]
Securities and Investments, Recorded at Either Fair Value or Cost	At June 30, 2016, we held the following securities and investments, recorded at either fair value or cost. Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 11,516 $ 1,628 $ (49 ) $ 13,095 Corporate bonds 54,044 149 (61 ) 54,132 Municipal fixed-rate bonds 16,889 59 - 16,948 Asset-backed bonds 23,526 53 (6 ) 23,573 Mortgage/Agency-backed bonds 19,214 44 (39 ) 19,219 U.S. Government bonds 33,498 308 - 33,806 Variable rate demand notes 11,740 - - 11,740 Marketable equity securities 32,948 1,901 (1,478 ) 33,371 Available-for-sale securities held at fair value $ 203,375 $ 4,142 $ (1,633 ) $ 205,884 Restricted investment held at cost 30,000 Other investments held at cost 1,232 Total carrying value of available-for-sale investments $ 237,116 At December 31, 2015, we held the following securities and investments, recorded at either fair value or cost. Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 11,325 $ 1,575 $ (66 ) $ 12,834 Corporate bonds 58,328 20 (734 ) 57,614 Municipal fixed-rate bonds 26,414 28 (18 ) 26,424 Asset-backed bonds 19,281 2 (44 ) 19,239 Mortgage/Agency-backed bonds 15,463 1 (91 ) 15,373 U.S. Government bonds 35,646 - (248 ) 35,398 Marketable equity securities 31,643 4,301 (1,693 ) 34,251 Available-for-sale securities held at fair value $ 198,100 $ 5,927 $ (2,894 ) $ 201,133 Restricted investment held at cost 30,000 Other investments held at cost 1,289 Total carrying value of available-for-sale investments $ 232,422
Contractual Maturities of Corporate,Municipal Fixed-Rate, asset-backed, mortgage/agency-backed and U.S. government bonds Bonds	As of June 30, 2016, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, and U.S. government bonds had the following contractual maturities: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset- backed bonds Mortgage / Agency- backed bonds U.S. Government bonds Less than one year $ 20,729 $ 10,473 $ - $ 4,972 $ 2,953 One to two years 24,884 4,488 822 2,569 7,481 Two to three years 6,099 1,536 9,077 2,058 11,344 Three to five years 2,420 451 10,991 - 12,028 Five to ten years - - 2,506 1,036 - More than ten years - - 177 8,584 - Total $ 54,132 $ 16,948 $ 23,573 $ 19,219 $ 33,806
Gross Realized Gains and Losses on Sale of Securities	The following table presents gross realized gains and losses related to our investments. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Gross realized gains $ 1,517 $ 3,459 $ 3,881 $ 6,604 Gross realized losses $ (407 ) $ (204 ) $ (1,043 ) $ (234 )
Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments	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 for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at June 30, 2016 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,915 $ 1,915 $ - $ - Commercial Paper 15,996 - 15,996 - Cash equivalents 17,911 1,915 15,996 - Available-for-sale securities Deferred compensation plan assets 13,095 13,095 - - Available-for-sale debt securities Corporate bonds 54,132 - 54,132 - Municipal fixed-rate bonds 16,948 - 16,948 - Asset-backed bonds 23,573 - 23,573 - Mortgage/Agency-backed bonds 19,219 - 19,219 - U.S. Government bonds 33,806 33,806 - - Variable rate demand notes 11,740 - 11,740 - Available-for-sale marketable equity securities Marketable equity securities – technology industry 4,386 4,386 - - Marketable equity securities – other 28,985 28,985 - - Available-for-sale securities 205,884 80,272 125,612 - Total $ 223,795 $ 82,187 $ 141,608 $ - Fair Value Measurements at December 31, 2015 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,271 $ 1,271 $ - $ - Commercial Paper 11,696 - 11,696 - Cash equivalents 12,967 1,271 11,696 - Available-for-sale securities Deferred compensation plan assets 12,834 12,834 - - Available-for-sale debt securities Corporate bonds 57,614 - 57,614 - Municipal fixed-rate bonds 26,424 - 26,424 - Asset-backed bonds 19,239 - 19,239 - Mortgage/Agency-backed bonds 15,373 - 15,373 - U.S. Government bonds 35,398 35,398 - - Available-for-sale marketable equity securities Marketable equity securities – technology industry 5,384 5,384 - - Marketable equity securities – other 28,867 28,867 - - Available-for-sale securities 201,133 82,483 118,650 - Total $ 214,100 $ 83,754 $ 130,346 $ -

Derivative Instruments and He25

Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 30, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2016 and December 31, 2015 were as follows: (In thousands) Balance Sheet Location June 30, 2016 December 31, 2015 Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – asset derivatives Other receivables $ 188 $ -
Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income	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, 2016 and 2015 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2016 2015 2016 2015 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ 237 $ (1,299 ) $ 190 $ 177

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2016
Inventory Disclosure [Abstract]
Components of Inventory	At June 30, 2016 and December 31, 2015, inventory consisted of the following: June 30, December 31, (In thousands) 2016 2015 Raw materials $ 35,761 $ 34,223 Work in process 2,322 2,893 Finished goods 48,853 54,417 Total $ 86,936 $ 91,533

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of June 30, 2016 and December 31, 2015: (In thousands) June 30, 2016 December 31, 2015 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 5,925 $ (2,966 ) $ 2,959 $ 5,828 $ (2,627 ) $ 3,201 Developed technology 5,778 (4,767 ) 1,011 5,720 (4,329 ) 1,391 Intellectual property 2,340 (2,021 ) 319 2,340 (1,854 ) 486 Trade names 270 (270 ) - 270 (265 ) 5 Total $ 14,313 $ (10,024 ) $ 4,289 $ 14,158 $ (9,075 ) $ 5,083
Estimated Future Amortization Expense Related to Intangible Assets	As of June 30, 2016, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2016 $ 807 2017 1,162 2018 702 2019 308 2020 285 Thereafter 1,025 Total $ 4,289

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2016
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the six months ended June 30, 2016 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2015 $ 480,160 Net income 15,242 Dividend payments (8,860 ) Dividends accrued for unvested restricted stock units (26 ) Net unrealized losses on available-for-sale securities (net of tax) (420 ) Defined benefit plan adjustments 67 Foreign currency translation adjustment 627 Proceeds from stock option exercises 541 Purchase of treasury stock (16,579 ) Income tax effect of stock compensation arrangements (137 ) Stock-based compensation expense 3,109 Balance, June 30, 2016 $ 473,724
Cash Dividends	During the six months ended June 30, 2016, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid February 4, 2016 February 18, 2016 $ 0.09 $ 4,453 April 28, 2016 May 12, 2016 $ 0.09 $ 4,407
Changes in Accumulated Other Comprehensive Income, Net of Tax by Component	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2016 and 2015: Three Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,677 $ (3,850 ) $ (5,778 ) $ (7,951 ) Other comprehensive income (loss) before reclassifications 481 - (601 ) (120 ) Amounts reclassified from accumulated other comprehensive income (646 ) 22 - (624 ) Net current period other comprehensive income (loss) (165 ) 22 (601 ) (744 ) Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) Three Months Ended June 30, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 8,461 $ (5,689 ) $ (6,600 ) $ (3,828 ) Other comprehensive income (loss) before reclassifications 177 - 872 1,049 Amounts reclassified from accumulated other comprehensive income (1,960 ) 72 - (1,888 ) Net current period other comprehensive income (loss) (1,783 ) 72 872 (839 ) Ending balance $ 6,678 $ (5,617 ) $ (5,728 ) $ (4,667 ) The following tables present changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2016 and 2015: Six Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 1,239 - 627 1,866 Amounts reclassified from accumulated other comprehensive income (1,659 ) 67 - (1,592 ) Net current period other comprehensive income (loss) (420 ) 67 627 274 Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) Six Months Ended June 30, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 8,964 $ (5,757 ) $ (3,282 ) $ (75 ) Other comprehensive income (loss) before reclassifications 1,537 - (2,446 ) (909 ) Amounts reclassified from accumulated other comprehensive income (3,823 ) 140 - (3,683 ) Net current period other comprehensive income (loss) (2,286 ) 140 (2,446 ) (4,592 ) Ending balance $ 6,678 $ (5,617 ) $ (5,728 ) $ (4,667 )
Reclassifications Out of Accumulated Other Comprehensive Income	The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2016 and 2015: (In thousands) Three Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,354 Net realized investment gain Impairment expense (295 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (33 ) (1) Total reclassifications for the period, before tax 1,026 Tax (expense) benefit (402 ) Total reclassifications for the period, net of tax $ 624 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 30, 2015 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,264 Net realized investment gain Impairment expense (51 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (105 ) (1) Total reclassifications for the period, before tax 3,108 Tax (expense) benefit (1,220 ) Total reclassifications for the period, net of tax $ 1,888 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2016 and 2015: (In thousands) Six Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,115 Net realized investment gain Impairment expense (395 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,622 Tax (expense) benefit (1,030 ) Total reclassifications for the period, net of tax $ 1,592 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 30, 2015 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 6,340 Net realized investment gain Impairment expense (73 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (203 ) (1) Total reclassifications for the period, before tax 6,064 Tax (expense) benefit (2,381 ) Total reclassifications for the period, net of tax $ 3,683 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements.
Other Comprehensive Income	The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2016 and 2015: Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 789 $ (308 ) $ 481 $ 290 $ (113 ) $ 177 Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,059 ) 413 (646 ) (3,213 ) 1,253 (1,960 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 33 (11 ) 22 105 (33 ) 72 Foreign currency translation adjustment (601 ) - (601 ) 872 - 872 Total Other Comprehensive Income (Loss) $ (838 ) $ 94 $ (744 ) $ (1,946 ) $ 1,107 $ (839 ) The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2016 and 2015: Six Months Ended June 30, 2016 Six Months Ended June 30, 2015 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 2,031 $ (792 ) $ 1,239 $ 2,520 $ (983 ) $ 1,537 Reclassification adjustment for amounts related to available-for-sale investments included in net income (2,720 ) 1,061 (1,659 ) (6,267 ) 2,444 (3,823 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 98 (31 ) 67 203 (63 ) 140 Foreign currency translation adjustment 627 - 627 (2,446 ) - (2,446 ) Total Other Comprehensive Income (Loss) $ 36 $ 238 $ 274 $ (5,990 ) $ 1,398 $ (4,592 )

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings Per Share	A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2016 and 2015 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2016 2015 2016 2015 Numerator Net income $ 10,228 $ 2,544 $ 15,242 $ 5,861 Denominator Weighted average number of shares – basic 48,831 51,822 49,026 52,607 Effect of dilutive securities Stock options 161 72 138 122 Restricted stock and restricted stock units 56 23 54 13 Weighted average number of shares – diluted 49,048 51,917 49,218 52,742 Net income per share – basic $ 0.21 $ 0.05 $ 0.31 $ 0.11 Net income per share – diluted $ 0.21 $ 0.05 $ 0.31 $ 0.11

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Sales and Gross Profit of Reportable Segments	The following table presents information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2016 and 2015. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2016 June 30, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 138,549 $ 70,705 $ 144,098 $ 59,888 Services & Support 24,152 8,250 16,040 8,358 Total $ 162,701 $ 78,955 $ 160,138 $ 68,246 Six Months Ended June 30, 2016 June 30, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 262,432 $ 130,515 $ 273,603 $ 117,833 Services & Support 42,473 14,234 29,370 15,976 Total $ 304,905 $ 144,749 $ 302,973 $ 133,809
Sales Information by Category	The table below presents sales information by category for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Access & Aggregation $ 102,232 $ 112,732 $ 196,087 $ 205,583 Customer Devices 40,876 30,042 73,229 61,746 Traditional & Other Products 19,593 17,364 35,589 35,644 Total $ 162,701 $ 160,138 $ 304,905 $ 302,973

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	6 Months Ended
	Jun. 30, 2016
Product Warranties Disclosures [Abstract]
Summary of Warranty Expense and Write-Off Activity	A summary of warranty expense and write-off activity for the three and six months ended June 30, 2016 and 2015 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Balance at beginning of period $ 9,042 $ 8,684 $ 8,739 $ 8,415 Plus:Amounts charged to cost and expenses 1,431 667 2,329 1,128 Less:Deductions (1,538 ) (418 ) (2,133 ) (610 ) Balance at end of period $ 8,935 $ 8,933 $ 8,935 $ 8,933

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Effective tax rate	37.90%	39.10%

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 310	$ 324	$ 607	$ 664
Interest cost	184	152	360	311
Expected return on plan assets	(271)	(250)	(530)	(511)
Amortization of actuarial losses	45	100	88	205
Net periodic pension cost	$ 268	$ 326	$ 525	$ 669

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, Restricted Stock Units (RSUs) and Restricted Stock (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,551	$ 1,475	$ 3,109	$ 3,114
Tax benefit for expense associated with non-qualified options	(213)	(222)	(425)	(402)
Total stock-based compensation expense, net of tax	1,338	1,253	2,684	2,712
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	95	53	194	143
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	788	723	1,557	1,414
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	668	699	1,358	1,557
Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,456	$ 1,422	$ 2,915	$ 2,971

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, granted		0	1,000
Estimated forfeitures for stock options			3.70%
Total pre-tax intrinsic value of options exercised	$ 0.1		$ 0.1
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs and restricted stock grants in period	0	0	0	0
Number of RSUs and restricted stock vesting in period	0	0	0	0
Number of RSUs and restricted stock forfeitures in period				12,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs and restricted stock grants in period			2,000
Number of RSUs and restricted stock vesting in period		2,000		2,000
Recognition period of non-vested compensation cost			2 years 4 months 24 days
RSUs and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate for RSUs and restricted stock			0.00%
Compensation cost related to non-vested stock options not yet recognized	$ 11.5		$ 11.5

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) - Stock Options [Member] - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	34.74%	34.74%	38.75%
Risk-free interest rate	1.33%	1.33%	1.46%
Expected dividend yield	1.91%	1.91%	1.60%
Expected life (in years)	6 years 3 months 4 days	6 years 3 months 4 days	6 years 5 months 19 days
Weighted-average estimated value	$ 5.42	$ 5.42	$ 7.63

Stock-Based Compensation - Su37

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, outstanding, Beginning Balance		7,108
Number of Options, granted	0	1
Number of Options, exercised		(33)
Number of Options, forfeited		(42)
Number of Options, expired		(54)
Number of Options, outstanding, Ending Balance		6,980	7,108
Number of Options, vested and expected to vest, Ending Balance		6,865
Number of Options, Options exercisable		4,420
Weighted Average Exercise Price, outstanding, Beginning Balance		$ 21.97
Weighted Average Exercise Price, granted		18.83
Weighted Average Exercise Price, exercised		16.58
Weighted Average Exercise Price, forfeited		17.88
Weighted Average Exercise Price, expired		25.65
Weighted Average Exercise Price, outstanding, Ending Balance		22	$ 21.97
Weighted Average Exercise Price, vested and expected to vest, Ending Balance		22.09
Weighted Average Exercise Price, Options exercisable		$ 24.35
Weighted Average Remaining Contractual Life In Years, Options outstanding		5 years 11 months 5 days	6 years 5 months 1 day
Weighted Average Remaining Contractual Life In Years, Options vested and expected to vest		5 years 10 months 17 days
Weighted Average Remaining Contractual Life In Years, Options exercisable		4 years 5 months 9 days
Aggregate Intrinsic Value, Options outstanding, Beginning Balance		$ 3,284
Aggregate Intrinsic Value, Options outstanding, Ending Balance		6,522	$ 3,284
Aggregate Intrinsic Value, Options vested and expected to vest		6,260
Aggregate Intrinsic Value, Options exercisable		$ 2,298

Investments - Securities and In

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 203,375	$ 198,100
Gross Unrealized Gains	4,142	5,927
Gross Unrealized Losses	(1,633)	(2,894)
Available-for-sale-securities, Carrying Value	205,884	201,133
Restricted investment held at cost	30,000	30,000
Other investments held at cost	1,232	1,289
Total carrying value of available-for-sale investments	237,116	232,422
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,516	11,325
Gross Unrealized Gains	1,628	1,575
Gross Unrealized Losses	(49)	(66)
Available-for-sale-securities, Carrying Value	13,095	12,834
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54,044	58,328
Gross Unrealized Gains	149	20
Gross Unrealized Losses	(61)	(734)
Available-for-sale-securities, Carrying Value	54,132	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,889	26,414
Gross Unrealized Gains	59	28
Gross Unrealized Losses		(18)
Available-for-sale-securities, Carrying Value	16,948	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,526	19,281
Gross Unrealized Gains	53	2
Gross Unrealized Losses	(6)	(44)
Available-for-sale-securities, Carrying Value	23,573	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,214	15,463
Gross Unrealized Gains	44	1
Gross Unrealized Losses	(39)	(91)
Available-for-sale-securities, Carrying Value	19,219	15,373
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,498	35,646
Gross Unrealized Gains	308
Gross Unrealized Losses		(248)
Available-for-sale-securities, Carrying Value	33,806	35,398
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,740
Available-for-sale-securities, Carrying Value	11,740
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,948	31,643
Gross Unrealized Gains	1,901	4,301
Gross Unrealized Losses	(1,478)	(1,693)
Available-for-sale-securities, Carrying Value	$ 33,371	$ 34,251

Investments - Contractual Matur

Investments - Contractual Maturities of Corporate Bonds, Municipal Fixed-Rate Bonds, Asset-Backed Bonds, Mortgage/Agency-Backed Bonds and U.S. Government Bonds (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale-securities, Fair Value/Carrying Value	$ 205,884	$ 201,133
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	20,729
One to two years	24,884
Two to three years	6,099
Three to five years	2,420
Available-for-sale-securities, Fair Value/Carrying Value	54,132	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	10,473
One to two years	4,488
Two to three years	1,536
Three to five years	451
Available-for-sale-securities, Fair Value/Carrying Value	16,948	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	822
Two to three years	9,077
Three to five years	10,991
Five to ten years	2,506
More than ten years	177
Available-for-sale-securities, Fair Value/Carrying Value	23,573	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	4,972
One to two years	2,569
Two to three years	2,058
Five to ten years	1,036
More than ten years	8,584
Available-for-sale-securities, Fair Value/Carrying Value	19,219	15,373
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,953
One to two years	7,481
Two to three years	11,344
Three to five years	12,028
Available-for-sale-securities, Fair Value/Carrying Value	$ 33,806	$ 35,398

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Restricted certificate of deposit held	$ 30,000	$ 30,000
Identification of potential other-than-temporary impairments	25.00%
Alabama State Industrial Development Authority [Member]
Schedule of Investments [Line Items]
Maturity date of bond	Jan. 1, 2020
Percentage of interest on bond	2.00%
Alabama State Industrial Development Authority [Member] | Taxable Revenue Bond [Member]
Schedule of Investments [Line Items]
Collateral deposit against outstanding principal amount	$ 28,900	$ 28,900
Alabama State Industrial Development Authority [Member] | Taxable Revenue Bond [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Investments [Line Items]
Estimated fair value of bond	$ 29,400
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member]
Schedule of Investments [Line Items]
Investment concentration risk percentage	5.00%

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Investments Debt And Equity Securities [Abstract]
Gross realized gains	$ 1,517	$ 3,459	$ 3,881	$ 6,604
Gross realized losses	$ (407)	$ (204)	$ (1,043)	$ (234)

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 205,884	$ 201,133
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,095	12,834
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	54,132	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,948	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	23,573	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	19,219	15,373
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	33,806	35,398
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	11,740
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	17,911	12,967
Available-for-sale securities	205,884	201,133
Total	223,795	214,100
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,915	1,271
Available-for-sale securities	80,272	82,483
Total	82,187	83,754
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	15,996	11,696
Available-for-sale securities	125,612	118,650
Total	141,608	130,346
Fair Value, Measurements [Member] | Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,915	1,271
Fair Value, Measurements [Member] | Money Market Funds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,915	1,271
Fair Value, Measurements [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	15,996	11,696
Fair Value, Measurements [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	15,996	11,696
Fair Value, Measurements [Member] | Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,095	12,834
Fair Value, Measurements [Member] | Deferred Compensation Plan Assets [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,095	12,834
Fair Value, Measurements [Member] | Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	54,132	57,614
Fair Value, Measurements [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	54,132	57,614
Fair Value, Measurements [Member] | Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,948	26,424
Fair Value, Measurements [Member] | Municipal Fixed-Rate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,948	26,424
Fair Value, Measurements [Member] | Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	23,573	19,239
Fair Value, Measurements [Member] | Asset-Backed Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	23,573	19,239
Fair Value, Measurements [Member] | Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	19,219	15,373
Fair Value, Measurements [Member] | Mortgage/Agency-Backed Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	19,219	15,373
Fair Value, Measurements [Member] | U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	33,806	35,398
Fair Value, Measurements [Member] | U.S. Government Bonds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	33,806	35,398
Fair Value, Measurements [Member] | Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	11,740
Fair Value, Measurements [Member] | Variable Rate Demand Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	11,740
Fair Value, Measurements [Member] | Marketable Equity Securities - Technology Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,386	5,384
Fair Value, Measurements [Member] | Marketable Equity Securities - Technology Industry [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,386	5,384
Fair Value, Measurements [Member] | Marketable Equity Securities - Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	28,985	28,867
Fair Value, Measurements [Member] | Marketable Equity Securities - Other [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 28,985	$ 28,867

Derivative Instruments and He43

Derivative Instruments and Hedging Activities - Additional Information (Detail) - 6 months ended Jun. 30, 2016	USD ($)	EUR (€)
Derivative [Line Items]
Maximum contractual period for derivatives	12 months
Forward Contracts [Member]
Derivative [Line Items]
Derivative, notional amount	$ 6,700,000	€ 6,000,000
Derivative maturity year	2,016

Derivative Instruments and He44

Derivative Instruments and Hedging Activities - Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) $ in Thousands	Jun. 30, 2016USD ($)
Significant Other Observable Inputs (Level 2) [Member] | Foreign Exchange Contracts [Member] | Other Receivables [Member]
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives asset, fair value	$ 188

Derivative Instruments and He45

Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ 237	$ (1,299)	$ 190	$ 177

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 35,761	$ 34,223
Work in process	2,322	2,893
Finished goods	48,853	54,417
Total	$ 86,936	$ 91,533

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 18	$ 17.5
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 9.8	$ 9.2

Goodwill and Intangible Asset48

Goodwill and Intangible Assets - Additional Information (Detail)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2016USD ($)	Mar. 31, 2016Segment	Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)Segment	Jun. 30, 2015USD ($)	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Goodwill, relates to acquisition				$ 3,500,000		$ 3,500,000
Number of reportable segments | Segment		2		2
Impairment losses				$ 0
Amortization expense	$ 400,000		$ 500,000	900,000	$ 1,000,000
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition				3,100,000
Services & Support [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition				$ 400,000

Goodwill and Intangible Asset49

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Goodwill [Line Items]
Gross Value	$ 14,313	$ 14,158
Accumulated Amortization	(10,024)	(9,075)
Net Value	4,289	5,083
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	5,925	5,828
Accumulated Amortization	(2,966)	(2,627)
Net Value	2,959	3,201
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	5,778	5,720
Accumulated Amortization	(4,767)	(4,329)
Net Value	1,011	1,391
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	2,340	2,340
Accumulated Amortization	(2,021)	(1,854)
Net Value	319	486
Trade Names [Member]
Goodwill [Line Items]
Gross Value	270	270
Accumulated Amortization	$ (270)	(265)
Net Value		$ 5

Goodwill and Intangible Asset50

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Remainder of 2016	$ 807
2,017	1,162
2,018	702
2,019	308
2,020	285
Thereafter	1,025
Net Value	$ 4,289	$ 5,083

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Beginning Balance			$ 480,160
Net income	$ 10,228	$ 2,544	15,242	$ 5,861
Dividend payments			(8,860)
Dividends accrued for unvested restricted stock units			(26)
Net unrealized losses on available-for-sale securities (net of tax)	(165)	(1,783)	(420)	(2,286)
Defined benefit plan adjustments			67
Foreign currency translation adjustment	(601)	$ 872	627	(2,446)
Proceeds from stock option exercises			541	$ 833
Purchase of treasury stock			(16,579)
Income tax effect of stock compensation arrangements			(137)
Stock-based compensation expense			3,109
Ending Balance	$ 473,724		$ 473,724

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	50,000,000
Stock repurchased, shares	900,000
Shares repurchased, average price per share	$ 18.48
Additional shares authorized for purchase	4,900,000
Number of Options, exercised	33,000
Exercise price of stock options, lower range limit	$ 15.29
Exercise price of stock options, upper range limit	$ 18.97
Proceeds from stock option exercises	$ 541	$ 833

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Dividends Payable [Line Items]
Record Date			Jul. 28, 2016
Payment Date			Aug. 11, 2016
Per Share Amount	$ 0.09	$ 0.09	$ 0.18	$ 0.18
Total Dividend Paid			$ 8,860	$ 9,509
Cash Dividends Paid in February [Member]
Dividends Payable [Line Items]
Record Date			Feb. 4, 2016
Payment Date			Feb. 18, 2016
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,453
Cash Dividends Paid in May [Member]
Dividends Payable [Line Items]
Record Date			Apr. 28, 2016
Payment Date			May 12, 2016
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,407

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (7,951)	$ (3,828)	$ (8,969)	$ (75)
Other comprehensive income (loss) before reclassifications	(120)	1,049	1,866	(909)
Amounts reclassified from accumulated other comprehensive income	(624)	(1,888)	(1,592)	(3,683)
Other Comprehensive Income (Loss), net of tax	(744)	(839)	274	(4,592)
Ending balance	(8,695)	(4,667)	(8,695)	(4,667)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,677	8,461	1,932	8,964
Other comprehensive income (loss) before reclassifications	481	177	1,239	1,537
Amounts reclassified from accumulated other comprehensive income	(646)	(1,960)	(1,659)	(3,823)
Other Comprehensive Income (Loss), net of tax	(165)	(1,783)	(420)	(2,286)
Ending balance	1,512	6,678	1,512	6,678
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(3,850)	(5,689)	(3,895)	(5,757)
Amounts reclassified from accumulated other comprehensive income	22	72	67	140
Other Comprehensive Income (Loss), net of tax	22	72	67	140
Ending balance	(3,828)	(5,617)	(3,828)	(5,617)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,778)	(6,600)	(7,006)	(3,282)
Other comprehensive income (loss) before reclassifications	(601)	872	627	(2,446)
Other Comprehensive Income (Loss), net of tax	(601)	872	627	(2,446)
Ending balance	$ (6,379)	$ (5,728)	$ (6,379)	$ (5,728)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Income before provision for income taxes	$ 16,456	$ 4,111	$ 24,534	$ 9,621
Tax (expense) benefit	(6,228)	(1,567)	(9,292)	(3,760)
Total reclassifications for the period, net of tax	10,228	2,544	15,242	5,861
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit plan adjustments – actuarial losses	(33)	(105)	(98)	(203)
Income before provision for income taxes	1,026	3,108	2,622	6,064
Tax (expense) benefit	(402)	(1,220)	(1,030)	(2,381)
Total reclassifications for the period, net of tax	624	1,888	1,592	3,683
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gain	1,354	3,264	3,115	6,340
Impairment Expense [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gain	$ (295)	$ (51)	$ (395)	$ (73)

Stockholders' Equity - Other Co

Stockholders' Equity - Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 789	$ 290	$ 2,031	$ 2,520
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	(1,059)	(3,213)	(2,720)	(6,267)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	33	105	98	203
Foreign currency translation adjustment, Before-Tax Amount	(601)	872	627	(2,446)
Total Other Comprehensive Income (Loss), Before-Tax Amount	(838)	(1,946)	36	(5,990)
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(308)	(113)	(792)	(983)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	413	1,253	1,061	2,444
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(11)	(33)	(31)	(63)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	94	1,107	238	1,398
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	481	177	1,239	1,537
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	(646)	(1,960)	(1,659)	(3,823)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	22	72	67	140
Foreign currency translation adjustment, Net-of-Tax Amount	(601)	872	627	(2,446)
Other Comprehensive Income (Loss), net of tax	$ (744)	$ (839)	$ 274	$ (4,592)

Earnings Per Share - Summary of

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator
Net income	$ 10,228	$ 2,544	$ 15,242	$ 5,861
Denominator
Weighted average number of shares – basic	48,831	51,822	49,026	52,607
Effect of dilutive securities
Stock options	161	72	138	122
Restricted stock and restricted stock units	56	23	54	13
Weighted average number of shares – diluted	49,048	51,917	49,218	52,742
Net income per share – basic	$ 0.21	$ 0.05	$ 0.31	$ 0.11
Net income per share – diluted	$ 0.21	$ 0.05	$ 0.31	$ 0.11

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Anti-dilutive options, Total	5.6	6.1	5.8	5.7

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Mar. 31, 2016Segment	Jun. 30, 2016SegmentCategory
Segment Reporting [Abstract]
Number of reportable segments | Segment	2	2
Number of categories | Category		3

Segment Information - Sales and

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Sales	$ 162,701	$ 160,138	$ 304,905	$ 302,973
Gross Profit	78,955	68,246	144,749	133,809
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	138,549	144,098	262,432	273,603
Gross Profit	70,705	59,888	130,515	117,833
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	24,152	16,040	42,473	29,370
Gross Profit	$ 8,250	$ 8,358	$ 14,234	$ 15,976

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue from External Customer [Line Items]
Sales	$ 162,701	$ 160,138	$ 304,905	$ 302,973
Access & Aggregation [Member]
Revenue from External Customer [Line Items]
Sales	102,232	112,732	196,087	205,583
Customer Devices [Member]
Revenue from External Customer [Line Items]
Sales	40,876	30,042	73,229	61,746
Traditional & Other Products [Member]
Revenue from External Customer [Line Items]
Sales	$ 19,593	$ 17,364	$ 35,589	$ 35,644

Liability for Warranty Return62

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Product Warranties Disclosures [Abstract]
Period of warranty for product defects	90 days to ten years
Liability for warranty obligations	$ 8,935	$ 9,042	$ 8,739	$ 8,933	$ 8,684	$ 8,415

Liability for Warranty Return63

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 9,042	$ 8,684	$ 8,739	$ 8,415
Plus:Amounts charged to cost and expenses	1,431	667	2,329	1,128
Less:Deductions	(1,538)	(418)	(2,133)	(610)
Balance at end of period	$ 8,935	$ 8,933	$ 8,935	$ 8,933

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Jun. 30, 2016USD ($)EquityUnit
Contingencies And Commitments [Line Items]
Number of private equity funds | EquityUnit	2
Commitments towards private equity funds	$ 7.7
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds	7.9
Private Equity Funds [Member]
Contingencies And Commitments [Line Items]
Contribution to private equity funds	$ 8.4

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Aug. 05, 2016	Jul. 12, 2016	Jun. 30, 2016	Aug. 11, 2016
Subsequent Event [Line Items]
Dividend declaration date			Jul. 12, 2016
Dividend record date			Jul. 28, 2016
Dividend payment date			Aug. 11, 2016
Stock repurchased, shares			900,000
Shares repurchased, average price per share			$ 18.48
Additional shares authorized for purchase			4,900,000
Subsequent Events [Member]
Subsequent Event [Line Items]
Common stock dividends per share declared		$ 0.09
Quarterly dividend payable subsequent to balance sheet date				$ 4.3
Stock repurchased, shares	300,000
Shares repurchased, average price per share	$ 17.99
Additional shares authorized for purchase	4,600,000