ADTRAN (ADTN) 10-Q 4 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 22, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
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		48,971,260

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 91,609	$ 84,550
Short-term investments	29,303	34,396
Accounts receivable, less allowance for doubtful accounts of $19 at March 31, 2016 and December 31, 2015	67,492	71,917
Other receivables	9,199	19,321
Inventory, net	92,107	91,533
Prepaid expenses and other current assets	13,096	10,145
Deferred tax assets, net	17,967	18,924
Total Current Assets	320,773	330,786
Property, plant and equipment, net	73,511	73,233
Deferred tax assets, net	18,878	18,091
Goodwill	3,492	3,492
Other assets	9,157	9,276
Long-term investments	195,683	198,026
Total Assets	621,494	632,904
Current Liabilities
Accounts payable	42,635	48,668
Unearned revenue	18,683	16,615
Accrued expenses	13,513	12,108
Accrued wages and benefits	11,064	12,857
Income tax payable, net	2,739	2,395
Total Current Liabilities	88,634	92,643
Non-current unearned revenue	7,288	7,965
Other non-current liabilities	25,283	24,236
Bonds payable	27,900	27,900
Total Liabilities	$ 149,105	$ 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 48,993 shares outstanding at March 31, 2016 and 79,652 shares issued and 49,558 shares outstanding at December 31, 2015	$ 797	$ 797
Additional paid-in capital	248,305	246,879
Accumulated other comprehensive loss	(7,951)	(8,969)
Retained earnings	906,820	906,772
Less treasury stock at cost: 30,659 and 30,094 shares at March 31, 2016 and December 31, 2015, respectively	(675,582)	(665,319)
Total Stockholders' Equity	472,389	480,160
Total Liabilities and Stockholders' Equity	$ 621,494	$ 632,904

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 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	48,993,000	49,558,000
Treasury stock, shares	30,659,000	30,094,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Sales
Products	$ 123,883	$ 129,505
Services	18,321	13,330
Total Sales	142,204	142,835
Cost of sales
Products	64,073	71,560
Services	12,337	5,712
Total Cost of Sales	76,410	77,272
Gross Profit	65,794	65,563
Selling, general and administrative expenses	30,785	31,064
Research and development expenses	29,488	32,536
Operating Income	5,521	1,963
Interest and dividend income	855	933
Interest expense	(145)	(148)
Net realized investment gain	1,728	3,115
Other income (expense), net	119	(353)
Income before provision for income taxes	8,078	5,510
Provision for income taxes	(3,064)	(2,193)
Net Income	$ 5,014	$ 3,317
Weighted average shares outstanding - basic	49,220	53,399
Weighted average shares outstanding - diluted	49,389	53,634
Earnings per common share - basic	$ 0.10	$ 0.06
Earnings per common share - diluted	0.10	0.06
Dividend per share	$ 0.09	$ 0.09

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 5,014	$ 3,317
Other Comprehensive Income (Loss), net of tax:
Net unrealized losses on available-for-sale securities	(255)	(503)
Defined benefit plan adjustments	45	68
Foreign currency translation	1,228	(3,318)
Other Comprehensive Income (Loss), net of tax	1,018	(3,753)
Comprehensive Income (Loss), net of tax	$ 6,032	$ (436)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 5,014	$ 3,317
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,347	3,728
Amortization of net premium on available-for-sale investments	220	910
Net realized gain on long-term investments	(1,728)	(3,115)
Net loss on disposal of property, plant and equipment	3	8
Stock-based compensation expense	1,558	1,639
Deferred income taxes	435	(692)
Tax benefit from stock option exercises		8
Excess tax benefits from stock-based compensation arrangements		(9)
Changes in operating assets and liabilities:
Accounts receivable, net	4,752	(4,571)
Other receivables	10,200	511
Inventory	163	(7,784)
Prepaid expenses and other assets	(3,083)	(213)
Accounts payable	(6,520)	20,084
Accrued expenses and other liabilities	902	(282)
Income tax payable, net	413	(524)
Net cash provided by operating activities	15,676	13,015
Cash flows from investing activities:
Purchases of property, plant and equipment	(3,166)	(2,442)
Proceeds from sales and maturities of available-for-sale investments	60,586	58,075
Purchases of available-for-sale investments	(52,053)	(44,584)
Net cash provided by investing activities	5,367	11,049
Cash flows from financing activities:
Proceeds from stock option exercises	247	280
Purchases of treasury stock	(11,003)	(3,035)
Dividend payments	(4,453)	(4,811)
Excess tax benefits from stock-based compensation arrangements		9
Net cash used in financing activities	(15,209)	(7,557)
Net increase in cash and cash equivalents	5,834	16,507
Effect of exchange rate changes	1,225	(2,937)
Cash and cash equivalents, beginning of period	84,550	73,439
Cash and cash equivalents, end of period	91,609	87,009
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 485	$ 784

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 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. Out of Period Adjustment In connection with the preparation of our Condensed Consolidated Financial Statements, we recorded corrections of certain out of period, immaterial misstatements that occurred in prior periods, the most significant of which resulted in an increase in Other Expense of $1.3 million in the first quarter of 2015. The aggregate impact of the corrections was a $0.8 million reduction to pre-tax income for the three months ended March 31, 2015 and was not material to the prior year quarterly or annual results. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers Revenue Recognition 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	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	2. INCOME TAXES Our effective tax rate decreased from 39.8% in the three months ended March 31, 2015 to 37.9% in the three months ended March 31, 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	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015: Three Months Ended March 31, (In thousands) 2016 2015 Service cost $ 297 $ 340 Interest cost 176 159 Expected return on plan assets (259 ) (261 ) Amortization of actuarial losses 43 105 Net periodic pension cost $ 257 $ 343

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based 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 months ended March 31, 2016 and 2015, which was recognized as follows: Three Months Ended (In thousands) 2016 2015 Stock-based compensation expense included in cost of sales $ 99 $ 90 Selling, general and administrative expense 769 691 Research and development expense 690 858 Stock-based compensation expense included in operating expenses 1,459 1,549 Total stock-based compensation expense 1,558 1,639 Tax benefit for expense associated with non-qualified options (212 ) (180 ) Total stock-based compensation expense, net of tax $ 1,346 $ 1,459 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 March 31, 2016. The weighted-average assumptions and value of options granted during the three months ended March 31, 2015 were as follows: Three Months Ended March 31, 2015 Expected volatility 38.75 % Risk-free interest rate 1.46 % Expected dividend yield 1.60 % Expected life (in years) 6.47 Weighted-average estimated value $ 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 months ended March 31, 2016 and 2015. Twelve thousand RSUs were forfeited during the three months ended March 31, 2015. The fair value of restricted stock is equal to the closing price of our stock on the date of grant. No restricted stock vested or was forfeited during the three months ended March 31, 2016 and 2015. Two thousand shares of restricted stock were granted during the three months ended March 31, 2016. Stock-based compensation expense recognized in our Consolidated Statements of Income for the three months ended March 31, 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 March 31, 2016, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $13.2 million, which is expected to be recognized over an average remaining recognition period of 2.53 years. The following table is a summary of our stock options outstanding as of December 31, 2015 and March 31, 2016 and the changes that occurred during the three months ended March 31, 2016: (In thousands, except per share amounts) Number of Weighted Avg. Weighted Avg. Aggregate Options outstanding, December 31, 2015 7,108 $ 21.97 6.42 $ 3,284 Options granted — $ — Options exercised (15 ) $ 16.65 Options forfeited (23 ) $ 17.84 Options expired (26 ) $ 24.40 Options outstanding, March 31, 2016 7,044 $ 22.00 6.18 $ 11,580 Options vested and expected to vest, March 31, 2016 6,910 $ 22.10 6.12 $ 11,095 Options exercisable, March 31, 2016 4,466 $ 24.33 4.69 $ 4,191 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 March 31, 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 months ended March 31, 2016 was $36 thousand.

Investments

Investments	3 Months Ended
	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Investments	5. INVESTMENTS At March 31, 2016, we held the following securities and investments, recorded at either fair value or cost. (In thousands) Amortized Gross Unrealized Carrying Gains Losses Deferred compensation plan assets $ 11,440 $ 1,634 $ (70 ) $ 13,004 Corporate bonds 61,154 89 (386 ) 60,857 Municipal fixed-rate bonds 15,659 54 (1 ) 15,712 Asset-backed bonds 20,540 28 (8 ) 20,560 Mortgage/Agency-backed bonds 14,959 19 (82 ) 14,896 Government bonds 33,205 216 (2 ) 33,419 Variable Rate Demand Notes 2,235 — — 2,235 Marketable equity securities 31,798 2,886 (1,647 ) 33,037 Available-for-sale securities held at fair value $ 190,990 $ 4,926 $ (2,196 ) $ 193,720 Restricted investment held at cost 30,000 Other investments held at cost 1,266 Total carrying value of available-for-sale investments $ 224,986 At December 31, 2015, we held the following securities and investments, recorded at either fair value or cost. (In thousands) Amortized Gross Unrealized Carrying Gains Losses 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 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 March 31, 2016, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, and government bonds had the following contractual maturities: (In thousands) Corporate Municipal Asset- Mortgage / Government Less than one year $ 17,668 $ 7,147 $ — $ 1,000 $ 1,253 One to two years 29,883 5,566 190 1,300 4,751 Two to three years 12,490 1,373 8,158 1,774 17,992 Three to five years 816 226 9,496 — 9,423 Five to ten years — — 2,540 1,180 — More than ten years — 1,400 176 9,642 — Total $ 60,857 $ 15,712 $ 20,560 $ 14,896 $ 33,419 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 March 31, 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). At March 31, 2016, the estimated fair value of the Bond using a level 2 valuation technique was approximately $29.1 million, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of AAA. For more information on the Bond, see “Debt” under “Liquidity and Capital Resources” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in Item 2 of Part I of this report. We review our investment portfolio for potential “other-than-temporary” declines in value on an individual investment basis. We assess, on a quarterly basis, significant declines in value which may be considered other-than-temporary and, if necessary, recognize and record the appropriate charge to write-down the carrying value of such investments. In making this assessment, we take into consideration qualitative and quantitative information, including but not limited to the following: the magnitude and duration of historical declines in market prices, credit rating activity, assessments of liquidity, public filings, and statements made by the issuer. We generally begin our identification of potential other-than-temporary impairments by reviewing any security with a fair value that has declined from its original or adjusted cost basis by 25% or more for six or more consecutive months. We then evaluate the individual security based on the previously identified factors to determine the amount of the write-down, if any. For the three months ended March 31, 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 March 31, (In thousands) 2016 2015 Gross realized gains $ 2,364 $ 3,145 Gross realized losses $ (636 ) $ (30 ) As of March 31, 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 March 31, 2016 Using (In thousands) Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) Cash equivalents Money market funds $ 2,110 $ 2,110 $ — $ — Commercial Paper 26,442 — 26,442 — Cash equivalents 28,552 2,110 26,442 — Available-for-sale securities Deferred compensation plan assets 13,004 13,004 — — Available-for-sale debt securities Corporate bonds 60,857 — 60,857 — Municipal fixed-rate bonds 15,712 — 15,712 — Asset-backed bonds 20,560 — 20,560 — Mortgage/Agency-backed bonds 14,896 — 14,896 — Government bonds 33,419 33,419 — — Variable Rate Demand Notes 2,235 — 2,235 — Available-for-sale marketable equity securities Marketable equity securities – technology industry 4,709 4,709 — — Marketable equity securities – other 28,328 28,328 — — Available-for-sale securities 193,720 79,460 114,260 — Total $ 222,272 $ 81,570 $ 140,702 $ — Fair Value Measurements at December 31, 2015 Using (In thousands) Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (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 — 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 municipal variable rate demand notes have a structure that implies a standard expected market price. The frequent interest rate resets make it reasonable to expect the price to stay at par. These securities are priced at the expected market price.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 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. 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 March 31, 2016, we had forward contracts outstanding with notional amounts totaling €1.8 million ($2.0 million), which mature in the second quarter of 2016. The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of March 31, 2016 and December 31, 2015 were as follows: (In thousands) Balance Sheet March 31, 2016 December 31, Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – liability derivatives Accounts payable $ (48 ) $ — The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three months ended March 31, 2016 and 2015 were as follows: Three Months Ended Income Statement Location March 31, (In thousands) 2016 2015 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ (47 ) $ 1,476

Inventory

Inventory	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Inventory	7. INVENTORY At March 31, 2016 and December 31, 2015, inventory consisted of the following: March 31, December 31, (In thousands) 2016 2015 Raw materials $ 35,879 $ 34,223 Work in process 2,829 2,893 Finished goods 53,399 54,417 Total $ 92,107 $ 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 March 31, 2016 and December 31, 2015, raw materials reserves totaled $18.5 million and $17.5 million, respectively, and finished goods inventory reserves totaled $9.0 million and $9.2 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2016 and December 31, 2015: (In thousands) March 31, 2016 December 31, 2015 Gross Accumulated Net Value Gross Accumulated Net Value Customer relationships $ 6,031 $ (2,856 ) $ 3,175 $ 5,828 $ (2,627 ) $ 3,201 Developed technology 5,840 (4,618 ) 1,222 5,720 (4,329 ) 1,391 Intellectual property 2,340 (1,937 ) 403 2,340 (1,854 ) 486 Trade names 270 (270 ) — 270 (265 ) 5 Total $ 14,481 $ (9,681 ) $ 4,800 $ 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 March 31, 2016 and 2015, respectively. As of March 31, 2016, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2016 $ 1,257 2017 1,175 2018 710 2019 316 2020 292 Thereafter 1,050 Total $ 4,800

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Stockholders' Equity	9. STOCKHOLDERS’ EQUITY A summary of the changes in stockholders’ equity for the three months ended March 31, 2016 is as follows: (In thousands) Stockholders’ Balance, December 31, 2015 $ 480,160 Net income 5,014 Dividend payments (4,453 ) Dividends accrued for unvested restricted stock units (20 ) Net unrealized losses on available-for-sale securities (net of tax) (255 ) Defined benefit plan adjustments 45 Foreign currency translation adjustment 1,228 Proceeds from stock option exercises 247 Purchase of treasury stock (11,003 ) Income tax effect of stock compensation arrangements (132 ) Stock-based compensation expense 1,558 Balance, March 31, 2016 $ 472,389 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 three months ended March 31, 2016, we repurchased 0.6 million shares of our common stock at an average price of $18.38 per share. As of March 31, 2016, we have the authority to purchase an additional 5.2 million shares of our common stock under the current plans approved by the Board of Directors. Stock Option Exercises We issued 15 thousand shares of treasury stock during the three months ended March 31, 2016 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $18.97. We received proceeds totaling $0.2 million from the exercise of these stock options during the three months ended March 31, 2016. Dividend Payments During the three months ended March 31, 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 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 March 31, 2016 and 2015: Three Months Ended March 31, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Foreign Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 759 — 1,228 1,987 Amounts reclassified from accumulated other comprehensive income (1,013 ) 44 — (969 ) Net current period other comprehensive income (loss) (254 ) 44 1,228 1,018 Ending balance $ 1,678 $ (3,851 ) $ (5,778 ) $ (7,951 ) Three Months Ended March 31, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Foreign Total Beginning balance $ 8,964 $ (5,757 ) $ (3,282 ) $ (75 ) Other comprehensive income (loss) before reclassifications 1,360 — (3,318 ) (1,958 ) Amounts reclassified from accumulated other comprehensive income (1,863 ) 68 — (1,795 ) Net current period other comprehensive income (loss) (503 ) 68 (3,318 ) (3,753 ) Ending balance $ 8,461 $ (5,689 ) $ (6,600 ) $ (3,828 ) The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended March 31, 2016 and 2015: (In thousands) Three Months Ended March 31, 2016 Details about Accumulated Other Comprehensive Income Amount from Other Income Affected Line Item in the Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 1,761 Net realized investment gain Impairment expense (100 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (64 ) (1) Total reclassifications for the period, before tax 1,597 Tax (expense) benefit (628 ) Total reclassifications for the period, net of tax $ 969 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended March 31, 2015 Details about Accumulated Other Comprehensive Income Amount from Other Affected Line Item in the Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 3,076 Net realized investment gain Impairment expense (22 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,956 Tax (expense) benefit (1,161 ) Total reclassifications for the period, net of tax $ 1,795 (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 March 31, 2016 and 2015: Three Months Ended March 31, 2016 Three Months Ended March 31, 2015 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Benefit Net-of-Tax Unrealized gains (losses) on available-for-sale securities $ 1,244 $ (485 ) $ 759 $ 2,230 $ (870 ) $ 1,360 Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,661 ) 648 (1,013 ) (3,054 ) 1,191 (1,863 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 64 (20 ) 44 98 (30 ) 68 Foreign currency translation adjustment 1,228 — 1,228 (3,318 ) — (3,318 ) Total Other Comprehensive Income (Loss) $ 875 $ 143 $ 1,018 $ (4,044 ) $ 291 $ (3,753 )

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015 is as follows: Three Months Ended March 31, (In thousands, except per share amounts) 2016 2015 Numerator Net income $ 5,014 $ 3,317 Denominator Weighted average number of shares – basic 49,220 53,399 Effect of dilutive securities Stock options 120 220 Restricted stock and restricted stock units 49 15 Weighted average number of shares – diluted 49,389 53,634 Net income per share – basic $ 0.10 $ 0.06 Net income per share – diluted $ 0.10 $ 0.06 Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 5.9 million and 5.6 million for the three months ended March 31, 2016 and 2015, respectively.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended March 31, 2016 March 31, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 123,883 $ 59,810 $ 129,505 $ 57,945 Services & Support 18,321 5,984 13,330 7,618 Total $ 142,204 $ 65,794 $ 142,835 $ 65,563 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 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 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 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 months ended March 31, 2016 and 2015: Three Months Ended March 31, (In thousands) 2016 2015 Access & Aggregation $ 93,855 $ 92,851 Customer Devices 32,353 31,704 Traditional & Other Products 15,996 18,280 Total $ 142,204 $ 142,835

Liability for Warranty Returns

Liability for Warranty Returns	3 Months Ended
	Mar. 31, 2016
Guarantees [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 $9.0 million and $8.7 million at March 31, 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 months ended March 31, 2016 and 2015 is as follows: Three Months Ended March 31, (In thousands) 2016 2015 Balance at beginning of period $ 8,739 $ 8,415 Plus: Amounts charged to cost and expenses 898 461 Less: Deductions (595 ) (192 ) Balance at end of period $ 9,042 $ 8,684

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 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 March 31, 2016, of which $7.7 million has been applied to these commitments.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	14. SUBSEQUENT EVENTS On April 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 April 28, 2016. The payment date will be May 12, 2016. The quarterly dividend payment will be approximately $4.4 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 second quarter and as of May 4, 2016, we have repurchased 30 thousand shares of our common stock through open market purchases at an average cost of $18.64 per share. We currently have the authority to purchase an additional 5.2 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)	3 Months Ended
	Mar. 31, 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.
Out of Period Adjustment	Out of Period Adjustment In connection with the preparation of our Condensed Consolidated Financial Statements, we recorded corrections of certain out of period, immaterial misstatements that occurred in prior periods, the most significant of which resulted in an increase in Other Expense of $1.3 million in the first quarter of 2015. The aggregate impact of the corrections was a $0.8 million reduction to pre-tax income for the three months ended March 31, 2015 and was not material to the prior year quarterly or annual results.
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 Revenue Recognition 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)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015: Three Months Ended March 31, (In thousands) 2016 2015 Service cost $ 297 $ 340 Interest cost 176 159 Expected return on plan assets (259 ) (261 ) Amortization of actuarial losses 43 105 Net periodic pension cost $ 257 $ 343

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based 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 months ended March 31, 2016 and 2015, which was recognized as follows: Three Months Ended (In thousands) 2016 2015 Stock-based compensation expense included in cost of sales $ 99 $ 90 Selling, general and administrative expense 769 691 Research and development expense 690 858 Stock-based compensation expense included in operating expenses 1,459 1,549 Total stock-based compensation expense 1,558 1,639 Tax benefit for expense associated with non-qualified options (212 ) (180 ) Total stock-based compensation expense, net of tax $ 1,346 $ 1,459
Summary of Weighted-Average Assumptions and Value of Options Granted	The weighted-average assumptions and value of options granted during the three months ended March 31, 2015 were as follows: Three Months Ended March 31, 2015 Expected volatility 38.75 % Risk-free interest rate 1.46 % Expected dividend yield 1.60 % Expected life (in years) 6.47 Weighted-average estimated value $ 7.63
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2015 and March 31, 2016 and the changes that occurred during the three months ended March 31, 2016: (In thousands, except per share amounts) Number of Weighted Avg. Weighted Avg. Aggregate Options outstanding, December 31, 2015 7,108 $ 21.97 6.42 $ 3,284 Options granted — $ — Options exercised (15 ) $ 16.65 Options forfeited (23 ) $ 17.84 Options expired (26 ) $ 24.40 Options outstanding, March 31, 2016 7,044 $ 22.00 6.18 $ 11,580 Options vested and expected to vest, March 31, 2016 6,910 $ 22.10 6.12 $ 11,095 Options exercisable, March 31, 2016 4,466 $ 24.33 4.69 $ 4,191

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Securities and Investments, Recorded at Either Fair Value or Cost	At March 31, 2016, we held the following securities and investments, recorded at either fair value or cost. (In thousands) Amortized Gross Unrealized Carrying Gains Losses Deferred compensation plan assets $ 11,440 $ 1,634 $ (70 ) $ 13,004 Corporate bonds 61,154 89 (386 ) 60,857 Municipal fixed-rate bonds 15,659 54 (1 ) 15,712 Asset-backed bonds 20,540 28 (8 ) 20,560 Mortgage/Agency-backed bonds 14,959 19 (82 ) 14,896 Government bonds 33,205 216 (2 ) 33,419 Variable Rate Demand Notes 2,235 — — 2,235 Marketable equity securities 31,798 2,886 (1,647 ) 33,037 Available-for-sale securities held at fair value $ 190,990 $ 4,926 $ (2,196 ) $ 193,720 Restricted investment held at cost 30,000 Other investments held at cost 1,266 Total carrying value of available-for-sale investments $ 224,986 At December 31, 2015, we held the following securities and investments, recorded at either fair value or cost. (In thousands) Amortized Gross Unrealized Carrying Gains Losses 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 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 government bonds Bonds	As of March 31, 2016, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, and government bonds had the following contractual maturities: (In thousands) Corporate Municipal Asset- Mortgage / Government Less than one year $ 17,668 $ 7,147 $ — $ 1,000 $ 1,253 One to two years 29,883 5,566 190 1,300 4,751 Two to three years 12,490 1,373 8,158 1,774 17,992 Three to five years 816 226 9,496 — 9,423 Five to ten years — — 2,540 1,180 — More than ten years — 1,400 176 9,642 — Total $ 60,857 $ 15,712 $ 20,560 $ 14,896 $ 33,419
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 March 31, (In thousands) 2016 2015 Gross realized gains $ 2,364 $ 3,145 Gross realized losses $ (636 ) $ (30 )
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 March 31, 2016 Using (In thousands) Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (Level 3) Cash equivalents Money market funds $ 2,110 $ 2,110 $ — $ — Commercial Paper 26,442 — 26,442 — Cash equivalents 28,552 2,110 26,442 — Available-for-sale securities Deferred compensation plan assets 13,004 13,004 — — Available-for-sale debt securities Corporate bonds 60,857 — 60,857 — Municipal fixed-rate bonds 15,712 — 15,712 — Asset-backed bonds 20,560 — 20,560 — Mortgage/Agency-backed bonds 14,896 — 14,896 — Government bonds 33,419 33,419 — — Variable Rate Demand Notes 2,235 — 2,235 — Available-for-sale marketable equity securities Marketable equity securities – technology industry 4,709 4,709 — — Marketable equity securities – other 28,328 28,328 — — Available-for-sale securities 193,720 79,460 114,260 — Total $ 222,272 $ 81,570 $ 140,702 $ — Fair Value Measurements at December 31, 2015 Using (In thousands) Fair Value Quoted Prices (Level 1) Significant (Level 2) Significant (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 — 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)	3 Months Ended
	Mar. 31, 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 March 31, 2016 and December 31, 2015 were as follows: (In thousands) Balance Sheet March 31, 2016 December 31, Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – liability derivatives Accounts payable $ (48 ) $ —
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 months ended March 31, 2016 and 2015 were as follows: Three Months Ended Income Statement Location March 31, (In thousands) 2016 2015 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ (47 ) $ 1,476

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Components of Inventory	At March 31, 2016 and December 31, 2015, inventory consisted of the following: March 31, December 31, (In thousands) 2016 2015 Raw materials $ 35,879 $ 34,223 Work in process 2,829 2,893 Finished goods 53,399 54,417 Total $ 92,107 $ 91,533

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of March 31, 2016 and December 31, 2015: (In thousands) March 31, 2016 December 31, 2015 Gross Accumulated Net Value Gross Accumulated Net Value Customer relationships $ 6,031 $ (2,856 ) $ 3,175 $ 5,828 $ (2,627 ) $ 3,201 Developed technology 5,840 (4,618 ) 1,222 5,720 (4,329 ) 1,391 Intellectual property 2,340 (1,937 ) 403 2,340 (1,854 ) 486 Trade names 270 (270 ) — 270 (265 ) 5 Total $ 14,481 $ (9,681 ) $ 4,800 $ 14,158 $ (9,075 ) $ 5,083
Estimated Future Amortization Expense Related to Intangible Assets	As of March 31, 2016, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2016 $ 1,257 2017 1,175 2018 710 2019 316 2020 292 Thereafter 1,050 Total $ 4,800

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the three months ended March 31, 2016 is as follows: (In thousands) Stockholders’ Balance, December 31, 2015 $ 480,160 Net income 5,014 Dividend payments (4,453 ) Dividends accrued for unvested restricted stock units (20 ) Net unrealized losses on available-for-sale securities (net of tax) (255 ) Defined benefit plan adjustments 45 Foreign currency translation adjustment 1,228 Proceeds from stock option exercises 247 Purchase of treasury stock (11,003 ) Income tax effect of stock compensation arrangements (132 ) Stock-based compensation expense 1,558 Balance, March 31, 2016 $ 472,389
Cash Dividends	During the three months ended March 31, 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
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 March 31, 2016 and 2015: Three Months Ended March 31, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Foreign Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 759 — 1,228 1,987 Amounts reclassified from accumulated other comprehensive income (1,013 ) 44 — (969 ) Net current period other comprehensive income (loss) (254 ) 44 1,228 1,018 Ending balance $ 1,678 $ (3,851 ) $ (5,778 ) $ (7,951 ) Three Months Ended March 31, 2015 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Foreign Total Beginning balance $ 8,964 $ (5,757 ) $ (3,282 ) $ (75 ) Other comprehensive income (loss) before reclassifications 1,360 — (3,318 ) (1,958 ) Amounts reclassified from accumulated other comprehensive income (1,863 ) 68 — (1,795 ) Net current period other comprehensive income (loss) (503 ) 68 (3,318 ) (3,753 ) Ending balance $ 8,461 $ (5,689 ) $ (6,600 ) $ (3,828 )
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 March 31, 2016 and 2015: (In thousands) Three Months Ended March 31, 2016 Details about Accumulated Other Comprehensive Income Amount from Other Income Affected Line Item in the Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 1,761 Net realized investment gain Impairment expense (100 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (64 ) (1) Total reclassifications for the period, before tax 1,597 Tax (expense) benefit (628 ) Total reclassifications for the period, net of tax $ 969 (1) Included in the computation of net periodic pension cost. See Note 3 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended March 31, 2015 Details about Accumulated Other Comprehensive Income Amount from Other Affected Line Item in the Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 3,076 Net realized investment gain Impairment expense (22 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,956 Tax (expense) benefit (1,161 ) Total reclassifications for the period, net of tax $ 1,795 (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 March 31, 2016 and 2015: Three Months Ended March 31, 2016 Three Months Ended March 31, 2015 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Benefit Net-of-Tax Unrealized gains (losses) on available-for-sale securities $ 1,244 $ (485 ) $ 759 $ 2,230 $ (870 ) $ 1,360 Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,661 ) 648 (1,013 ) (3,054 ) 1,191 (1,863 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 64 (20 ) 44 98 (30 ) 68 Foreign currency translation adjustment 1,228 — 1,228 (3,318 ) — (3,318 ) Total Other Comprehensive Income (Loss) $ 875 $ 143 $ 1,018 $ (4,044 ) $ 291 $ (3,753 )

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015 is as follows: Three Months Ended March 31, (In thousands, except per share amounts) 2016 2015 Numerator Net income $ 5,014 $ 3,317 Denominator Weighted average number of shares – basic 49,220 53,399 Effect of dilutive securities Stock options 120 220 Restricted stock and restricted stock units 49 15 Weighted average number of shares – diluted 49,389 53,634 Net income per share – basic $ 0.10 $ 0.06 Net income per share – diluted $ 0.10 $ 0.06

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2016 and 2015. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended March 31, 2016 March 31, 2015 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 123,883 $ 59,810 $ 129,505 $ 57,945 Services & Support 18,321 5,984 13,330 7,618 Total $ 142,204 $ 65,794 $ 142,835 $ 65,563
Sales Information by Category	The table below presents sales information by category for the three months ended March 31, 2016 and 2015: Three Months Ended March 31, (In thousands) 2016 2015 Access & Aggregation $ 93,855 $ 92,851 Customer Devices 32,353 31,704 Traditional & Other Products 15,996 18,280 Total $ 142,204 $ 142,835

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	3 Months Ended
	Mar. 31, 2016
Guarantees [Abstract]
Summary of Warranty Expense and Write-Off Activity	A summary of warranty expense and write-off activity for the three months ended March 31, 2016 and 2015 is as follows: Three Months Ended March 31, (In thousands) 2016 2015 Balance at beginning of period $ 8,739 $ 8,415 Plus: Amounts charged to cost and expenses 898 461 Less: Deductions (595 ) (192 ) Balance at end of period $ 9,042 $ 8,684

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2015USD ($)
Accounting Policies [Abstract]
Reduction of pre-tax income	$ 0.8
Increase in other expenses	$ 1.3

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Effective tax rate	37.90%	39.80%

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 297	$ 340
Interest cost	176	159
Expected return on plan assets	(259)	(261)
Amortization of actuarial losses	43	105
Net periodic pension cost	$ 257	$ 343

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
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,558	$ 1,639
Tax benefit for expense associated with non-qualified options	(212)	(180)
Total stock-based compensation expense, net of tax	1,346	1,459
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	99	90
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	769	691
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	690	858
Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,459	$ 1,549

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, granted	0
Estimated forfeitures for stock options	3.70%
Total pre-tax intrinsic value of options exercised	$ 36
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
Number of RSUs and restricted stock forfeitures in period		12,000
Number of RSUs and restricted stock vesting in period	0	0
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 forfeitures in period	0	0
Number of RSUs and restricted stock vesting in period	0	0
Recognition period of non-vested compensation cost	2 years 6 months 11 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	$ 13,200

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) - Stock Options [Member]	3 Months Ended
	Mar. 31, 2015$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	38.75%
Risk-free interest rate	1.46%
Expected dividend yield	1.60%
Expected life (in years)	6 years 5 months 19 days
Weighted-average estimated value	$ 7.63

Stock-Based Compensation - Su38

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Aggregate Intrinsic Value, Options outstanding, Beginning Balance		$ 3,284
Number of Options, outstanding, Beginning Balance	7,108
Number of Options, granted	0
Number of Options, exercised	(15)
Number of Options, forfeited	(23)
Number of Options, expired	(26)
Number of Options, outstanding, Ending Balance	7,044	7,108
Number of Options, vested and expected to vest, Ending Balance	6,910
Number of Options, Options exercisable	4,466
Weighted Average Exercise Price, outstanding, Beginning Balance	$ 21.97
Weighted Average Exercise Price, granted	0
Weighted Average Exercise Price, exercised	16.65
Weighted Average Exercise Price, forfeited	17.84
Weighted Average Exercise Price, expired	24.40
Weighted Average Exercise Price, outstanding, Ending Balance	22	$ 21.97
Weighted Average Exercise Price, vested and expected to vest, Ending Balance	22.10
Weighted Average Exercise Price, Options exercisable	$ 24.33
Weighted Average Remaining Contractual Life In Years, Options outstanding	6 years 2 months 5 days	6 years 5 months 1 day
Weighted Average Remaining Contractual Life In Years, Options vested and expected to vest	6 years 1 month 13 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	4 years 8 months 9 days
Aggregate Intrinsic Value, Options outstanding, Ending Balance	$ 11,580
Aggregate Intrinsic Value, Options vested and expected to vest	11,095
Aggregate Intrinsic Value, Options exercisable	$ 4,191

Investments - Securities and In

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 190,990	$ 198,100
Gross Unrealized Gains	4,926	5,927
Gross Unrealized Losses	(2,196)	(2,894)
Available-for-sale-securities, Carrying Value	193,720	201,133
Restricted investment held at cost	30,000	30,000
Other investments held at cost	1,266	1,289
Total carrying value of available-for-sale investments	224,986	232,422
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,440	11,325
Gross Unrealized Gains	1,634	1,575
Gross Unrealized Losses	(70)	(66)
Available-for-sale-securities, Carrying Value	13,004	12,834
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,154	58,328
Gross Unrealized Gains	89	20
Gross Unrealized Losses	(386)	(734)
Available-for-sale-securities, Carrying Value	60,857	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,659	26,414
Gross Unrealized Gains	54	28
Gross Unrealized Losses	(1)	(18)
Available-for-sale-securities, Carrying Value	15,712	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,540	19,281
Gross Unrealized Gains	28	2
Gross Unrealized Losses	(8)	(44)
Available-for-sale-securities, Carrying Value	20,560	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,959	15,463
Gross Unrealized Gains	19	1
Gross Unrealized Losses	(82)	(91)
Available-for-sale-securities, Carrying Value	14,896	15,373
Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,205	35,646
Gross Unrealized Gains	216
Gross Unrealized Losses	(2)	(248)
Available-for-sale-securities, Carrying Value	33,419	35,398
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,235
Available-for-sale-securities, Carrying Value	2,235
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,798	31,643
Gross Unrealized Gains	2,886	4,301
Gross Unrealized Losses	(1,647)	(1,693)
Available-for-sale-securities, Carrying Value	$ 33,037	$ 34,251

Investments - Contractual Matur

Investments - Contractual Maturities of Corporate Bonds, Municipal Fixed-Rate Bonds, Asset-Backed Bonds, Mortgage/Agency-Backed Bonds and Government Bonds (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale-securities, Fair Value/Carrying Value	$ 193,720	$ 201,133
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	17,668
One to two years	29,883
Two to three years	12,490
Three to five years	816
Available-for-sale-securities, Fair Value/Carrying Value	60,857	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	7,147
One to two years	5,566
Two to three years	1,373
Three to five years	226
More than ten years	1,400
Available-for-sale-securities, Fair Value/Carrying Value	15,712	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	190
Two to three years	8,158
Three to five years	9,496
Five to ten years	2,540
More than ten years	176
Available-for-sale-securities, Fair Value/Carrying Value	20,560	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,000
One to two years	1,300
Two to three years	1,774
Five to ten years	1,180
More than ten years	9,642
Available-for-sale-securities, Fair Value/Carrying Value	14,896	15,373
Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,253
One to two years	4,751
Two to three years	17,992
Three to five years	9,423
Available-for-sale-securities, Fair Value/Carrying Value	$ 33,419	$ 35,398

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 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] | Taxable Revenue Bond [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Investments [Line Items]
Estimated fair value of bond	$ 29,100
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
	Mar. 31, 2016	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 2,364	$ 3,145
Gross realized losses	$ (636)	$ (30)

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 193,720	$ 201,133
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,004	12,834
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	60,857	57,614
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	15,712	26,424
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	20,560	19,239
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	14,896	15,373
Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	33,419	35,398
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,235
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	28,552	12,967
Available-for-sale securities	193,720	201,133
Total	222,272	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	2,110	1,271
Available-for-sale securities	79,460	82,483
Total	81,570	83,754
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	26,442	11,696
Available-for-sale securities	114,260	118,650
Total	140,702	130,346
Fair Value, Measurements [Member] | Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,110	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	2,110	1,271
Fair Value, Measurements [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	26,442	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	26,442	11,696
Fair Value, Measurements [Member] | Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,004	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	13,004	12,834
Fair Value, Measurements [Member] | Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	60,857	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	60,857	57,614
Fair Value, Measurements [Member] | Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	15,712	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	15,712	26,424
Fair Value, Measurements [Member] | Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	20,560	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	20,560	19,239
Fair Value, Measurements [Member] | Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	14,896	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	14,896	15,373
Fair Value, Measurements [Member] | Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	33,419	35,398
Fair Value, Measurements [Member] | 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	33,419	35,398
Fair Value, Measurements [Member] | Marketable Equity Securities - Technology Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,709	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	4,709	5,384
Fair Value, Measurements [Member] | Marketable Equity Securities - Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	28,328	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	28,328	$ 28,867
Fair Value, Measurements [Member] | Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,235
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	$ 2,235

Derivative Instruments and He44

Derivative Instruments and Hedging Activities - Additional Information (Detail) - 3 months ended Mar. 31, 2016	USD ($)	EUR (€)
Derivative [Line Items]
Maximum contractual period for derivatives	12 months
Forward Contracts [Member]
Derivative [Line Items]
Derivative, notional amount	$ 2,000,000	€ 1,800,000
Derivative maturity year	2,016

Derivative Instruments and He45

Derivative Instruments and Hedging Activities - Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) $ in Thousands	Mar. 31, 2016USD ($)
Significant Other Observable Inputs (Level 2) [Member] | Foreign Exchange Contracts [Member] | Accounts Payable [Member]
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives liability, fair value	$ (48)

Derivative Instruments and He46

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
	Mar. 31, 2016	Mar. 31, 2015
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ (47)	$ 1,476

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 35,879	$ 34,223
Work in process	2,829	2,893
Finished goods	53,399	54,417
Total	$ 92,107	$ 91,533

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 18.5	$ 17.5
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 9	$ 9.2

Goodwill and Intangible Asset49

Goodwill and Intangible Assets - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2016USD ($)Segments	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Goodwill, relates to acquisition	$ 3,500,000		$ 3,500,000
Number of reportable segments | Segments	2
Impairment losses	$ 0
Amortization expense	400,000	$ 500,000
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 Asset50

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Gross Value	$ 14,481	$ 14,158
Accumulated Amortization	(9,681)	(9,075)
Net Value	4,800	5,083
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	6,031	5,828
Accumulated Amortization	(2,856)	(2,627)
Net Value	3,175	3,201
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	5,840	5,720
Accumulated Amortization	(4,618)	(4,329)
Net Value	1,222	1,391
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	2,340	2,340
Accumulated Amortization	(1,937)	(1,854)
Net Value	403	486
Trade Names [Member]
Goodwill [Line Items]
Gross Value	270	270
Accumulated Amortization	$ (270)	(265)
Net Value		$ 5

Goodwill and Intangible Asset51

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2016	$ 1,257
2,017	1,175
2,018	710
2,019	316
2,020	292
Thereafter	1,050
Net Value	$ 4,800	$ 5,083

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity [Abstract]
Beginning Balance	$ 480,160
Net income	5,014	$ 3,317
Dividend payments	(4,453)
Dividends accrued for unvested restricted stock units	(20)
Net unrealized losses on available-for-sale securities (net of tax)	(255)	(503)
Defined benefit plan adjustments	45	68
Foreign currency translation adjustment	1,228	(3,318)
Proceeds from stock option exercises	247	$ 280
Purchase of treasury stock	(11,003)
Income tax effect of stock compensation arrangements	(132)
Stock-based compensation expense	1,558
Ending Balance	$ 472,389

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity [Abstract]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	50,000,000
Stock repurchased, shares	600,000
Shares repurchased, average price per share	$ 18.38
Additional shares authorized for purchase	5,200,000
Number of Options, exercised	15,000
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	$ 247	$ 280

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Dividends Payable [Line Items]
Record Date	Apr. 28, 2016
Payment Date	May 12, 2016
Per Share Amount	$ 0.09	$ 0.09
Total Dividend Paid	$ 4,453	$ 4,811
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

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (8,969)	$ (75)
Other comprehensive income (loss) before reclassifications	1,987	(1,958)
Amounts reclassified from accumulated other comprehensive income	(969)	(1,795)
Other Comprehensive Income (Loss), net of tax	1,018	(3,753)
Ending balance	(7,951)	(3,828)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,932	8,964
Other comprehensive income (loss) before reclassifications	759	1,360
Amounts reclassified from accumulated other comprehensive income	(1,013)	(1,863)
Other Comprehensive Income (Loss), net of tax	(254)	(503)
Ending balance	1,678	8,461
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(3,895)	(5,757)
Amounts reclassified from accumulated other comprehensive income	44	68
Other Comprehensive Income (Loss), net of tax	44	68
Ending balance	(3,851)	(5,689)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(7,006)	(3,282)
Other comprehensive income (loss) before reclassifications	1,228	(3,318)
Other Comprehensive Income (Loss), net of tax	1,228	(3,318)
Ending balance	$ (5,778)	$ (6,600)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Income before provision for income taxes	$ 8,078	$ 5,510
Tax (expense) benefit	(3,064)	(2,193)
Total reclassifications for the period, net of tax	5,014	3,317
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit plan adjustments - actuarial losses	(64)	(98)
Income before provision for income taxes	1,597	2,956
Tax (expense) benefit	(628)	(1,161)
Total reclassifications for the period, net of tax	969	1,795
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	1,761	3,076
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	$ (100)	$ (22)

Stockholders' Equity - Other Co

Stockholders' Equity - Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 1,244	$ 2,230
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	(1,661)	(3,054)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	64	98
Foreign currency translation adjustment, Before-Tax Amount	1,228	(3,318)
Total Other Comprehensive Income (Loss), Before-Tax Amount	875	(4,044)
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(485)	(870)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	648	1,191
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(20)	(30)
Foreign currency translation adjustment, Tax (Expense) Benefit	0	0
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	143	291
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	759	1,360
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	(1,013)	(1,863)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	44	68
Foreign currency translation adjustment, Net-of-Tax Amount	1,228	(3,318)
Other Comprehensive Income (Loss), net of tax	$ 1,018	$ (3,753)

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
	Mar. 31, 2016	Mar. 31, 2015
Numerator
Net income	$ 5,014	$ 3,317
Denominator
Weighted average number of shares - basic	49,220	53,399
Effect of dilutive securities
Stock options	120	220
Restricted stock and restricted stock units	49	15
Weighted average number of shares - diluted	49,389	53,634
Net income per share - basic	$ 0.10	$ 0.06
Net income per share - diluted	$ 0.10	$ 0.06

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Anti-dilutive options, Total	5.9	5.6

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016SegmentsCategory
Segment Reporting [Abstract]
Number of operating reportable segments | Segments	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
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Sales	$ 142,204	$ 142,835
Gross Profit	65,794	65,563
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	123,883	129,505
Gross Profit	59,810	57,945
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	18,321	13,330
Gross Profit	$ 5,984	$ 7,618

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue from External Customer [Line Items]
Sales	$ 142,204	$ 142,835
Access & Aggregation [Member]
Revenue from External Customer [Line Items]
Sales	93,855	92,851
Customer Devices [Member]
Revenue from External Customer [Line Items]
Sales	32,353	31,704
Traditional & Other Products [Member]
Revenue from External Customer [Line Items]
Sales	$ 15,996	$ 18,280

Liability for Warranty Return63

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 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	$ 9,042	$ 8,739	$ 8,684	$ 8,415

Liability for Warranty Return64

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 8,739	$ 8,415
Plus: Amounts charged to cost and expenses	898	461
Less: Deductions	(595)	(192)
Balance at end of period	$ 9,042	$ 8,684

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Mar. 31, 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	May. 04, 2016	Apr. 12, 2016	Mar. 31, 2016	May. 12, 2016
Subsequent Event [Line Items]
Dividend declaration date			Apr. 12, 2016
Dividend record date			Apr. 28, 2016
Dividend payment date			May 12, 2016
Stock repurchased, shares			600,000
Shares repurchased, average price per share			$ 18.38
Additional shares authorized for purchase			5,200,000
Subsequent Events [Member]
Subsequent Event [Line Items]
Common stock dividends per share declared		$ 0.09
Quarterly dividend payable subsequent to balance sheet date				$ 4.4
Stock repurchased, shares	30,000,000
Shares repurchased, average price per share	$ 18.64
Additional shares authorized for purchase	5,200,000