ADTRAN (ADTN) 10-Q 6 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 21, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	ADTN
Entity Registrant Name	ADTRAN INC
Entity Central Index Key	926282
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,319,159

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current Assets
Cash and cash equivalents	$87,009	$73,439
Short-term investments	78,760	46,919
Accounts receivable, less allowance for doubtful accounts of $20 and $136 at March 31, 2015 and December 31, 2014, respectively	90,869	88,502
Other receivables	29,962	33,295
Inventory, net	93,123	86,710
Prepaid expenses	5,092	5,129
Deferred tax assets, net	16,297	17,095
Total Current Assets	401,112	351,089
Property, plant and equipment, net	73,987	74,828
Deferred tax assets, net	18,831	17,694
Goodwill	3,492	3,492
Other assets	10,080	10,942
Long-term investments	236,678	280,649
Total Assets	744,180	738,694
Current Liabilities
Accounts payable	73,696	56,414
Unearned revenue	16,815	22,762
Accrued expenses	12,773	11,077
Accrued wages and benefits	15,605	13,855
Income tax payable, net	13,088	14,901
Total Current Liabilities	131,977	119,009
Non-current unearned revenue	10,088	10,948
Other non-current liabilities	30,646	30,924
Bonds payable	28,800	28,800
Total Liabilities	201,511	189,681
Commitments and contingencies (see Note 14)
Stockholders' Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 53,319 shares outstanding at March 31, 2015 and 79,652 shares issued and 53,431 shares outstanding at December 31, 2014	797	797
Additional paid-in capital	243,476	241,829
Accumulated other comprehensive loss	-3,828	-75
Retained earnings	905,884	907,751
Less treasury stock at cost: 26,333 and 26,221 shares at March 31, 2015 and December 31, 2014, respectively	-603,660	-601,289
Total Stockholders' Equity	542,669	549,013
Total Liabilities and Stockholders' Equity	$744,180	$738,694

Consolidated_Balance_Sheets_Un1

Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$20	$136
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	53,319,000	53,431,000
Treasury stock, shares	26,333,000	26,221,000

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Sales	$142,835	$147,004
Cost of sales	77,272	69,214
Gross Profit	65,563	77,790
Selling, general and administrative expenses	31,064	33,939
Research and development expenses	32,536	32,553
Operating Income	1,963	11,298
Interest and dividend income	933	1,294
Interest expense	-148	-227
Net realized investment gain	3,115	2,192
Other income (expense), net	-353	122
Income before provision for income taxes	5,510	14,679
Provision for income taxes	-2,193	-5,072
Net Income	$3,317	$9,607
Weighted average shares outstanding - basic	53,399	56,751
Weighted average shares outstanding - diluted	53,634	57,368
Earnings per common share - basic	$0.06	$0.17
Earnings per common share - diluted	$0.06	$0.17
Dividend per share	$0.09	$0.09

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$3,317	$9,607
Other Comprehensive Loss, net of tax:
Net unrealized losses on available-for-sale securities	-503	-921
Defined benefit plan adjustments	68
Foreign currency translation	-3,318	252
Other Comprehensive Loss, net of tax	-3,753	-669
Comprehensive Income (Loss), net of tax	($436)	$8,938

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net Income	$3,317	$9,607
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,728	3,580
Amortization of net premium on available-for-sale investments	910	1,135
Net realized gain on long-term investments	-3,115	-2,192
Net (gain) loss on disposal of property, plant and equipment	8	-3
Stock-based compensation expense	1,639	2,057
Deferred income taxes	-692	627
Tax benefit from stock option exercises	8	57
Excess tax benefits from stock-based compensation arrangements	-9	-55
Changes in operating assets and liabilities:
Accounts receivable, net	-4,571	-15,971
Other receivables	511	-9,407
Inventory	-7,784	2,739
Prepaid expenses and other assets	-213	-2,024
Accounts payable	20,084	11,043
Accrued expenses and other liabilities	-282	8,431
Income tax payable, net	-524	275
Net cash provided by operating activities	13,015	9,899
Cash flows from investing activities:
Purchases of property, plant and equipment	-2,442	-2,042
Proceeds from disposals of property, plant and equipment		1
Proceeds from sales and maturities of available-for-sale investments	58,075	85,072
Purchases of available-for-sale investments	-44,584	-69,182
Net cash provided by investing activities	11,049	13,849
Cash flows from financing activities:
Proceeds from stock option exercises	280	1,541
Purchases of treasury stock	-3,035	-9,427
Dividend payments	-4,811	-5,102
Payments on long-term debt		-16,500
Excess tax benefits from stock-based compensation arrangements	9	55
Net cash used in financing activities	-7,557	-29,433
Net increase (decrease) in cash and cash equivalents	16,507	-5,685
Effect of exchange rate changes	-2,937	202
Cash and cash equivalents, beginning of period	73,439	58,298
Cash and cash equivalents, end of period	87,009	52,815
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$784	$85

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation
	The accompanying unaudited consolidated financial statements of ADTRAN®, Inc. and its subsidiaries (ADTRAN) have been prepared pursuant to the rules and regulations for reporting on Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles for complete financial statements are not included herein. The December 31, 2014 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2014, filed on February 24, 2015 with the SEC.
	Changes in Classifications
	We reclassified $2.3 million from other receivables to accounts receivable at December 31, 2014 to conform to the current period presentation.
	Out of Period Adjustment
	In connection with the preparation of our Condensed Consolidated Financial Statements, we recorded corrections of certain out of period, immaterial misstatements that occurred in prior periods, the most significant of which resulted in an increase in Other Expense of $1.3 million in the first quarter. 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 is not expected to be material to the current year annual results.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), which supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, and early application is not permitted. ASU 2014-09 allows for either full retrospective or modified retrospective adoption. We are currently evaluating the transition method that will be elected and the impact that the adoption of ASU 2014-09 will have on our financial position, results of operations and cash flows.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	2. INCOME TAXES
	Our effective tax rate increased from 34.6% in the three months ended March 31, 2014 to 39.8% in the three months ended March 31, 2015. The increase in the effective tax rate between the two periods is primarily attributable to the release of a valuation allowance attributable to a foreign subsidiary in 2014.

Pension_Benefit_Plan

Pension Benefit Plan	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014:
		Three Months Ended
		March 31,
	(In thousands)	2015			2014
	Service cost	$	340		$	305
	Interest cost		159			215
	Expected return on plan assets		(261	)		(279	)
	Amortization of actuarial losses		105			—
	Net periodic pension cost	$	343		$	241

StockBased_Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014, which was recognized as follows:
		Three Months Ended
		March 31,
	(In thousands)	2015			2014
	Stock-based compensation expense included in cost of sales	$	90		$	116
	Selling, general and administrative expense		691			1,026
	Research and development expense		858			915
	Stock-based compensation expense included in operating expenses		1,549			1,941
	Total stock-based compensation expense		1,639			2,057
	Tax benefit for expense associated with		(180	)		(284	)
	non-qualified options
	Total stock-based compensation expense, net of tax	$	1,459		$	1,773
	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.
	The weighted-average assumptions and value of options granted for the three months ended March 31, 2015 and 2014 are summarized as follows:
		Three Months Ended
		March 31,			March 31,
		2015			2014
	Expected volatility		38.75	%		39.57	%
	Risk-free interest rate		1.46	%		1.86	%
	Expected dividend yield		1.6	%		1.38	%
	Expected life (in years)		6.47			6.25
	Weighted-average estimated value	$	7.63		$	9.28
	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, 2015 or 2014. 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 was granted, forfeited, or vested during the three months ended March 31, 2015 or 2014.
	Stock-based compensation expense recognized in our Consolidated Statements of Income for the three months ended March 31, 2015 and 2014 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 3.1% 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, 2015, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $15.2 million, which is expected to be recognized over an average remaining recognition period of 2.7 years.
	The following table is a summary of our stock options outstanding as of December 31, 2014 and March 31, 2015 and the changes that occurred during the three months ended March 31, 2015:
	(In thousands, except per share amounts)	Number of			Weighted Avg.			Weighted Avg.		Aggregate
		Options			Exercise Price			Remaining		Intrinsic
								Contractual		Value
								Life In Years
	Options outstanding, December 31, 2014		6,981		$	23.62			6.45	$	10,625
	Options granted		2		$	22.56
	Options forfeited		(79	)	$	20.87
	Options expired		(19	)	$	27.19
	Options exercised		(17	)	$	16.58
	Options outstanding, March 31, 2015		6,868		$	23.66			6.18	$	3,037
	Options vested and expected to vest, March 31, 2015		6,678		$	23.73			6.11	$	2,553
	Options exercisable, March 31, 2015		4,362		$	25.17			4.74	$	2,303
	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, 2015. 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, 2015 was $0.1 million.

Investments

Investments	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investments	5. INVESTMENTS
	At March 31, 2015, we held the following securities and investments, recorded at either fair value or cost.
	(In thousands)	Amortized			Gross Unrealized						Carrying
		Cost			Gains			Losses			Value
	Deferred compensation plan assets	$	14,071		$	2,555		$	(54	)	$	16,572
	Corporate bonds		132,343			250			(205	)		132,388
	Municipal fixed-rate bonds		92,810			318			(11	)		93,117
	Municipal variable rate demand notes		4,245			—			—			4,245
	Marketable equity securities		26,608			11,496			(481	)		37,623
	Available-for-sale securities held at fair value	$	270,077		$	14,619		$	(751	)	$	283,945
	Restricted investment held at cost											30,000
	Other investments held at cost											1,493
	Total carrying value of available-for-sale investments										$	315,438
	At December 31, 2014, we held the following securities and investments, recorded at either fair value or cost.
	(In thousands)	Amortized			Gross Unrealized						Carrying
		Cost			Gains			Losses			Value
	Deferred compensation plan assets	$	13,897		$	2,409		$	(12	)	$	16,294
	Corporate bonds		111,261			186			(186	)		111,261
	Municipal fixed-rate bonds		127,341			480			(34	)		127,787
	Municipal variable rate demand notes		2,465			—			—			2,465
	Marketable equity securities		26,399			12,395			(539	)		38,255
	Available-for-sale securities held at fair value	$	281,363		$	15,470		$	(771	)	$	296,062
	Restricted investment held at cost											30,000
	Other investments held at cost											1,506
	Total carrying value of available-for-sale investments										$	327,568
	As of March 31, 2015, our corporate bonds and municipal fixed-rate bonds had the following contractual maturities:
	(In thousands)	Corporate			Municipal
		bonds			fixed-rate
					bonds
	Less than one year	$	44,108		$	30,407
	One to two years		39,163			39,660
	Two to three years		49,117			21,826
	Three to five years		—			1,224
	Total	$	132,388		$	93,117
	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, 2015, 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, 2015, the estimated fair value of the Bond using a level 2 valuation technique was approximately $29.7 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, 2015 and 2014, 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)	2015			2014
	Gross realized gains	$	3,145		$	2,228
	Gross realized losses	$	(30	)	$	(36	)
	As of March 31, 2015 and 2014, 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, 2015 Using
	(In thousands)	Fair Value			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Market for			Observable			Inputs
					Identical			Inputs			(Level 3)
					Assets			(Level 2)
					(Level 1)
	Cash equivalents
	Commercial paper	$	11,997		$	—		$	11,997		$	—
	Money market funds		3,228			3,228			—			—
	Cash equivalents		15,225			3,228			11,997			—
	Available-for-sale securities
	Deferred compensation plan assets		16,572			16,572			—			—
	Available-for-sale debt securities
	Corporate bonds		132,388			—			132,388			—
	Municipal fixed-rate bonds		93,117			—			93,117			—
	Municipal variable rate demand notes		4,245			—			4,245			—
	Available-for-sale marketable equity securities
Marketable equity securities – technology industry		9,034			9,034			—			—
Marketable equity securities – other		28,589			28,589			—			—
Available-for-sale securities		283,945			54,195			229,750			—
Total	$	299,170		$	57,423		$	241,747		$	—
	Fair Value Measurements at December 31, 2014 Using
(In thousands)	Fair Value			Quoted Prices			Significant			Significant
				in Active			Other			Unobservable
				Market for			Observable			Inputs
				Identical			Inputs			(Level 3)
				Assets			(Level 2)
				(Level 1)
Cash equivalents
Money market funds	$	1,163		$	1,163		$	—		$	—
Available-for-sale securities
Deferred compensation plan assets		16,294			16,294			—			—
Available-for-sale debt securities
Corporate bonds		111,261			—			111,261			—
Municipal fixed-rate bonds		127,787			—			127,787			—
Municipal variable rate demand notes		2,465			—			2,465			—
Available-for-sale marketable equity securities
Marketable equity securities – technology industry		9,661			9,661			—			—
Marketable equity securities – other		28,594			28,594			—			—
Available-for-sale securities		296,062			54,549			241,513			—
Total	$	297,225		$	55,712		$	241,513		$	—
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_Hed

Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2015
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, 2015, we had forward contracts outstanding with notional amounts totaling €63.0 million ($67.7 million), which mature at various times throughout 2015.
	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of March 31, 2015 and December 31, 2014 were as follows:
	(In thousands)	Balance Sheet	March 31,			December 31,
		Location	2015			2014
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	1,692		$	249
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(607	)	$	(10	)
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three months ended March 31, 2015 and 2014 were as follows:
			Three Months Ended
		Income Statement	March 31,
	(In thousands)	Location	2015			2014
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	1,476		$	(110	)

Inventory

Inventory	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Inventory	7. INVENTORY
	At March 31, 2015 and December 31, 2014, inventory consisted of the following:
	(In thousands)	March 31,		December 31,
		2015		2014
	Raw materials	$	35,891	$	34,831
	Work in process		2,613		3,750
	Finished goods		54,619		48,129
	Total	$	93,123	$	86,710
	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, 2015 and December 31, 2014, raw materials reserves totaled $16.9 million, and finished goods inventory reserves totaled $7.6 million and $7.8 million, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2015
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. and is included in our Enterprise Networks division, was $3.5 million at March 31, 2015 and December 31, 2014. 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. There have been no impairment losses recorded since acquisition.
	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, 2015 and December 31, 2014:
	(In thousands)	March 31, 2015							December 31, 2014
		Gross		Accumulated			Net Value		Gross		Accumulated			Net Value
		Value		Amortization					Value		Amortization
	Customer relationships	$	5,787	$	(2,146	)	$	3,641	$	6,310	$	(2,136	)	$	4,174
	Developed technology		5,696		(3,660	)		2,036		6,005		(3,577	)		2,428
	Intellectual property		2,340		(1,603	)		737		2,340		(1,520	)		820
	Trade names		270		(220	)		50		270		(205	)		65
	Other		11		(11	)		—		12		(11	)		1
	Total	$	14,104	$	(7,640	)	$	6,464	$	14,937	$	(7,449	)	$	7,488
	Amortization expense, all of which relates to business acquisitions, was $0.5 million and $0.6 million for the three months ended March 31, 2015 and 2014, respectively.
	As of March 31, 2015, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)	Amount
	Remainder of 2015	$	1,413
	2016		1,648
	2017		1,145
	2018		691
	2019		298
	Thereafter		1,269
	Total	$	6,464

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Stockholders' Equity	9. STOCKHOLDERS’ EQUITY
	A summary of the changes in stockholders’ equity for the three months ended March 31, 2015 is as follows:
	(In thousands)		Stockholders’
			Equity
	Balance, December 31, 2014		$	549,013
	Net income			3,317
	Dividend payments			(4,811	)
	Dividends accrued for unvested restricted stock units			11
	Net unrealized losses on available-for-sale securities (net of tax)			(503	)
	Defined benefit plan adjustments			68
	Foreign currency translation adjustment			(3,318	)
	Proceeds from stock option exercises			280
	Purchase of treasury stock			(3,035	)
	Income tax benefit from exercise of stock options			8
	Stock-based compensation expense			1,639
	Balance, March 31, 2015		$	542,669
	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 45.0 million shares of our common stock. During the three months ended March 31, 2015, we repurchased 0.1 million shares of our common stock at an average price of $21.52 per share. We currently have the authority to purchase an additional 4.7 million shares of our common stock under the current plans approved by the Board of Directors.
	Stock Option Exercises
	We issued 17 thousand shares of treasury stock during the three months ended March 31, 2015 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $22.53. We received proceeds totaling $0.3 million from the exercise of these stock options during the three months ended March 31, 2015.
	Dividend Payments
	During the three months ended March 31, 2015, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date		Payment Date			Per Share Amount			Total Dividend Paid
	February 5, 2015			February 19, 2015		$	0.09		$	4,811
	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, 2015 and 2014:
			Three Months Ended March 31, 2015
	(In thousands)		Unrealized			Defined			Foreign			Total
			Gains			Benefit Plan			Currency
			(Losses) on			Adjustments			Adjustments
			Available-
			for-Sale
			Securities
	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	)
			Three Months Ended March 31, 2014
	(In thousands)		Unrealized			Defined			Foreign			Total
			Gains			Benefit Plan			Currency
			(Losses) on			Adjustments			Adjustments
			Available-
			for-Sale
			Securities
	Beginning balance		$	10,737		$	(891	)	$	907		$	10,753
	Other comprehensive income (loss) before reclassifications			402			—			252			654
	Amounts reclassified from accumulated other comprehensive income			(1,323	)		—			—			(1,323	)
	Net current period other comprehensive income(loss)			(921	)		—			252			(669	)
	Ending balance		$	9,816		$	(891	)	$	1,159		$	10,084
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended March 31, 2015 and 2014:
	(In thousands)		Three Months Ended March 31, 2015
	Details about Accumulated Other Comprehensive Income		Amount Reclassified			Affected Line Item in the
	Components		from Accumulated			Statement Where Net
			Other Comprehensive			Income Is Presented
			Income
	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.
(In thousands)		Three Months Ended March 31, 2014
Details about Accumulated Other Comprehensive Income		Amount Reclassified			Affected Line Item in the
Components		from Accumulated			Statement Where Net
		Other Comprehensive			Income Is Presented
		Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities		$	2,170			Net realized investment gain
Impairment expense			—			Net realized investment gain
Total reclassifications for the period, before tax			2,170
Tax (expense) benefit			(847	)
Total reclassifications for the period, net of tax		$	1,323
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, 2015 and 2014:
		Three Months Ended									Three Months Ended
		March 31, 2015									March 31, 2014
(In thousands)		Before-Tax			Tax			Net-of-Tax			Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount			Amount			Benefit			Amount
					Benefit
Unrealized gains (losses) on available-for-sale securities		$	2,230		$	(870	)	$	1,360		$	659		$	(257	)	$	402
Reclassification adjustment for amounts included in net income			(2,956	)		1,161			(1,795	)		(2,170	)		847			(1,323	)
Foreign currency translation adjustment			(3,318	)		—			(3,318	)		252			—			252
Total Other Comprehensive Income (Loss)		$	(4,044	)	$	291		$	(3,753	)	$	(1,259	)	$	590		$	(669	)

Earnings_per_Share

Earnings per Share	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014 is as follows:
		Three Months Ended
		March 31,
	(In thousands, except per share amounts)	2015		2014
	Numerator
	Net income	$	3,317	$	9,607
	Denominator
	Weighted average number of shares – basic		53,399		56,751
	Effect of dilutive securities
	Stock options		220		602
	Restricted stock and restricted stock units		15		15
	Weighted average number of shares – diluted		53,634		57,368
	Net income per share – basic	$	0.06	$	0.17
	Net income per share – diluted	$	0.06	$	0.17
	Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 5.6 million and 3.1 million for the three months ended March 31, 2015 and 2014, respectively.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	11. SEGMENT INFORMATION
	We operate in two reportable segments: (1) the Carrier Networks Division and (2) the Enterprise Networks Division. We evaluate the performance of our 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 an entity-wide basis only. 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, 2015 and 2014. Asset information by reportable segment is not reported, since we do not produce such information internally.
			Three Months Ended
			March 31, 2015				March 31, 2014
	(In thousands)		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	116,014	$	49,859	$	118,162	$	61,353
	Enterprise Networks			26,821		15,704		28,842		16,437
	Total		$	142,835	$	65,563	$	147,004	$	77,790
	Sales by Product
	Our three major product categories are Carrier Systems, Business Networking and Loop Access.
	Carrier Systems products are used by communications service providers to provide data, voice, and video services to consumers and enterprises. This category includes the following product areas and related services:
		•		Broadband Access
		•		Total Access® 5000 Series of Multi-Service Access Node (MSAN)
		•		hiX 5600 Series of MSANs
		•		Total Access 1100/1200 Series of Fiber to the Node (FTTN) products
		•		hiX 1100 Series of Fiber to the Node (FTTN) products
		•		VDSL2 Vectoring based Digital Subscriber Line Access Multiplexer (DSLAM) products
		•		ADTRAN 500 Series of FTTdp G.fast Distribution Point Units (DPU)
		•		Optical
		•		Optical Networking Edge (ONE)
		•		NetVanta 8000 Series of Fiber Ethernet Access Devices (EAD)
		•		NetVanta 8400 Series of 10Gig Multi-service Edge Switches
		•		OPTI-6100 and Total Access 3000 optical Multi-Service Provisioning Platforms (MSPP)
		•		Pluggable Optical Products, including SFP, XFP, and SFP+
		•		Time Division Multiplexed (TDM) systems
	Business Networking products provide access to communication services and facilitate the delivery of cloud connectivity and enterprise communications to the small and mid-sized enterprise (SME) market. This category includes the following product areas and related services:
		•		Internetworking products
		•		Total Access IP Business Gateways
		•		Optical Network Terminals (ONTs)
		•		Bluesocket® virtual Wireless LAN (vWLAN®)
		•		NetVanta®
		•		Access Routers
		•		Enterprise Session Border Controllers (eSBC)
		•		Managed Ethernet Switches
		•		IP Business Gateways
		•		Unified Communications (UC) solutions
		•		Carrier Ethernet Network Terminating Equipment (NTE)
		•		Carrier Ethernet Routers and Gateways
		•		Network Management Solutions
	Loop Access products are used by carrier and enterprise customers for access to copper-based communications networks. This category includes the following product areas and related services:
		•		High bit-rate Digital Subscriber Line (HDSL) products
		•		Digital Data Service (DDS)
		•		Integrated Services Digital Network (ISDN) products
		•		T1/E1/T3 Channel Service Units/Data Service Units (CSUs/DSUs)
		•		TRACER fixed-wireless products
	The table below presents sales information by product category for the three months ended March 31, 2015 and 2014:
			Three Months Ended
			March 31,
	(In thousands)		2015		2014
	Carrier Systems		$	100,439	$	99,553
	Business Networking			35,381		37,919
	Loop Access			7,015		9,532
	Total		$	142,835	$	147,004
	In addition, we identify subcategories of product revenues, which we divide into core products and legacy products. Our core products consist of Broadband Access and Optical products (included in Carrier Systems), and Internetworking products (included in Business Networking). Our legacy products include HDSL products (included in Loop Access) and other products not included in the aforementioned core products.
	The table below presents subcategory revenues for the three months ended March 31, 2015 and 2014:
			Three Months Ended
			March 31,
	(In thousands)		2015		2014
	Core Products
	Broadband Access (included in Carrier Systems)		$	84,794	$	81,527
	Optical (included in Carrier Systems)			12,504		12,789
	Internetworking (included in Business Networking)			34,159		36,946
	Subtotal			131,457		131,262
Legacy Products
HDSL (does not include T1) (included in Loop Access)			6,703		8,877
Other products (excluding HDSL)			4,675		6,865
Subtotal			11,378		15,742
Total		$	142,835	$	147,004

Liability_for_Warranty_Returns

Liability for Warranty Returns	3 Months Ended
	Mar. 31, 2015
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	12. LIABILITY FOR WARRANTY RETURNS
	Our products generally include warranties of 90 days to ten years for product defects. We accrue for warranty returns at the time revenue is recognized based on our estimate of the cost to repair or replace the defective products. We engage in extensive product quality programs and processes, including actively monitoring and evaluating the quality of our component suppliers. Our products continue to become more complex in both size and functionality as many of our product offerings migrate from line card applications to systems products. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage, and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $8.7 million at March 31, 2015 and $8.4 million at December 31, 2014. 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, 2015 and 2014 is as follows:
		Three Months Ended
		March 31,
		2015			2014
	(In thousands)
	Balance at beginning of period	$	8,415		$	8,977
	Plus: Amounts charged to cost and expenses		461			434
	Less: Deductions		(192	)		(2,019	)
	Balance at end of period	$	8,684		$	7,392

Related_Party_Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	13. RELATED PARTY TRANSACTIONS
	During 2014, we employed the law firm of our director emeritus for legal services. All bills for services rendered by this firm were reviewed and approved by our Chief Financial Officer. We believe that the fees for such services were comparable to those charged by other firms for services rendered to us. The services of our director emeritus ended with his death on September 7, 2014. For the three months ended March 31, 2014, we incurred fees of $10 thousand per month for these legal services.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. 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, 2015, of which $7.7 million has been applied to these commitments.

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	15. SUBSEQUENT EVENTS
	On April 21, 2015, 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 May 7, 2015. The payment date will be May 21, 2015. The quarterly dividend payment will be approximately $4.7 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 6, 2015, we have repurchased 1.2 million shares of our common stock through open market purchases at an average cost of $16.33 per share. We currently have the authority to purchase an additional 3.4 million shares of our common stock under the current plan approved by the Board of Directors.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	The accompanying unaudited consolidated financial statements of ADTRAN®, Inc. and its subsidiaries (ADTRAN) have been prepared pursuant to the rules and regulations for reporting on Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles for complete financial statements are not included herein. The December 31, 2014 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2014, filed on February 24, 2015 with the SEC.
Changes in Classifications	Changes in Classifications
	We reclassified $2.3 million from other receivables to accounts receivable at December 31, 2014 to conform to the current period presentation.
Out of Period Adjustment	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. 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 is not expected to be material to the current year 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 issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), which supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, and early application is not permitted. ASU 2014-09 allows for either full retrospective or modified retrospective adoption. We are currently evaluating the transition method that will be elected and the impact that the adoption of ASU 2014-09 will have on our financial position, results of operations and cash flows.

Pension_Benefit_Plan_Tables

Pension Benefit Plan (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014:
		Three Months Ended
		March 31,
	(In thousands)	2015			2014
	Service cost	$	340		$	305
	Interest cost		159			215
	Expected return on plan assets		(261	)		(279	)
	Amortization of actuarial losses		105			—
	Net periodic pension cost	$	343		$	241

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014, which was recognized as follows:
		Three Months Ended
		March 31,
	(In thousands)	2015			2014
	Stock-based compensation expense included in cost of sales	$	90		$	116
	Selling, general and administrative expense		691			1,026
	Research and development expense		858			915
	Stock-based compensation expense included in operating expenses		1,549			1,941
	Total stock-based compensation expense		1,639			2,057
	Tax benefit for expense associated with		(180	)		(284	)
	non-qualified options
	Total stock-based compensation expense, net of tax	$	1,459		$	1,773
Summary of Weighted-Average Assumptions and Value of Options Granted	The weighted-average assumptions and value of options granted for the three months ended March 31, 2015 and 2014 are summarized as follows:
		Three Months Ended
		March 31,			March 31,
		2015			2014
	Expected volatility		38.75	%		39.57	%
	Risk-free interest rate		1.46	%		1.86	%
	Expected dividend yield		1.6	%		1.38	%
	Expected life (in years)		6.47			6.25
	Weighted-average estimated value	$	7.63		$	9.28
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2014 and March 31, 2015 and the changes that occurred during the three months ended March 31, 2015:
	(In thousands, except per share amounts)	Number of			Weighted Avg.			Weighted Avg.		Aggregate
		Options			Exercise Price			Remaining		Intrinsic
								Contractual		Value
								Life In Years
	Options outstanding, December 31, 2014		6,981		$	23.62			6.45	$	10,625
	Options granted		2		$	22.56
	Options forfeited		(79	)	$	20.87
	Options expired		(19	)	$	27.19
	Options exercised		(17	)	$	16.58
	Options outstanding, March 31, 2015		6,868		$	23.66			6.18	$	3,037
	Options vested and expected to vest, March 31, 2015		6,678		$	23.73			6.11	$	2,553
	Options exercisable, March 31, 2015		4,362		$	25.17			4.74	$	2,303

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Securities and Investments, Recorded at Either Fair Value or Cost	At March 31, 2015, we held the following securities and investments, recorded at either fair value or cost.
	(In thousands)	Amortized			Gross Unrealized						Carrying
		Cost			Gains			Losses			Value
	Deferred compensation plan assets	$	14,071		$	2,555		$	(54	)	$	16,572
	Corporate bonds		132,343			250			(205	)		132,388
	Municipal fixed-rate bonds		92,810			318			(11	)		93,117
	Municipal variable rate demand notes		4,245			—			—			4,245
	Marketable equity securities		26,608			11,496			(481	)		37,623
	Available-for-sale securities held at fair value	$	270,077		$	14,619		$	(751	)	$	283,945
	Restricted investment held at cost											30,000
	Other investments held at cost											1,493
	Total carrying value of available-for-sale investments										$	315,438
	At December 31, 2014, we held the following securities and investments, recorded at either fair value or cost.
	(In thousands)	Amortized			Gross Unrealized						Carrying
		Cost			Gains			Losses			Value
	Deferred compensation plan assets	$	13,897		$	2,409		$	(12	)	$	16,294
	Corporate bonds		111,261			186			(186	)		111,261
	Municipal fixed-rate bonds		127,341			480			(34	)		127,787
	Municipal variable rate demand notes		2,465			—			—			2,465
	Marketable equity securities		26,399			12,395			(539	)		38,255
	Available-for-sale securities held at fair value	$	281,363		$	15,470		$	(771	)	$	296,062
	Restricted investment held at cost											30,000
	Other investments held at cost											1,506
	Total carrying value of available-for-sale investments										$	327,568
Contractual Maturities of Corporate Bonds and Municipal Fixed-Rate Bonds	As of March 31, 2015, our corporate bonds and municipal fixed-rate bonds had the following contractual maturities:
	(In thousands)	Corporate			Municipal
		bonds			fixed-rate
					bonds
	Less than one year	$	44,108		$	30,407
	One to two years		39,163			39,660
	Two to three years		49,117			21,826
	Three to five years		—			1,224
	Total	$	132,388		$	93,117
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)	2015			2014
	Gross realized gains	$	3,145		$	2,228
	Gross realized losses	$	(30	)	$	(36	)
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, 2015 Using
	(In thousands)	Fair Value			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Market for			Observable			Inputs
					Identical			Inputs			(Level 3)
					Assets			(Level 2)
					(Level 1)
	Cash equivalents
	Commercial paper	$	11,997		$	—		$	11,997		$	—
	Money market funds		3,228			3,228			—			—
	Cash equivalents		15,225			3,228			11,997			—
	Available-for-sale securities
	Deferred compensation plan assets		16,572			16,572			—			—
	Available-for-sale debt securities
	Corporate bonds		132,388			—			132,388			—
	Municipal fixed-rate bonds		93,117			—			93,117			—
	Municipal variable rate demand notes		4,245			—			4,245			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		9,034			9,034			—			—
	Marketable equity securities – other		28,589			28,589			—			—
	Available-for-sale securities		283,945			54,195			229,750			—
	Total	$	299,170		$	57,423		$	241,747		$	—
		Fair Value Measurements at December 31, 2014 Using
	(In thousands)	Fair Value			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Market for			Observable			Inputs
					Identical			Inputs			(Level 3)
					Assets			(Level 2)
					(Level 1)
	Cash equivalents
	Money market funds	$	1,163		$	1,163		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		16,294			16,294			—			—
	Available-for-sale debt securities
	Corporate bonds		111,261			—			111,261			—
	Municipal fixed-rate bonds		127,787			—			127,787			—
	Municipal variable rate demand notes		2,465			—			2,465			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		9,661			9,661			—			—
	Marketable equity securities – other		28,594			28,594			—			—
	Available-for-sale securities		296,062			54,549			241,513			—
	Total	$	297,225		$	55,712		$	241,513		$	—

Derivative_Instruments_and_Hed1

Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and December 31, 2014 were as follows:
	(In thousands)	Balance Sheet	March 31,			December 31,
		Location	2015			2014
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	1,692		$	249
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(607	)	$	(10	)
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, 2015 and 2014 were as follows:
			Three Months Ended
		Income Statement	March 31,
	(In thousands)	Location	2015			2014
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	1,476		$	(110	)

Inventory_Tables

Inventory (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Components of Inventory	At March 31, 2015 and December 31, 2014, inventory consisted of the following:
	(In thousands)	March 31,		December 31,
		2015		2014
	Raw materials	$	35,891	$	34,831
	Work in process		2,613		3,750
	Finished goods		54,619		48,129
	Total	$	93,123	$	86,710

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of March 31, 2015 and December 31, 2014:
	(In thousands)	March 31, 2015							December 31, 2014
		Gross		Accumulated			Net Value		Gross		Accumulated			Net Value
		Value		Amortization					Value		Amortization
	Customer relationships	$	5,787	$	(2,146	)	$	3,641	$	6,310	$	(2,136	)	$	4,174
	Developed technology		5,696		(3,660	)		2,036		6,005		(3,577	)		2,428
	Intellectual property		2,340		(1,603	)		737		2,340		(1,520	)		820
	Trade names		270		(220	)		50		270		(205	)		65
	Other		11		(11	)		—		12		(11	)		1
	Total	$	14,104	$	(7,640	)	$	6,464	$	14,937	$	(7,449	)	$	7,488
Estimated Future Amortization Expense Related to Intangible Asset	As of March 31, 2015, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)	Amount
	Remainder of 2015	$	1,413
	2016		1,648
	2017		1,145
	2018		691
	2019		298
	Thereafter		1,269
	Total	$	6,464

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the three months ended March 31, 2015 is as follows:
	(In thousands)		Stockholders’
			Equity
	Balance, December 31, 2014		$	549,013
	Net income			3,317
	Dividend payments			(4,811	)
	Dividends accrued for unvested restricted stock units			11
	Net unrealized losses on available-for-sale securities (net of tax)			(503	)
	Defined benefit plan adjustments			68
	Foreign currency translation adjustment			(3,318	)
	Proceeds from stock option exercises			280
	Purchase of treasury stock			(3,035	)
	Income tax benefit from exercise of stock options			8
	Stock-based compensation expense			1,639
	Balance, March 31, 2015		$	542,669
Cash Dividends	During the three months ended March 31, 2015, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date		Payment Date			Per Share Amount			Total Dividend Paid
	February 5, 2015			February 19, 2015		$	0.09		$	4,811
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, 2015 and 2014:
			Three Months Ended March 31, 2015
	(In thousands)		Unrealized			Defined			Foreign			Total
			Gains			Benefit Plan			Currency
			(Losses) on			Adjustments			Adjustments
			Available-
			for-Sale
			Securities
	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	)
			Three Months Ended March 31, 2014
	(In thousands)		Unrealized			Defined			Foreign			Total
			Gains			Benefit Plan			Currency
			(Losses) on			Adjustments			Adjustments
			Available-
			for-Sale
			Securities
	Beginning balance		$	10,737		$	(891	)	$	907		$	10,753
	Other comprehensive income (loss) before reclassifications			402			—			252			654
	Amounts reclassified from accumulated other comprehensive income			(1,323	)		—			—			(1,323	)
	Net current period other comprehensive income(loss)			(921	)		—			252			(669	)
	Ending balance		$	9,816		$	(891	)	$	1,159		$	10,084
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, 2015 and 2014:
	(In thousands)		Three Months Ended March 31, 2015
	Details about Accumulated Other Comprehensive Income		Amount Reclassified			Affected Line Item in the
	Components		from Accumulated			Statement Where Net
			Other Comprehensive			Income Is Presented
			Income
	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.
	(In thousands)		Three Months Ended March 31, 2014
	Details about Accumulated Other Comprehensive Income		Amount Reclassified			Affected Line Item in the
	Components		from Accumulated			Statement Where Net
			Other Comprehensive			Income Is Presented
			Income
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities		$	2,170			Net realized investment gain
	Impairment expense			—			Net realized investment gain
	Total reclassifications for the period, before tax			2,170
	Tax (expense) benefit			(847	)
	Total reclassifications for the period, net of tax		$	1,323
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, 2015 and 2014:
			Three Months Ended									Three Months Ended
			March 31, 2015									March 31, 2014
	(In thousands)		Before-Tax			Tax			Net-of-Tax			Before-Tax			Tax			Net-of-Tax
			Amount			(Expense)			Amount			Amount			Benefit			Amount
						Benefit
	Unrealized gains (losses) on available-for-sale securities		$	2,230		$	(870	)	$	1,360		$	659		$	(257	)	$	402
	Reclassification adjustment for amounts included in net income			(2,956	)		1,161			(1,795	)		(2,170	)		847			(1,323	)
	Foreign currency translation adjustment			(3,318	)		—			(3,318	)		252			—			252
	Total Other Comprehensive Income (Loss)		$	(4,044	)	$	291		$	(3,753	)	$	(1,259	)	$	590		$	(669	)

Earnings_per_Share_Tables

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014 is as follows:
		Three Months Ended
		March 31,
	(In thousands, except per share amounts)	2015		2014
	Numerator
	Net income	$	3,317	$	9,607
	Denominator
	Weighted average number of shares – basic		53,399		56,751
	Effect of dilutive securities
	Stock options		220		602
	Restricted stock and restricted stock units		15		15
	Weighted average number of shares – diluted		53,634		57,368
	Net income per share – basic	$	0.06	$	0.17
	Net income per share – diluted	$	0.06	$	0.17

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014. Asset information by reportable segment is not reported, since we do not produce such information internally.
		Three Months Ended
		March 31, 2015				March 31, 2014
	(In thousands)	Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	116,014	$	49,859	$	118,162	$	61,353
	Enterprise Networks		26,821		15,704		28,842		16,437
	Total	$	142,835	$	65,563	$	147,004	$	77,790
Sales Information by Product Category	The table below presents sales information by product category for the three months ended March 31, 2015 and 2014:
		Three Months Ended
		March 31,
	(In thousands)	2015		2014
	Carrier Systems	$	100,439	$	99,553
	Business Networking		35,381		37,919
	Loop Access		7,015		9,532
	Total	$	142,835	$	147,004
Subcategory Revenues	The table below presents subcategory revenues for the three months ended March 31, 2015 and 2014:
		Three Months Ended
		March 31,
	(In thousands)	2015		2014
	Core Products
	Broadband Access (included in Carrier Systems)	$	84,794	$	81,527
	Optical (included in Carrier Systems)		12,504		12,789
	Internetworking (included in Business Networking)		34,159		36,946
	Subtotal		131,457		131,262
	Legacy Products
	HDSL (does not include T1) (included in Loop Access)		6,703		8,877
	Other products (excluding HDSL)		4,675		6,865
	Subtotal		11,378		15,742
	Total	$	142,835	$	147,004

Liability_for_Warranty_Returns1

Liability for Warranty Returns (Tables)	3 Months Ended
	Mar. 31, 2015
Product Warranties Disclosures [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, 2015 and 2014 is as follows:
		Three Months Ended
		March 31,
		2015			2014
	(In thousands)
	Balance at beginning of period	$	8,415		$	8,977
	Plus: Amounts charged to cost and expenses		461			434
	Less: Deductions		(192	)		(2,019	)
	Balance at end of period	$	8,684		$	7,392

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policy [Line Items]
Reduction of pre-tax income	$0.80
Increase in other expenses	1.3
Other Receivables [Member]
Summary of Significant Accounting Policy [Line Items]
Prior period reclassification adjustment		-2.3
Accounts Receivable [Member]
Summary of Significant Accounting Policy [Line Items]
Prior period reclassification adjustment		$2.30

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Effective tax rate	39.80%	34.60%

Pension_Benefit_Plan_Summariza

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$340	$305
Interest cost	159	215
Expected return on plan assets	-261	-279
Amortization of actuarial losses	105
Net periodic pension cost	$343	$241

StockBased_Compensation_StockB

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, Restricted Stock Units (RSUs) and Restricted Stock (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$1,639	$2,057
Tax benefit for expense associated with non-qualified options	-180	-284
Total stock-based compensation expense, net of tax	1,459	1,773
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	90	116
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	691	1,026
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	858	915
Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$1,549	$1,941

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) (Stock Options [Member], USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	38.75%	39.57%
Risk-free interest rate	1.46%	1.86%
Expected dividend yield	1.60%	1.38%
Expected life (in years)	6 years 5 months 19 days	6 years 3 months
Weighted-average estimated value	$7.63	$9.28

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeitures for stock options	3.10%
Compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized	15.2
Recognition period of non-vested compensation cost	2 years 8 months 12 days
Total pre-tax intrinsic value of options exercised	0.1
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs and restricted stock grants in period	0	0
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	0	0
Number of RSUs and restricted stock forfeitures in period	0	0
Number of RSUs and restricted stock vesting in period	0	0
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%

StockBased_Compensation_Summar1

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) (USD $)	3 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Options, outstanding, Beginning Balance	6,981
Number of Options, granted	2
Number of Options, forfeited	-79
Number of Options, expired	-19
Number of Options, exercised	-17
Number of Options, outstanding, Ending Balance	6,868	6,981
Number of Options, vested and expected to vest, Ending Balance	6,678
Number of Options, Options exercisable	4,362
Weighted Average Exercise Price, outstanding, Beginning Balance	$23.62
Weighted Average Exercise Price, granted	$22.56
Weighted Average Exercise Price, forfeited	$20.87
Weighted Average Exercise Price, expired	$27.19
Weighted Average Exercise Price, exercised	$16.58
Weighted Average Exercise Price, outstanding, Ending Balance	$23.66	$23.62
Weighted Average Exercise Price, vested and expected to vest, Ending Balance	$23.73
Weighted Average Exercise Price, Options exercisable	$25.17
Weighted Average Remaining Contractual Life In Years, Options outstanding	6 years 2 months 5 days	6 years 5 months 12 days
Weighted Average Remaining Contractual Life In Years, Options vested and expected to vest	6 years 1 month 10 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	4 years 8 months 27 days
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$3,037	$10,625
Aggregate Intrinsic Value, Options vested and expected to vest	2,553
Aggregate Intrinsic Value, Options exercisable	$2,303

Investments_Securities_and_Inv

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$270,077	$281,363
Gross Unrealized Gains	14,619	15,470
Gross Unrealized Losses	-751	-771
Available-for-sale-securities, Carrying Value	283,945	296,062
Restricted investment held at cost	30,000	30,000
Other investments held at cost	1,493	1,506
Total carrying value of available-for-sale investments	315,438	327,568
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,071	13,897
Gross Unrealized Gains	2,555	2,409
Gross Unrealized Losses	-54	-12
Available-for-sale-securities, Carrying Value	16,572	16,294
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	132,343	111,261
Gross Unrealized Gains	250	186
Gross Unrealized Losses	-205	-186
Available-for-sale-securities, Carrying Value	132,388	111,261
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	92,810	127,341
Gross Unrealized Gains	318	480
Gross Unrealized Losses	-11	-34
Available-for-sale-securities, Carrying Value	93,117	127,787
Municipal Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,245	2,465
Available-for-sale-securities, Carrying Value	4,245	2,465
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,608	26,399
Gross Unrealized Gains	11,496	12,395
Gross Unrealized Losses	-481	-539
Available-for-sale-securities, Carrying Value	$37,623	$38,255

Investments_Contractual_Maturi

Investments - Contractual Maturities of Corporate Bonds and Municipal Fixed-Rate Bonds (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale-securities, Fair Value/Carrying Value	$283,945	$296,062
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	44,108
One to two years	39,163
Two to three years	49,117
Available-for-sale-securities, Fair Value/Carrying Value	132,388	111,261
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	30,407
One to two years	39,660
Two to three years	21,826
Three to five years	1,224
Available-for-sale-securities, Fair Value/Carrying Value	$93,117	$127,787

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Restricted certificate of deposit held	$30,000,000	$30,000,000
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	$29,700,000
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_Gai

Investments - Gross Realized Gains and Losses on Sale of Securities (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$3,145	$2,228
Gross realized losses	($30)	($36)

Investments_Fair_Value_Measure

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$283,945	$296,062
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,572	16,294
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	132,388	111,261
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	93,117	127,787
Municipal Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,245	2,465
Fair Value, Measurements, Recurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	15,225
Available-for-sale securities	283,945	296,062
Total	299,170	297,225
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	3,228
Available-for-sale securities	54,195	54,549
Total	57,423	55,712
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	11,997
Available-for-sale securities	229,750	241,513
Total	241,747	241,513
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	3,228	1,163
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	3,228	1,163
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	11,997
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	11,997
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,572	16,294
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	16,572	16,294
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	132,388	111,261
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	132,388	111,261
Fair Value, Measurements, Recurring [Member] | Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	93,117	127,787
Fair Value, Measurements, Recurring [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	93,117	127,787
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,245	2,465
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	4,245	2,465
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,034	9,661
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,034	9,661
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	28,589	28,594
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$28,589	$28,594

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2015	Mar. 31, 2015
		Forward Contracts [Member]	Forward Contracts [Member]
		USD ($)	EUR (€)
Derivative [Line Items]
Maximum contractual period for derivatives	12 months
Derivative, notional amount		$67,700,000	€ 63,000,000
Derivative maturity year		2015	2015

Derivative_Instruments_and_Hed3

Derivative Instruments and Hedging Activities - Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) (Significant Other Observable Inputs (Level 2) [Member], Foreign Exchange Contracts [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Other Receivables [Member]
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives asset, fair value	$1,692	$249
Accounts Payable [Member]
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives liability, fair value	($607)	($10)

Derivative_Instruments_and_Hed4

Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail) (Foreign Exchange Contracts [Member], Other Income (Expense) [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$1,476	($110)

Inventory_Components_of_Invent

Inventory - Components of Inventory (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]
Raw materials	$35,891	$34,831
Work in process	2,613	3,750
Finished goods	54,619	48,129
Total	$93,123	$86,710

Inventory_Additional_Informati

Inventory - Additional Information (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$16.90	$16.90
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$7.60	$7.80

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, relates to acquisition	$3,500,000		$3,500,000
Impairment losses	0
Amortization expense	$500,000	$600,000

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill [Line Items]
Gross Value	$14,104	$14,937
Accumulated Amortization	-7,640	-7,449
Net Value	6,464	7,488
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	5,787	6,310
Accumulated Amortization	-2,146	-2,136
Net Value	3,641	4,174
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	5,696	6,005
Accumulated Amortization	-3,660	-3,577
Net Value	2,036	2,428
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	2,340	2,340
Accumulated Amortization	-1,603	-1,520
Net Value	737	820
Trade Names [Member]
Goodwill [Line Items]
Gross Value	270	270
Accumulated Amortization	-220	-205
Net Value	50	65
Other [Member]
Goodwill [Line Items]
Gross Value	11	12
Accumulated Amortization	-11	-11
Net Value		$1

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2015	$1,413
2016	1,648
2017	1,145
2018	691
2019	298
Thereafter	1,269
Net Value	$6,464	$7,488

Stockholders_Equity_Summary_of

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Beginning Balance	$549,013
Net Income	3,317	9,607
Dividend payments	-4,811
Dividends accrued for unvested restricted stock units	11
Net unrealized losses on available-for-sale securities (net of tax)	-503	-921
Defined benefit plan adjustments	68
Foreign currency translation adjustment	-3,318	252
Proceeds from stock option exercises	280	1,541
Purchase of treasury stock	-3,035
Income tax benefit from exercise of stock options	8
Stock-based compensation expense	1,639	2,057
Ending Balance	$542,669

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Stock repurchased, shares	100,000
Shares repurchased, average price per share	$21.52
Additional shares authorized for purchase	4,700,000
Number of Options, exercised	-17,000
Exercise price of stock options, lower range limit	$15.29
Exercise price of stock options, upper range limit	$22.53
Proceeds from stock option exercises	$280	$1,541
Predecessor [Member]
Equity, Class of Treasury Stock [Line Items]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	45,000,000

Stockholders_Equity_Cash_Divid

Stockholders' Equity - Cash Dividends (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Dividends Payable [Line Items]
Record Date	7-May-15
Payment Date	21-May-15
Per Share Amount	$0.09	$0.09
Total Dividend Paid	$4,811	$5,102
Cash dividends paid in February [Member]
Dividends Payable [Line Items]
Record Date	5-Feb-15
Payment Date	19-Feb-15
Per Share Amount	$0.09
Total Dividend Paid	$4,811

Stockholders_Equity_Changes_in

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	($75)	$10,753
Other comprehensive income (loss) before reclassifications	-1,958	654
Amounts reclassified from accumulated other comprehensive income	-1,795	-1,323
Other Comprehensive Loss, net of tax	-3,753	-669
Ending balance	-3,828	10,084
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	8,964	10,737
Other comprehensive income (loss) before reclassifications	1,360	402
Amounts reclassified from accumulated other comprehensive income	-1,863	-1,323
Other Comprehensive Loss, net of tax	-503	-921
Ending balance	8,461	9,816
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	-5,757		-891
Amounts reclassified from accumulated other comprehensive income	68
Other Comprehensive Loss, net of tax	68
Ending balance	-5,689	-891	-891
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	-3,282	907
Other comprehensive income (loss) before reclassifications	-3,318	252
Other Comprehensive Loss, net of tax	-3,318	252
Ending balance	($6,600)	$1,159

Stockholders_Equity_Reclassifi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, before tax	$5,510	$14,679
Tax (expense) benefit	-2,193	-5,072
Total reclassifications for the period, net of tax	3,317	9,607
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit plan adjustments - actuarial losses	-98
Total reclassifications for the period, before tax	2,956	2,170
Tax (expense) benefit	-1,161	-847
Total reclassifications for the period, net of tax	1,795	1,323
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	3,076	2,170
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	($22)

Stockholders_Equity_Other_Comp

Stockholders' Equity - Other Comprehensive Income (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$2,230	$659
Reclassification adjustment for amounts included in net income, Before-Tax Amount	-2,956	-2,170
Foreign currency translation adjustment, Before-Tax Amount	-3,318	252
Total Other Comprehensive Income (Loss), Before-Tax Amount	-4,044	-1,259
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	-870	-257
Reclassification adjustment for amounts included in net income, Tax Benefit	1,161	847
Foreign currency translation adjustment, Tax Benefit	0	0
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	291	590
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	1,360	402
Reclassification adjustment for amounts included in net income, Net-of-Tax Amount	-1,795	-1,323
Foreign currency translation adjustment, Net-of-Tax Amount	-3,318	252
Other Comprehensive Loss, net of tax	($3,753)	($669)

Earnings_Per_Share_Summary_of_

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Numerator
Net Income	$3,317	$9,607
Denominator
Weighted average number of shares - basic	53,399	56,751
Effect of dilutive securities
Stock options	220	602
Restricted stock and restricted stock units	15	15
Weighted average number of shares - diluted	53,634	57,368
Net income per share - basic	$0.06	$0.17
Net income per share - diluted	$0.06	$0.17

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Anti-dilutive options, Total	5.6	3.1

Segment_Information_Additional

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
	Product_Category
	Segment
Segment Reporting [Abstract]
Number of operating reportable segments	2
Number of product categories	3

Segment_Information_Sales_and_

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Sales	$142,835	$147,004
Gross Profit	65,563	77,790
Carrier Networks [Member]
Segment Reporting Information [Line Items]
Sales	116,014	118,162
Gross Profit	49,859	61,353
Enterprise Networks [Member]
Segment Reporting Information [Line Items]
Sales	26,821	28,842
Gross Profit	$15,704	$16,437

Segment_Information_Sales_Info

Segment Information - Sales Information by Product Category (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Sales	$142,835	$147,004
Carrier Systems [Member]
Revenue from External Customer [Line Items]
Sales	100,439	99,553
Business Networking [Member]
Revenue from External Customer [Line Items]
Sales	35,381	37,919
Loop Access [Member]
Revenue from External Customer [Line Items]
Sales	$7,015	$9,532

Segment_Information_Subcategor

Segment Information - Subcategory Revenues (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Sales	$142,835	$147,004
Core Products [Member]
Revenue from External Customer [Line Items]
Sales	131,457	131,262
Legacy Products [Member]
Revenue from External Customer [Line Items]
Sales	11,378	15,742
Broadband Access (Included in Carrier Systems) [Member] | Core Products [Member]
Revenue from External Customer [Line Items]
Sales	84,794	81,527
Optical (Included in Carrier Systems) [Member] | Core Products [Member]
Revenue from External Customer [Line Items]
Sales	12,504	12,789
Internetworking (Included in Business Networking) [Member] | Core Products [Member]
Revenue from External Customer [Line Items]
Sales	34,159	36,946
HDSL (Does not Include T1) (Included in Loop Access) [Member] | Legacy Products [Member]
Revenue from External Customer [Line Items]
Sales	6,703	8,877
Other Products (Excluding HDSL) [Member] | Legacy Products [Member]
Revenue from External Customer [Line Items]
Sales	$4,675	$6,865

Liability_for_Warranty_Returns2

Liability for Warranty Returns - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Product Warranties Disclosures [Abstract]
Period of warranty for product defects	90 days to ten years
Liability for warranty obligations	$8,684	$8,415	$7,392	$8,977

Liability_for_Warranty_Returns3

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$8,415	$8,977
Plus: Amounts charged to cost and expenses	461	434
Less: Deductions	-192	-2,019
Balance at end of period	$8,684	$7,392

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (Director Emeritus [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014
Director Emeritus [Member]
Related Party Transaction
Related party legal fees	$10

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	Mar. 31, 2015
	EquityUnit
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds	$7,900,000
Number of private equity funds	2
Commitments towards private equity funds	7,700,000
Private Equity Funds [Member]
Contingencies And Commitments [Line Items]
Contribution to private equity funds	$8,400,000

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	6-May-15	Apr. 21, 2015	21-May-15
Subsequent Event [Line Items]
Dividend declaration date	21-Apr-15
Dividend record date	7-May-15
Dividend payment date	21-May-15
Stock repurchased, shares	100,000
Shares repurchased, average price per share	$21.52
Additional shares authorized for purchase	4,700,000
Subsequent Events [Member]
Subsequent Event [Line Items]
Cash dividend per common share			$0.09
Cash dividend				$4.70
Stock repurchased, shares		1,200,000
Shares repurchased, average price per share		$16.33
Additional shares authorized for purchase		3,400,000