ADTRAN (ADTN) 10-Q 6 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 22, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Entity Registrant Name	'ADTRAN INC	'
Entity Central Index Key	'0000926282	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	54,704,954

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$58,903	$58,298
Short-term investments	45,930	105,760
Accounts receivable, less allowance for doubtful accounts of $116 and $130 at June 30, 2014 and December 31, 2013, respectively	115,538	85,814
Other receivables	23,841	18,249
Inventory	89,239	90,111
Prepaid expenses	5,295	4,325
Deferred tax assets, net	15,054	17,083
Total Current Assets	353,800	379,640
Property, plant and equipment, net	75,265	76,739
Deferred tax assets, net	11,092	9,622
Goodwill	3,492	3,492
Other assets	12,087	11,180
Long-term investments	311,622	309,225
Total Assets	767,358	789,898
Current Liabilities	'	'
Accounts payable	62,103	48,282
Unearned revenue	26,364	22,205
Accrued expenses	11,865	12,776
Accrued wages and benefits	15,930	14,040
Income tax payable, net	9,400	5,002
Total Current Liabilities	125,662	102,305
Non-current unearned revenue	15,213	14,643
Other non-current liabilities	24,424	22,144
Bonds payable	30,000	46,200
Total Liabilities	195,299	185,292
Commitments and contingencies (see Note 15)	'	'
Stockholders' Equity	'	'
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 54,698 shares outstanding at June 30, 2014 and 79,652 shares issued and 56,918 shares outstanding at December 31, 2013	797	797
Additional paid-in capital	237,727	233,511
Accumulated other comprehensive income	11,437	10,753
Retained earnings	897,414	884,451
Less treasury stock at cost: 24,954 and 22,734 shares at June 30, 2014 and December 31, 2013, respectively	-575,316	-524,906
Total Stockholders' Equity	572,059	604,606
Total Liabilities and Stockholders' Equity	$767,358	$789,898

Consolidated_Balance_Sheets_Un1

Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$116	$130
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	79,652	79,652
Common stock, shares outstanding	54,698	56,918
Treasury stock, shares	24,954	22,734

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]	'	'	'	'
Sales	$176,129	$162,233	$323,133	$305,246
Cost of sales	89,332	82,435	158,546	155,771
Gross Profit	86,797	79,798	164,587	149,475
Selling, general and administrative expenses	33,788	32,685	67,727	63,288
Research and development expenses	33,670	33,060	66,223	65,571
Operating Income	19,339	14,053	30,637	20,616
Interest and dividend income	1,054	1,674	2,348	3,442
Interest expense	-148	-575	-375	-1,156
Net realized investment gain	2,340	1,553	4,532	5,198
Other income (expense), net	-774	129	-652	-1,543
Income before provision for income taxes	21,811	16,834	36,490	26,557
Provision for income taxes	-7,416	-6,975	-12,488	-8,808
Net Income	$14,395	$9,859	$24,002	$17,749
Weighted average shares outstanding - basic	55,409	59,056	56,077	60,443
Weighted average shares outstanding - diluted	55,729	59,311	56,559	60,660
Earnings per common share - basic	$0.26	$0.17	$0.43	$0.29
Earnings per common share - diluted	$0.26	$0.17	$0.42	$0.29
Dividend per share	$0.09	$0.09	$0.18	$0.18

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Net income	$14,395	$9,859	$24,002	$17,749
Other Comprehensive Income (Loss), net of tax:	'	'	'	'
Net unrealized gains (losses) on available-for-sale securities	1,219	-1,698	298	-3,342
Foreign currency translation	134	-1,713	386	-1,390
Other Comprehensive Income (Loss), net of tax	1,353	-3,411	684	-4,732
Comprehensive Income, net of tax	$15,748	$6,448	$24,686	$13,017

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:	'	'
Net income	$24,002	$17,749
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	7,467	7,373
Amortization of net premium on available-for-sale investments	2,272	3,315
Net realized gain on long-term investments	-4,532	-5,198
Net loss on disposal of property, plant and equipment	37	17
Stock-based compensation expense	4,149	4,340
Deferred income taxes	377	150
Tax benefit from stock option exercises	67	21
Excess tax benefits from stock-based compensation arrangements	-58	-21
Changes in operating assets and liabilities:	'	'
Accounts receivable, net	-29,949	-23,018
Other receivables	-5,706	-2,727
Inventory	841	13,336
Prepaid expenses and other assets	-3,103	-665
Accounts payable	14,425	19,786
Accrued expenses and other liabilities	8,248	-6,587
Income tax payable, net	4,442	1,094
Net cash provided by operating activities	22,979	28,965
Cash flows from investing activities:	'	'
Purchases of property, plant and equipment	-4,919	-3,201
Proceeds from disposals of property, plant and equipment	1	'
Proceeds from sales and maturities of available-for-sale investments	166,518	224,163
Purchases of available-for-sale investments	-106,406	-179,730
Net cash provided by investing activities	55,194	41,232
Cash flows from financing activities:	'	'
Proceeds from stock option exercises	1,781	819
Purchases of treasury stock	-53,091	-89,917
Dividend payments	-10,137	-10,982
Payments on long-term debt	-16,500	'
Excess tax benefits from stock-based compensation arrangements	58	21
Net cash used in financing activities	-77,889	-100,059
Net increase (decrease) in cash and cash equivalents	284	-29,862
Effect of exchange rate changes	321	-1,036
Cash and cash equivalents, beginning of period	58,298	68,457
Cash and cash equivalents, end of period	58,903	37,559
Supplemental disclosure of non-cash investing activities	'	'
Purchases of property, plant and equipment included in accounts payable	$423	$574

Summary_of_Significant_Account

Summary of Significant Accounting Policies	35 Months Ended
	Jun. 30, 2014
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, 2013 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary for a fair presentation of these interim statements have been 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, 2013, filed on February 27, 2014 with the SEC.
	Changes in Classifications
	We corrected immaterial misclassifications between the operating and investing sections of our consolidated statements of cash flows and adjusted our cash flows for the six months ended June 30, 2013 in these categories by $0.5 million in order to be consistent with the 2014 presentation.
	Out of Period Adjustment
	During the year ended December 31, 2013, we identified two adjustments in the acquired NSN (formerly Nokia Siemens Networks) Broadband Access business (NSN BBA business) relating to customer payment discounts for one customer, and recoverable VAT taxes on certain vendor freight invoices that should have been recorded in prior periods. These adjustments resulted from a $0.5 million understatement of net income in the first two quarters of 2013. We evaluated the impact of the adjustments on the results of our previously issued financial statements for the second quarter of 2013 and concluded that the impact was not material. We also evaluated the impact of the cumulative effect of the adjustments in 2013 and concluded that the impact is not material to our results for the year 2013. Accordingly, during the three months ended September 30, 2013 we recorded an out of period adjustment to correct these issues.
	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 working capital adjustments under negotiation related to the NSN BBA business acquisition, 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.

Business_Combination

Business Combination	35 Months Ended
	Jun. 30, 2014
Business Combinations [Abstract]	'
Business Combination	'
	2. BUSINESS COMBINATION
	On May 4, 2012, we acquired the NSN BBA business. This acquisition provides us with an established customer base in key markets and complementary, market-focused products and was accounted for as a business combination. We have included the financial results of the NSN BBA business in our consolidated financial statements since the date of acquisition. These revenues are included in the Carrier Networks division in the Broadband Access subcategory.
	The following supplemental pro forma information presents the financial results of the combined entity for the years ended December 31, 2012 and 2011. The pro forma results of the acquired NSN BBA business for the period January 1, 2012 to May 4, 2012 and January 1, 2011 to December 31, 2011 were not included in our consolidated financial results for the years ended December 31, 2012 or 2011. There were no material, non-recurring pro forma adjustments to the historical data.
	This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2011, nor are they indicative of any future results.
	(In thousands) (Unaudited)	2012		2011
	Pro forma revenue	$	672,044	$	913,485
	Pro forma pre-tax loss	$	57,906	$	169,162
	Weighted average exchange rate during the period (EURO/USD)	€	1.00/$1.29	€	1.00/$1.38

Income_Taxes

Income Taxes	35 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	3. INCOME TAXES
	Our effective tax rate increased from 33.2% in the six months ended June 30, 2013 to 34.2% in the six months ended June 30, 2014. The increase in the effective tax rate between the two periods is primarily attributable to the net effect of the exclusion of a benefit for the research tax credit, which expired on December 31, 2013, offset by the release of a valuation allowance attributable to a foreign subsidiary in 2014.

Pension_Benefit_Plan

Pension Benefit Plan	35 Months Ended
	Jun. 30, 2014
Compensation And Retirement Disclosure [Abstract]	'
Pension Benefit Plan	'
	4. PENSION BENEFIT PLAN
	We maintain a defined benefit pension plan covering employees in certain foreign countries.
	The following table summarizes the components of net periodic pension cost for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Service cost	$	306		$	294		$	611		$	594
	Interest cost		216			182			431			369
	Expected return on plan assets		(280	)		(248	)		(559	)		(501	)
	Net periodic pension cost	$	242		$	228		$	483		$	462

StockBased_Compensation

Stock-Based Compensation	35 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation	'
	5. STOCK-BASED COMPENSATION
	The following table summarizes the stock-based compensation expense related to stock options, restricted stock units (RSUs) and restricted stock for the three and six months ended June 30, 2014 and 2013, which was recognized as follows:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Stock-based compensation expense included in cost of sales	$	119		$	110		$	235		$	216
	Selling, general and administrative expense		1,015			1,042			2,041			2,105
	Research and development expense		958			956			1,873			2,019
	Stock-based compensation expense included in operating expenses		1,973			1,998			3,914			4,124
	Total stock-based compensation expense		2,092			2,108			4,149			4,340
	Tax benefit for expense associated with non-qualified options		(296	)		(310	)		(580	)		(617	)
	Total stock-based compensation expense, net of tax	$	1,796		$	1,798		$	3,569		$	3,723
	The fair value of our stock options was estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate.
	There were no options granted during the three months ended June 30, 2014 or the three and six months ended June 30, 2013. The weighted-average assumptions and value of options granted for the six months ended June 30, 2014 are summarized as follows:
		Six Months Ended
		June 30,
		2014
	Expected volatility		39.57	%
	Risk-free interest rate		1.86	%
	Expected dividend yield		1.38	%
	Expected life (in years)		6.25
	Weighted-average estimated value	$	9.28
	The fair value of our RSUs is calculated using a Monte Carlo Simulation valuation method. No RSUs were granted, forfeited, or vested during the three and six months ended June 30, 2014 or 2013.
	The fair value of restricted stock is equal to the closing price of our stock on the date of grant. We granted four thousand shares of restricted stock during the three and six months ended June 30, 2014 at a fair value of $21.30 per share. No restricted stock was forfeited or vested during the three and six months ended June 30, 2014 or 2013.
	Stock-based compensation expense recognized in our Consolidated Statements of Income for the three and six months ended June 30, 2014 and 2013 is based on options, RSUs and restricted stock ultimately expected to vest, and has been reduced for estimated forfeitures. Estimated forfeitures for stock options were based upon historical experience and approximate 2.5% annually. We estimated a 0% forfeiture rate for our RSUs and restricted stock due to the limited number of recipients and historical experience for these awards.
	As of June 30, 2014, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $14.1 million, which is expected to be recognized over an average remaining recognition period of 2.4 years.
	The following table is a summary of our stock options outstanding as of December 31, 2013 and June 30, 2014 and the changes that occurred during the six months ended June 30, 2014:
	(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, 2013		6,358		$	24.43			6.6		$	25,878
	Options granted		2		$	26.03
	Options cancelled/forfeited		(144	)	$	26.02
	Options exercised		(91	)	$	19.56
	Options outstanding, June 30, 2014		6,125		$	24.46			6.09		$	8,724
	Options exercisable, June 30, 2014		3,776		$	24.81			4.68		$	4,900
	The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between the closing price of our stock on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on June 30, 2014. The aggregate intrinsic value will change based on the fair market value of our stock.
	The total pre-tax intrinsic value of options exercised during the three and six months ended June 30, 2014 was $0.1 million and $0.6 million, respectively.

Investments

Investments	35 Months Ended
	Jun. 30, 2014
Investments Debt And Equity Securities [Abstract]	'
Investments	'
	6. INVESTMENTS
	At June 30, 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	$	12,733		$	3,037		$	(15	)	$	15,755
	Corporate bonds		98,995			403			(7	)		99,391
	Municipal fixed-rate bonds		155,171			825			(14	)		155,982
	Municipal variable rate demand notes		15,120			—			—			15,120
	Marketable equity securities		25,896			14,249			(418	)		39,727
	Available-for-sale securities held at fair value	$	307,915		$	18,514		$	(454	)	$	325,975
	Restricted investment held at cost											30,000
	Other investments held at cost											1,577
	Total carrying value of available-for-sale investments										$	357,552
	At December 31, 2013, 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	$	12,300		$	2,847		$	(24	)	$	15,123
	Corporate bonds		166,370			534			(45	)		166,859
	Municipal fixed-rate bonds		135,773			583			(54	)		136,302
	Municipal variable rate demand notes		8,310			—			—			8,310
	Marketable equity securities		24,654			13,975			(177	)		38,452
	Available-for-sale securities held at fair value	$	347,407		$	17,939		$	(300	)	$	365,046
	Restricted investment held at cost											48,250
	Other investments held at cost											1,689
	Total carrying value of available-for-sale investments										$	414,985
	As of June 30, 2014, 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	$	7,187		$	25,826
	One to two years		46,881			66,823
	Two to three years		45,323			49,269
	Three to five years		—			14,064
	Total	$	99,391		$	155,982
	Our investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5% of the market value of our total investment portfolio.
	At June 30, 2014, 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). During the first quarter of 2014, we made a principal payment on the Bond of $16.5 million. At June 30, 2014, 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 and six months ended June 30, 2014 and 2013, other-than-temporary impairment charges were not significant.
	Realized gains and losses on sales of securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our investments.
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Gross realized gains	$	2,407		$	1,728		$	4,635		$	5,455
	Gross realized losses	$	(67	)	$	(175	)	$	(103	)	$	(257	)
	As of June 30, 2014 and 2013, gross unrealized losses related to individual securities in a continuous loss position for 12 months or longer were not significant.
	We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1—Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
		Fair Value Measurements at June 30, 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	$	11,737		$	11,737		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		15,755			15,755			—			—
	Available-for-sale debt securities
	Corporate bonds		99,391			—			99,391			—
	Municipal fixed-rate bonds		155,982			—			155,982			—
	Municipal variable rate demand notes		15,120			—			15,120			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		12,085			12,085			—			—
	Marketable equity securities – other		27,642			27,642			—			—
Available-for-sale securities		325,975			55,482			270,493			—
Total	$	337,712		$	67,219		$	270,493		$	—
	Fair Value Measurements at December 31, 2013 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	$	3,949		$	3,949		$	—		$	—
Available-for-sale securities
Deferred compensation plan assets		15,123			15,123			—			—
Available-for-sale debt securities
Corporate bonds		166,859			—			166,859			—
Municipal fixed-rate bonds		136,302			—			136,302			—
Municipal variable rate demand notes		8,310			—			8,310			—
Available-for-sale marketable equity securities
Marketable equity securities – technology industry		11,398			11,398			—			—
Marketable equity securities – other		27,054			27,054			—			—
Available-for-sale securities		365,046			53,575			311,471			—
Total	$	368,995		$	57,524		$	311,471		$	—
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	35 Months Ended
	Jun. 30, 2014
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Hedging Activities	'
	7. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES
	We have certain international customers who are billed in their local currency. Changes in the monetary exchange rates may adversely affect our results of operations and financial condition. When appropriate, we enter into various derivative transactions to enhance our ability to manage the volatility relating to these typical business exposures. We do not hold or issue derivative instruments for trading or other speculative purposes. Our derivative instruments are recorded in the Consolidated Balance Sheets at their fair values. Our derivative instruments do not qualify for hedge accounting, and accordingly, all changes in the fair value of the instruments are recognized as other income (expense) in the Consolidated Statements of Income. The maximum contractual period for our derivatives is currently less than twelve months. Our derivative instruments are not subject to master netting arrangements and are not offset in the Consolidated Balance Sheets.
	As of June 30, 2014, we had forward contracts outstanding with notional amounts totaling €19.3 million ($26.4 million), which mature through 2014.
	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2014 and December 31, 2013 were as follows:
	(In thousands)	Balance Sheet	June 30,			December 31,
		Location	2014			2013
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	4		$	18
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(232	)	$	(15	)
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and six months ended June 30, 2014 were as follows:
		Income Statement	Three Months Ended						Six Months Ended
		Location	June 30,						June 30,
	(In thousands)		2014			2013			2014			2013
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	(438	)	$	138		$	(548	)	$	(86	)

Inventory

Inventory	35 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Inventory	'
	8. INVENTORY
	At June 30, 2014 and December 31, 2013, inventory consisted of the following:
	(In thousands)	June 30,		December 31,
		2014		2013
	Raw materials	$	39,557	$	44,093
	Work in process		7,086		3,484
	Finished goods		42,596		42,534
	Total	$	89,239	$	90,111
	We establish reserves for estimated excess, obsolete, or unmarketable inventory equal to the difference between the cost of the inventory and the estimated fair value of the inventory based upon assumptions about future demand and market conditions. At June 30, 2014 and December 31, 2013, raw materials reserves totaled $17.1 million and $16.9 million, respectively, and finished goods inventory reserves totaled $6.0 million and $6.1 million, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	35 Months Ended
	Jun. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets	'
	9. GOODWILL AND INTANGIBLE ASSETS
	We evaluate the carrying value of goodwill, generated from our acquisition of Bluesocket, Inc. and assigned to our Enterprise Networks division, during the fourth quarter of each year. We may perform additional evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we compare the fair value of the reporting unit to which the goodwill is assigned to the reporting unit’s carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, then the amount of the impairment loss is measured. There 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 acquisition of Objectworld Communications Corporation on September 15, 2009, Bluesocket, Inc. on August 4, 2011, and the NSN BBA business on May 4, 2012.
	The following table presents our intangible assets as of June 30, 2014 and December 31, 2013:
	(In thousands)	June 30, 2014							December 31, 2013
		Gross		Accumulated			Net Value		Gross		Accumulated			Net Value
		Value		Amortization					Value		Amortization
	Customer relationships	$	6,914	$	(1,923	)	$	4,991	$	6,996	$	(1,555	)	$	5,441
	Developed technology		6,363		(3,208	)		3,155		6,537		(2,692	)		3,845
	Intellectual property		2,340		(1,353	)		987		2,340		(1,185	)		1,155
	Trade names		270		(175	)		95		270		(145	)		125
	Other		14		(10	)		4		14		(8	)		6
	Total	$	15,901	$	(6,669	)	$	9,232	$	16,157	$	(5,585	)	$	10,572
	Amortization expense, all of which relates to business acquisitions, was $0.6 million for the three months ended June 30, 2014 and 2013, and $1.2 million for the six months ended June 30, 2014 and 2013.
	As of June 30, 2014, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)	Amount
	Remainder of 2014	$	1,140
	2015		2,157
	2016		1,883
	2017		1,284
	2018		778
	Thereafter		1,990
	Total	$	9,232

Stockholders_Equity

Stockholders' Equity	35 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Stockholders' Equity	'
	10. STOCKHOLDERS’ EQUITY
	A summary of the changes in stockholders’ equity for the six months ended June 30, 2014 is as follows:
	(In thousands)	Stockholders’
		Equity
	Balance, December 31, 2013	$	604,606
	Net income		24,002
	Dividend payments		(10,137	)
	Dividends accrued for unvested restricted stock units		(2	)
	Net unrealized gains (losses) on available-for-sale securities (net of tax)		298
	Foreign currency translation adjustment		386
	Proceeds from stock option exercises		1,781
	Purchase of treasury stock		(53,091	)
	Income tax benefit from exercise of stock options		67
	Stock-based compensation expense		4,149
	Balance, June 30, 2014	$	572,059
	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 40.0 million shares of our common stock. On May 14, 2014, our Board of Directors authorized the repurchase of an additional 5.0 million shares of our common stock (bringing the total shares authorized for repurchase to 45.0 million), which will commence upon completion of the repurchase plan announced May 1, 2013. This new authorization will be implemented through open market or private purchases from time to time as conditions warrant.
	During the six months ended June 30, 2014, we repurchased 2.3 million shares of our common stock at an average price of $22.73 per share. We currently have the authority to purchase an additional 6.1 million shares of our common stock under the current plans approved by the Board of Directors.
	Stock Option Exercises
	We issued 0.1 million shares of treasury stock during the six months ended June 30, 2014 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $23.46. We received proceeds totaling $1.8 million from the exercise of these stock options during the six months ended June 30, 2014.
	Dividend Payments
	During the six months ended June 30, 2014, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date	Payment Date		Per Share Amount	Total Dividend Paid
	February 6, 2014	February 20, 2014		$0.09	$5,102
	May 1, 2014	May 15, 2014		$0.09	$5,035
	Other Comprehensive Income
	Other comprehensive income consists of unrealized gains (losses) on available-for-sale securities, reclassification adjustments for amounts included in net income related to impairments of available-for-sale securities and realized gains (losses) on available-for-sale securities, defined benefit plan adjustments and foreign currency translation adjustments.
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2014 and 2013:
		Three Months Ended June 30, 2014
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains			Benefit Plan			Currency
		(Losses) on			Adjustments			Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	9,816		$	(891	)	$	1,159		$	10,084
	Other comprehensive income (loss) before		2,516			—			134			2,650
	reclassifications
	Amounts reclassified from accumulated other		(1,297	)		—			—			(1,297	)
	comprehensive income
	Net current period other comprehensive income (loss)		1,219			—			134			1,353
	Ending balance	$	11,035		$	(891	)	$	1,293		$	11,437
		Three Months Ended June 30, 2013
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains			Benefit Plan			Currency
		(Losses) on			Adjustments			Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	8,464		$	(1,952	)	$	3,435		$	9,947
	Other comprehensive income (loss) before		(802	)		—			(1,713	)		(2,515	)
	reclassifications
	Amounts reclassified from accumulated other		(896	)		—			—			(896	)
	comprehensive income
	Net current period other comprehensive income (loss)		(1,698	)		—			(1,713	)		(3,411	)
	Ending balance	$	6,766		$	(1,952	)	$	1,722		$	6,536
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2014 and 2013:
		Six Months Ended June 30, 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		2,918			—			386			3,304
reclassifications
Amounts reclassified from accumulated other		(2,620	)		—			—			(2,620	)
comprehensive income
Net current period other comprehensive income (loss)		298			—			386			684
Ending balance	$	11,035		$	(891	)	$	1,293		$	11,437
	Six Months Ended June 30, 2013
(In thousands)	Unrealized			Defined			Foreign			Total
	Gains			Benefit Plan			Currency
	(Losses) on			Adjustments			Adjustments
	Available-
	for-Sale
	Securities
Beginning balance	$	10,108		$	(1,952	)	$	3,112		$	11,268
Other comprehensive income (loss) before		(348	)		—			(1,390	)		(1,738	)
reclassifications
Amounts reclassified from accumulated other		(2,994	)		—			—			(2,994	)
comprehensive income
Net current period other comprehensive income (loss)		(3,342	)		—			(1,390	)		(4,732	)
Ending balance	$	6,766		$	(1,952	)	$	1,722		$	6,536
The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2014 and 2013:
(In thousands)	Three Months Ended June 30, 2014
Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
Comprehensive Income 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	$	2,160		Net realized investment gain
Impairment expense		(34	)	Net realized investment gain
Total reclassifications for the period, before tax		2,126
Tax (expense) benefit		(829	)
Total reclassifications for the period, net of tax	$	1,297
(In thousands)	Three Months Ended June 30, 2013
Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
Comprehensive Income 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	$	1,469		Net realized investment gain
Impairment expense		—		Net realized investment gain
Total reclassifications for the period, before tax		1,469
Tax (expense) benefit		(573	)
Total reclassifications for the period, net of tax	$	896
The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2014 and 2013:
(In thousands)	Six Months Ended June 30, 2014
Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
Comprehensive Income 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	$	4,330		Net realized investment gain
Impairment expense		(34	)	Net realized investment gain
Total reclassifications for the period, before tax		4,296
Tax (expense) benefit		(1,676	)
Total reclassifications for the period, net of tax	$	2,620
(In thousands)	Six Months Ended June 30, 2013
Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
	from Accumulated			Statement Where Net Income
Comprehensive Income Components	Other Comprehensive			Is Presented
	Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities	$	4,913			Net realized investment gain
Impairment expense		(4	)		Net realized investment gain
Total reclassifications for the period, before tax		4,909
Tax (expense) benefit		(1,915	)
Total reclassifications for the period, net of tax	$	2,994
The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2014 and 2013:
	Three Months Ended									Three Months Ended
	June 30, 2014									June 30, 2013
(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	$	4,125		$	(1,609	)	$	2,516		$	(1,315	)	$	513	$	(802	)
Reclassification adjustment for amounts included in net income		(2,126	)		829			(1,297	)		(1,469	)		573		(896	)
Foreign currency translation adjustment		134			—			134			(1,713	)		—		(1,713	)
Total Other Comprehensive Income (Loss)	$	2,133		$	(780	)	$	1,353		$	(4,497	)	$	1,086	$	(3,411	)
The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2014 and 2013:
	Six Months Ended									Six Months Ended
	June 30, 2014									June 30, 2013
(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	$	4,784		$	(1,866	)	$	2,918		$	(571	)	$	223	$	(348	)
Reclassification adjustment for amounts included in net income		(4,296	)		1,676			(2,620	)		(4,909	)		1,915		(2,994	)
Foreign currency translation adjustment		386			—			386			(1,390	)		—		(1,390	)
Total Other Comprehensive Income (Loss)	$	874		$	(190	)	$	684		$	(6,870	)	$	2,138	$	(4,732	)

Earnings_Per_Share

Earnings Per Share	35 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	11. EARNINGS PER SHARE
	A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2014 and 2013 is as follows:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In thousands, except per share amounts)	2014		2013		2014		2013
	Numerator
	Net income	$	14,395	$	9,859	$	24,002	$	17,749
	Denominator
	Weighted average number of shares – basic		55,409		59,056		56,077		60,443
	Effect of dilutive securities
	Stock options		288		209		459		177
	Restricted stock and restricted stock units		32		46		23		40
	Weighted average number of shares – diluted		55,729		59,311		56,559		60,660
	Net income per share – basic	$	0.26	$	0.17	$	0.43	$	0.29
	Net income per share – diluted	$	0.26	$	0.17	$	0.42	$	0.29
	Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 4.3 million for the three months ended June 30, 2014 and 2013, and 3.1 million and 5.1 million for the six months ended June 30, 2014 and 2013, respectively.

Segment_Information

Segment Information	35 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	12. 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 tables present information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2014 and 2013. Asset information by reportable segment is not reported, since we do not produce such information internally.
			Three Months Ended
			June 30, 2014				June 30, 2013
	(In thousands)		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	143,455	$	68,053	$	123,333	$	57,913
	Enterprise Networks			32,674		18,744		38,900		21,885
	Total		$	176,129	$	86,797	$	162,233	$	79,798
			Six Months Ended
			June 30, 2014				June 30, 2013
	(In thousands)		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	261,617	$	129,406	$	233,220	$	109,504
	Enterprise Networks			61,516		35,181		72,026		39,971
	Total		$	323,133	$	164,587	$	305,246	$	149,475
	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 Multi-Service Access Node (MSAN)
		•		hiX family of MSANs
		•		Total Access 1100/1200 Series of Fiber to the Node (FTTN) products
		•		Ultra Broadband Ethernet (UBE)
		•		Digital Subscriber Line Access Multiplexer (DSLAM) products
		•		Optical
		•		Optical Networking Edge (ONE)
		•		NetVanta 8000 Series of Fiber Ethernet Access Devices (EAD)
		•		OPTI-6100 and Total Access 3000 optical Multi-Service Provisioning Platforms (MSPP)
		•		Pluggable Optical Products, including SFP, XFP, and SFP+
		•		TDM systems
	Business Networking products provide access to communication services and facilitate the delivery of cloud connectivity and enterprise communications to distributed enterprises and small and medium-sized businesses. 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®
		•		Multiservice Routers
		•		Managed Ethernet Switches
		•		IP Business Gateways
		•		Unified Communications (UC) solutions
		•		Carrier Ethernet Network Terminating Equipment (NTE)
		•		Network Management Solutions
		•		Integrated Access Devices (IADs)
	Loop Access products are used by carrier and enterprise customers for access to copper-based communications networks. The Loop Access 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 and six months ended June 30, 2014 and 2013:
			Three Months Ended				Six Months Ended
			June 30,				June 30,
	(In thousands)		2014		2013		2014		2013
	Carrier Systems		$	128,824	$	105,537	$	228,377	$	198,341
	Business Networking			41,969		45,379		79,888		83,455
	Loop Access			5,336		11,317		14,868		23,450
	Total		$	176,129	$	162,233	$	323,133	$	305,246
	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 and six months ended June 30, 2014 and 2013:
			Three Months Ended				Six Months Ended
			June 30,				June 30,
	(In thousands)		2014		2013		2014		2013
	Core Products
Broadband Access (included in Carrier Systems)		$	108,309	$	81,628	$	189,836	$	153,862
Optical (included in Carrier Systems)			15,833		15,986		28,622		24,860
Internetworking (included in Business Networking)			40,986		43,922		77,932		80,834
Subtotal			165,128		141,536		296,390		259,556
Legacy Products
HDSL (does not include T1) (included in Loop Access)			4,798		10,289		13,675		21,696
Other products (excluding HDSL)			6,203		10,408		13,068		23,994
Subtotal			11,001		20,697		26,743		45,690
Total		$	176,129	$	162,233	$	323,133	$	305,246

Liability_for_Warranty_Returns

Liability for Warranty Returns	35 Months Ended
	Jun. 30, 2014
Guarantees [Abstract]	'
Liability for Warranty Returns	'
	13. 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 $8.3 million at June 30, 2014 and $9.0 million at December 31, 2013. The decrease from December 31, 2013 to June 30, 2014 includes a $1.5 million decrease related to the settlement of an outstanding warranty claim, which corresponds to a reduction in Other Receivables. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets.
	A summary of warranty expense and write-off activity for the six months ended June 30, 2014 and 2013 is as follows:
		Six Months Ended
		June 30,
	(In thousands)	2014			2013
	Balance at beginning of period	$	8,977		$	9,653
	Plus: Amounts charged to cost and expenses		1,339			470
	Less: Deductions		(1,999	)		(2,182	)
	Balance at end of period	$	8,317		$	7,941
	Deductions for the six months ended June 30, 2014 include a $1.5 million reduction that relates to the settlement of an outstanding warranty claim, which corresponds to a reduction in Other Receivables.

Related_Party_Transactions

Related Party Transactions	35 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	14. RELATED PARTY TRANSACTIONS
	We employ the law firm of our director emeritus for legal services. All bills for services rendered by this firm are reviewed and approved by our Chief Financial Officer. We believe that the fees for such services are comparable to those charged by other firms for services rendered to us. For the three and six months ended June 30, 2014 and 2013, we incurred fees of $10 thousand per month for these legal services.

Commitments_and_Contingencies

Commitments and Contingencies	35 Months Ended
	Jun. 30, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	15. COMMITMENTS AND CONTINGENCIES
	In the ordinary course of business, we may be subject to various legal proceedings and claims, including employment disputes, patent claims, disputes over contract agreements and other commercial disputes. In some cases, claimants seek damages or other relief, such as royalty payments related to patents, which, if granted, could require significant expenditures. Although the outcome of any claim or litigation can never be certain, it is our opinion that the outcome of all contingencies of which we are currently aware will not materially affect our business, operations, financial condition or cash flows.
	We have committed to invest up to an aggregate of $7.9 million in two private equity funds, and we have contributed $8.4 million as of June 30, 2014, of which $7.7 million has been applied to these commitments.

Subsequent_Events

Subsequent Events	35 Months Ended
	Jun. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	16. SUBSEQUENT EVENTS
	On July 15, 2014, we announced that our Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to stockholders of record at the close of business on July 31, 2014. The payment date will be August 14, 2014. The quarterly dividend payment will be approximately $4.9 million. In July 2003, our Board of Directors elected to begin declaring quarterly dividends on our common stock considering the tax treatment of dividends and adequate levels of Company liquidity.
	During the third quarter and as of August 6, 2014, we have repurchased 45 thousand shares of our common stock through open market purchases at an average cost of $21.93 per share. We currently have the authority to purchase an additional 6.1 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)	35 Months Ended
	Jun. 30, 2014
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, 2013 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary for a fair presentation of these interim statements have been 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, 2013, filed on February 27, 2014 with the SEC.
Changes in Classifications	'
	Changes in Classifications
	We corrected immaterial misclassifications between the operating and investing sections of our consolidated statements of cash flows and adjusted our cash flows for the six months ended June 30, 2013 in these categories by $0.5 million in order to be consistent with the 2014 presentation.
Out of Period Adjustment	'
	Out of Period Adjustment
	During the year ended December 31, 2013, we identified two adjustments in the acquired NSN (formerly Nokia Siemens Networks) Broadband Access business (NSN BBA business) relating to customer payment discounts for one customer, and recoverable VAT taxes on certain vendor freight invoices that should have been recorded in prior periods. These adjustments resulted from a $0.5 million understatement of net income in the first two quarters of 2013. We evaluated the impact of the adjustments on the results of our previously issued financial statements for the second quarter of 2013 and concluded that the impact was not material. We also evaluated the impact of the cumulative effect of the adjustments in 2013 and concluded that the impact is not material to our results for the year 2013. Accordingly, during the three months ended September 30, 2013 we recorded an out of period adjustment to correct these issues.
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 working capital adjustments under negotiation related to the NSN BBA business acquisition, 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.
Stock based Compensation	'
	The fair value of our stock options was estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate.
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.
Goodwill and Intangible Assets	'
	We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we compare the fair value of the reporting unit to which the goodwill is assigned to the reporting unit’s carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, then the amount of the impairment loss is measured.
Other Comprehensive Income	'
	Other Comprehensive Income
	Other comprehensive income consists of unrealized gains (losses) on available-for-sale securities, reclassification adjustments for amounts included in net income related to impairments of available-for-sale securities and realized gains (losses) on available-for-sale securities, defined benefit plan adjustments and foreign currency translation adjustments.
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.

Business_Combination_Tables

Business Combination (Tables)	35 Months Ended
	Jun. 30, 2014
Business Combinations [Abstract]	'
Supplemental Pro Forma Information	'
	This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2011, nor are they indicative of any future results.
	(In thousands) (Unaudited)	2012		2011
	Pro forma revenue	$	672,044	$	913,485
	Pro forma pre-tax loss	$	57,906	$	169,162
	Weighted average exchange rate during the period (EURO/USD)	€	1.00/$1.29	€	1.00/$1.38

Pension_Benefit_Plan_Tables

Pension Benefit Plan (Tables)	35 Months Ended
	Jun. 30, 2014
Compensation And Retirement Disclosure [Abstract]	'
Summarization of Components of Net Periodic Pension Cost	'
	The following table summarizes the components of net periodic pension cost for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Service cost	$	306		$	294		$	611		$	594
	Interest cost		216			182			431			369
	Expected return on plan assets		(280	)		(248	)		(559	)		(501	)
	Net periodic pension cost	$	242		$	228		$	483		$	462

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	35 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation Expense Related to Stock Options, Restricted Stock Units (RSUs) and Restricted Stock	'
	The following table summarizes the stock-based compensation expense related to stock options, restricted stock units (RSUs) and restricted stock for the three and six months ended June 30, 2014 and 2013, which was recognized as follows:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Stock-based compensation expense included in cost of sales	$	119		$	110		$	235		$	216
	Selling, general and administrative expense		1,015			1,042			2,041			2,105
	Research and development expense		958			956			1,873			2,019
	Stock-based compensation expense included in operating expenses		1,973			1,998			3,914			4,124
	Total stock-based compensation expense		2,092			2,108			4,149			4,340
	Tax benefit for expense associated with non-qualified options		(296	)		(310	)		(580	)		(617	)
	Total stock-based compensation expense, net of tax	$	1,796		$	1,798		$	3,569		$	3,723
Summary of Weighted-Average Assumptions and Value of Options Granted	'
	The weighted-average assumptions and value of options granted for the six months ended June 30, 2014 are summarized as follows:
		Six Months Ended
		June 30,
		2014
	Expected volatility		39.57	%
	Risk-free interest rate		1.86	%
	Expected dividend yield		1.38	%
	Expected life (in years)		6.25
	Weighted-average estimated value	$	9.28
Summary of Stock Options Outstanding	'
	The following table is a summary of our stock options outstanding as of December 31, 2013 and June 30, 2014 and the changes that occurred during the six months ended June 30, 2014:
	(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, 2013		6,358		$	24.43			6.6		$	25,878
	Options granted		2		$	26.03
	Options cancelled/forfeited		(144	)	$	26.02
	Options exercised		(91	)	$	19.56
	Options outstanding, June 30, 2014		6,125		$	24.46			6.09		$	8,724
	Options exercisable, June 30, 2014		3,776		$	24.81			4.68		$	4,900

Investments_Tables

Investments (Tables)	35 Months Ended
	Jun. 30, 2014
Investments Debt And Equity Securities [Abstract]	'
Securities and Investments, Recorded at Either Fair Value or Cost	'
	At June 30, 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	$	12,733		$	3,037		$	(15	)	$	15,755
	Corporate bonds		98,995			403			(7	)		99,391
	Municipal fixed-rate bonds		155,171			825			(14	)		155,982
	Municipal variable rate demand notes		15,120			—			—			15,120
	Marketable equity securities		25,896			14,249			(418	)		39,727
	Available-for-sale securities held at fair value	$	307,915		$	18,514		$	(454	)	$	325,975
	Restricted investment held at cost											30,000
	Other investments held at cost											1,577
	Total carrying value of available-for-sale investments										$	357,552
	At December 31, 2013, 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	$	12,300		$	2,847		$	(24	)	$	15,123
	Corporate bonds		166,370			534			(45	)		166,859
	Municipal fixed-rate bonds		135,773			583			(54	)		136,302
	Municipal variable rate demand notes		8,310			—			—			8,310
	Marketable equity securities		24,654			13,975			(177	)		38,452
	Available-for-sale securities held at fair value	$	347,407		$	17,939		$	(300	)	$	365,046
	Restricted investment held at cost											48,250
	Other investments held at cost											1,689
	Total carrying value of available-for-sale investments										$	414,985
Contractual Maturities of Corporate and Municipal Fixed-Rate Bonds	'
	As of June 30, 2014, 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	$	7,187		$	25,826
	One to two years		46,881			66,823
	Two to three years		45,323			49,269
	Three to five years		—			14,064
	Total	$	99,391		$	155,982
Gross Realized Gains and Losses on Sale of Securities	'
	The following table presents gross realized gains and losses related to our investments.
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In thousands)	2014			2013			2014			2013
	Gross realized gains	$	2,407		$	1,728		$	4,635		$	5,455
	Gross realized losses	$	(67	)	$	(175	)	$	(103	)	$	(257	)
Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments	'
	We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1—Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
		Fair Value Measurements at June 30, 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	$	11,737		$	11,737		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		15,755			15,755			—			—
	Available-for-sale debt securities
	Corporate bonds		99,391			—			99,391			—
	Municipal fixed-rate bonds		155,982			—			155,982			—
	Municipal variable rate demand notes		15,120			—			15,120			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		12,085			12,085			—			—
	Marketable equity securities – other		27,642			27,642			—			—
	Available-for-sale securities		325,975			55,482			270,493			—
	Total	$	337,712		$	67,219		$	270,493		$	—
		Fair Value Measurements at December 31, 2013 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	$	3,949		$	3,949		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		15,123			15,123			—			—
	Available-for-sale debt securities
	Corporate bonds		166,859			—			166,859			—
	Municipal fixed-rate bonds		136,302			—			136,302			—
	Municipal variable rate demand notes		8,310			—			8,310			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		11,398			11,398			—			—
	Marketable equity securities – other		27,054			27,054			—			—
	Available-for-sale securities		365,046			53,575			311,471			—
	Total	$	368,995		$	57,524		$	311,471		$	—

Derivative_Instruments_and_Hed1

Derivative Instruments and Hedging Activities (Tables)	35 Months Ended
	Jun. 30, 2014
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet	'
	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2014 and December 31, 2013 were as follows:
	(In thousands)	Balance Sheet	June 30,			December 31,
		Location	2014			2013
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	4		$	18
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(232	)	$	(15	)
Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income	'
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and six months ended June 30, 2014 were as follows:
		Income Statement	Three Months Ended						Six Months Ended
		Location	June 30,						June 30,
	(In thousands)		2014			2013			2014			2013
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	(438	)	$	138		$	(548	)	$	(86	)

Inventory_Tables

Inventory (Tables)	35 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Components of Inventory	'
	At June 30, 2014 and December 31, 2013, inventory consisted of the following:
	(In thousands)	June 30,		December 31,
		2014		2013
	Raw materials	$	39,557	$	44,093
	Work in process		7,086		3,484
	Finished goods		42,596		42,534
	Total	$	89,239	$	90,111

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	35 Months Ended
	Jun. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]	'
Summary of Intangible Assets	'
	The following table presents our intangible assets as of June 30, 2014 and December 31, 2013:
	(In thousands)	June 30, 2014							December 31, 2013
		Gross		Accumulated			Net Value		Gross		Accumulated			Net Value
		Value		Amortization					Value		Amortization
	Customer relationships	$	6,914	$	(1,923	)	$	4,991	$	6,996	$	(1,555	)	$	5,441
	Developed technology		6,363		(3,208	)		3,155		6,537		(2,692	)		3,845
	Intellectual property		2,340		(1,353	)		987		2,340		(1,185	)		1,155
	Trade names		270		(175	)		95		270		(145	)		125
	Other		14		(10	)		4		14		(8	)		6
	Total	$	15,901	$	(6,669	)	$	9,232	$	16,157	$	(5,585	)	$	10,572
Estimated Future Amortization Expense Related to Intangible Assets	'
	As of June 30, 2014, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)	Amount
	Remainder of 2014	$	1,140
	2015		2,157
	2016		1,883
	2017		1,284
	2018		778
	Thereafter		1,990
	Total	$	9,232

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	35 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Summary of Changes in Stockholders' Equity	'
	A summary of the changes in stockholders’ equity for the six months ended June 30, 2014 is as follows:
	(In thousands)	Stockholders’
		Equity
	Balance, December 31, 2013	$	604,606
	Net income		24,002
	Dividend payments		(10,137	)
	Dividends accrued for unvested restricted stock units		(2	)
	Net unrealized gains (losses) on available-for-sale securities (net of tax)		298
	Foreign currency translation adjustment		386
	Proceeds from stock option exercises		1,781
	Purchase of treasury stock		(53,091	)
	Income tax benefit from exercise of stock options		67
	Stock-based compensation expense		4,149
	Balance, June 30, 2014	$	572,059
Cash Dividends	'
	During the six months ended June 30, 2014, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date	Payment Date		Per Share Amount	Total Dividend Paid
	February 6, 2014	February 20, 2014		$0.09	$5,102
	May 1, 2014	May 15, 2014		$0.09	$5,035
Changes in Accumulated Other Comprehensive Income, Net of Tax by Component	'
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2014 and 2013:
		Three Months Ended June 30, 2014
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains			Benefit Plan			Currency
		(Losses) on			Adjustments			Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	9,816		$	(891	)	$	1,159		$	10,084
	Other comprehensive income (loss) before		2,516			—			134			2,650
	reclassifications
	Amounts reclassified from accumulated other		(1,297	)		—			—			(1,297	)
	comprehensive income
	Net current period other comprehensive income (loss)		1,219			—			134			1,353
	Ending balance	$	11,035		$	(891	)	$	1,293		$	11,437
		Three Months Ended June 30, 2013
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains			Benefit Plan			Currency
		(Losses) on			Adjustments			Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	8,464		$	(1,952	)	$	3,435		$	9,947
	Other comprehensive income (loss) before		(802	)		—			(1,713	)		(2,515	)
	reclassifications
	Amounts reclassified from accumulated other		(896	)		—			—			(896	)
	comprehensive income
	Net current period other comprehensive income (loss)		(1,698	)		—			(1,713	)		(3,411	)
	Ending balance	$	6,766		$	(1,952	)	$	1,722		$	6,536
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2014 and 2013:
		Six Months Ended June 30, 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		2,918			—			386			3,304
	reclassifications
	Amounts reclassified from accumulated other		(2,620	)		—			—			(2,620	)
	comprehensive income
	Net current period other comprehensive income (loss)		298			—			386			684
	Ending balance	$	11,035		$	(891	)	$	1,293		$	11,437
		Six Months Ended June 30, 2013
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains			Benefit Plan			Currency
		(Losses) on			Adjustments			Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	10,108		$	(1,952	)	$	3,112		$	11,268
	Other comprehensive income (loss) before		(348	)		—			(1,390	)		(1,738	)
	reclassifications
	Amounts reclassified from accumulated other		(2,994	)		—			—			(2,994	)
	comprehensive income
	Net current period other comprehensive income (loss)		(3,342	)		—			(1,390	)		(4,732	)
	Ending balance	$	6,766		$	(1,952	)	$	1,722		$	6,536
Reclassifications Out of Accumulated Other Comprehensive Income	'
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2014 and 2013:
	(In thousands)	Three Months Ended June 30, 2014
	Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
	Comprehensive Income 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	$	2,160		Net realized investment gain
	Impairment expense		(34	)	Net realized investment gain
	Total reclassifications for the period, before tax		2,126
	Tax (expense) benefit		(829	)
	Total reclassifications for the period, net of tax	$	1,297
	(In thousands)	Three Months Ended June 30, 2013
	Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
	Comprehensive Income 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	$	1,469		Net realized investment gain
	Impairment expense		—		Net realized investment gain
	Total reclassifications for the period, before tax		1,469
	Tax (expense) benefit		(573	)
	Total reclassifications for the period, net of tax	$	896
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2014 and 2013:
	(In thousands)	Six Months Ended June 30, 2014
	Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
	Comprehensive Income 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	$	4,330		Net realized investment gain
	Impairment expense		(34	)	Net realized investment gain
	Total reclassifications for the period, before tax		4,296
	Tax (expense) benefit		(1,676	)
	Total reclassifications for the period, net of tax	$	2,620
	(In thousands)	Six Months Ended June 30, 2013
	Details about Accumulated Other	Amount Reclassified			Affected Line Item in the
		from Accumulated			Statement Where Net Income
	Comprehensive Income Components	Other Comprehensive			Is Presented
		Income
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	4,913			Net realized investment gain
	Impairment expense		(4	)		Net realized investment gain
	Total reclassifications for the period, before tax		4,909
	Tax (expense) benefit		(1,915	)
	Total reclassifications for the period, net of tax	$	2,994
Other Comprehensive Income	'
	The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2014 and 2013:
		Three Months Ended									Three Months Ended
		June 30, 2014									June 30, 2013
	(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	$	4,125		$	(1,609	)	$	2,516		$	(1,315	)	$	513	$	(802	)
	Reclassification adjustment for amounts included in net income		(2,126	)		829			(1,297	)		(1,469	)		573		(896	)
	Foreign currency translation adjustment		134			—			134			(1,713	)		—		(1,713	)
	Total Other Comprehensive Income (Loss)	$	2,133		$	(780	)	$	1,353		$	(4,497	)	$	1,086	$	(3,411	)
	The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2014 and 2013:
		Six Months Ended									Six Months Ended
		June 30, 2014									June 30, 2013
	(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	$	4,784		$	(1,866	)	$	2,918		$	(571	)	$	223	$	(348	)
	Reclassification adjustment for amounts included in net income		(4,296	)		1,676			(2,620	)		(4,909	)		1,915		(2,994	)
	Foreign currency translation adjustment		386			—			386			(1,390	)		—		(1,390	)
	Total Other Comprehensive Income (Loss)	$	874		$	(190	)	$	684		$	(6,870	)	$	2,138	$	(4,732	)

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	35 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Summary of Calculation of Basic and Diluted Earnings Per Share	'
	A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2014 and 2013 is as follows:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In thousands, except per share amounts)	2014		2013		2014		2013
	Numerator
	Net income	$	14,395	$	9,859	$	24,002	$	17,749
	Denominator
	Weighted average number of shares – basic		55,409		59,056		56,077		60,443
	Effect of dilutive securities
	Stock options		288		209		459		177
	Restricted stock and restricted stock units		32		46		23		40
	Weighted average number of shares – diluted		55,729		59,311		56,559		60,660
	Net income per share – basic	$	0.26	$	0.17	$	0.43	$	0.29
	Net income per share – diluted	$	0.26	$	0.17	$	0.42	$	0.29

Segment_Information_Tables

Segment Information (Tables)	35 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Sales and Gross Profit of Reportable Segments	'
	The following tables present information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2014 and 2013. Asset information by reportable segment is not reported, since we do not produce such information internally.
		Three Months Ended
		June 30, 2014				June 30, 2013
	(In thousands)	Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	143,455	$	68,053	$	123,333	$	57,913
	Enterprise Networks		32,674		18,744		38,900		21,885
	Total	$	176,129	$	86,797	$	162,233	$	79,798
		Six Months Ended
		June 30, 2014				June 30, 2013
	(In thousands)	Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	261,617	$	129,406	$	233,220	$	109,504
	Enterprise Networks		61,516		35,181		72,026		39,971
	Total	$	323,133	$	164,587	$	305,246	$	149,475
Sales Information by Product Category	'
	The table below presents sales information by product category for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In thousands)	2014		2013		2014		2013
	Carrier Systems	$	128,824	$	105,537	$	228,377	$	198,341
	Business Networking		41,969		45,379		79,888		83,455
	Loop Access		5,336		11,317		14,868		23,450
	Total	$	176,129	$	162,233	$	323,133	$	305,246
Subcategory Revenues	'
	The table below presents subcategory revenues for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In thousands)	2014		2013		2014		2013
	Core Products
	Broadband Access (included in Carrier Systems)	$	108,309	$	81,628	$	189,836	$	153,862
	Optical (included in Carrier Systems)		15,833		15,986		28,622		24,860
	Internetworking (included in Business Networking)		40,986		43,922		77,932		80,834
	Subtotal		165,128		141,536		296,390		259,556
	Legacy Products
	HDSL (does not include T1) (included in Loop Access)		4,798		10,289		13,675		21,696
	Other products (excluding HDSL)		6,203		10,408		13,068		23,994
	Subtotal		11,001		20,697		26,743		45,690
	Total	$	176,129	$	162,233	$	323,133	$	305,246

Liability_for_Warranty_Returns1

Liability for Warranty Returns (Tables)	35 Months Ended
	Jun. 30, 2014
Guarantees [Abstract]	'
Summary of Warranty Expense and Write-Off Activity	'
	A summary of warranty expense and write-off activity for the six months ended June 30, 2014 and 2013 is as follows:
		Six Months Ended
		June 30,
	(In thousands)	2014			2013
	Balance at beginning of period	$	8,977		$	9,653
	Plus: Amounts charged to cost and expenses		1,339			470
	Less: Deductions		(1,999	)		(2,182	)
	Balance at end of period	$	8,317		$	7,941

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013
	Adjustments to Operating Activities [Member]	Adjustments to Investing Activities [Member]	Immaterial Corrections [Member]
Summary of Significant Accounting Policy [Line Items]	'	'	'
Prior period reclassification adjustment	$0.50	$0.50	'
Understatement of net income in the first two quarters of 2013	'	'	$0.50

Business_Combination_Supplemen

Business Combination - Supplemental Pro Forma Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Business Combinations [Abstract]	'	'
Pro forma revenue	$672,044	$913,485
Pro forma pre-tax loss	$57,906	$169,162
Weighted average exchange rate during the period (EURO/USD)	1.29	1.38

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Income Tax Disclosure [Abstract]	'	'
Effective tax rate	34.20%	33.20%

Pension_Benefit_Plan_Summariza

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'	'	'	'
Service cost	$306	$294	$611	$594
Interest cost	216	182	431	369
Expected return on plan assets	-280	-248	-559	-501
Net periodic pension cost	$242	$228	$483	$462

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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Total stock-based compensation expense	$2,092	$2,108	$4,149	$4,340
Tax benefit for expense associated with non-qualified options	-296	-310	-580	-617
Total stock-based compensation expense, net of tax	1,796	1,798	3,569	3,723
Cost of Sales [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Total stock-based compensation expense	119	110	235	216
Selling, General and Administrative Expense [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Total stock-based compensation expense	1,015	1,042	2,041	2,105
Research and Development Expense [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Total stock-based compensation expense	958	956	1,873	2,019
Operating Expenses [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Total stock-based compensation expense	$1,973	$1,998	$3,914	$4,124

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of Options, granted	0	0	2,000	0
Estimated forfeitures for stock options	'	'	2.50%	'
Forfeiture rate for RSUs and restricted stock	'	'	0.00%	'
Compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized	$14.10	'	$14.10	'
Recognition period of non-vested compensation cost	'	'	'2 years 4 months 24 days	'
Total pre-tax intrinsic value of options exercised	$0.10	'	$0.60	'
Restricted Stock Units (RSUs) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of RSUs and restricted stock grants in period	0	0	0	0
Number of RSUs and restricted stock forfeitures in period	0	0	0	0
Number of RSUs and restricted stock vesting in period	0	0	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	4,000	'	4,000	'
Number of RSUs and restricted stock forfeitures in period	0	0	0	0
Number of RSUs and restricted stock vesting in period	0	0	0	0
Restricted stock grants , fair value	$21.30	'	$21.30	'

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Expected volatility	39.57%
Risk-free interest rate	1.86%
Expected dividend yield	1.38%
Expected life (in years)	'6 years 3 months
Weighted-average estimated value	$9.28

StockBased_Compensation_Summar1

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'	'	'
Number of Options, outstanding, Beginning Balance	'	'	6,358	'	'
Number of Options, granted	0	0	2	0	'
Number of Options, cancelled/forfeited	'	'	-144	'	'
Number of Options, exercised	'	'	-91	'	'
Number of Options, outstanding, Ending Balance	6,125	'	6,125	'	6,358
Number of Options, Options exercisable	3,776	'	3,776	'	'
Weighted Average Exercise Price, outstanding, Beginning Balance	'	'	$24.43	'	'
Weighted Average Exercise Price, granted	'	'	$26.03	'	'
Weighted Average Exercise Price, cancelled/forfeited	'	'	$26.02	'	'
Weighted Average Exercise Price, exercised	'	'	$19.56	'	'
Weighted Average Exercise Price, outstanding, Ending Balance	$24.46	'	$24.46	'	$24.43
Weighted Average Exercise Price, Options exercisable	$24.81	'	$24.81	'	'
Weighted Average Remaining Contractual Life In Years, Options outstanding	'	'	'6 years 1 month 2 days	'	'6 years 7 months 6 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	'	'	'4 years 8 months 5 days	'	'
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$8,724	'	$8,724	'	$25,878
Aggregate Intrinsic Value, Options exercisable	$4,900	'	$4,900	'	'

Investments_Securities_and_Inv

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$307,915	$347,407
Gross Unrealized Gains	18,514	17,939
Gross Unrealized Losses	-454	-300
Available-for-sale-securities, Fair Value/Carrying Value	325,975	365,046
Restricted investment held at cost	30,000	48,250
Other investments held at cost	1,577	1,689
Total carrying value of available-for-sale investments	357,552	414,985
Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	12,733	12,300
Gross Unrealized Gains	3,037	2,847
Gross Unrealized Losses	-15	-24
Available-for-sale-securities, Fair Value/Carrying Value	15,755	15,123
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	98,995	166,370
Gross Unrealized Gains	403	534
Gross Unrealized Losses	-7	-45
Available-for-sale-securities, Fair Value/Carrying Value	99,391	166,859
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	155,171	135,773
Gross Unrealized Gains	825	583
Gross Unrealized Losses	-14	-54
Available-for-sale-securities, Fair Value/Carrying Value	155,982	136,302
Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	15,120	8,310
Available-for-sale-securities, Fair Value/Carrying Value	15,120	8,310
Marketable Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	25,896	24,654
Gross Unrealized Gains	14,249	13,975
Gross Unrealized Losses	-418	-177
Available-for-sale-securities, Fair Value/Carrying Value	$39,727	$38,452

Investments_Contractual_Maturi

Investments - Contractual Maturities of Corporate and Municipal Fixed-Rate Bonds (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale-securities, Fair Value/Carrying Value	$325,975	$365,046
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	7,187	'
One to two years	46,881	'
Two to three years	45,323	'
Available-for-sale-securities, Fair Value/Carrying Value	99,391	166,859
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	25,826	'
One to two years	66,823	'
Two to three years	49,269	'
Three to five years	14,064	'
Available-for-sale-securities, Fair Value/Carrying Value	$155,982	$136,302

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]	'	'	'
Restricted certificate of deposit held	'	$30,000,000	$48,250,000
Principal payment on the Bond	16,500,000	16,500,000	'
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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Investments Debt And Equity Securities [Abstract]	'	'	'	'
Gross realized gains	$2,407	$1,728	$4,635	$5,455
Gross realized losses	($67)	($175)	($103)	($257)

Investments_Fair_Value_Measure

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	$325,975	$365,046
Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,755	15,123
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	99,391	166,859
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	155,982	136,302
Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,120	8,310
Fair Value, Measurements, Recurring [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	325,975	365,046
Total	337,712	368,995
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	55,482	53,575
Total	67,219	57,524
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	270,493	311,471
Total	270,493	311,471
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Total	0	0
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalent	11,737	3,949
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalent	11,737	3,949
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalent	0	'
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalent	0	0
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,755	15,123
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,755	15,123
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	99,391	166,859
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
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	99,391	166,859
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	155,982	136,302
Fair Value, Measurements, Recurring [Member] | Municipal Fixed-Rate Bonds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
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	155,982	136,302
Fair Value, Measurements, Recurring [Member] | Municipal Fixed-Rate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,120	8,310
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
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	15,120	8,310
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	12,085	11,398
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	12,085	11,398
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	27,642	27,054
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	27,642	27,054
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	0	'
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	$0	$0

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities - Additional Information (Detail)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
		Forward Contracts [Member]	Forward Contracts [Member]
		USD ($)	EUR (€)
Derivative [Line Items]	'	'	'
Maximum contractual period for derivatives	'12 months	'	'
Derivative, notional amount	'	$26.40	€ 19.30
Derivative maturity year	'	'2014	'2014

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 $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Receivables [Member]	'	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'	'
Derivatives asset, fair value	$4	$18
Accounts Payable [Member]	'	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'	'
Derivatives liability, fair value	($232)	($15)

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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]	'	'	'	'
Derivatives Not Designated as Hedging Instruments:	'	'	'	'
Derivative instrument, gain or loss	($438)	$138	($548)	($86)

Inventory_Components_of_Invent

Inventory - Components of Inventory (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials	$39,557	$44,093
Work in process	7,086	3,484
Finished goods	42,596	42,534
Total	$89,239	$90,111

Inventory_Additional_Informati

Inventory - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Raw Materials [Member]	'	'
Inventory valuation reserves	$17.10	$16.90
Finished Goods [Member]	'	'
Inventory valuation reserves	$6	$6.10

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		35 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]	'	'	'	'	'
Impairment losses	'	'	'	'	$0
Amortization expense	$600,000	$600,000	$1,200,000	$1,200,000	'

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill [Line Items]	'	'
Gross Value	$15,901	$16,157
Accumulated Amortization	-6,669	-5,585
Net Value	9,232	10,572
Customer Relationships [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,914	6,996
Accumulated Amortization	-1,923	-1,555
Net Value	4,991	5,441
Developed Technology [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,363	6,537
Accumulated Amortization	-3,208	-2,692
Net Value	3,155	3,845
Intellectual Property [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	2,340	2,340
Accumulated Amortization	-1,353	-1,185
Net Value	987	1,155
Trade Names [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	270	270
Accumulated Amortization	-175	-145
Net Value	95	125
Other [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	14	14
Accumulated Amortization	-10	-8
Net Value	$4	$6

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Reminder of 2014	$1,140	'
2015	2,157	'
2016	1,883	'
2017	1,284	'
2018	778	'
Thereafter	1,990	'
Net Value	$9,232	$10,572

Stockholders_Equity_Summary_of

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]	'	'	'	'
Beginning Balance	'	'	$604,606	'
Net income	14,395	9,859	24,002	17,749
Dividend payments	'	'	-10,137	'
Dividends accrued for unvested restricted stock units	'	'	-2	'
Net unrealized gains (losses) on available-for-sale securities (net of tax)	1,219	-1,698	298	-3,342
Foreign currency translation adjustment	134	-1,713	386	-1,390
Proceeds from stock option exercises	'	'	1,781	819
Purchase of treasury stock	'	'	-53,091	'
Income tax benefit from exercise of stock options	'	'	67	'
Stock-based compensation expense	2,092	2,108	4,149	4,340
Ending Balance	$572,059	'	$572,059	'

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	14-May-14	13-May-14
Equity [Abstract]	'	'	'	'
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	45,000,000	'	5,000,000	40,000,000
Stock repurchased, shares	2,300,000	'	'	'
Shares repurchased, average price per share	$22.73	'	'	'
Additional shares authorized for purchase	6,100,000	'	'	'
Number of options, exercised	91,000	'	'	'
Exercise price of stock options, lower range limit	$15.29	'	'	'
Exercise price of stock options, upper range limit	$23.46	'	'	'
Proceeds from stock option exercise	$1,781	$819	'	'

Stockholders_Equity_Cash_Divid

Stockholders' Equity - Cash Dividends (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Dividends Payable [Line Items]	'	'	'	'
Per Share Amount	$0.09	$0.09	$0.18	$0.18
Total Dividend Paid	'	'	$10,137	$10,982
Cash dividends paid in February [Member]	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	6-Feb-14	'
Payment Date	'	'	20-Feb-14	'
Per Share Amount	'	'	$0.09	'
Total Dividend Paid	'	'	5,102	'
Cash dividends paid in May [Member]	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	1-May-14	'
Payment Date	'	'	15-May-14	'
Per Share Amount	'	'	$0.09	'
Total Dividend Paid	'	'	$5,035	'

Stockholders_Equity_Changes_in

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended								3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
					Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Defined Benefit Plan Adjustments [Member]	Defined Benefit Plan Adjustments [Member]	Defined Benefit Plan Adjustments [Member]	Defined Benefit Plan Adjustments [Member]	Defined Benefit Plan Adjustments [Member]	Defined Benefit Plan Adjustments [Member]	Foreign Currency Adjustments [Member]	Foreign Currency Adjustments [Member]	Foreign Currency Adjustments [Member]	Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Beginning balance	$10,084	$9,947	$10,753	$11,268	$9,816	$8,464	$10,737	$10,108	($891)	($891)	($891)	($1,952)	($1,952)	($1,952)	$1,159	$3,435	$907	$3,112
Other comprehensive income (loss) before reclassifications	2,650	-2,515	3,304	-1,738	2,516	-802	2,918	-348	'	'	'	'	'	'	134	-1,713	386	-1,390
Amounts reclassified from accumulated other comprehensive income	-1,297	-896	-2,620	-2,994	-1,297	-896	-2,620	-2,994	'	'	'	'	'	'	'	'	'	'
Other Comprehensive Income (Loss), net of tax	1,353	-3,411	684	-4,732	1,219	-1,698	298	-3,342	'	'	'	'	'	'	134	-1,713	386	-1,390
Ending balance	$11,437	$6,536	$11,437	$6,536	$11,035	$6,766	$11,035	$6,766	($891)	($891)	($891)	($1,952)	($1,952)	($1,952)	$1,293	$1,722	$1,293	$1,722

Stockholders_Equity_Reclassifi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net realized investment gain	$2,340	$1,553	$4,532	$5,198
Total reclassifications for the period, before tax	21,811	16,834	36,490	26,557
Tax (expense) benefit	-7,416	-6,975	-12,488	-8,808
Total reclassifications for the period, net of tax	14,395	9,859	24,002	17,749
Reclassification out of accumulated other comprehensive income [Member]	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Total reclassifications for the period, before tax	2,126	1,469	4,296	4,909
Tax (expense) benefit	-829	-573	-1,676	-1,915
Total reclassifications for the period, net of tax	1,297	896	2,620	2,994
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	2,160	1,469	4,330	4,913
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	($34)	'	($34)	($4)

Stockholders_Equity_Other_Comp

Stockholders' Equity - Other Comprehensive Income (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]	'	'	'	'
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$4,125	($1,315)	$4,784	($571)
Reclassification adjustment for amounts included in net income, Before-Tax Amount	-2,126	-1,469	-4,296	-4,909
Foreign currency translation adjustment, Before-Tax Amount	134	-1,713	386	-1,390
Total Other Comprehensive Income (Loss), Before-Tax Amount	2,133	-4,497	874	-6,870
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	-1,609	513	-1,866	223
Reclassification adjustment for amounts included in net income, Tax Benefit	829	573	1,676	1,915
Foreign currency translation adjustment, Tax Benefit	0	'	0	'
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	-780	1,086	-190	2,138
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	2,516	-802	2,918	-348
Reclassification adjustment for amounts included in net income, Net-of-Tax Amount	-1,297	-896	-2,620	-2,994
Foreign currency translation adjustment, Net-of-Tax Amount	134	-1,713	386	-1,390
Other Comprehensive Income (Loss), net of tax	$1,353	($3,411)	$684	($4,732)

Earnings_Per_Share_Summary_of_

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator	'	'	'	'
Net income	$14,395	$9,859	$24,002	$17,749
Denominator	'	'	'	'
Weighted average number of shares - basic	55,409	59,056	56,077	60,443
Effect of dilutive securities	'	'	'	'
Stock options	288	209	459	177
Restricted stock and restricted stock units	32	46	23	40
Weighted average number of shares - diluted	55,729	59,311	56,559	60,660
Net income per share - basic	$0.26	$0.17	$0.43	$0.29
Net income per share - diluted	$0.26	$0.17	$0.42	$0.29

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Anti-dilutive options, Total	4.3	4.3	3.1	5.1

Segment_Information_Additional

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2014
	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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]	'	'	'	'
Sales	$176,129	$162,233	$323,133	$305,246
Gross Profit	86,797	79,798	164,587	149,475
Carrier Networks [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Sales	143,455	123,333	261,617	233,220
Gross Profit	68,053	57,913	129,406	109,504
Enterprise Networks [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Sales	32,674	38,900	61,516	72,026
Gross Profit	$18,744	$21,885	$35,181	$39,971

Segment_Information_Sales_Info

Segment Information - Sales Information by Product Category (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$176,129	$162,233	$323,133	$305,246
Carrier Systems [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	128,824	105,537	228,377	198,341
Business Networking [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	41,969	45,379	79,888	83,455
Loop Access [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$5,336	$11,317	$14,868	$23,450

Segment_Information_Subcategor

Segment Information - Subcategory Revenues (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$176,129	$162,233	$323,133	$305,246
Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	165,128	141,536	296,390	259,556
Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	11,001	20,697	26,743	45,690
Broadband Access (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	108,309	81,628	189,836	153,862
Optical (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	15,833	15,986	28,622	24,860
Internetworking (Included in Business Networking) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	40,986	43,922	77,932	80,834
HDSL (Does not Include T1) (Included in Loop Access) [Member] | Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	4,798	10,289	13,675	21,696
Other Products (Excluding HDSL) [Member] | Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$6,203	$10,408	$13,068	$23,994

Liability_for_Warranty_Returns2

Liability for Warranty Returns - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Product Warranties Disclosures [Abstract]	'	'	'	'
Period of warranty for product defects	'90 days to ten years	'	'	'
Liability for warranty obligations	$8,317,000	$8,977,000	$7,941,000	$9,653,000
Settlement of an Outstanding warranty claim	$1,500,000	'	'	'

Liability_for_Warranty_Returns3

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Product Warranties Disclosures [Abstract]	'	'
Balance at beginning of period	$8,977	$9,653
Plus: Amounts charged to cost and expenses	1,339	470
Less: Deductions	-1,999	-2,182
Balance at end of period	$8,317	$7,941

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Related Party Transactions [Abstract]	'	'	'	'
Related party legal fees per month	$10	$10	$10	$10

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified	EquityUnit
Schedule of Investments [Line Items]	'
Aggregate investment committed in private equity funds	$7.90
Number of private equity funds	2
Commitments towards private equity funds	7.7
Private Equity Funds [Member]	'
Schedule of Investments [Line Items]	'
Contribution to private equity funds	$8.40

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	6 Months Ended		0 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Aug. 06, 2014	Jul. 31, 2014
		Scenario, Forecast [Member]	Subsequent Events [Member]	Subsequent Events [Member]
Subsequent Event [Line Items]	'	'	'	'
Dividend declaration date	15-Jul-14	'	'	'
Cash dividend per common share	'	'	'	$0.09
Dividend record date	'	'	'	31-Jul-14
Dividend payment date	'	'	'	14-Aug-14
Cash dividend	'	$4.90	'	'
Stock repurchased, shares	2,300,000	'	45,000	'
Shares repurchased, average price per share	$22.73	'	$21.93	'
Additional shares authorized for purchase	6,100,000	'	6,100,000	'