ADTRAN (ADTN) 10-Q 1 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 23, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
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	'	57,689,485

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$54,311	$68,457
Short-term investments	136,640	160,481
Accounts receivable, less allowance for doubtful accounts of $15 and $6 at September 30, 2013 and December 31, 2012, respectively	108,018	81,194
Other receivables	20,268	16,253
Inventory	92,972	102,583
Prepaid expenses	4,693	4,148
Deferred tax assets, net	13,494	13,055
Total Current Assets	430,396	446,171
Property, plant and equipment, net	77,658	80,246
Deferred tax assets, net	11,605	10,261
Goodwill	3,492	3,492
Other assets	11,711	13,482
Long-term investments	298,122	332,729
Total Assets	832,984	886,381
Current Liabilities	'	'
Accounts payable	73,672	42,173
Unearned revenue	19,658	38,051
Accrued expenses	16,527	10,309
Accrued wages and benefits	16,594	15,022
Income tax payable, net	548	1,211
Total Current Liabilities	126,999	106,766
Non-current unearned revenue	26,373	23,803
Other non-current liabilities	20,459	17,406
Bonds payable	46,500	46,000
Total Liabilities	220,331	193,975
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 57,687 shares outstanding at September 30, 2013 and 79,652 shares issued and 62,310 shares outstanding at December 31, 2012	797	797
Additional paid-in capital	231,146	224,517
Accumulated other comprehensive income	8,990	11,268
Retained earnings	878,384	861,465
Less treasury stock at cost: 21,965 and 17,342 shares at September 30, 2013 and December 31, 2012, respectively	-506,664	-405,641
Total Stockholders' Equity	612,653	692,406
Total Liabilities and Stockholders' Equity	$832,984	$886,381

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$15	$6
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	57,687	62,310
Treasury stock, shares	21,965	17,342

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]	'	'	'	'
Sales	$177,404	$162,125	$482,650	$480,858
Cost of sales	94,857	82,153	250,628	231,598
Gross Profit	82,547	79,972	232,022	249,260
Selling, general and administrative expenses	32,794	34,114	96,082	103,130
Research and development expenses	32,543	35,582	98,114	92,835
Operating Income	17,210	10,276	37,826	53,295
Interest and dividend income	1,579	1,864	5,021	5,651
Interest expense	-581	-587	-1,737	-1,756
Net realized investment gain	1,751	2,530	6,949	7,353
Other income (expense), net	22	-368	-1,521	265
Gain on bargain purchase of a business	'	'	'	1,753
Income before provision for income taxes	19,981	13,715	46,538	66,561
Provision for income taxes	-3,776	-4,443	-12,584	-23,259
Net Income	$16,205	$9,272	$33,954	$43,302
Weighted average shares outstanding - basic	57,947	63,066	59,561	63,495
Weighted average shares outstanding - diluted	58,617	63,304	59,929	64,139
Earnings per common share - basic	$0.28	$0.15	$0.57	$0.68
Earnings per common share - diluted	$0.28	$0.15	$0.57	$0.68
Dividend per share	$0.09	$0.09	$0.27	$0.27

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Net Income	$16,205	$9,272	$33,954	$43,302
Other Comprehensive Income (Loss), net of tax:	'	'	'	'
Net unrealized gains (losses) on available-for-sale securities	2,562	497	-780	2,019
Foreign currency translation	-108	134	-1,498	191
Other Comprehensive Income (Loss), net of tax	2,454	631	-2,278	2,210
Comprehensive Income, net of tax	$18,659	$9,903	$31,676	$45,512

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:	'	'
Net Income	$33,954	$43,302
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	11,021	10,366
Amortization of net premium on available-for-sale investments	4,688	6,343
Net realized gain on long-term investments	-6,949	-7,353
Net (gain) loss on disposal of property, plant and equipment	6	-213
Gain on bargain purchase of a business	'	-1,753
Stock-based compensation expense	6,516	6,783
Deferred income taxes	-1,296	-1,156
Tax benefit from stock option exercises	113	1,813
Excess tax benefits from stock-based compensation arrangements	-106	-1,412
Changes in operating assets and liabilities:	'	'
Accounts receivable, net	-25,844	-26,178
Other receivables	-3,724	1,866
Inventory	8,584	2,142
Prepaid expenses and other assets	-417	-1,193
Accounts payable	30,460	17,607
Accrued expenses and other liabilities	-4,339	12,769
Income tax payable, net	-678	1,022
Net cash provided by operating activities	51,989	64,755
Cash flows from investing activities:	'	'
Purchases of property, plant and equipment	-6,510	-10,759
Proceeds from disposals of property, plant and equipment	'	266
Proceeds from sales and maturities of available-for-sale investments	275,581	198,566
Purchases of available-for-sale investments	-216,129	-220,355
Acquisition of business	'	7,496
Net cash provided by (used in) investing activities	52,942	-24,786
Cash flows from financing activities:	'	'
Proceeds from stock option exercises	2,332	4,932
Purchases of treasury stock	-104,147	-28,578
Dividend payments	-16,220	-17,173
Excess tax benefits from stock-based compensation arrangements	106	1,412
Net cash used in financing activities	-117,929	-39,407
Net increase (decrease) in cash and cash equivalents	-12,998	562
Effect of exchange rate changes	-1,148	-6
Cash and cash equivalents, beginning of period	68,457	42,979
Cash and cash equivalents, end of period	$54,311	$43,535

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
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, 2012 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary for a fair presentation of these interim statements have been recorded, including the out of period adjustment discussed below. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2012, filed on February 28, 2013 with the SEC.
	Changes in Classifications
	Certain changes in classifications have been made to the prior period balances in other comprehensive income to conform to the current period’s presentation as a result of our adoption of Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Comprehensive Income.
	Out of Period Adjustment
	During the three months ended September 30, 2013, we identified two adjustments in the acquired 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 $0.4 million understatement of net income in 2012 and $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 each of the prior periods affected and concluded that the impact was not material. We also evaluated the impact of the cumulative effect of the adjustments in the current year and concluded that the impact is not material to our projected 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 allowance for doubtful accounts, obsolete and excess inventory reserves, warranty reserves, customer rebates, allowance for sales returns, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated working capital adjustments under negotiation related to the Nokia Siemens Networks Broadband Access business acquisition, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
	Recent Accounting Pronouncements
	During the nine months ended September 30, 2013, we adopted the following accounting standard, which had no material effect on our consolidated results of operations or financial condition:
	In February 2013, the FASB issued Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU 2013-02). ASU 2013-02 requires entities to provide information about the amounts reclassified out of accumulated other comprehensive income by component either on the face of the financial statements or in the footnotes. ASU 2013-02 does not change the current requirements for reporting net income or other comprehensive income in the financial statements. This update is effective prospectively for reporting periods beginning after December 15, 2012. We adopted this amendment during the first quarter of 2013, and we have provided the disclosures required for the periods ended September 30, 2013 and 2012 in Note 10 of Notes to Consolidated Financial Statements.

Business_Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Business Combinations	'
	2	BUSINESS COMBINATIONS
	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.
	We received a cash payment of $7.5 million from NSN and recorded a bargain purchase gain of $1.8 million, net of income taxes, in the second quarter of 2012, subject to customary working capital adjustments between the parties as defined in the purchase agreement. As of September 30, 2013, the parties were in the process of resolving the working capital adjustments. We adjusted the purchase price allocation during the fourth quarter of 2012 to record additional estimated liabilities and an estimated receivable from NSN related to working capital adjustments under negotiation. The bargain purchase gain of $1.8 million represents the excess of the consideration exchanged over the fair value of the assets acquired and liabilities assumed. We have assessed the recognition and measurements of the assets acquired and liabilities assumed based on historical and pro forma data for future periods and have concluded that our valuation procedures and resulting measures were appropriate.
	The allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date is as follows:
	(In Thousands)
	Other receivables		$	9,486
	Inventory			21,068
	Property, plant and equipment			5,035
	Accounts payable			(5,194	)
	Unearned revenue			(18,203	)
	Accrued expenses			(1,931	)
	Accrued wages and benefits			(2,251	)
	Deferred tax liability			(788	)
	Non-current unearned revenue			(21,316	)
	Net liabilities assumed			(14,094	)
	Customer relationships			5,162
	Developed technology			3,176
	Other			13
	Gain on bargain purchase of a business, net of tax			(1,753	)
	Net consideration received from seller		$	(7,496	)
	The fair value of the customer relationships acquired was calculated using a discounted cash flow method (excess earnings) and is being amortized using a declining balance method derived from projected customer revenue over an average estimated useful life of 13 years. The fair value of the developed technology acquired was calculated using a discounted cash flow method (relief from royalty) and is being amortized using the straight-line method over an estimated useful life of five years.
	The following supplemental pro forma information presents the financial results of the acquired NSN BBA business for the nine months ended September 30, 2012. The pro forma results for the period January 1, 2012 to May 4, 2012 are not included in our consolidated financial statements.
	This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2012, nor are they indicative of any future results.
			Nine Months Ended
	(In thousands)		September 30, 2012
	Pro forma revenue		$	100,413
	Pro forma pre-tax loss		$	(18,006	)
	Weighted average exchange rate during the period (EURO/USD)		€	1.00/$1.29
	For the three and nine months ended September 30, 2013, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $0.6 million and $2.2 million related to this acquisition.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	3	INCOME TAXES
	Our effective tax rate decreased from 34.9% in the nine months ended September 30, 2012 to 27.0% in the nine months ended September 30, 2013. The decrease in the effective tax rate between the two periods is primarily attributable to an acquired business that incurred losses in the prior year for which no tax benefit was recognized and the improved profitability for that business in the current year, the net effect of recording the benefit for the research tax credit for the 2012 tax year in January 2013 pursuant to the American Taxpayer Relief Act of 2012, and the inclusion of the benefit of the estimated 2013 research tax credit in the estimated annual effective rate for 2013.

Pension_Benefit_Plan

Pension Benefit Plan	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'
Pension Benefit Plan	'
	4	PENSION BENEFIT PLAN
	As a result of our acquisition of the NSN BBA business, we assumed a defined benefit obligation of $17.0 million as of May 4, 2012. We established a Contribution Trust Arrangement (CTA) to hold the pension assets, and NSN transferred assets to us equal to the defined benefit obligation.
	The following table summarizes the components of net periodic pension cost for the three months ended September 30, 2013 and 2012, the nine months ended September 30, 2013, and the period May 4, 2012 to September 30, 2012:
			Three Months Ended						Nine Months Ended			May 4, 2012 to
			September 30,						September 30,			September 30,
	(In thousands)		2013			2012			2013			2012
	Service cost		$	297		$	288		$	891		$	478
	Interest cost			185			187			554			314
	Expected return on plan assets			(250	)		(250	)		(751	)		(415	)
	Net periodic pension cost		$	232		$	225		$	694		$	377

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2013
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 nine months ended September 30, 2013 and 2012, which was recognized as follows:
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
	(In thousands)		2013			2012			2013			2012
	Stock-based compensation expense included in cost of sales		$	118		$	106		$	334		$	304
	Selling, general and administrative expense			1,024			1,107			3,129			3,205
	Research and development expense			1,034			1,138			3,053			3,274
	Stock-based compensation expense included in operating expenses			2,058			2,245			6,182			6,479
	Total stock-based compensation expense			2,176			2,351			6,516			6,783
	Tax benefit for expense associated with non-qualified options			(307	)		(313	)		(924	)		(916	)
	Total stock-based compensation expense, net of tax		$	1,869		$	2,038		$	5,592		$	5,867
	The fair value of our stock options was estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate.
	There were no options granted during the three and nine months ended September 30, 2013. The weighted-average assumptions and value of options granted for the three and nine months ended September 30, 2012 are summarized as follows:
			Three Months Ended			Nine Months Ended
			September 30,			September 30,
			2012			2012
	Expected volatility			40.2	%		40.2	%
	Risk-free interest rate			0.63	%		0.63	%
	Expected dividend yield			1.3	%		1.3	%
	Expected life (in years)			4.95			4.95
	Weighted-average estimated value		$	8.69		$	8.69
	The fair value of our RSUs is calculated using a Monte Carlo Simulation valuation method. There were no RSU grants during the three and nine months ended September 30, 2013 or 2012.
	The fair value of restricted stock is equal to the closing price of our stock on the date of grant. There were no restricted stock grants during the three and nine months ended September 30, 2013 or 2012.
	Stock-based compensation expense recognized in our Consolidated Statements of Income for the three and nine months ended September 30, 2013 and 2012 is based on options, RSUs and restricted stock ultimately expected to vest, and has been reduced for estimated forfeitures. Estimated forfeitures for stock options were based upon historical experience and approximate 1.7% annually. We estimated a 0% forfeiture rate for our RSUs and restricted stock due to the limited number of recipients and historical experience for these awards.
	As of September 30, 2013, total compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized was approximately $11.8 million, which is expected to be recognized over an average remaining recognition period of 2.1 years.
	The following table is a summary of our stock options outstanding as of December 31, 2012 and September 30, 2013 and the changes that occurred during the nine months ended September 30, 2013:
	(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, 2012			6,035		$	24.81			6.69		$	5,154
	Options granted			—		$	—
	Options cancelled/forfeited			(188	)	$	26.23
	Options exercised			(123	)	$	18.93
	Options outstanding, September 30, 2013			5,724		$	24.89			5.96		$	21,878
	Options exercisable, September 30, 2013			3,618		$	25.33			4.68		$	11,955
	The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between the closing 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 September 30, 2013. 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 nine months ended September 30, 2013 was $0.5 million and $0.8 million, respectively.
	The following table is a summary of our RSUs and restricted stock outstanding as of December 31, 2012 and September 30, 2013 and the changes that occurred during the nine months ended September 30, 2013:
	(In thousands, except per share amounts)		Number			Weighted
			of Shares			Average
						Grant Date
						Fair Value
	Unvested RSUs and restricted stock outstanding, December 31, 2012			103		$	29.25
	RSUs and restricted stock granted			—		$	—
	RSUs and restricted stock vested			—		$	—
	RSUs and restricted stock cancelled/forfeited			—		$	—
	Unvested RSUs and restricted stock, September 30, 2013			103		$	29.25

Investments

Investments	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Investments	'
	6	INVESTMENTS
	At September 30, 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		$	11,308		$	2,490		$	(18	)	$	13,780
	Corporate bonds			177,798			446			(103	)		178,141
	Municipal fixed-rate bonds			145,509			497			(71	)		145,935
	Municipal variable rate demand notes			11,960			—			—			11,960
	Marketable equity securities			22,825			12,393			(275	)		34,943
	Available-for-sale securities held at fair value		$	369,400		$	15,826		$	(467	)	$	384,759
	Restricted investment held at cost												48,250
	Other investments held at cost												1,753
	Total carrying value of available-for-sale investments											$	434,762
	At December 31, 2012, 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		$	10,688		$	846		$	(7	)	$	11,527
	Corporate bonds			185,464			966			(18	)		186,412
	Municipal fixed-rate bonds			174,530			627			(73	)		175,084
	Municipal variable rate demand notes			34,375			—			—			34,375
	Fixed income bond fund			444			12			—			456
	Marketable equity securities			20,966			14,630			(392	)		35,204
	Available-for-sale securities held at fair value		$	426,467		$	17,081		$	(490	)	$	443,058
	Restricted investment held at cost												48,250
	Other investments held at cost												1,902
	Total carrying value of available-for-sale investments											$	493,210
	As of September 30, 2013, 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		$	66,267		$	58,413
	One to two years			32,231			18,638
	Two to three years			76,460			58,389
	Three to five years			3,183			10,495
	Total		$	178,141		$	145,935
	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 September 30, 2013, we held a $48.3 million restricted certificate of deposit, which is carried at cost. This investment serves as a collateral deposit against the principal amount outstanding under loans made to ADTRAN pursuant to an Alabama State Industrial Development Authority revenue bond (the Bond). At September 30, 2013, the estimated fair value of the Bond using a level 2 valuation technique was approximately $44.9 million, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of A-. For more information on the Bond, see “Debt” under “Liquidity and Capital Resources” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in Item 2 of Part I of this report.
	We review our investment portfolio for potential “other-than-temporary” declines in value on an individual investment basis. We assess, on a quarterly basis, significant declines in value which may be considered other-than-temporary and, if necessary, recognize and record the appropriate charge to write-down the carrying value of such investments. In making this assessment, we take into consideration qualitative and quantitative information, including but not limited to the following: the magnitude and duration of historical declines in market prices, credit rating activity, assessments of liquidity, public filings, and statements made by the issuer. We generally begin our identification of potential other-than-temporary impairments by reviewing any security with a fair value that has declined from its original or adjusted cost basis by 25% or more for six or more consecutive months. We then evaluate the individual security based on the previously identified factors to determine the amount of the write-down, if any. As a result of our review, we recorded an other-than-temporary impairment charge of $13 thousand during the nine months ended September 30, 2013 related to five marketable securities. For the nine months ended September 30, 2012, we recorded an other-than-temporary impairment charge of $0.1 million related to 21 marketable equity securities.
	Realized gains and losses on sales of securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our investments.
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
	(In thousands)		2013			2012			2013			2012
	Gross realized gains		$	1,797		$	3,388		$	7,252		$	8,688
	Gross realized losses		$	(46	)	$	(858	)	$	(303	)	$	(1,335	)
	As of September 30, 2013 and 2012, gross unrealized losses related to individual securities in a continuous loss position for 12 months or longer were not significant.
	We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 – Values based on unadjusted, quoted prices in active markets for identical assets or liabilities; Level 2 – Values based on inputs other than quoted prices included within Level 1 that are directly or indirectly observable for the asset or liability; Level 3 – Values based on unobservable inputs for the asset or liability. These inputs include information supplied by investees.
			Fair Value Measurements at September 30, 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		$	6,594		$	6,594		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets			13,780			13,780			—			—
	Available-for-sale debt securities
	Corporate bonds			178,141			—			178,141			—
	Municipal fixed-rate bonds			145,935			—			145,935			—
	Municipal variable rate demand notes			11,960			—			11,960			—
	Available-for-sale marketable equity securities
	Equity securities – technology industry			9,973			9,973			—			—
Equity securities – other			24,970			24,970			—			—
Available-for-sale securities			384,759			48,723			336,036			—
Total		$	391,353		$	55,317		$	336,036		$	—
		Fair Value Measurements at December 31, 2012 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		$	28,071		$	28,071		$	—		$	—
Available-for-sale securities
Deferred compensation plan assets			11,527			11,527			—			—
Available-for-sale debt securities
Corporate bonds			186,412			—			186,412			—
Municipal fixed-rate bonds			175,084			—			175,084			—
Municipal variable rate demand notes			34,375			—			34,375			—
Fixed income bond fund			456			456			—			—
Available-for-sale marketable equity securities
Equity securities – technology industry			14,099			14,099			—			—
Equity securities – other			21,105			21,105			—			—
Available-for-sale securities			443,058			47,187			395,871			—
Total		$	471,129		$	75,258		$	395,871		$	—
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	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013, we had forward contracts outstanding with notional amounts totaling €19.8 million ($26.8 million), which mature through 2013.
	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of September 30, 2013 were as follows:
			September 30, 2013
	(In thousands)		Balance Sheet	Fair Value
			Location
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives		Other receivables	$	40
	Foreign exchange contracts – liability derivatives		Accounts payable	$	(6	)
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and nine months ended September 30, 2013 were as follows:
	(In thousands)		Income Statement Location	Three Months			Nine Months
				Ended			Ended
				September 30,			September 30,
				2013			2013
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts		Other income (expense)	$	52		$	(34	)

Inventory

Inventory	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]	'
Inventory	'
	8	INVENTORY
	At September 30, 2013 and December 31, 2012, inventory consisted of the following:
			September 30,		December 31,
	(In thousands)		2013		2012
	Raw materials		$	40,947	$	47,054
	Work in process			3,562		3,262
	Finished goods			48,463		52,267
	Total		$	92,972	$	102,583
	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 September 30, 2013 and December 31, 2012, raw materials reserves totaled $15.9 million and $9.9 million, respectively, and finished goods inventory reserves totaled $5.0 million and $2.1 million, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets	'
	9	GOODWILL AND INTANGIBLE ASSETS
	The change in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the nine months ended September 30, 2013 is as follows:
	(In thousands)
	Balance, December 31, 2012		$	3,492
	Acquisitions			—
	Impairment losses			—
	Balance, September 30, 2013		$	3,492
	Balance as of September 30, 2013
	Goodwill		$	3,492
	Accumulated impairment losses			—
	Total goodwill		$	3,492
	We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If we determine that the two-step quantitative test is necessary, then we compare the fair value of the reporting unit to which the goodwill is assigned to the reporting unit’s carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, then the amount of the impairment loss is measured. There were no impairment losses recorded during the nine months ended September 30, 2013 or 2012.
	Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangibles acquired in conjunction with our acquisition of Objectworld Communications Corporation on September 15, 2009, Bluesocket, Inc. on August 4, 2011, and the NSN BBA business on May 4, 2012.
	The following table presents our intangible assets as of September 30, 2013 and December 31, 2012:
	(In thousands)		September 30, 2013							December 31, 2012
			Gross		Accumulated			Net Value		Gross		Accumulated			Net Value
			Value		Amortization					Value		Amortization
	Customer relationships		$	6,906	$	(1,348	)	$	5,558	$	6,769	$	(766	)	$	6,003
	Developed technology			6,481		(2,347	)		4,134		6,397		(1,354	)		5,043
	Intellectual property			2,340		(1,102	)		1,238		2,340		(851	)		1,489
	Trade names			270		(130	)		140		270		(85	)		185
	Other			14		(6	)		8		13		(3	)		10
	Total		$	16,011	$	(4,933	)	$	11,078	$	15,789	$	(3,059	)	$	12,730
	Amortization expense, all of which relates to business acquisitions, was $0.6 million for the three months ended September 30, 2013 and 2012, and $1.8 million and $1.4 million for the nine months ended September 30, 2013 and 2012, respectively.
	As of September 30, 2013, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)		Amount
	Remainder of 2013		$	618
	2014			2,315
	2015			2,179
	2016			1,905
	2017			1,291
	Thereafter			2,770
	Total		$	11,078

Stockholders_Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Stockholders' Equity	'
	10	STOCKHOLDERS’ EQUITY
	A summary of the changes in stockholders’ equity for the nine months ended September 30, 2013 is as follows:
	(In thousands)		Stockholders’
			Equity
	Balance, December 31, 2012		$	692,406
	Net income			33,954
	Dividend payments			(16,220	)
	Dividends accrued for unvested restricted stock units			(23	)
	Net unrealized gains (losses) on available-for-sale securities (net of tax)			(780	)
	Foreign currency translation adjustment			(1,498	)
	Proceeds from stock option exercises			2,332
	Purchase of treasury stock			(104,147	)
	Income tax benefit from exercise of stock options			113
	Stock-based compensation expense			6,516
	Balance, September 30, 2013		$	612,653
	Stock Repurchase Program
	Since 1997, our Board of Directors has approved multiple share repurchase programs that have authorized open market repurchase transactions of up to 35 million shares of our common stock. On May 1, 2013, our Board of Directors authorized the repurchase of an additional 5.0 million shares of our common stock, which commenced upon completion of the repurchase plan announced on October 11, 2011. This new authorization is being implemented through open market or private purchases from time to time as conditions warrant.
	During the nine months ended September 30, 2013, we repurchased 4.8 million shares of our common stock at an average price of $21.89 per share. We currently have the authority to purchase an additional 4.3 million shares of our common stock under the current plan approved by the Board of Directors on May 1, 2013.
	Stock Option Exercises
	We issued 0.1 million shares of treasury stock during the nine months ended September 30, 2013 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $26.06. We received proceeds totaling $2.3 million from the exercise of these stock options during the nine months ended September 30, 2013.
	Dividend Payments
	During the nine months ended September 30, 2013, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date		Payment Date		Per Share Amount				Total Dividend Paid
	February 7, 2013		February 21, 2013		$	0.09			$	5,586
	April 25, 2013		May 9, 2013		$	0.09			$	5,396
	July 25, 2013		August 8, 2013		$	0.09			$	5,238
	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 September 30, 2013 and 2012:
			Three Months Ended September 30, 2013
	(In thousands)		Unrealized				Defined				Foreign			Total
			Gains				Benefit Plan				Currency
			(Losses) on				Adjustments				Adjustments
			Available-
			for-Sale
			Securities
	Beginning balance		$	6,766			$	(1,952	)		$	1,722		$	6,536
	Other comprehensive income (loss) before reclassifications			3,522				—				(108	)		3,414
	Amounts reclassified from accumulated other comprehensive income			(960	)			—				—			(960	)
	Net current period other comprehensive income (loss)			2,562				—				(108	)		2,454
	Ending balance		$	9,328			$	(1,952	)		$	1,614		$	8,990
			Three Months Ended September 30, 2012
	(In thousands)		Unrealized				Foreign				Total
			Gains				Currency
			(Losses) on				Adjustments
			Available-
			for-Sale
			Securities
	Beginning balance		$	11,682			$	2,999			$	14,681
	Other comprehensive income before reclassifications			1,905				134				2,039
	Amounts reclassified from accumulated other comprehensive income			(1,408	)			—				(1,408	)
	Net current period other comprehensive income			497				134				631
	Ending balance		$	12,179			$	3,133			$	15,312
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the nine months ended September 30, 2013 and 2012:
			Nine Months Ended September 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 reclassifications			3,174				—				(1,498	)		1,676
Amounts reclassified from accumulated other comprehensive income			(3,954	)			—				—			(3,954	)
Net current period other comprehensive (loss)			(780	)			—				(1,498	)		(2,278	)
Ending balance		$	9,328			$	(1,952	)		$	1,614		$	8,990
		Nine Months Ended September 30, 2012
(In thousands)		Unrealized				Foreign				Total
		Gains				Currency
		(Losses) on				Adjustments
		Available-
		for-Sale
		Securities
Beginning balance		$	10,160			$	2,942			$	13,102
Other comprehensive income before reclassifications			6,230				191				6,421
Amounts reclassified from accumulated other comprehensive income			(4,211	)			—				(4,211	)
Net current period other comprehensive income			2,019				191				2,210
Ending balance		$	12,179			$	3,133			$	15,312
The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended September 30, 2013 and 2012:
(In thousands)		Three Months Ended September 30, 2013
Details about Accumulated Other Comprehensive Income		Amount Reclassified				Affected Line Item in the
Components		from Accumulated				Statement Where Net
		Other Comprehensive				Income Is Presented
		Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities		$	1,583			Net realized investment gain
Impairment expense			(9	)		Net realized investment gain
Total reclassifications for the period, before tax			1,574
Tax (expense) benefit			(614	)
Total reclassifications for the period, net of tax		$	960
(In thousands)		Three Months Ended September 30, 2012
Details about Accumulated Other Comprehensive Income		Amount Reclassified				Affected Line Item in the
Components		from Accumulated				Statement Where Net
		Other Comprehensive				Income Is Presented
		Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities		$	2,939			Net realized investment gain
Impairment expense			(631	)		Net realized investment gain
Total reclassifications for the period, before tax			2,308
Tax (expense) benefit			(900	)
Total reclassifications for the period, net of tax		$	1,408
The following tables present the details of reclassifications out of accumulated other comprehensive income for the nine months ended September 30, 2013 and 2012:
(In thousands)		Nine Months Ended September 30, 2013
Details about Accumulated Other Comprehensive Income		Amount Reclassified				Affected Line Item in the
Components		from Accumulated				Statement Where Net
		Other Comprehensive				Income Is Presented
		Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities		$	6,496			Net realized investment gain
Impairment expense			(13	)		Net realized investment gain
Total reclassifications for the period, before tax			6,483
Tax (expense) benefit			(2,529	)
Total reclassifications for the period, net of tax		$	3,954
(In thousands)		Nine Months Ended September 30, 2012
Details about Accumulated Other Comprehensive Income		Amount Reclassified				Affected Line Item in the
Components		from Accumulated				Statement Where Net
		Other Comprehensive				Income Is Presented
		Income
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities		$	7,567			Net realized investment gain
Impairment expense			(664	)		Net realized investment gain
Total reclassifications for the period, before tax			6,903
Tax (expense) benefit			(2,692	)
Total reclassifications for the period, net of tax		$	4,211
The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended September 30, 2013 and 2012:
		Three Months Ended											Three Months Ended
		September 30, 2013											September 30, 2012
(In thousands)		Before-Tax				Tax				Net-of-Tax			Before-Tax			Tax			Net-of-Tax
		Amount				(Expense)				Amount			Amount			(Expense)			Amount
						Benefit										Benefit
Unrealized gains (losses) on available-for-sale securities		$	5,774			$	(2,252	)		$	3,522		$	3,123		$	(1,218	)	$	1,905
Reclassification adjustment for amounts included in net income			(1,574	)			614				(960	)		(2,308	)		900			(1,408	)
Foreign currency translation adjustment			(108	)			—				(108	)		134			—			134
Total Other Comprehensive Income (Loss)		$	4,092			$	(1,638	)		$	2,454		$	949		$	(318	)	$	631
The following table presents the tax effects related to the change in each component of other comprehensive income for the nine months ended September 30, 2013 and 2012:
		Nine Months Ended											Nine Months Ended
		September 30, 2013											September 30, 2012
(In thousands)		Before-Tax				Tax				Net-of-Tax			Before-Tax			Tax			Net-of-Tax
		Amount				(Expense)				Amount			Amount			(Expense)			Amount
						Benefit										Benefit
Unrealized gains (losses) on available-for-sale securities		$	5,203			$	(2,029	)		$	3,174		$	10,213		$	(3,983	)	$	6,230
Reclassification adjustment for amounts included in net income			(6,483	)			2,529				(3,954	)		(6,903	)		2,692			(4,211	)
Foreign currency translation adjustment			(1,498	)			—				(1,498	)		191			—			191
Total Other Comprehensive Income (Loss)		$	(2,778	)		$	500			$	(2,278	)	$	3,501		$	(1,291	)	$	2,210

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
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 nine months ended September 30, 2013 and 2012 is as follows:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(In thousands, except per share amounts)		2013		2012		2013		2012
	Numerator
	Net income		$	16,205	$	9,272	$	33,954	$	43,302
	Denominator
	Weighted average number of shares – basic			57,947		63,066		59,561		63,495
	Effect of dilutive securities
	Stock options			613		225		321		637
	Restricted stock and restricted stock units			57		13		47		7
	Weighted average number of shares – diluted			58,617		63,304		59,929		64,139
	Net income per share – basic		$	0.28	$	0.15	$	0.57	$	0.68
	Net income per share – diluted		$	0.28	$	0.15	$	0.57	$	0.68
	Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 2.5 million and 4.4 million for the three months ended September 30, 2013 and 2012, respectively, and 3.3 million and 2.6 million for the nine months ended September 30, 2013 and 2012, respectively.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
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 expense, research and development expenses, interest income and dividend income, interest expense, net realized investment gain/loss, other income/expense and provision for taxes are reported on an entity-wide basis only. There are no inter-segment revenues.
	The following table presents information about the reported sales and gross profit of our reportable segments for the three and nine months ended September 30, 2013 and 2012. Asset information by reportable segment is not reported, since we do not produce such information internally.
			Three Months Ended
			September 30, 2013				September 30, 2012
	(In thousands)		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	141,278	$	63,066	$	131,942	$	63,827
	Enterprise Networks			36,126		19,481		30,183		16,145
	Total		$	177,404	$	82,547	$	162,125	$	79,972
			Nine Months Ended
			September 30, 2013				September 30, 2012
	(In thousands)		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	374,498	$	172,570	$	381,303	$	195,448
	Enterprise Networks			108,152		59,452		99,555		53,812
	Total		$	482,650	$	232,022	$	480,858	$	249,260
	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 and Aggregation Platform (MSAP)
		•		hiX family of MSAPs
		•		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
		•		OPTI and TA 3000 optical products
		•		Small Form-Factor Pluggable (SFP) products
		•		TDM systems
		•		Network Management Solutions
	Business Networking products provide access to telecommunication services and facilitate the delivery of cloud connectivity, enterprise communications and virtual mobility to the small and mid-sized enterprise (SME) market. This category includes the following product areas and related services:
		•		Internetworking products
		•		Total Access IP Business Gateways
		•		Optical Network Terminals (ONTs)
		•		Bluesocket® virtual Wireless LAN (WLAN)
		•		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 telecommunications networks. The Loop Access category includes the following product areas:
		•		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 nine months ended September 30, 2013 and 2012:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(In thousands)		2013		2012		2013		2012
	Carrier Systems		$	120,778	$	111,577	$	319,119	$	309,590
	Business Networking			44,213		36,600		127,668		116,332
	Loop Access			12,413		13,948		35,863		54,936
	Total		$	177,404	$	162,125	$	482,650	$	480,858
	In addition, we identify subcategories of product revenues, which we divide into our 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 nine months ended September 30, 2013 and 2012:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(In thousands)		2013		2012		2013		2012
Core Products
Broadband Access (included in Carrier Systems)		$	98,132	$	94,464	$	251,994	$	249,988
Optical (included in Carrier Systems)			16,640		11,160		41,500		39,418
Internetworking (included in Business Networking)			43,329		35,411		124,163		111,320
Subtotal			158,101		141,035		417,657		400,726
Legacy Products
HDSL (does not include T1) (included in Loop Access)			11,487		12,926		33,183		51,350
Other products (excluding HDSL)			7,816		8,164		31,810		28,782
Subtotal			19,303		21,090		64,993		80,132
Total		$	177,404	$	162,125	$	482,650	$	480,858

Liability_for_Warranty_Returns

Liability for Warranty Returns	9 Months Ended
	Sep. 30, 2013
Product Warranties Disclosures [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 $8.6 million at September 30, 2013 and $9.7 million at December 31, 2012. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets.
	A summary of warranty expense and write-off activity for the nine months ended September 30, 2013 and 2012 is as follows:
			Nine Months Ended
			September 30,
			2013			2012
	(In thousands)
	Balance at beginning of period		$	9,653		$	4,118
	Plus: Amounts charged to cost and expenses			2,078			3,910
	Amounts assumed on acquisition			—			1,932
	Less: Deductions			(3,120	)		(2,709	)
	Balance at end of period		$	8,611		$	7,251

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2013
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 nine month periods ended September 30, 2013 and 2012, we incurred fees of $10 thousand per month for these legal services.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013, of which $7.7 million has been applied to these commitments.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	16	SUBSEQUENT EVENTS
	On October 8, 2013, 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 October 24, 2013. The payment date will be November 7, 2013. The quarterly dividend payment will be approximately $5.2 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 fourth quarter of 2013 and as of November 1, 2013, we repurchased 0.4 million shares of our common stock through open market purchases at an average cost of $23.85 per share. We currently have the authority to purchase an additional 3.9 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)	9 Months Ended
	Sep. 30, 2013
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, 2012 Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States.
	In the opinion of management, all adjustments necessary for a fair presentation of these interim statements have been recorded, including the out of period adjustment discussed below. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2012, filed on February 28, 2013 with the SEC.
Changes in Classifications	'
	Changes in Classifications
	Certain changes in classifications have been made to the prior period balances in other comprehensive income to conform to the current period’s presentation as a result of our adoption of Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Comprehensive Income.
Out of Period Adjustment	'
	Out of Period Adjustment
	During the three months ended September 30, 2013, we identified two adjustments in the acquired 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 $0.4 million understatement of net income in 2012 and $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 each of the prior periods affected and concluded that the impact was not material. We also evaluated the impact of the cumulative effect of the adjustments in the current year and concluded that the impact is not material to our projected 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 allowance for doubtful accounts, obsolete and excess inventory reserves, warranty reserves, customer rebates, allowance for sales returns, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated working capital adjustments under negotiation related to the Nokia Siemens Networks Broadband Access business acquisition, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	During the nine months ended September 30, 2013, we adopted the following accounting standard, which had no material effect on our consolidated results of operations or financial condition:
	In February 2013, the FASB issued Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU 2013-02). ASU 2013-02 requires entities to provide information about the amounts reclassified out of accumulated other comprehensive income by component either on the face of the financial statements or in the footnotes. ASU 2013-02 does not change the current requirements for reporting net income or other comprehensive income in the financial statements. This update is effective prospectively for reporting periods beginning after December 15, 2012. We adopted this amendment during the first quarter of 2013, and we have provided the disclosures required for the periods ended September 30, 2013 and 2012 in Note 10 of Notes to Consolidated Financial Statements.

Business_Combinations_Tables

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Allocation of Purchase Price to Estimated Fair Value of Assets Acquired and Liabilities Assumed at Acquisition Date	'
	The allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date is as follows:
	(In Thousands)
	Other receivables	$	9,486
	Inventory		21,068
	Property, plant and equipment		5,035
	Accounts payable		(5,194	)
	Unearned revenue		(18,203	)
	Accrued expenses		(1,931	)
	Accrued wages and benefits		(2,251	)
	Deferred tax liability		(788	)
	Non-current unearned revenue		(21,316	)
	Net liabilities assumed		(14,094	)
	Customer relationships		5,162
	Developed technology		3,176
	Other		13
	Gain on bargain purchase of a business, net of tax		(1,753	)
	Net consideration received from seller	$	(7,496	)
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, 2012, nor are they indicative of any future results.
	(In thousands)	Nine Months Ended
		September 30, 2012
	Pro forma revenue	$	100,413
	Pro forma pre-tax loss	$	(18,006	)
	Weighted average exchange rate during the period	€	1.00/$1.29
	(EURO/USD)

Pension_Benefit_Plan_Tables

Pension Benefit Plan (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'
Summarization of Components of Net Periodic Pension Cost	'
	The following table summarizes the components of net periodic pension cost for the three months ended September 30, 2013 and 2012, the nine months ended September 30, 2013, and the period May 4, 2012 to September 30, 2012:
		Three Months  Ended						Nine Months Ended			May 4, 2012 to
		September 30,						September 30,			September 30,
	(In thousands)	2013			2012			2013			2012
	Service cost	$	297		$	288		$	891		$	478
	Interest cost		185			187			554			314
	Expected return on plan assets		(250	)		(250	)		(751	)		(415	)
	Net periodic pension cost	$	232		$	225		$	694		$	377

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
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 nine months ended September 30, 2013 and 2012, which was recognized as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(In thousands)	2013			2012			2013			2012
	Stock-based compensation expense included in cost of sales	$	118		$	106		$	334		$	304
	Selling, general and administrative expense		1,024			1,107			3,129			3,205
	Research and development expense		1,034			1,138			3,053			3,274
	Stock-based compensation expense included in operating expenses		2,058			2,245			6,182			6,479
	Total stock-based compensation expense		2,176			2,351			6,516			6,783
	Tax benefit for expense associated with non-qualified options		(307	)		(313	)		(924	)		(916	)
	Total stock-based compensation expense, net of tax	$	1,869		$	2,038		$	5,592		$	5,867
Summary of Weighted-Average Assumptions and Value of Options Granted	'
	The weighted-average assumptions and value of options granted for the three and nine months ended September 30, 2012 are summarized as follows:
		Three Months Ended			Nine Months Ended
		September 30,			September 30,
		2012			2012
	Expected volatility		40.2	%		40.2	%
	Risk-free interest rate		0.63	%		0.63	%
	Expected dividend yield		1.3	%		1.3	%
	Expected life (in years)		4.95			4.95
	Weighted-average estimated value	$	8.69		$	8.69
Summary of Stock Options Outstanding	'
	The following table is a summary of our stock options outstanding as of December 31, 2012 and September 30, 2013 and the changes that occurred during the nine months ended September 30, 2013:
	(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, 2012		6,035		$	24.81			6.69		$	5,154
	Options granted		—		$	—
	Options cancelled/forfeited		(188	)	$	26.23
	Options exercised		(123	)	$	18.93
	Options outstanding, September 30, 2013		5,724		$	24.89			5.96		$	21,878
	Options exercisable, September 30, 2013		3,618		$	25.33			4.68		$	11,955
Summary of RSUs and Restricted Stock Outstanding	'
	The following table is a summary of our RSUs and restricted stock outstanding as of December 31, 2012 and September 30, 2013 and the changes that occurred during the nine months ended September 30, 2013:
	(In thousands, except per share amounts)	Number			Weighted
		of Shares			Average
					Grant Date
					Fair Value
	Unvested RSUs and restricted stock outstanding, December 31, 2012		103		$	29.25
	RSUs and restricted stock granted		—		$	—
	RSUs and restricted stock vested		—		$	—
	RSUs and restricted stock cancelled/forfeited		—		$	—
	Unvested RSUs and restricted stock, September 30, 2013		103		$	29.25

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Securities and Investments, Recorded at Either Fair Value or Cost	'
	At September 30, 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	$	11,308		$	2,490		$	(18	)	$	13,780
	Corporate bonds		177,798			446			(103	)		178,141
	Municipal fixed-rate bonds		145,509			497			(71	)		145,935
	Municipal variable rate demand notes		11,960			—			—			11,960
	Marketable equity securities		22,825			12,393			(275	)		34,943
	Available-for-sale securities held at fair value	$	369,400		$	15,826		$	(467	)	$	384,759
	Restricted investment held at cost											48,250
	Other investments held at cost											1,753
	Total carrying value of available-for-sale investments										$	434,762
	At December 31, 2012, 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	$	10,688		$	846		$	(7	)	$	11,527
	Corporate bonds		185,464			966			(18	)		186,412
	Municipal fixed-rate bonds		174,530			627			(73	)		175,084
	Municipal variable rate demand notes		34,375			—			—			34,375
	Fixed income bond fund		444			12			—			456
	Marketable equity securities		20,966			14,630			(392	)		35,204
	Available-for-sale securities held at fair value	$	426,467		$	17,081		$	(490	)	$	443,058
	Restricted investment held at cost											48,250
	Other investments held at cost											1,902
	Total carrying value of available-for-sale investments										$	493,210
Contractual Maturities of Corporate and Municipal Fixed-Rate Bonds	'
	As of September 30, 2013, 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	$	66,267		$	58,413
	One to two years		32,231			18,638
	Two to three years		76,460			58,389
	Three to five years		3,183			10,495
	Total	$	178,141		$	145,935
Realized Gains and Losses on Sales of Securities	'
	The following table presents gross realized gains and losses related to our investments.
		Three Months  Ended						Nine Months  Ended
		September 30,						September 30,
	(In thousands)	2013			2012			2013			2012
	Gross realized gains	$	1,797		$	3,388		$	7,252		$	8,688
	Gross realized losses	$	(46	)	$	(858	)	$	(303	)	$	(1,335	)
Fair Value Measurement 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 in active markets for identical assets or liabilities; Level 2 – Values based on inputs other than quoted prices included within Level 1 that are directly or indirectly observable for the asset or liability; Level 3 – Values based on unobservable inputs for the asset or liability. These inputs include information supplied by investees.
		Fair Value Measurements at September 30, 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	$	6,594		$	6,594		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		13,780			13,780			—			—
	Available-for-sale debt securities
	Corporate bonds		178,141			—			178,141			—
	Municipal fixed-rate bonds		145,935			—			145,935			—
	Municipal variable rate demand notes		11,960			—			11,960			—
	Available-for-sale marketable equity securities
	Equity securities – technology industry		9,973			9,973			—			—
	Equity securities – other		24,970			24,970			—			—
	Available-for-sale securities		384,759			48,723			336,036			—
	Total	$	391,353		$	55,317		$	336,036		$	—
		Fair Value Measurements at December 31, 2012 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	$	28,071		$	28,071		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		11,527			11,527			—			—
	Available-for-sale debt securities
	Corporate bonds		186,412			—			186,412			—
	Municipal fixed-rate bonds		175,084			—			175,084			—
	Municipal variable rate demand notes		34,375			—			34,375			—
	Fixed income bond fund		456			456			—			—
	Available-for-sale marketable equity securities
	Equity securities – technology industry		14,099			14,099			—			—
	Equity securities – other		21,105			21,105			—			—
	Available-for-sale securities		443,058			47,187			395,871			—
	Total	$	471,129		$	75,258		$	395,871		$	—

Derivative_Instruments_and_Hed1

Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 were as follows:
		September 30, 2013
	(In thousands)	Balance Sheet		Fair Value
		Location
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables		$	40
	Foreign exchange contracts – liability derivatives	Accounts payable		$	(6	)
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 nine months ended September 30, 2013 were as follows:
	(In thousands)	Income Statement Location				Three Months		Nine Months
						Ended		Ended
						September 30,		September 30,
						2013		2013
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts		Other income (expense)			$	52	$	(34	)

Inventory_Tables

Inventory (Tables)	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]	'
Components of Inventory	'
	At September 30, 2013 and December 31, 2012, inventory consisted of the following:
	(In thousands)	September 30,		December 31,
		2013		2012
	Raw materials	$	40,947	$	47,054
	Work in process		3,562		3,262
	Finished goods		48,463		52,267
	Total	$	92,972	$	102,583

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Change in Carrying Value of Goodwill	'
	The change in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the nine months ended September 30, 2013 is as follows:
	(In thousands)
	Balance, December 31, 2012	$	3,492
	Acquisitions		—
	Impairment losses		—
	Balance, September 30, 2013	$	3,492
	Balance as of September 30, 2013
	Goodwill	$	3,492
	Accumulated impairment losses		—
	Total goodwill	$	3,492
Summary of Intangible Assets	'
	The following table presents our intangible assets as of September 30, 2013 and December 31, 2012:
	(In thousands)	September 30, 2013							December 31, 2012
		Gross		Accumulated			Net		Gross		Accumulated			Net
		Value		Amortization			Value		Value		Amortization			Value
	Customer relationships	$	6,906	$	(1,348	)	$	5,558	$	6,769	$	(766	)	$	6,003
	Developed technology		6,481		(2,347	)		4,134		6,397		(1,354	)		5,043
	Intellectual property		2,340		(1,102	)		1,238		2,340		(851	)		1,489
	Trade names		270		(130	)		140		270		(85	)		185
	Other		14		(6	)		8		13		(3	)		10
	Total	$	16,011	$	(4,933	)	$	11,078	$	15,789	$	(3,059	)	$	12,730
Estimated Future Amortization Expense Related to Intangible Assets	'
	As of September 30, 2013, the estimated future amortization expense of our intangible assets is as follows:
	(In thousands)	Amount
	Remainder of 2013	$	618
	2014		2,315
	2015		2,179
	2016		1,905
	2017		1,291
	Thereafter		2,770
	Total	$	11,078

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Summary of Changes in Stockholders' Equity	'
	A summary of the changes in stockholders’ equity for the nine months ended September 30, 2013 is as follows:
	(In thousands)	Stockholders’
		Equity
	Balance, December 31, 2012	$	692,406
	Net income		33,954
	Dividend payments		(16,220	)
	Dividends accrued for unvested restricted stock units		(23	)
	Net unrealized gains (losses) on available-for-sale securities (net of tax)		(780	)
	Foreign currency translation adjustment		(1,498	)
	Proceeds from stock option exercises		2,332
	Purchase of treasury stock		(104,147	)
	Income tax benefit from exercise of stock options		113
	Stock-based compensation expense		6,516
	Balance, September 30, 2013	$	612,653
Cash Dividends	'
	During the nine months ended September 30, 2013, we paid cash dividends as follows (in thousands except per share amounts):
	Record Date	Payment Date		Per Share Amount				Total Dividend Paid
	February 7, 2013	February 21, 2013		$	0.09			$	5,586
	April 25, 2013	May 9, 2013		$	0.09			$	5,396
	July 25, 2013	August 8, 2013		$	0.09			$	5,238
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 September 30, 2013 and 2012:
		Three Months Ended September 30, 2013
	(In thousands)	Unrealized				Defined				Foreign			Total
		Gains				Benefit Plan				Currency
		(Losses) on				Adjustments				Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	6,766			$	(1,952	)		$	1,722		$	6,536
	Other comprehensive income (loss) before reclassifications		3,522				—				(108	)		3,414
	Amounts reclassified from accumulated other comprehensive income		(960	)			—				—			(960	)
	Net current period other comprehensive income (loss)		2,562				—				(108	)		2,454
	Ending balance	$	9,328			$	(1,952	)		$	1,614		$	8,990
		Three Months Ended September 30, 2012
	(In thousands)	Unrealized				Foreign				Total
		Gains				Currency
		(Losses) on				Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	11,682			$	2,999			$	14,681
	Other comprehensive income before reclassifications		1,905				134				2,039
	Amounts reclassified from accumulated other comprehensive income		(1,408	)			—				(1,408	)
	Net current period other comprehensive income		497				134				631
	Ending balance	$	12,179			$	3,133			$	15,312
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the nine months ended September 30, 2013 and 2012:
		Nine Months Ended September 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 reclassifications		3,174				—				(1,498	)		1,676
	Amounts reclassified from accumulated other comprehensive income		(3,954	)			—				—			(3,954	)
	Net current period other comprehensive (loss)		(780	)			—				(1,498	)		(2,278	)
	Ending balance	$	9,328			$	(1,952	)		$	1,614		$	8,990
		Nine Months Ended September 30, 2012
	(In thousands)	Unrealized				Foreign				Total
		Gains				Currency
		(Losses) on				Adjustments
		Available-
		for-Sale
		Securities
	Beginning balance	$	10,160			$	2,942			$	13,102
	Other comprehensive income before reclassifications		6,230				191				6,421
	Amounts reclassified from accumulated other comprehensive income		(4,211	)			—				(4,211	)
	Net current period other comprehensive income		2,019				191				2,210
	Ending balance	$	12,179			$	3,133			$	15,312
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 September 30, 2013 and 2012:
	(In thousands)	Three Months Ended September 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	$	1,583			Net realized investment gain
	Impairment expense		(9	)		Net realized investment gain
	Total reclassifications for the period, before tax		1,574
	Tax (expense) benefit		(614	)
	Total reclassifications for the period, net of tax	$	960
	(In thousands)	Three Months Ended September 30, 2012
	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	$	2,939			Net realized investment gain
	Impairment expense		(631	)		Net realized investment gain
	Total reclassifications for the period, before tax		2,308
	Tax (expense) benefit		(900	)
	Total reclassifications for the period, net of tax	$	1,408
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the nine months ended September 30, 2013 and 2012:
	(In thousands)	Nine Months Ended September 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	$	6,496			Net realized investment gain
	Impairment expense		(13	)		Net realized investment gain
	Total reclassifications for the period, before tax		6,483
	Tax (expense) benefit		(2,529	)
	Total reclassifications for the period, net of tax	$	3,954
	(In thousands)	Nine Months Ended September 30, 2012
	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	$	7,567				Net realized investment gain
	Impairment expense		(664	)			Net realized investment gain
	Total reclassifications for the period, before tax		6,903
	Tax (expense) benefit		(2,692	)
	Total reclassifications for the period, net of tax	$	4,211
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 September 30, 2013 and 2012:
		Three Months Ended											Three Months Ended
		September 30, 2013											September 30, 2012
	(In thousands)	Before-Tax				Tax				Net-of-Tax			Before-Tax			Tax			Net-of-Tax
		Amount				(Expense)				Amount			Amount			(Expense)			Amount
						Benefit										Benefit
	Unrealized gains (losses) on available-for-sale securities	$	5,774			$	(2,252	)		$	3,522		$	3,123		$	(1,218	)	$	1,905
	Reclassification adjustment for amounts included in net income		(1,574	)			614				(960	)		(2,308	)		900			(1,408	)
	Foreign currency translation adjustment		(108	)			—				(108	)		134			—			134
	Total Other Comprehensive Income (Loss)	$	4,092			$	(1,638	)		$	2,454		$	949		$	(318	)	$	631
	The following table presents the tax effects related to the change in each component of other comprehensive income for the nine months ended September 30, 2013 and 2012:
		Nine Months Ended											Nine Months Ended
		September 30, 2013											September 30, 2012
	(In thousands)	Before-Tax				Tax				Net-of-Tax			Before-Tax			Tax			Net-of-Tax
		Amount				(Expense)				Amount			Amount			(Expense)			Amount
						Benefit										Benefit
	Unrealized gains (losses) on available-for-sale securities	$	5,203			$	(2,029	)		$	3,174		$	10,213		$	(3,983	)	$	6,230
	Reclassification adjustment for amounts included in net income		(6,483	)			2,529				(3,954	)		(6,903	)		2,692			(4,211	)
	Foreign currency translation adjustment		(1,498	)			—				(1,498	)		191			—			191
	Total Other Comprehensive Income (Loss)	$	(2,778	)		$	500			$	(2,278	)	$	3,501		$	(1,291	)	$	2,210

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	A summary of the calculation of basic and diluted earnings per share for the three and nine months ended September 30, 2013 and 2012 is as follows:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(In thousands, except per share amounts)	2013		2012		2013		2012
	Numerator
	Net income	$	16,205	$	9,272	$	33,954	$	43,302
	Denominator
	Weighted average number of shares – basic		57,947		63,066		59,561		63,495
	Effect of dilutive securities
	Stock options		613		225		321		637
	Restricted stock and restricted stock units		57		13		47		7
	Weighted average number of shares – diluted		58,617		63,304		59,929		64,139
	Net income per share – basic	$	0.28	$	0.15	$	0.57	$	0.68
	Net income per share – diluted	$	0.28	$	0.15	$	0.57	$	0.68

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Sales and Gross Profit of Reportable Segments	'
	The following table presents information about the reported sales and gross profit of our reportable segments for the three and nine months ended September 30, 2013 and 2012. Asset information by reportable segment is not reported, since we do not produce such information internally.
		Three Months Ended
		September 30, 2013				September 30, 2012
	(In thousands)	Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	141,278	$	63,066	$	131,942	$	63,827
	Enterprise Networks		36,126		19,481		30,183		16,145
	Total	$	177,404	$	82,547	$	162,125	$	79,972
		Nine Months Ended
		September 30, 2013				September 30, 2012
	(In thousands)	Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	374,498	$	172,570	$	381,303	$	195,448
	Enterprise Networks		108,152		59,452		99,555		53,812
	Total	$	482,650	$	232,022	$	480,858	$	249,260
Sales Information by Product Category	'
	The table below presents sales information by product category for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(In thousands)	2013		2012		2013		2012
	Carrier Systems	$	120,778	$	111,577	$	319,119	$	309,590
	Business Networking		44,213		36,600		127,668		116,332
	Loop Access		12,413		13,948		35,863		54,936
	Total	$	177,404	$	162,125	$	482,650	$	480,858
Subcategory Revenues	'
	The table below presents subcategory revenues for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(In thousands)	2013		2012		2013		2012
	Core Products
	Broadband Access (included in Carrier Systems)	$	98,132	$	94,464	$	251,994	$	249,988
	Optical (included in Carrier Systems)		16,640		11,160		41,500		39,418
	Internetworking (included in Business Networking)		43,329		35,411		124,163		111,320
	Subtotal		158,101		141,035		417,657		400,726
	Legacy Products
	HDSL (does not include T1) (included in Loop Access)		11,487		12,926		33,183		51,350
	Other products (excluding HDSL)		7,816		8,164		31,810		28,782
	Subtotal		19,303		21,090		64,993		80,132
	Total	$	177,404	$	162,125	$	482,650	$	480,858

Liability_for_Warranty_Returns1

Liability for Warranty Returns (Tables)	9 Months Ended
	Sep. 30, 2013
Product Warranties Disclosures [Abstract]	'
Summary of Warranty Expense and Write-Off Activity	'
	A summary of warranty expense and write-off activity for the nine months ended September 30, 2013 and 2012 is as follows:
		Nine Months Ended
		September 30,
		2013			2012
	(In thousands)
	Balance at beginning of period	$	9,653		$	4,118
	Plus: Amounts charged to cost and expenses		2,078			3,910
	Amounts assumed on acquisition		—			1,932
	Less: Deductions		(3,120	)		(2,709	)
	Balance at end of period	$	8,611		$	7,251

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (Immaterial Corrections [Member], USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Immaterial Corrections [Member]	'	'
Summary Of Significant Accounting Policy [Line Items]	'	'
Understatement of net income of previous year	'	$0.40
Understatement of net income of previous quarters	$0.50	'

Business_Combinations_Addition

Business Combinations - Additional Information (Detail) (USD $)	9 Months Ended	3 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2013	Jun. 30, 2012	Sep. 30, 2013	4-May-12	Sep. 30, 2013	Sep. 30, 2013
		Nokia Siemens Networks [Member]	Nokia Siemens Networks [Member]	Nokia Siemens Networks [Member]	Nokia Siemens Networks [Member]	Nokia Siemens Networks [Member]	Nokia Siemens Networks [Member]
						Customer Relationships [Member]	Developed Technology [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'
Purchase price, net of consideration	'	'	'	'	$7,496,000	'	'
Bargain purchase gain, net of tax	1,753,000	'	1,800,000	'	'	'	'
Average estimated useful life	'	'	'	'	'	'13 years	'5 years
Acquisition and integration related expenses and amortization of acquired intangibles	'	$600,000	'	$2,200,000	'	'	'

Business_Combinations_Allocati

Business Combinations - Allocation of Purchase Price to Estimated Fair Value of Assets Acquired and Liabilities Assumed at Acquisition Date (Detail) (Nokia Siemens Networks [Member], USD $)	4-May-12
In Thousands, unless otherwise specified
Business Acquisition [Line Items]	'
Other receivables	$9,486
Inventory	21,068
Property, plant and equipment	5,035
Accounts payable	-5,194
Unearned revenue	-18,203
Accrued expenses	-1,931
Accrued wages and benefits	-2,251
Deferred tax liability	-788
Non-current unearned revenue	-21,316
Net liabilities assumed	-14,094
Gain on bargain purchase of a business, net of tax	-1,753
Net consideration received from seller	-7,496
Customer Relationships [Member]	'
Business Acquisition [Line Items]	'
Intangible assets	5,162
Developed Technology [Member]	'
Business Acquisition [Line Items]	'
Intangible assets	3,176
Other [Member]	'
Business Acquisition [Line Items]	'
Intangible assets	$13

Business_Combinations_Suppleme

Business Combinations - Supplemental Pro Forma Information (Detail)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
	USD ($)	EUR (€)
Business Combinations [Abstract]	'	'
Pro forma revenue	$100,413,000	'
Pro forma pre-tax loss	-18,006,000	'
Weighted average exchange rate during the period (EURO/USD)	$1.29	€ 1

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]	'	'
Effective tax rate	27.00%	34.90%

Pension_Benefit_Plan_Additiona

Pension Benefit Plan - Additional Information (Detail) (Nokia Siemens Networks [Member], USD $)	4-May-12
In Millions, unless otherwise specified
Nokia Siemens Networks [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Amount of the defined benefit obligation	$17

Pension_Benefit_Plan_Summariza

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) (USD $)	3 Months Ended		5 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'	'	'	'
Service cost	$297	$288	$478	$891
Interest cost	185	187	314	554
Expected return on plan assets	-250	-250	-415	-751
Net periodic pension cost	$232	$225	$377	$694

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		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation expense	$2,176	$2,351	$6,516	$6,783
Tax benefit for expense associated with non-qualified options	-307	-313	-924	-916
Total stock-based compensation expense, net of tax	1,869	2,038	5,592	5,867
Cost of Sales [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation expense	118	106	334	304
Selling, General and Administrative Expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation expense	1,024	1,107	3,129	3,205
Research and Development Expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation expense	1,034	1,138	3,053	3,274
Operating Expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation expense	$2,058	$2,245	$6,182	$6,479

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of Options, granted	0	'	0	'
Number of RSUs and restricted stock granted	'	'	'	'
Estimated forfeitures for stock options	'	'	1.70%	'
Forfeiture rate for RSUs and restricted stock	'	'	0.00%	'
compensation expense related to non-vested stock options, RSUs and restricted stock not yet recognized	11.8	'	11.8	'
Recognition period of non-vested compensation cost	'	'	'2 years 1 month 6 days	'
Total pre-tax intrinsic value of options exercised	0.5	'	0.8	'
Restricted Stock Units (RSUs) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of RSUs and restricted stock granted	0	0	0	0
Restricted Stock [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of RSUs and restricted stock granted	0	0	0	0

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Expected volatility	40.20%	40.20%
Risk-free interest rate	0.63%	0.63%
Expected dividend yield	1.30%	1.30%
Expected life (in years)	'4 years 11 months 12 days	'4 years 11 months 12 days
Weighted-average estimated value	$8.69	$8.69

StockBased_Compensation_Summar1

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'
Number of Options, outstanding, Beginning Balance	'	6,035	'
Number of Options, granted	0	0	'
Number of Options, cancelled/forfeited	'	-188	'
Number of Options, exercised	'	-123	'
Number of Options, outstanding, Ending Balance	5,724	5,724	6,035
Number of Options, Options exercisable	3,618	3,618	'
Weighted Average Exercise Price, outstanding, Beginning Balance	'	$24.81	'
Weighted Average Exercise Price, granted	'	'	'
Weighted Average Exercise Price, cancelled/forfeited	'	$26.23	'
Weighted Average Exercise Price, exercised	'	$18.93	'
Weighted Average Exercise Price, outstanding, Ending Balance	$24.89	$24.89	$24.81
Weighted Average Exercise Price, Options exercisable	$25.33	$25.33	'
Weighted Average Remaining Contractual Life In Years, Options outstanding	'	'5 years 11 months 16 days	'6 years 8 months 9 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	'	'4 years 8 months 5 days	'
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	'	$5,154	'
Aggregate Intrinsic Value, Options outstanding, Ending Balance	21,878	21,878	5,154
Aggregate Intrinsic Value, Options exercisable	$11,955	$11,955	'

StockBased_Compensation_Summar2

Stock-Based Compensation - Summary of RSUs and Restricted Stock Outstanding (Detail) (USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Number of Unvested RSUs and restricted stock outstanding, Beginning balance	103
Number of RSUs and restricted stock granted	'
Number of RSUs and restricted stock vested	'
Number of RSUs and restricted stock cancelled/forfeited	'
Number of Unvested RSUs and restricted stock outstanding, Ending balance	103
Weighted Average Grant Date Fair Value, Unvested RSUs and restricted stock outstanding, Beginning balance	$29.25
Weighted Average Grant Date Fair Value, RSUs and restricted stock granted	'
Weighted Average Grant Date Fair Value, RSUs and restricted stock vested	'
Weighted Average Grant Date Fair Value, RSUs and restricted stock cancelled/forfeited	'
Weighted Average Grant Date Fair Value, Unvested RSUs and restricted stock, Ending balance	$29.25

Investments_Securities_and_Inv

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$369,400	$426,467
Gross Unrealized Gains	15,826	17,081
Gross Unrealized Losses	-467	-490
Available-for-sale-securities, carrying value	384,759	443,058
Restricted investment held at cost	48,250	48,250
Other investments held at cost	1,753	1,902
Total carrying value of available-for-sale investments	434,762	493,210
Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	11,308	10,688
Gross Unrealized Gains	2,490	846
Gross Unrealized Losses	-18	-7
Available-for-sale-securities, carrying value	13,780	11,527
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	177,798	185,464
Gross Unrealized Gains	446	966
Gross Unrealized Losses	-103	-18
Available-for-sale-securities, carrying value	178,141	186,412
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	145,509	174,530
Gross Unrealized Gains	497	627
Gross Unrealized Losses	-71	-73
Available-for-sale-securities, carrying value	145,935	175,084
Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	11,960	34,375
Available-for-sale-securities, carrying value	11,960	34,375
Marketable Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	22,825	20,966
Gross Unrealized Gains	12,393	14,630
Gross Unrealized Losses	-275	-392
Available-for-sale-securities, carrying value	34,943	35,204
Fixed Income Bond Fund [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	'	444
Gross Unrealized Gains	'	12
Available-for-sale-securities, carrying value	'	$456

Investments_Contractual_Maturi

Investments - Contractual Maturities of Corporate and Municipal Fixed-Rate Bonds (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale-securities, carrying value	$384,759	$443,058
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	66,267	'
One to two years	32,231	'
Two to three years	76,460	'
Three to five years	3,183	'
Available-for-sale-securities, carrying value	178,141	186,412
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	58,413	'
One to two years	18,638	'
Two to three years	58,389	'
Three to five years	10,495	'
Available-for-sale-securities, carrying value	$145,935	$175,084

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
	Securities	Securities
Schedule of Investments [Line Items]	'	'	'
Restricted certificate of deposit held	$48,250,000	'	$48,250,000
Identification of potential other-than-temporary impairments	25.00%	'	'
Impairment of investments	13,000	100,000	'
Number of marketable equity securities in unrealized loss position	5	21	'
Significant Other Observable Inputs (Level 2) [Member]	'	'	'
Schedule of Investments [Line Items]	'	'	'
Estimated fair value of bond	$44,900,000	'	'
Investment [Member]	'	'	'
Schedule of Investments [Line Items]	'	'	'
Investment concentration risk percentage	5.00%	'	'

Investments_Realized_Gains_and

Investments - Realized Gains and Losses on Sales of Securities (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Investments Debt And Equity Securities [Abstract]	'	'	'	'
Gross realized gains	$1,797	$3,388	$7,252	$8,688
Gross realized losses	($46)	($858)	($303)	($1,335)

Investments_Fair_Value_Measure

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	$384,759	$443,058
Fair Value, Measurements, Recurring [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	384,759	443,058
Total	391,353	471,129
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	48,723	47,187
Total	55,317	75,258
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	336,036	395,871
Total	336,036	395,871
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'
Total	'	'
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalents	6,594	28,071
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 equivalents	6,594	28,071
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalents	'	'
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	13,780	11,527
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	13,780	11,527
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	'	'
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	178,141	186,412
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	178,141	186,412
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	'	'
Fair Value, Measurements, Recurring [Member] | Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	145,935	175,084
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	145,935	175,084
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	'	'
Fair Value, Measurements, Recurring [Member] | Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	11,960	34,375
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	11,960	34,375
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	'	'
Fair Value, Measurements, Recurring [Member] | Fixed Income Bond Fund [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	456
Fair Value, Measurements, Recurring [Member] | Fixed Income Bond Fund [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	456
Fair Value, Measurements, Recurring [Member] | Fixed Income Bond Fund [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'
Fair Value, Measurements, Recurring [Member] | Equity Securities - Technology Industry [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	9,973	14,099
Fair Value, Measurements, Recurring [Member] | 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	9,973	14,099
Fair Value, Measurements, Recurring [Member] | Equity Securities - Technology Industry [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'
Fair Value, Measurements, Recurring [Member] | Equity Securities - Other [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	24,970	21,105
Fair Value, Measurements, Recurring [Member] | 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	24,970	21,105
Fair Value, Measurements, Recurring [Member] | Equity Securities - Other [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities - Additional Information (Detail)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
		Forward Contracts [Member]	Forward Contracts [Member]
		USD ($)	EUR (€)
Derivative [Line Items]	'	'	'
Maximum contractual period for derivatives	'12 months	'	'
Derivative, notional amount	'	$26.80	€ 19.80
Derivative maturity year	'	'2013	'2013

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 $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Other Receivables [Member]	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'
Derivatives asset, fair value	$40
Accounts Payable [Member]	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'
Derivatives liability, fair value	($6)

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) (Other Income (Expense) [Member], Foreign Exchange Contracts [Member], USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Other Income (Expense) [Member] | Foreign Exchange Contracts [Member]	'	'
Derivatives Not Designated as Hedging Instruments:	'	'
Derivative instrument, gain or loss	$52	($34)

Inventory_Components_of_Invent

Inventory - Components of Inventory (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials	$40,947	$47,054
Work in process	3,562	3,262
Finished goods	48,463	52,267
Total	$92,972	$102,583

Inventory_Additional_Informati

Inventory - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials reserves, total	$15.90	$9.90
Finished goods inventory reserves, total	$5	$2.10

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Change in Carrying Value of Goodwill (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Goodwill, Beginning balance	$3,492	'
Acquisitions	'	'
Impairment losses	0	0
Accumulated impairment losses	'	'
Goodwill, Ending balance	$3,492	'

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Goodwill And Intangible Assets Disclosure [Abstract]	'	'	'	'
Impairment losses	'	'	$0	$0
Amortization expense	$600,000	$600,000	$1,800,000	$1,400,000

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill [Line Items]	'	'
Gross Value	$16,011	$15,789
Accumulated Amortization	-4,933	-3,059
Net Value	11,078	12,730
Customer Relationships [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,906	6,769
Accumulated Amortization	-1,348	-766
Net Value	5,558	6,003
Developed Technology [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,481	6,397
Accumulated Amortization	-2,347	-1,354
Net Value	4,134	5,043
Intellectual Property [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	2,340	2,340
Accumulated Amortization	-1,102	-851
Net Value	1,238	1,489
Trade Names [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	270	270
Accumulated Amortization	-130	-85
Net Value	140	185
Other [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	14	13
Accumulated Amortization	-6	-3
Net Value	$8	$10

Goodwill_and_Intangible_Assets5

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Remainder of 2013	$618	'
2014	2,315	'
2015	2,179	'
2016	1,905	'
2017	1,291	'
Thereafter	2,770	'
Net Value	$11,078	$12,730

Stockholders_Equity_Summary_of

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]	'	'	'	'
Beginning Balance	'	'	$692,406	'
Net Income	16,205	9,272	33,954	43,302
Dividend payments	'	'	-16,220	'
Dividends accrued for unvested restricted stock units	'	'	-23	'
Net unrealized gains (losses) on available-for-sale securities (net of tax)	2,562	497	-780	2,019
Foreign currency translation adjustment	-108	134	-1,498	191
Proceeds from stock option exercises	'	'	2,332	4,932
Purchase of treasury stock	'	'	-104,147	'
Income tax benefit from exercise of stock options	'	'	113	'
Stock-based compensation expense	2,176	2,351	6,516	6,783
Ending Balance	$612,653	'	$612,653	'

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	1-May-13
Equity [Abstract]	'	'	'
Maximum shares authorized for repurchase	35,000,000	'	'
Additional shares authorized for purchase	4,300,000	'	5,000,000
Stock repurchased, shares	4,800,000	'	'
Shares repurchased, average price per share	$21.89	'	'
Number of Options, exercised	123,000	'	'
Exercise price of stock options, lower range limit	$15.29	'	'
Exercise price of stock options, upper range limit	$26.06	'	'
Proceeds from stock option exercise	$2,332	$4,932	'

Stockholders_Equity_Cash_Divid

Stockholders' Equity - Cash Dividends (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	24-Oct-13	'
Payment Date	'	'	7-Nov-13	'
Per Share Amount	$0.09	$0.09	$0.27	$0.27
Total Dividend Paid	'	'	$16,220	$17,173
Record Date, February 7, 2013 [Member]	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	7-Feb-13	'
Payment Date	'	'	21-Feb-13	'
Per Share Amount	'	'	$0.09	'
Total Dividend Paid	'	'	5,586	'
Record Date, April 25, 2013 [Member]	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	25-Apr-13	'
Payment Date	'	'	9-May-13	'
Per Share Amount	'	'	$0.09	'
Total Dividend Paid	'	'	5,396	'
Record Date, July 25, 2013 [Member]	'	'	'	'
Dividends Payable [Line Items]	'	'	'	'
Record Date	'	'	25-Jul-13	'
Payment Date	'	'	8-Aug-13	'
Per Share Amount	'	'	$0.09	'
Total Dividend Paid	'	'	$5,238	'

Stockholders_Equity_Changes_in

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	$6,536	$14,681	$11,268	$13,102
Other comprehensive income (loss) before reclassifications	3,414	2,039	1,676	6,421
Amounts reclassified from accumulated other comprehensive income	-960	-1,408	-3,954	-4,211
Other Comprehensive Income (Loss), net of tax	2,454	631	-2,278	2,210
Ending balance	8,990	15,312	8,990	15,312
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	6,766	11,682	10,108	10,160
Other comprehensive income (loss) before reclassifications	3,522	1,905	3,174	6,230
Amounts reclassified from accumulated other comprehensive income	-960	-1,408	-3,954	-4,211
Other Comprehensive Income (Loss), net of tax	2,562	497	-780	2,019
Ending balance	9,328	12,179	9,328	12,179
Defined Benefit Plan Adjustments [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	-1,952	'	-1,952	'
Other comprehensive income (loss) before reclassifications	'	'	'	'
Amounts reclassified from accumulated other comprehensive income	'	'	'	'
Other Comprehensive Income (Loss), net of tax	'	'	'	'
Ending balance	-1,952	'	-1,952	'
Foreign Currency Adjustments [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	1,722	2,999	3,112	2,942
Other comprehensive income (loss) before reclassifications	-108	134	-1,498	191
Other Comprehensive Income (Loss), net of tax	-108	134	-1,498	191
Ending balance	$1,614	$3,133	$1,614	$3,133

Stockholders_Equity_Reclassifi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net realized investment gain	$1,751	$2,530	$6,949	$7,353
Total reclassifications for the period, before tax	19,981	13,715	46,538	66,561
Tax (expense) benefit	-3,776	-4,443	-12,584	-23,259
Total reclassifications for the period, net of tax	16,205	9,272	33,954	43,302
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	1,574	2,308	6,483	6,903
Tax (expense) benefit	-614	-900	-2,529	-2,692
Total reclassifications for the period, net of tax	960	1,408	3,954	4,211
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net realized investment gain	1,583	2,939	6,496	7,567
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	($9)	($631)	($13)	($664)

Stockholders_Equity_Other_Comp

Stockholders' Equity - Other Comprehensive Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]	'	'	'	'
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$5,774	$3,123	$5,203	$10,213
Reclassification adjustment for amounts included in net income, Before-Tax Amount	-1,574	-2,308	-6,483	-6,903
Foreign currency translation adjustment, Before-Tax Amount	-108	134	-1,498	191
Total Other Comprehensive Income (Loss), Before-Tax Amount	4,092	949	-2,778	3,501
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	-2,252	-1,218	-2,029	-3,983
Reclassification adjustment for amounts included in net income, Tax (Expense) Benefit	614	900	2,529	2,692
Foreign currency translation adjustment, Tax (Expense) Benefit	'	'	'	'
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	-1,638	-318	500	-1,291
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	3,522	1,905	3,174	6,230
Reclassification adjustment for amounts included in net income, Net-of-Tax Amount	-960	-1,408	-3,954	-4,211
Foreign currency translation adjustment, Net-of-Tax Amount	-108	134	-1,498	191
Other Comprehensive Income (Loss), net of tax	$2,454	$631	($2,278)	$2,210

Earnings_Per_Share_Earnings_Pe

Earnings Per Share - Earnings Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator	'	'	'	'
Net Income	$16,205	$9,272	$33,954	$43,302
Denominator	'	'	'	'
Weighted average number of shares - basic	57,947	63,066	59,561	63,495
Effect of dilutive securities	'	'	'	'
Stock options	613	225	321	637
Restricted stock and restricted stock units	57	13	47	7
Weighted average number of shares - diluted	58,617	63,304	59,929	64,139
Net income per share - basic	$0.28	$0.15	$0.57	$0.68
Net income per share - diluted	$0.28	$0.15	$0.57	$0.68

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]	'	'	'	'
Anti-dilutive options, Total	2.5	4.4	3.3	2.6

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	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		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]	'	'	'	'
Sales	$177,404	$162,125	$482,650	$480,858
Gross Profit	82,547	79,972	232,022	249,260
Carrier Networks [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Sales	141,278	131,942	374,498	381,303
Gross Profit	63,066	63,827	172,570	195,448
Enterprise Networks [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Sales	36,126	30,183	108,152	99,555
Gross Profit	$19,481	$16,145	$59,452	$53,812

Segment_Information_Sales_Info

Segment Information - Sales Information by Product Category (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$177,404	$162,125	$482,650	$480,858
Carrier Systems [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	120,778	111,577	319,119	309,590
Business Networking [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	44,213	36,600	127,668	116,332
Loop Access [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$12,413	$13,948	$35,863	$54,936

Segment_Information_Subcategor

Segment Information - Subcategory Revenues (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$177,404	$162,125	$482,650	$480,858
Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	158,101	141,035	417,657	400,726
Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	19,303	21,090	64,993	80,132
Broadband Access (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	98,132	94,464	251,994	249,988
Optical (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	16,640	11,160	41,500	39,418
Internetworking (Included in Business Networking) [Member] | Core Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	43,329	35,411	124,163	111,320
HDSL (Does Not Include T1) (Included in Loop Access) [Member] | Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	11,487	12,926	33,183	51,350
Other Products (Excluding HDSL) [Member] | Legacy Products [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Sales	$7,816	$8,164	$31,810	$28,782

Liability_for_Warranty_Returns2

Liability for Warranty Returns - Additional Information (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Product Warranties Disclosures [Abstract]	'	'	'	'
Period of warranty for product defects	'90 days to ten years	'	'	'
Liability for warranty obligations	$8,611	$9,653	$7,251	$4,118

Liability_for_Warranty_Returns3

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Product Warranties Disclosures [Abstract]	'	'
Balance at beginning of period	$9,653	$4,118
Plus: Amounts charged to cost and expenses	2,078	3,910
Amounts assumed on acquisition	'	1,932
Less: Deductions	-3,120	-2,709
Balance at end of period	$8,611	$7,251

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Related Party Transactions [Abstract]	'	'	'	'
Related party legal fees per month	$10	$10	$10	$10

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 30, 2013
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 $)	9 Months Ended		1 Months Ended		3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	1-May-13	Nov. 01, 2013	Oct. 08, 2013	Dec. 31, 2013	Nov. 07, 2013
			Subsequent Events [Member]	Subsequent Events [Member]	Subsequent Events [Member]	Subsequent Events [Member]
Subsequent Event [Line Items]	'	'	'	'	'	'
Dividend declaration date	8-Oct-13	'	'	'	'	'
Cash dividend per common share	'	'	'	$0.09	'	'
Dividend record date	24-Oct-13	'	'	'	'	'
Dividend payment date	7-Nov-13	'	'	'	'	'
Cash dividend	'	'	'	'	'	$5.20
Stock repurchased, shares	4.8	'	0.4	'	0.4	'
Shares repurchased, average price per share	$21.89	'	$23.85	'	$23.85	'
Additional shares authorized for purchase	4.3	5	3.9	'	'	'