ADTRAN (ADTN) 10-K 27 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 10, 2014	Jun. 30, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Entity Registrant Name	'ADTRAN INC	'	'
Entity Central Index Key	'0000926282	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	56,643,368	'
Entity Public Float	'	'	$1,424,546,508

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$58,298	$68,457
Short-term investments	105,760	160,481
Accounts receivable, less allowance for doubtful accounts of $130 and $6 at December 31, 2013 and 2012, respectively	85,814	79,675
Other receivables	18,249	16,253
Inventory, net	90,111	101,377
Prepaid expenses	4,325	4,148
Deferred tax assets, net	17,083	13,055
Total Current Assets	379,640	443,446
Property, plant and equipment, net	76,739	80,246
Deferred tax assets, net	9,622	10,261
Goodwill	3,492	3,492
Other assets	11,180	13,482
Long-term investments	309,225	332,729
Total Assets	789,898	883,656
Current Liabilities	'	'
Accounts payable	48,282	42,173
Unearned revenue	22,205	35,326
Accrued expenses	12,776	11,735
Accrued wages and benefits	14,040	15,022
Income tax payable, net	5,002	1,211
Total Current Liabilities	102,305	105,467
Non-current unearned revenue	14,643	22,377
Other non-current liabilities	22,144	17,406
Bonds payable	46,200	46,000
Total Liabilities	185,292	191,250
Commitments and contingencies (see Note 13)	'	'
Stockholders' Equity	'	'
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 56,918 shares outstanding at December 31, 2013 and 79,652 shares issued and 62,310 shares outstanding at December 31, 2012	797	797
Additional paid-in capital	233,511	224,517
Accumulated other comprehensive income	10,753	11,268
Retained earnings	884,451	861,465
Less treasury stock at cost: 22,734 and 17,342 shares at December 31, 2013 and 2012, respectively	-524,906	-405,641
Total Stockholders' Equity	604,606	692,406
Total Liabilities and Stockholders' Equity	$789,898	$883,656

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$130	$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	56,918	62,310
Treasury stock, shares	22,734	17,342

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]	'	'	'
Sales	$641,744	$620,614	$717,229
Cost of sales	332,858	303,971	302,911
Gross Profit	308,886	316,643	414,318
Selling, general and administrative expenses	129,366	134,523	124,879
Research and development expenses	131,055	125,951	100,301
Operating Income	48,465	56,169	189,138
Interest and dividend income	7,012	7,657	7,642
Interest expense	-2,325	-2,347	-2,398
Net realized investment gain	8,614	9,550	12,454
Other income (expense), net	-911	183	-694
Gain on bargain purchase of a business	'	1,753	'
Income before provision for income taxes	60,855	72,965	206,142
Provision for income taxes	-15,061	-25,702	-67,565
Net Income	$45,794	$47,263	$138,577
Weighted average shares outstanding - basic	59,001	63,259	64,145
Weighted average shares outstanding - diluted	59,424	63,774	65,416
Earnings per common share - basic	$0.78	$0.75	$2.16
Earnings per common share - diluted	$0.77	$0.74	$2.12

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]	'	'	'
Net Income	$45,794	$47,263	$138,577
Other Comprehensive Loss, net of tax:	'	'	'
Net unrealized gains (losses) on available-for-sale securities	629	-52	-13,692
Defined benefit plan adjustments	1,061	-1,952	'
Foreign currency translation	-2,205	170	-154
Other Comprehensive Income (Loss), net of tax	-515	-1,834	-13,846
Comprehensive Income, net of tax	$45,279	$45,429	$124,731

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]
In Thousands
Beginning Balance at Dec. 31, 2010	$572,322	$797	$193,866	$731,962	($381,251)	$26,948
Beginning Balance, Shares at Dec. 31, 2010	'	79,652	'	'	'	'
Net Income	138,577	'	'	138,577	'	'
Other comprehensive loss, net of tax	-13,846	'	'	'	'	-13,846
Dividend payments	-23,124	'	'	-23,124	'	'
Dividends accrued for unvested restricted stock units	-52	'	'	-52	'	'
Stock options exercised	34,125	'	'	-6,345	40,470	'
Restricted stock units vested	'	'	'	-812	812	'
Purchase of treasury stock	-35,565	'	'	'	-35,565	'
Income tax benefit from exercise of stock options	10,525	'	10,525	'	'	'
Stock-based compensation expense	9,169	'	9,169	'	'	'
Ending Balance at Dec. 31, 2011	692,131	797	213,560	840,206	-375,534	13,102
Ending Balance, Shares at Dec. 31, 2011	'	79,652	'	'	'	'
Net Income	47,263	'	'	47,263	'	'
Other comprehensive loss, net of tax	-1,834	'	'	'	'	-1,834
Dividend payments	-22,813	'	'	-22,813	'	'
Dividends accrued for unvested restricted stock units	15	'	'	15	'	'
Stock options exercised	6,049	'	'	-2,659	8,708	'
Restricted stock units vested	-212	'	-212	-547	547	'
Purchase of treasury stock	-39,362	'	'	'	-39,362	'
Income tax benefit from exercise of stock options	1,905	'	1,905	'	'	'
Stock-based compensation expense	9,264	'	9,264	'	'	'
Ending Balance at Dec. 31, 2012	692,406	797	224,517	861,465	-405,641	11,268
Ending Balance, Shares at Dec. 31, 2012	'	79,652	'	'	'	'
Net Income	45,794	'	'	45,794	'	'
Other comprehensive loss, net of tax	-515	'	'	'	'	-515
Dividend payments	-21,412	'	'	-21,412	'	'
Dividends accrued for unvested restricted stock units	-23	'	'	-23	'	'
Stock options exercised	3,629	'	'	-762	4,391	'
Restricted stock units vested	-248	'	-248	-611	611	'
Purchase of treasury stock	-124,267	'	'	'	-124,267	'
Income tax benefit from exercise of stock options	169	'	169	'	'	'
Stock-based compensation expense	9,073	'	9,073	'	'	'
Ending Balance at Dec. 31, 2013	$604,606	$797	$233,511	$884,451	($524,906)	$10,753
Ending Balance, Shares at Dec. 31, 2013	'	79,652	'	'	'	'

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Purchase of treasury stock, shares	5,608	1,786	1,112
Treasury stock, shares issued	217	393	1,813
Treasury stock, received	0	0	7
Treasury Stock [Member]	'	'	'
Purchase of treasury stock, shares	5,608	1,786	1,112

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities	'	'	'
Net Income	$45,794	$47,263	$138,577
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'
Depreciation and amortization	14,628	14,079	11,499
Amortization of net premium on available-for-sale investments	5,956	8,257	6,617
Net realized gain on long-term investments	-8,614	-9,550	-12,454
Net (gain) loss on disposal of property, plant and equipment	3	-214	6
Gain on bargain purchase of a business	'	-1,753	'
Stock-based compensation expense	9,073	9,264	9,169
Deferred income taxes	-4,058	-3,785	575
Tax benefit from stock option exercises	169	1,905	10,525
Excess tax benefits from stock-based compensation arrangements	-158	-1,456	-9,373
Change in operating assets and liabilities:	'	'	'
Accounts receivable, net	-5,541	-2,847	-4,939
Other receivables	-1,549	2,977	-5,781
Income tax receivable, net	'	'	2,741
Inventory	10,265	8,333	-12,734
Prepaid expenses and other assets	-11	-1,045	522
Accounts payable	5,206	7,510	6,044
Accrued expenses and other liabilities	-15,146	8,895	6,309
Income taxes payable, net	3,747	-1,960	3,169
Net cash provided by operating activities	59,764	85,873	150,472
Cash flows from investing activities	'	'	'
Purchases of property, plant and equipment	-8,173	-12,320	-11,778
Proceeds from disposals of property, plant and equipment	'	266	'
Proceeds from sales and maturities of available-for-sale investments	343,567	282,039	466,243
Purchases of available-for-sale investments	-261,625	-282,740	-554,629
Acquisition of business, net of cash acquired	'	7,496	-22,661
Net cash provided by (used in) investing activities	73,769	-5,259	-122,825
Cash flows from financing activities	'	'	'
Proceeds from stock option exercises	3,629	6,049	34,125
Purchases of treasury stock	-124,267	-39,362	-35,565
Dividend payments	-21,412	-22,813	-23,124
Payments on long-term debt	'	-500	-1,000
Excess tax benefits from stock-based compensation arrangements	158	1,456	9,373
Net cash used in financing activities	-141,892	-55,170	-16,191
Net increase (decrease) in cash and cash equivalents	-8,359	25,444	11,456
Effect of exchange rate changes	-1,800	34	-154
Cash and cash equivalents, beginning of year	68,457	42,979	31,677
Cash and cash equivalents, end of year	58,298	68,457	42,979
Supplemental disclosure of cash flow information	'	'	'
Cash paid during the year for interest	2,325	2,348	2,396
Cash paid during the year for income taxes	15,431	31,021	51,402
Supplemental disclosure of non-cash investing activities	'	'	'
Purchases of property, plant and equipment included in accounts payable	$444	$108	$353

Nature_of_Business_and_Summary

Nature of Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Nature of Business and Summary of Significant Accounting Policies	'
	Note 1 – Nature of Business and Summary of Significant Accounting Policies
	ADTRAN, Inc. is a leading global provider of networking and communications equipment. Our solutions enable voice, data, video and Internet communications across a variety of network infrastructures. These solutions are deployed by some of the world’s largest service providers, distributed enterprises and small and medium-sized businesses, public and private enterprises, and millions of individual users worldwide.
	Principles of Consolidation
	Our consolidated financial statements include ADTRAN and its wholly owned subsidiaries. All inter-company accounts and transactions have been eliminated in consolidation.
	Changes in Classifications
	Certain balance sheet amounts (including inventory, accounts receivable, unearned revenue and accrued expenses) and related disclosures have been revised to correct immaterial misclassifications in 2012 that were corrected in 2013. The revisions decreased both total assets and total liabilities each by $2.7 million at December 31, 2012. The revisions had no impact on our previously reported stockholders’ equity, income statement, comprehensive income, or earnings per share. Additionally, we corrected immaterial misclassifications between the operating and investing sections of our consolidated statements of cash flows and adjusted our 2012 and 2011 cash flows in these categories by $0.2 million and $0.1 million, respectively, in order to be consistent with the 2013 presentation.
	Additionally, 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 year ended December 31, 2013, we identified two adjustments in the acquired NSN (formerly Nokia Siemens Networks) Broadband Access business (NSN BBA business) relating to customer payment discounts for one customer, and recoverable VAT taxes on certain vendor freight invoices that should have been recorded in prior periods. These adjustments resulted from a $0.4 million understatement of net income in 2012. We evaluated the impact of the adjustments on the results of our previously issued financial statements for the prior period 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 was not material to our results for the year 2013. Accordingly, during the year ended December 31, 2013 we recorded an out of period adjustment to correct these issues.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated working capital adjustments under negotiation related to the NSN BBA business acquisition, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
	Cash and Cash Equivalents
	Cash and cash equivalents represent demand deposits, money market funds, and short-term investments classified as available-for-sale with original maturities of three months or less. We maintain depository investments with certain financial institutions. Although these depository investments may exceed government insured depository limits, we have evaluated the credit worthiness of these applicable financial institutions, and determined the risk of material financial loss due to the exposure of such credit risk to be minimal. As of December 31, 2013, $53.5 million of our cash and cash equivalents, primarily certain domestic money market funds and foreign depository accounts, were in excess of government provided insured depository limits.
	Financial Instruments
	The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the immediate or short-term maturity of these financial instruments. The carrying amount reported for bonds payable was $46.5 million, compared to an estimated fair value of $45.4 million, based on a debt security with a comparable interest rate and maturity and a Standard & Poor’s credit rating of A-.
	Investments with contractual maturities beyond one year, such as our municipal variable rate demand notes, may be classified as short-term based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. Despite the long-term nature of their stated contractual maturities, we routinely buy and sell these securities and we believe we have the ability to quickly sell them to the remarketing agent, tender agent, or issuer at par value plus accrued interest in the event we decide to liquidate our investment in a particular variable rate demand note. All income generated from these investments was recorded as interest income. We have not been required to record any losses relating to municipal variable rate demand notes.
	Long-term investments represent a restricted certificate of deposit held at cost, municipal fixed-rate bonds, corporate bonds, a fixed income bond fund, marketable equity securities, and other equity investments. Marketable equity securities are reported at fair value as determined by the most recently traded price of the securities at the balance sheet date, although the securities may not be readily marketable due to the size of the available market. Unrealized gains and losses, net of tax, are reported as a separate component of stockholders’ equity. Realized gains and losses on sales of securities are computed under the specific identification method and are included in current income. We periodically review our investment portfolio for investments considered to have sustained an other-than-temporary decline in value. Impairment charges for other-than-temporary declines in value are recorded as realized losses in the accompanying consolidated statements of income. All of our investments at December 31, 2013 and 2012 are classified as available-for-sale securities. See Note 4 of Notes to Consolidated Financial Statements for additional information.
	Accounts Receivable
	We record accounts receivable at net realizable value. Prior to issuing payment terms to a new customer, we perform a detailed credit review of the customer. Credit limits are established for each new customer based on the results of this credit review. Payment terms are established for each new customer, and collection experience is reviewed periodically in order to determine if the customer’s payment terms and credit limits need to be revised. At December 31, 2013, one customer accounted for 13.1% of our total accounts receivable. At December 31, 2012, one customer accounted for 10.4% of our total accounts receivable.
	We maintain an allowance for doubtful accounts for losses resulting from the inability of our customers to make required payments. We regularly review the allowance for doubtful accounts and consider factors such as the age of accounts receivable balances, the current economic conditions that may affect a customer’s ability to pay, significant one-time events and our historical experience. If the financial condition of a customer deteriorates, resulting in an impairment of their ability to make payments, we may be required to record an allowance for doubtful accounts. If circumstances change with regard to individual receivable balances that have previously been determined to be uncollectible (and for which a specific reserve has been established), a reduction in our allowance for doubtful accounts may be required. Our allowance for doubtful accounts was $130 thousand at December 31, 2013 and $6 thousand at December 31, 2012.
	Other Receivables
	Other receivables are comprised primarily of amounts due from subcontract manufacturers for product component transfers, accrued interest on investments and on a restricted certificate of deposit, and amounts due from employee stock option exercises. At December 31, 2013 and 2012, other receivables also included an estimated receivable due from NSN related to working capital adjustments that are currently under negotiation.
	Inventory
	Inventory is carried at the lower of cost or market, with cost being determined using the first-in, first-out method. Standard costs for material, labor and manufacturing overhead are used to value inventory. Standard costs are updated at least quarterly; therefore, inventory costs approximate actual costs at the end of each reporting period. 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. When we dispose of excess and obsolete inventories, the related write-downs are charged against the inventory reserve. See Note 6 of Notes to Consolidated Financial Statements for additional information.
	Property, Plant and Equipment
	Property, plant and equipment, which is stated at cost, is depreciated using the straight-line method over the estimated useful lives of the assets. We depreciate building and land improvements from five to 39 years, office machinery and equipment from three to seven years, engineering machinery and equipment from three to seven years, and computer software from three to five years. Expenditures for repairs and maintenance are charged to expense as incurred. Betterments that materially prolong the lives of the assets are capitalized. The cost of assets retired or otherwise disposed of and the related accumulated depreciation are removed from the accounts, and the gain or loss on such disposition is included in other income (expense), net in the accompanying consolidated statements of income. See Note 7 of Notes to Consolidated Financial Statements for additional information.
	Liability for Warranty
	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 $9.0 million and $9.7 million at December 31, 2013 and 2012, respectively. These liabilities are included in accrued expenses in the accompanying consolidated balance sheets.
	A summary of warranty expense and write-off activity for the years ended December 31, 2013 and 2012 is as follows:
	Year Ended December 31,	2013			2012
	(In thousands)
	Balance at beginning of period	$	9,653		$	4,118
	Plus: Amounts charged to cost and expenses		4,051			5,363
	Amounts assumed on acquisition		—			3,781
	Less: Deductions		(4,727	)		(3,609	)
	Balance at end of period	$	8,977		$	9,653
	Pension Benefit Plan Obligations
	As a result of our acquisition of the NSN BBA business, we assumed a defined benefit pension plan covering employees in certain foreign countries. Pension benefit plan obligations are based on various assumptions used by our actuaries in calculating these amounts. These assumptions include discount rates, compensation rate increases, expected return on plan assets, retirement rates and mortality rates. Actual results that differ from the assumptions and changes in assumptions could affect future expenses and obligations.
	Stock-Based Compensation
	We have two Board and stockholder approved stock option plans from which stock options and other awards are available for grant to employees and directors. All employee and director stock options granted under our stock option plans have an exercise price equal to the fair market value of the award, as defined in the plan, of the underlying common stock on the grant date. There are currently no vesting provisions tied to performance or market conditions for any option awards; vesting for all outstanding option grants is based only on continued service as an employee or director of ADTRAN. All of our outstanding stock option awards are classified as equity awards.
	Under the provisions of our approved plans, we made grants of performance-based restricted stock units to five of our executive officers in 2013, 2012 and 2011. The restricted stock units are subject to a market condition based on the relative total shareholder return of ADTRAN against all the companies in the NASDAQ Telecommunications Index and vest at the end of a three-year performance period. The restricted stock units are converted into shares of common stock upon vesting. Depending on the relative total shareholder return over the performance period, the executive officers may earn from 0% to 150% of the number of restricted stock units granted. The fair value of the award is based on the market price of our common stock on the date of grant, adjusted for the expected outcome of the impact of market conditions using a Monte Carlo Simulation valuation method. The recipients of the restricted stock units also earn dividend credits during the performance period, which will be paid in cash upon the issuance of common stock for the restricted stock units.
	Stock-based compensation expense recognized in 2013, 2012 and 2011 was approximately $9.1 million, $9.3 million and $9.2 million, respectively. As of December 31, 2013, total compensation cost related to non-vested stock options, restricted stock units and restricted stock not yet recognized was approximately $18.8 million, which is expected to be recognized over an average remaining recognition period of 2.7 years. See Note 3 of Notes to Consolidated Financial Statements for additional information.
	Impairment of Long-Lived Assets
	We review long-lived assets used in operations for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable and the undiscounted cash flows estimated to be generated by the asset are less than the asset’s carrying value. An impairment loss would be recognized in the amount by which the recorded value of the asset exceeds the fair value of the asset, measured by the quoted market price of an asset or an estimate based on the best information available in the circumstances. There were no impairment losses recognized during 2013, 2012 or 2011.
	Goodwill and Purchased Intangible Assets
	We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we 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 recognized during 2013, 2012 or 2011. Purchased intangible assets with finite lives are carried at cost, less accumulated amortization. Amortization is recorded over the estimated useful lives of the respective assets, which is 2.5 to 14 years.
	Research and Development Costs
	Research and development costs include compensation for engineers and support personnel, outside contracted services, depreciation and material costs associated with new product development, the enhancement of current products, and product cost reductions. We continually evaluate new product opportunities and engage in intensive research and product development efforts. Research and development costs totaled $131.1 million, $126.0 million and $100.3 million for the years ended December 31, 2013, 2012 and 2011, respectively.
	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 years ended December 31, 2011, 2012 and 2013:
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains (Losses)			Benefit Plan			Currency
		on Available-			Adjustments			Adjustments
		for-Sale
		Securities
	Balance at December 31, 2010	$	23,852		$	—		$	3,096		$	26,948
	Other comprehensive loss before reclassifications		(6,784	)		—			(154	)		(6,938	)
	Amounts reclassified from accumulated other comprehensive income		(6,908	)		—			—			(6,908	)
	Balance at December 31, 2011	$	10,160		$	—		$	2,942		$	13,102
	Other comprehensive income (loss) before reclassifications		5,426			(1,952	)		170			3,644
	Amounts reclassified from accumulated other comprehensive income		(5,478	)		—			—			(5,478	)
	Balance at December 31, 2012	$	10,108		$	(1,952	)	$	3,112		$	11,268
Other comprehensive income (loss) before reclassifications		5,508			1,061			(2,205	)		4,364
Amounts reclassified from accumulated other comprehensive income		(4,879	)		—			—			(4,879	)
Balance at December 31, 2013	$	10,737		$	(891	)	$	907		$	10,753
The following tables present the details of reclassifications out of accumulated other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
(In thousands)	2013
Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
Income Components	from Accumulated Other			Statement Where Net Income Is
	Comprehensive Income			Presented
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities	$	8,023		Net realized investment gain
Impairment expense		(25	)	Net realized investment gain
Total reclassifications for the period, before tax		7,998
Tax (expense) benefit		(3,119	)
Total reclassifications for the period, net of tax	$	4,879
(In thousands)	2012
Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
Income Components	from Accumulated Other			Statement Where Net Income
	Comprehensive Income			Is Presented
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities	$	9,662		Net realized investment gain
Impairment expense		(682	)	Net realized investment gain
Total reclassifications for the period, before tax		8,980
Tax (expense) benefit		(3,502	)
Total reclassifications for the period, net of tax	$	5,478
(In thousands)	2011
Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
Income Components	from Accumulated Other			Statement Where Net Income
	Comprehensive Income			Is Presented
Unrealized gains (losses) on available-for-sale securities:
Net realized gain on sales of securities	$	11,393		Net realized investment gain
Impairment expense		(68	)	Net realized investment gain
Total reclassifications for the period, before tax		11,325
Tax (expense) benefit		(4,417	)
Total reclassifications for the period, net of tax	$	6,908
The following tables present the tax effects related to the change in each component of other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
	2013
(In thousands)	Before-Tax			Tax			Net-of-Tax
	Amount			(Expense)			Amount
				Benefit
Unrealized gains (losses) on available-for-sale securities	$	9,030		$	(3,522	)	$	5,508
Reclassification adjustment for amounts included in net income		(7,998	)		3,119			(4,879	)
Defined benefit plan adjustments		1,061			—			1,061
Foreign currency translation adjustment		(2,205	)		—			(2,205	)
Total Other Comprehensive Income (Loss)	$	(112	)	$	(403	)	$	(515	)
	2012
(In thousands)	Before-Tax			Tax			Net-of-Tax
	Amount			(Expense)			Amount
				Benefit
Unrealized gains (losses) on available-for-sale securities	$	8,895		$	(3,469	)	$	5,426
Reclassification adjustment for amounts included in net income		(8,980	)		3,502			(5,478	)
Defined benefit plan adjustments		(1,952	)		—			(1,952	)
Foreign currency translation adjustment		170			—			170
Total Other Comprehensive Income (Loss)	$	(1,867	)	$	33		$	(1,834	)
	2011
(In thousands)	Before-Tax			Tax			Net-of-Tax
	Amount			(Expense)			Amount
				Benefit
Unrealized gains (losses) on available-for-sale securities	$	(11,121	)	$	4,337		$	(6,784	)
Reclassification adjustment for amounts included in net income		(11,325	)		4,417			(6,908	)
Foreign currency translation adjustment		(154	)		—			(154	)
Total Other Comprehensive Income (Loss)	$	(22,600	)	$	8,754		$	(13,846	)
Income Taxes
The provision for income taxes has been determined using the asset and liability approach of accounting for income taxes. Under this approach, deferred taxes represent the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. The provision for income taxes represents income taxes paid or payable for the current year plus the change in deferred taxes during the year. Deferred taxes result from the difference between financial and tax bases of our assets and liabilities and are adjusted for changes in tax rates and tax laws when such changes are enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized.
We establish reserves to remove some or all of the tax benefit of any of our tax positions at the time we determine that the positions become uncertain. We adjust these reserves, including any impact on the related interest and penalties, as facts and circumstances change.
Foreign Currency
We record transactions denominated in foreign currencies on a monthly basis using exchange rates from throughout the year. Assets and liabilities denominated in foreign currencies are translated at the balance sheet dates using the closing rates of exchange between those foreign currencies and the U.S. dollar with any transaction gains or losses reported in other income (expense). Adjustments resulting from translating financial statements of international subsidiaries are recorded as a component of accumulated other comprehensive income (loss).
Revenue Recognition
Revenue is generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the product price is fixed or determinable, collection of the resulting receivable is reasonably assured, and product returns are reasonably estimable. For product sales, revenue is generally recognized upon shipment of the product to our customer in accordance with the title transfer terms of the sales agreement, generally FOB shipping point. In the case of consigned inventory, revenue is recognized when the end customer assumes ownership of the product. Contracts that contain multiple deliverables are evaluated to determine the units of accounting, and the consideration from the arrangement is allocated to each unit of accounting based on the relative selling price and corresponding terms of the contract. We use vendor-specific objective evidence of selling price. When this evidence is not available, we are generally not able to determine third-party evidence of selling price because of the extent of customization among competing products or services from other companies. We record revenue associated with installation services when all contractual obligations are complete. In instances where customer acceptance is required, revenue is deferred until all acceptance criteria have been met. Contracts that include both installation services and product sales are evaluated for revenue recognition in accordance with contract terms. As a result, depending on contract terms, installation services may be considered a separate deliverable or may be considered a combined single unit of accounting with the delivered product. Generally, either the purchaser, ADTRAN, or a third party can perform the installation of our products. Shipping fees are recorded as revenue and the related cost is included in cost of sales. Sales taxes invoiced to customers are included in revenues, and represent less than one percent of total revenues. The corresponding sales taxes paid are included in cost of goods sold. Value added taxes collected from customers in international jurisdictions are recorded in accrued expenses as a liability. Revenue is recorded net of discounts. Sales returns are accrued based on historical sales return experience, which we believe provides a reasonable estimate of future returns.
A portion of Enterprise Networks products are sold to a non-exclusive distribution network of major technology distributors in the United States. These large organizations then distribute or provide fulfillment services to an extensive network of value-added resellers and system integrators. Value-added resellers and system integrators may be affiliated with us as a channel partner, or they may purchase from the distributor in an unaffiliated fashion. Additionally, with certain limitations our distributors may return unused and unopened product for stock-balancing purposes when such returns are accompanied by offsetting orders for products of equal or greater value.
We participate in cooperative advertising and market development programs with certain customers. We use these programs to reimburse customers for certain forms of advertising, and in general, to allow our customers credits up to a specified percentage of their net purchases. Our costs associated with these programs are estimated and included in marketing expenses in our consolidated statements of income. We also participate in rebate programs to provide sales incentives for certain products. Our costs associated with these programs are estimated and accrued at the time of sale, and are recorded as a reduction of sales in our consolidated statements of income.
Unearned Revenue
Unearned revenue primarily represents customer billings on our maintenance service programs and unearned revenues relating to multiple element contracts where we still have contractual obligations to our customers. We currently offer maintenance contracts ranging from one to five years, primarily on Enterprise Networks Division products sold through distribution channels. Revenue attributable to maintenance contracts is recognized on a straight-line basis over the related contract term. In addition, we provide software maintenance and a variety of hardware maintenance services to Carrier Networks Division customers, which include customers of the acquired NSN BBA business, under contracts with terms up to ten years. At December 31, 2013 and 2012, unearned revenue was as follows:
(In thousands)	2013			2012
Current unearned revenue	$	22,205		$	35,326
Non-current unearned revenue		14,643			22,377
Total	$	36,848		$	57,703
Other Income (Expense), Net
Other income (expense), net, is comprised primarily of miscellaneous income and expense, gains and losses on foreign currency transactions, investment account management fees, and gains or losses on the disposal of property, plant and equipment occurring in the normal course of business.
Earnings per Share
Earnings per common share, and earnings per common share assuming dilution, are based on the weighted average number of common shares and, when dilutive, common equivalent shares outstanding during the year. See Note 14 of Notes to Consolidated Financial Statements for additional information.
Dividends
The Board of Directors presently anticipates that it will declare a regular quarterly dividend as long as the current tax treatment of dividends exists and adequate levels of liquidity are maintained. During the years ended December 31, 2013, 2012 and 2011, we paid $21.4 million, $22.8 million and $23.1 million, respectively, in shareholder dividends. On January 21, 2014, the Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to shareholders of record at the close of business on February 6, 2014. The ex-dividend date was February 4, 2014 and the payment date was February 20, 2014. The quarterly dividend payment was $5.1 million.
Business Combinations
We use the acquisition method to account for business combinations. Under the acquisition method of accounting, we recognize the assets acquired and liabilities assumed at their fair value on the acquisition date. Goodwill is measured as the excess of the consideration transferred over the net assets acquired. Costs incurred to complete the business combination, such as legal, accounting or other professional fees, are charged to general and administrative expenses as they are incurred.
Recently Issued Accounting Standards
During 2013, we adopted the following accounting standards, 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 years ended December 31, 2013, 2012 and 2011 in Note 1 of Notes to Consolidated Financial Statements.

Business_Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Business Combinations	'
	Note 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.
	Upon acquisition, 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, subject to customary working capital adjustments between the parties as defined in the purchase agreement. As of December 31, 2013, the parties were in the process of negotiating final working capital adjustments. We have adjusted the purchase price allocation 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 gain is included in the line item “Gain on bargain purchase of a business” in the 2012 Consolidated Statements of Income.
	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		(3,361	)
	Accrued wages and benefits		(2,251	)
	Deferred tax liability		(788	)
	Non-current unearned revenue		(19,886	)
	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.
	For the years ended December 31, 2013 and 2012, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $2.9 million and $7.9 million, respectively, related to this acquisition.
	The following supplemental pro forma information presents the financial results of the acquired NSN BBA business for the years ended December 31, 2012 and 2011. The pro forma results for the period January 1, 2012 to May 4, 2012 and January 1, 2011 to December 31, 2011 are not included in our consolidated financial results.
	This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2011, nor are they indicative of any future results.
	(In thousands) (Unaudited)	2012			2011
	Pro forma revenue	$	119,600		$	196,256
	Pro forma pre-tax loss	$	(23,621	)	$	(36,980	)
	Weighted average exchange rate during the period (EURO/USD)	€	1.00/$1.29		€	1.00/$1.38
	On August 4, 2011, we acquired all of the outstanding stock of Bluesocket, Inc., a provider of wireless network solutions with virtual control, for $23.7 million in cash. The acquisition provides us with IEEE802.11N enterprise class wireless LAN expertise, technology, and products to address the growing transition within small-medium enterprises and large enterprises to wireless networks and mobile devices. We have included the financial results of Bluesocket in our consolidated financial statements since the date of acquisition. Pro forma results of operations prior to the closing date for the acquisition have not been presented because the effect of the acquisition was not material to our financial results. 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)
	Cash	$	1,027
	Accounts receivable		298
	Inventory		792
	Prepaid expenses		357
	Property, plant and equipment		173
	Deferred tax assets, net		12,962
	Accounts payable		(441	)
	Unearned revenue		(600	)
	Accrued expenses		(332	)
	Net assets acquired		14,236
	Customer relationships		1,530
	Developed technology		3,230
	Intellectual property		930
	Trade names		270
	Goodwill		3,492
	Total purchase price	$	23,688
	During the fourth quarter of 2011, the purchase price and purchase price allocation were adjusted for our final valuations. The adjustments resulted in a decrease to the goodwill recognized in the transaction.
	The net deferred tax assets acquired are primarily related to net operating losses and previously capitalized and unamortized research and development expense for tax deduction purposes.
	The fair value of the customer relationships, developed technology and intellectual property acquired was calculated using an income approach (excess earnings method) and is being amortized using the straight-line method. The customer relationships and intellectual property are being amortized over an estimated useful life of 7 years and the developed technology is being amortized over an average estimated useful life of 4.5 years.
	The fair value of the trade names acquired was calculated using an income approach (relief from royalty method) and is being amortized using the straight-line method over the estimated useful life of 4.5 years.
	The goodwill of $3.5 million generated from this acquisition is primarily related to expected synergies and was assigned to our Enterprise Networks division. The goodwill will not be deductible for U.S. federal income tax purposes.
	For the years ended December 31, 2013, 2012 and 2011, we incurred integration related expenses and amortization of acquired intangibles of $1.1 million, $1.5 million and $1.7 million, respectively, related to this acquisition.

Stock_Incentive_Plans

Stock Incentive Plans	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock Incentive Plans	'
	Note 3 – Stock Incentive Plans
	Stock Incentive Program Descriptions
	Our Board of Directors adopted the 1996 Employee Incentive Stock Option Plan (1996 Plan) effective February 14, 1996, as amended, under which 17.0 million shares of common stock were authorized for issuance to certain employees and officers through incentive stock options and non-qualified stock options. Options granted under the 1996 Plan typically become exercisable beginning after one year of continued employment, normally pursuant to a four or five-year vesting schedule beginning on the first anniversary of the grant date, and have a ten-year contractual term. The 1996 Plan expired February 14, 2006, and expiration dates of options outstanding at December 31, 2013 under the 1996 Plan range from 2014 to 2015.
	On January 23, 2006, the Board of Directors adopted the 2006 Employee Stock Incentive Plan (2006 Plan), which authorizes 13.0 million shares of common stock for issuance to certain employees and officers through incentive stock options and non-qualified stock options, stock appreciation rights, restricted stock and restricted stock units. The 2006 Plan was adopted by stockholder approval at our annual meeting of stockholders held on May 9, 2006. Options granted under the 2006 Plan typically become exercisable beginning after one year of continued employment, normally pursuant to a four-year vesting schedule beginning on the first anniversary of the grant date, and have a ten-year contractual term. Expiration dates of options outstanding at December 31, 2013 under the 2006 Plan range from 2016 to 2023.
	Our stockholders approved the 2010 Directors Stock Plan (2010 Directors Plan) on May 5, 2010, under which 0.5 million shares of common stock have been reserved. This plan replaces the 2005 Directors Stock Option Plan. The 2010 Directors Plan provides that the Company may issue stock options, restricted stock and restricted stock units to our non-employee directors. Stock awards issued under the 2010 Directors Plan normally become vested in full on the first anniversary of the grant date. Options issued under the 2010 Directors Plan have a ten-year contractual term. We currently also have options outstanding under the 1995 Directors Plan, as amended, and the 2005 Directors Stock Option Plan. Expiration dates of options outstanding under both plans at December 31, 2013 range from 2014 to 2019.
	The following table is a summary of our stock options outstanding as of December 31, 2012 and 2013 and the changes that occurred during 2013:
	(In thousands, except per share amounts)	Number of			Weighted			Weighted Avg.			Aggregate
		Options			Average			Remaining			Intrinsic Value
					Exercise Price			Contractual Life
								in Years
	Options outstanding, December 31, 2012		6,035		$	24.81			6.69		$	5,154
	Options granted		1,005		$	23.64
	Options cancelled/forfeited		(491	)	$	29.6
	Options exercised		(191	)	$	19.07
	Options outstanding, December 31, 2013		6,358		$	24.43			6.6		$	25,878
	Options exercisable, December 31, 2013		3,911		$	24.75			5.19		$	15,336
	All of the options above were issued at exercise prices that approximate fair market value at the date of grant. At December 31, 2013, 6.0 million options were available for grant under the shareholder approved plans.
	The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between ADTRAN’s closing stock price on the last trading day of 2013 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 December 31, 2013. The amount of aggregate intrinsic value will change based on the fair market value of ADTRAN’s stock.
	The total pre-tax intrinsic value of options exercised during 2013, 2012 and 2011 was $1.1 million, $4.5 million and $39.8 million, respectively. The fair value of options fully vesting during 2013, 2012 and 2011 was $7.7 million, $7.7 million and $7.3 million, respectively.
	The following table further describes our stock options outstanding as of December 31, 2013:
		Options Outstanding									Options Exercisable
	Range of	Options			Weighted Avg.			Weighted			Options		Weighted
	Exercise Prices	Outstanding at			Remaining			Average			Exercisable at		Average
		12/31/13			Contractual Life			Exercise			12/31/13		Exercise
		(In thousands)			in Years			Price			(In thousands)		Price
	$14.88 – 18.07		1,456			7.42		$	16.37			742	$	15.79
	$18.08 – 23.36		1,002			3.04		$	22.59			1,001	$	22.59
	$23.37 – 26.06		1,745			8.1		$	23.6			745	$	23.54
	$26.07 – 30.04		466			3.59		$	29.39			383	$	29.71
	$30.05 – 30.36		905			7.67		$	30.36			454	$	30.36
	$30.37 – 41.92		784			6.84		$	33.78			586	$	33.76
			6,358									3,911
	Restricted Stock Program Description
	On November 6, 2008, the Compensation Committee of the Board of Directors approved the Performance Shares Agreement under the 2006 Plan which sets forth the terms and conditions of awards of performance-based restricted stock units (RSUs). Of the 13.0 million shares of common stock authorized for issuance under the 2006 Plan, we may grant up to 5.0 million shares of common stock for issuance to certain employees and officers for awards other than stock options, which would include RSUs. Under a proposal that was approved by the Board of Directors and shareholders at the 2010 annual meeting, the number of shares available for awards other than stock options under all stock plans was reduced to 3.3 million. The number of shares of common stock earned by a recipient pursuant to the RSUs is subject to a market condition based on ADTRAN’s relative total shareholder return against all companies in the NASDAQ Telecommunications Index at the end of a three-year performance period. Depending on the relative total shareholder return over the performance period, the recipient may earn from 0% to 150% of the shares underlying the RSUs, with the shares earned distributed upon the vesting of the RSUs at the end of the three-year performance period. The fair value of the award is based on the market price of our common stock on the date of grant, adjusted for the expected outcome of the impact of market conditions using a Monte Carlo Simulation valuation method. A portion of the granted RSUs also vest and the underlying shares become deliverable upon the death or disability of the recipient or upon a change of control of ADTRAN, as defined by the 2006 Plan. The recipients of the RSUs receive dividend credits based on the shares of common stock underlying the RSUs. The dividend credits are vested and earned in the same manner as the RSUs and will be paid in cash upon the issuance of common stock for the RSUs.
	The following table is a summary of our RSUs and restricted stock outstanding as of December 31, 2012 and 2013 and the changes that occurred during 2013:
	(In thousands, except per share amounts)	Number of			Weighted
		shares			Average Grant
					Date Fair Value
	Unvested RSUs and restricted stock outstanding, December 31, 2012		103		$	29.25
	RSUs and restricted stock granted		41		$	27.47
	RSUs and restricted stock vested		(39	)	$	29.42
	Adjustments to shares granted due to shares earned at vesting		(10	)	$	39.21
	Unvested RSUs and restricted stock outstanding, December 31, 2013		95		$	28.38
	At December 31, 2013, total compensation cost related to the non-vested portion of RSUs and restricted stock not yet recognized was approximately $1.7 million, which is expected to be recognized over an average remaining recognition period of 1.9 years.
	Valuation and Expense Information
	We use the Black-Scholes option pricing model (Black-Scholes Model) for the purpose of determining the estimated fair value of stock option awards on the date of grant. The Black-Scholes Model requires the input of certain assumptions that involve judgment. Because our stock options have characteristics significantly different from those of traded options, and because changes in the input assumptions can materially affect the fair value estimate, existing models may not provide reliable measures of fair value of our stock options. We use a Monte Carlo Simulation valuation method to value our performance-based RSUs. The fair value of restricted stock issued is equal to the closing price of our stock on the date of grant. We will continue to assess the assumptions and methodologies used to calculate the estimated fair value of stock-based compensation. If circumstances change, and additional data becomes available over time, we may change our assumptions and methodologies, which may materially impact our fair value determination.
	The following table summarizes stock-based compensation expense related to stock options, RSUs and restricted stock for the years ended December 31, 2013, 2012 and 2011, which was recognized as follows:
	(In thousands)	2013			2012			2011
	Stock-based compensation expense included in cost of sales	$	465		$	422		$	412
	Selling, general and administrative expense		4,443			4,351			4,316
	Research and development expense		4,165			4,491			4,441
	Stock-based compensation expense included in operating expenses		8,608			8,842			8,757
	Total stock-based compensation expense		9,073			9,264			9,169
	Tax benefit for expense associated with non-qualified options		(1,298	)		(1,234	)		(1,321	)
	Total stock-based compensation expense, net of tax	$	7,775		$	8,030		$	7,848
	At December 31, 2013, total compensation cost related to non-vested stock options not yet recognized was approximately $17.1 million, which is expected to be recognized over an average remaining recognition period of 2.8 years.
	The stock option pricing model requires the use of several assumptions that impact the fair value estimate. These variables include, but are not limited to, the volatility of our stock price and employee exercise behaviors. There were no material changes made during 2013 to the methodology used to determine our assumptions.
	The weighted-average estimated fair value of stock options granted to employees and directors during the years ended December 31, 2013, 2012 and 2011 was $8.35 per share, $5.60 per share and $9.53 per share, respectively, with the following weighted-average assumptions:
		2013			2012			2011
	Expected volatility		39.92	%		39.46	%		38.32	%
	Risk-free interest rate		1.71	%		0.96	%		1.01	%
	Expected dividend yield		1.52	%		2.05	%		1.19	%
	Expected life (in years)		6.36			6.18			5.15
We based our estimate of expected volatility for the years ended December 31, 2013, 2012 and 2011 on the sequential historical daily trading data of our common stock for a period equal to the expected life of the options granted. The selection of the historical volatility method was based on available data indicating our historical volatility is as equally representative of our future stock price trends as is our implied volatility. We have no reason to believe the future volatility of our stock price is likely to differ from its past volatility.
The risk-free interest rate assumption is based upon implied yields of U.S. Treasury zero-coupon bonds on the date of grant having a remaining term equal to the expected life of the options granted. The dividend yield is based on our historical and expected dividend payouts.
The expected life of our stock options is based upon historical exercise and cancellation activity of our previous stock-based grants with a ten-year contractual term.
The RSU pricing model also requires the use of several significant assumptions that impact the fair value estimate. The estimated fair value of the RSUs granted to employees during the years ended December 31, 2013, 2012 and 2011 was $27.72 per share, $19.46 per share and $38.73 per share, respectively, with the following assumptions:
	2013			2012			2011
Expected volatility		38.83	%		37.75	%		39.32	%
Risk-free interest rate		0.61	%		0.38	%		0.37	%
Expected dividend yield		1.52	%		2.12	%		1.08	%
Stock-based compensation expense recognized in our Consolidated Statements of Income for the years ended December 31, 2013, 2012 and 2011 is based on RSUs and options ultimately expected to vest, and has been reduced for estimated forfeitures. Estimates for forfeiture rates are based upon historical experience and are evaluated quarterly. We expect our forfeiture rate for stock option awards to be approximately 2.5% annually. We estimated a 0% forfeiture rate for our RSUs and restricted stock due to the limited number of recipients and historical experience for these awards.

Investments

Investments	12 Months Ended
	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]	'
Investments	'
	Note 4 – Investments
	At December 31, 2013, we held the following securities and investments, recorded at either fair value or cost:
		Amortized			Gross Unrealized						Fair Value /
		Cost									Carrying
	(In thousands)				Gains			Losses			Value
	Deferred compensation plan assets	$	12,300		$	2,847		$	(24	)	$	15,123
	Corporate bonds		166,370			534			(45	)		166,859
	Municipal fixed-rate bonds		135,773			583			(54	)		136,302
	Municipal variable rate demand notes		8,310			—			—			8,310
	Marketable equity securities		24,654			13,975			(177	)		38,452
	Available-for-sale securities held at fair value	$	347,407		$	17,939		$	(300	)	$	365,046
	Restricted investment held at cost											48,250
	Other investments held at cost											1,689
	Total carrying value of available-for-sale investments										$	414,985
	At December 31, 2012, we held the following securities and investments, recorded at either fair value or cost:
		Amortized			Gross Unrealized						Fair Value /
		Cost									Carrying
	(In thousands)				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 December 31, 2013, corporate and municipal fixed-rate bonds had the following contractual maturities:
	(In thousands)	Corporate			Municipal
		bonds			fixed-rate bonds
	Less than one year	$	55,396		$	46,606
	One to two years		37,838			25,284
	Two to three years		70,447			55,358
	Three to five years		3,178			9,054
	Total	$	166,859		$	136,302
	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.
	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 $11 thousand during the fourth quarter of 2013. For each of the years ended December 31, 2013, 2012 and 2011 we recorded a charge of $25 thousand, $0.7 million and $68 thousand, respectively, related to the other-than-temporary impairment of certain marketable equity securities and our deferred compensation plan assets.
	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 for the years ended December 31, 2013, 2012 and 2011:
	Year Ended December 31,	2013			2012			2011
	(In thousands)
	Gross realized gains	$	8,932		$	11,006		$	13,641
	Gross realized losses	$	(318	)	$	(1,456	)	$	(1,187	)
	The following table presents the breakdown of investments with unrealized losses at December 31, 2013:
	(In thousands)	Continuous Unrealized						Continuous Unrealized						Total
		Loss Position for Less						Loss Position for 12
		than 12 Months						Months or Greater
		Fair Value			Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
	Deferred compensation plan assets	$	48		$	(6	)	$	409		$	(18	)	$	457	$	(24	)
	Corporate bonds		20,697			(45	)		—			—			20,697		(45	)
	Municipal fixed-rate bonds		13,733			(54	)		—			—			13,733		(54	)
	Marketable equity securities		2,758			(173	)		31			(4	)		2,789		(177	)
	Total	$	37,236		$	(278	)	$	440		$	(22	)	$	37,676	$	(300	)
	The following table presents the breakdown of investments with unrealized losses at December 31, 2012.
	(In thousands)	Continuous Unrealized						Continuous Unrealized						Total
		Loss Position for Less						Loss Position for 12
		than 12 Months						Months or Greater
		Fair Value			Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
	Deferred compensation plan assets	$	915		$	(7	)	$	—		$	—		$	915	$	(7	)
	Corporate bonds		20,204			(17	)		1,600			(1	)		21,804		(18	)
	Municipal fixed-rate bonds		34,297			(73	)		—			—			34,297		(73	)
Marketable equity securities		6,171			(355	)		230			(37	)		6,401		(392	)
Total	$	61,587		$	(452	)	$	1,830		$	(38	)	$	63,417	$	(490	)
The decrease in unrealized losses during 2013, as reflected in the table above, is primarily due to the restructuring of our investment portfolio relating to marketable equity securities in December 2013 resulting in the sale of several securities in an unrealized loss position. At December 31, 2013, a total of 168 of our marketable equity securities were in an unrealized loss position.
We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1—Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
	Fair Value Measurements at December 31, 2013 Using
(In thousands)	Fair Value			Quoted Prices			Significant			Significant
				in Active			Other			Unobservable
				Markets for			Observable			Inputs
				Identical Assets			Inputs			(Level 3)
				(Level 1)			(Level 2)
Cash equivalents
Money market funds	$	3,949		$	3,949		$	—		$	—
Available-for-sale securities
Deferred compensation plan assets		15,123			15,123			—			—
Available-for-sale debt securities
Corporate bonds		166,859			—			166,859			—
Municipal fixed-rate bonds		136,302			—			136,302			—
Municipal variable rate demand notes		8,310			—			8,310			—
Available-for-sale marketable equity securities
Marketable equity securities – technology industry		11,398			11,398			—			—
Marketable equity securities – other		27,054			27,054			—			—
Available-for-sale securities		365,046			53,575			311,471			—
Total	$	368,995		$	57,524		$	311,471		$	—
	Fair Value Measurements at December 31, 2012 Using
(In thousands)	Fair Value			Quoted Prices			Significant			Significant
				in Active			Other			Unobservable
				Markets for			Observable			Inputs
				Identical Assets			Inputs			(Level 3)
				(Level 1)			(Level 2)
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
Marketable equity securities – technology industry		14,099			14,099			—			—
Marketable 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	12 Months Ended
	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Hedging Activities	'
	Note 5 – 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 December 31, 2013, we had forward contracts outstanding with notional amounts totaling €18.5 million ($25.5 million), which mature through 2014.
	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of December 31, 2013 were as follows:
		December 31, 2013
	(In thousands)	Balance Sheet	Fair Value
		Location
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	18
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(15	)
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the year ended December 31, 2013 were as follows:
	(In thousands)	Income Statement	2013
		Location
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	750

Inventory

Inventory	12 Months Ended
	Dec. 31, 2013
Inventory Disclosure [Abstract]	'
Inventory	'
	Note 6 – Inventory
	At December 31, 2013 and 2012, inventory was comprised of the following:
	(In thousands)	2013		2012
	Raw materials	$	44,093	$	47,054
	Work in process		3,484		3,262
	Finished goods		42,534		51,061
	Total Inventory, net	$	90,111	$	101,377
	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 December 31, 2013 and 2012, raw materials reserves totaled $16.9 million and $9.9 million, respectively, and finished goods inventory reserves totaled $6.1 million and $2.1 million, respectively.

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Property, Plant and Equipment	'
	Note 7 – Property, Plant and Equipment
	At December 31, 2013 and 2012, property, plant and equipment were comprised of the following:
	(In thousands)	2013			2012
	Land	$	4,263		$	4,263
	Building and land improvements		21,776			20,915
	Building		68,479			68,479
	Furniture and fixtures		16,465			16,631
	Computer hardware and software		70,468			68,596
	Engineering and other equipment		104,584			99,081
	Total Property, Plant and Equipment		286,035			277,965
	Less accumulated depreciation		(209,296	)		(197,719	)
	Total Property, Plant and Equipment, net	$	76,739		$	80,246
	Depreciation expense was $12.2 million, $12.1 million and $10.8 million in 2013, 2012 and 2011, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets	'
	Note 8 – Goodwill and Intangible Assets
	The changes in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the year ended December 31, 2013 are as follows:
	(In thousands)
	Balance, December 31, 2012	$	3,492
	Acquisitions		—
	Impairment losses		—
	Balance, December 31, 2013	$	3,492
	Balance as of December 31, 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 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 recognized during 2013 or 2012.
	Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangible assets 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 December 31, 2013 and 2012:
	(In thousands)	2013							2012
		Gross Value		Accumulated			Net Value		Gross		Accumulated			Net Value
				Amortization					Value		Amortization
	Customer relationships	$	6,996	$	(1,555	)	$	5,441	$	6,769	$	(766	)	$	6,003
	Developed technology		6,537		(2,692	)		3,845		6,397		(1,354	)		5,043
	Intellectual property		2,340		(1,185	)		1,155		2,340		(851	)		1,489
	Trade names		270		(145	)		125		270		(85	)		185
	Other		14		(8	)		6		13		(3	)		10
	Total	$	16,157	$	(5,585	)	$	10,572	$	15,789	$	(3,059	)	$	12,730
	Amortization expense was $2.4 million, $2.0 million and $0.7 million in 2013, 2012 and 2011, respectively.
	As of December 31, 2013, the estimated future amortization expense of intangible assets is as follows:
	(In thousands)	Amount
	2014	$	2,335
	2015		2,199
	2016		1,925
	2017		1,302
	2018		784
	Thereafter		2,027
	Total	$	10,572

Alabama_State_Industrial_Devel

Alabama State Industrial Development Authority Financing and Economic Incentives	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Alabama State Industrial Development Authority Financing and Economic Incentives	'
	Note 9 – Alabama State Industrial Development Authority Financing and Economic Incentives
	In conjunction with an expansion of our Huntsville, Alabama, facility, we were approved for participation in an incentive program offered by the State of Alabama Industrial Development Authority (the “Authority”). Pursuant to the program, on January 13, 1995, the Authority issued $20.0 million of its taxable revenue bonds and loaned the proceeds from the sale of the bonds to ADTRAN. The bonds were originally purchased by AmSouth Bank of Alabama, Birmingham, Alabama (the “Bank”). Wachovia Bank, N.A., Nashville, Tennessee (formerly First Union National Bank of Tennessee) (the “Bondholder”), which was acquired by Wells Fargo & Company on December 31, 2008, purchased the original bonds from the Bank and made further advances to the Authority, bringing the total amount outstanding to $50.0 million. An Amended and Restated Taxable Revenue Bond (“Amended and Restated Bond”) was issued and the original financing agreement was amended. The Amended and Restated Bond bears interest, payable monthly. The interest rate is 5% per annum. The Amended and Restated Bond matures on January 1, 2020. The estimated fair value of the bond using a level 2 valuation technique at December 31, 2013 was approximately $45.4 million, based on a debt security with a comparable interest rate and maturity and a Standard & Poor’s credit rating of A-. We are required to make payments to the Authority in amounts necessary to pay the interest on the Amended and Restated Bond. Included in long-term investments at December 31, 2013 is $48.3 million which is invested in a restricted certificate of deposit. These funds serve as a collateral deposit against the principal of this bond, and we have the right to set-off the balance of the Bond with the collateral deposit in order to reduce the balance of the indebtedness.
	In conjunction with this program, we are eligible to receive certain economic incentives from the state of Alabama that reduce the amount of payroll withholdings that we are required to remit to the state for those employment positions that qualify under the program. For the years ended December 31, 2013, 2012 and 2011, we realized economic incentives related to payroll withholdings totaling $1.3 million, $1.4 million and $1.9 million, respectively.
	We did not make a principal payment for the year-ended December 31, 2013. We made a principal payment of $0.5 million for the year ended December 31, 2012. We anticipate making a principal payment in 2014. At December 31, 2013 and 2012, $0.3 million and $0.5 million, respectively, of the bond debt were classified as a current liability in accounts payable in the Consolidated Balance Sheets at December 31, 2013.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Note 10 – Income Taxes
	A summary of the components of the provision for income taxes for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands)	2013			2012			2011
	Current
	Federal	$	15,641		$	26,225		$	59,382
	State		2,041			3,766			7,177
	International		1,437			(504	)		431
	Total Current		19,119			29,487			66,990
	Deferred
	Federal		(3,606	)		(3,395	)		527
	State		(412	)		(388	)		60
	International		(40	)		(2	)		(12	)
	Total Deferred		(4,058	)		(3,785	)		575
	Total Provision for Income Taxes	$	15,061		$	25,702		$	67,565
	Our effective income tax rate differs from the federal statutory rate due to the following:
		2013			2012			2011
	Tax provision computed at the federal statutory rate		35	%		35	%		35	%
	State income tax provision, net of federal benefit		3.98			3.78			3.19
	Federal research credits		(9.24	)		—			(2.50	)
	International		(2.93	)		3.8			—
	Tax-exempt income		(1.11	)		(1.01	)		(0.27	)
	State tax incentives		(2.19	)		(4.46	)		(0.90	)
	Stock-based compensation		2.97			2.36			0.03
	Domestic production activity deduction		(1.80	)		(3.21	)		(1.84	)
	Other, net		0.07			(1.03	)		0.07
	Effective Tax Rate		24.75	%		35.23	%		32.78	%
	Income before provision for income taxes for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands)	2013			2012			2011
	U.S. entities	$	51,752		$	80,926		$	204,652
	International entities		9,103			(7,961	)		1,490
	Total	$	60,855		$	72,965		$	206,142
	Income before provision for income taxes for international entities reflects income based on statutory transfer pricing agreements. This amount does not correlate to consolidated international revenues, many of which occur from our U.S. entity.
	Deferred income taxes on the balance sheet result from temporary differences between the amount of assets and liabilities recognized for financial reporting and tax purposes. The principal components of our current and non-current deferred taxes are as follows:
	(In thousands)	2013			2012
	Current deferred tax assets
	Accounts receivable	$	51		$	2
	Inventory		9,877			7,507
	Accrued expenses		7,155			5,546
	Total Current Deferred Tax Assets		17,083			13,055
	Non-current deferred tax assets
	Accrued expenses		140			116
	Deferred compensation		5,972			4,456
	Stock-based compensation		5,331			4,569
	Uncertain tax positions related to state taxes and related interest		1,107			1,005
	Pensions		301			605
	Foreign losses		5,702			6,978
	State losses and credit carry-forwards		3,737			4,349
	Federal loss and research carry-forwards		8,322			12,210
	Valuation allowance		(8,842	)		(10,939	)
	Total Non-current Deferred Tax Assets		21,770			23,349
	Total Deferred Tax Assets	$	38,853		$	36,404
	Non-current deferred tax liabilities
	Property, plant and equipment	$	(5,499	)	$	(6,405	)
	Intellectual property		(1,006	)		(1,839	)
	Investments		(5,643	)		(4,844	)
	Total Non-current Deferred Tax Liabilities	$	(12,148	)	$	(13,088	)
	Net Deferred Tax Assets	$	26,705		$	23,316
	At December 31, 2013 and 2012, non-current deferred tax liabilities and non-current deferred tax assets, respectively, related to our investments, reflect deferred taxes on unrealized gains and losses on available-for-sale investments. The net change in non-current deferred taxes associated with these investments, a deferred tax expense of $0.4 million in 2013 and a deferred tax benefit of $33 thousand in 2012, is recorded as an adjustment to other comprehensive income, presented in the Consolidated Statements of Comprehensive Income.
	We have deferred tax assets for foreign and domestic loss carry-forwards, unamortized research and development costs and state credit carry-forwards of $19.0 million which will expire between 2014 and 2030. The foreign loss carry-forwards were generated through the acquisition of a foreign entity in 2009 and through current losses at a foreign subsidiary. The unamortized research and development costs are related to our acquisition of Bluesocket in 2011. The state credit carry-forwards result from tax credits in excess of our annual tax liability to an individual state where we do not generate sufficient state income to offset the credit. We believe it is more likely than not that we will not realize the full benefits of the deferred tax asset arising from these losses and credits in various states and foreign countries, and accordingly, we have provided a valuation allowance against these deferred tax assets. We do not provide for U.S. income tax on undistributed earnings of our foreign operations, whose earnings are intended to be permanently reinvested. These earnings are not required to service debt or fund our U.S. operations.
	During 2013, 2012 and 2011, we recorded an income tax benefit of $0.2 million, $1.9 million and $10.5 million, respectively, as an adjustment to equity. This deduction is calculated on the difference between the exercise price of stock option exercises and the market price of the underlying common stock upon exercise.
	The change in the unrecognized income tax benefits for 2013, 2012 and 2011 is reconciled below:
	(In thousands)	2013			2012			2011
	Balance at beginning of period	$	2,926		$	2,970		$	2,593
Increases for tax position related to:
Prior years		89			965			—
Current year		549			302			840
Decreases for tax positions related to:
Prior years		—			(49	)		(92	)
Settlements with taxing authorities		(141	)		(507	)		(354	)
Expiration of applicable statute of limitations		(183	)		(755	)		(17	)
Balance at end of period	$	3,240		$	2,926		$	2,970
As of December 31, 2013, 2012, and 2011, our total liability for unrecognized tax benefits was $3.2 million, $2.9 million, and $3.0 million, respectively, of which $2.5 million, $2.2 million, and $2.4 million, respectively, would reduce our effective tax rate if we were successful in upholding all of the uncertain positions and recognized the amounts recorded. We classify interest and penalties recognized on the liability for unrecognized tax benefits as income tax expense. As of December 31, 2013, 2012 and 2011, the balances of accrued interest and penalties were $1.0 million, $0.8 million and $1.2 million, respectively.
We do not anticipate a single tax position generating a significant increase or decrease in our liability for unrecognized tax benefits within 12 months of this reporting date. We file income tax returns in the U.S. federal and various state jurisdictions and several foreign jurisdictions. We have been audited by the Internal Revenue Service and the state of Alabama through the 2009 tax year. Generally, we are not subject to changes in income taxes by any taxing jurisdiction for the years prior to 2010.

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]	'
Employee Benefit Plans	'
	Note 11 – Employee Benefit Plans
	Pension Benefit Plan
	As a result of our acquisition of the NSN BBA business, we assumed a defined benefit pension plan covering employees in certain foreign countries. We established a Contribution Trust Arrangement (CTA) to hold the pension assets, and NSN transferred assets to us equal to the defined benefit obligation as of the May 4, 2012 acquisition date.
	The pension benefit plan obligations and funded status at December 31, 2013 and 2012, are as follows:
	(In thousands)	2013			2012
	Change in projected benefit obligation:
	Projected benefit obligation at beginning of period	$	(21,181	)	$	—
	Business combination		—			(18,063	)
	Service cost		(1,198	)		(766	)
	Interest cost		(745	)		(494	)
	Actuarial gain (loss)		779			(1,862	)
	Benefit payments		(1	)		—
	Foreign currency exchange rate changes		(1,008	)		4
	Projected benefit obligation at end of period	$	(23,354	)	$	(21,181	)
	Change in plan assets:
	Fair value of plan assets at beginning of period	$	18,620		$	—
	Business combination		—			18,063
	Actual return on plan assets		1,281			592
	Foreign currency exchange rate changes		872			(35	)
	Fair value of plan assets at end of period	$	20,773		$	18,620
	Funded status at end of period	$	(2,581	)	$	(2,561	)
	The accumulated benefit obligation was $22.9 million and $20.8 million at December 31, 2013 and 2012, respectively.
	The net amounts recognized in the balance sheet for the unfunded pension liability as of December 31, 2013 and 2012 are as follows:
	(In thousands)	2013			2012
	Current liability	$	—		$	(609	)
	Non-current liability		(2,581	)		(1,952	)
	Total	$	(2,581	)	$	(2,561	)
	The components of net periodic pension cost and amounts recognized in other comprehensive income for the year ended December 31, 2013 and the period May 4, 2012 to December 31, 2012 are as follows:
	(In thousands)	Year Ended			May 4, 2012 to
		December 31, 2013			December 31, 2012
	Net periodic benefit cost:
	Service cost	$	1,198		$	766
	Interest cost		745			494
	Expected return on plan assets		(1,010	)		(674	)
	Net periodic benefit cost		933			586
	Other changes in plan assets and benefit obligations recognized in other comprehensive income:
	Net actuarial (gain) loss		(779	)		1,862
	Net unrealized (gain) loss on plan assets		(282	)		90
	Other comprehensive (income) loss		(1,061	)		1,952
	Total recognized in net periodic benefit cost and other comprehensive income	$	(128	)	$	2,538
	The amounts recognized in accumulated other comprehensive income as of December 31, 2013 and 2012 are as follows:
	(In thousands)	2013			2012
	Net actuarial (gain) loss	$	1,083		$	1,862
	Net unrealized (gain) loss on plan assets		(192	)		90
	Total	$	891		$	1,952
	The defined benefit pension plan is accounted for on an actuarial basis, which requires the selection of various assumptions, including an expected rate of return on plan assets and a discount rate. The expected return on our German plan assets that is utilized in determining the benefit obligation and net periodic benefit cost is derived from periodic studies, which include a review of asset allocation strategies, anticipated future long-term performance of individual asset classes, risks using standard deviations and correlations of returns among the asset classes that comprise the plans’ asset mix. While the studies give appropriate consideration to recent plan performance and historical returns, the assumptions are primarily long-term, prospective rates of return.
	Another key assumption in determining net pension expense is the assumed discount rate to be used to discount plan obligations. The discount rate has been derived from the returns of high-quality, corporate bonds denominated in Euro currency with durations close to the duration of our pension obligations.
	The weighted-average assumptions that were used to determine the net periodic benefit cost for the year ended December 31, 2013 and the period May 4, 2012 to December 31, 2012 are as follows:
		Year Ended			May 4, 2012 to
		December 31, 2013			December 31, 2012
	Discount rates		3.5	%		3.96	%
	Rate of compensation increase		2.25	%		2.25	%
	Expected long-term rates of return		5.4	%		5.4	%
	The weighted-average assumptions that were used to determine the benefit obligation at December 31, 2013 and 2012:
		2013			2012
	Discount rates		3.7	%		3.5	%
	Rate of compensation increase		2.25	%		2.25	%
	No amounts will be amortized from accumulated other comprehensive income into net periodic benefit cost during 2014.
	We do not anticipate making a contribution to our pension plan in 2014. The following pension benefit payments, which reflect expected future service, as appropriate, are expected to be paid to participants:
	(In thousands)
	2014	$	357
	2015		312
	2016		223
2017		390
2018		650
2019 – 2023		4,427
Total	$	6,359
We have categorized our cash equivalents and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1—Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
				Fair Value Measurements at December 31, 2013 Using
(In thousands)	Fair Value			Quoted Prices			Significant		Significant
				in Active			Other		Unobservable
				Markets for			Observable		Inputs
				Identical Assets			Inputs		(Level 3)
				(Level 1)			(Level 2)
Cash equivalents	$	4		$	4		$	—	$	—
Available-for-sale securities
Bond funds:
Corporate bonds		12,976			12,976			—		—
Government bonds		1,915			1,915			—		—
Equity funds:
Large cap blend		4,720			4,720			—		—
Large cap value		287			287			—		—
Balanced fund		871			871			—		—
Available-for-sale securities		20,769			20,769			—		—
Total	$	20,773		$	20,773		$	—	$	—
				Fair Value Measurements at December 31, 2012 Using
(In thousands)	Fair Value			Quoted Prices			Significant		Significant
				in Active			Other		Unobservable
				Markets for			Observable		Inputs
				Identical Assets			Inputs		(Level 3)
				(Level 1)			(Level 2)
Cash equivalents	$	6		$	6		$	—	$	—
Available-for-sale securities
Bond funds:
Corporate bonds		12,041			12,041			—		—
Government bonds		1,839			1,839			—		—
Equity funds:
Large cap blend		3,740			3,740			—		—
Large cap value		235			235			—		—
Balanced fund		759			759			—		—
Available-for-sale securities		18,614			18,614			—		—
Total	$	18,620		$	18,620		$	—	$	—
Our investment policy includes various guidelines and procedures designed to ensure assets are invested in a manner necessary to meet expected future benefits earned by participants. The investments guidelines consider a broad range of economic conditions. Central to the policy are target allocation ranges by asset class, which is currently 75% for bond funds and 25% for equity funds.
The objectives of the target allocations are to maintain investment portfolios that diversify risk through prudent asset allocation parameters, achieve asset returns that meet or exceed the plans’ actuarial assumptions, and achieve asset returns that are competitive with like institutions employing similar investment strategies.
The investment policy is periodically reviewed by us and a designated third-party fiduciary for investment matters. The policy is established and administered in a manner that is compliant at all times with applicable government regulations.
401(k) Savings Plan
We maintain the ADTRAN, Inc. 401(k) Retirement Plan (Savings Plan) for the benefit of our eligible employees. The Savings Plan is intended to qualify under Sections 401(a) and 401(k) of the Internal Revenue Code of 1986, as amended (Code), and is intended to be a “safe harbor” 401(k) plan under Code Section 401(k)(12). The Savings Plan allows employees to save for retirement by contributing part of their compensation to the plan on a tax-deferred basis. The Savings Plan also requires us to contribute a “safe harbor” amount each year. We match up to 4% of employee contributions (100% of an employee’s first 3% of contributions and 50% of their next 2% of contributions), beginning on the employee’s one year anniversary date. In calculating our matching contribution, we only use compensation up to the statutory maximum under the Code ($255 thousand for 2013). All contributions under the Savings Plan are 100% vested. Expenses recorded for employer contributions and plan administration costs for the Savings Plan amounted to approximately $4.5 million, $4.6 million and $4.3 million in 2013, 2012 and 2011, respectively.
Deferred Compensation Plans
We maintain the ADTRAN, Inc. Deferred Compensation Plan (Deferred Compensation Plan). This plan is offered as a supplement to our tax-qualified 401(k) plan and is available to certain executive management employees who have been designated by our Board of Directors. The deferred compensation plan allows participants to defer all or a portion of certain specified bonuses and up to 25% of remaining cash compensation, and permits us to make matching contributions on a discretionary basis, without the limitations that apply to the 401(k) plan. To date, we have not made any matching contributions under this plan.
We also maintain the ADTRAN, Inc. Equity Deferral Program for Employees for the purpose of providing deferred compensation for certain executive management employees. Participants may elect to defer all or a portion of their vested Performance Share awards to the Plan. Such deferrals shall continue to be held and deemed to be invested in shares of ADTRAN stock unless and until the amounts are distributed or such deferrals are moved to another deemed investment pursuant to an election made by the Participant.
We have set aside the plan assets for both plans in a rabbi trust (Trust) and all contributions are credited to bookkeeping accounts for the participants. The Trust assets are subject to the claims of our creditors in the event of bankruptcy or insolvency. The assets of the Trust are deemed to be invested in pre-approved mutual funds as directed by each participant, and the participant’s bookkeeping account is credited with the earnings and losses attributable to those investments. Benefits are scheduled to be distributed six months after termination of employment in a single lump sum payment or annual installments paid over a three or ten year term. Distributions will be made on a pro rata basis from each of the hypothetical investments of the Participant’s account in cash. Any whole shares of ADTRAN, Inc. common stock that are distributed will be distributed in-kind.
Assets of the Trust are deemed invested in mutual funds that cover an investment spectrum ranging from equities to money market instruments. These mutual funds are publicly quoted and reported at fair value. The fair value of the assets held by the Trust and the amounts payable to the plan participants are as follows:
(In thousands)	2013			2012
Fair Value of Plan Assets
Long-term Investments	$	15,123		$	11,527
Total Fair Value of Plan Assets	$	15,123		$	11,527
Amounts Payable to Plan Participants
Non-current Liabilities	$	15,123		$	11,527
Total Amounts Payable to Plan Participants	$	15,123		$	11,527
Interest and dividend income of the Trust have been included in interest and dividend income in the accompanying 2013, 2012 and 2011 Consolidated Statements of Income. Changes in the fair value of the plan assets held by the Trust have been included in accumulated other comprehensive income in the accompanying 2013 and 2012 Consolidated Balance Sheets. Changes in the fair value of the deferred compensation liability are included as selling, general and administrative expense in the accompanying 2013, 2012 and 2011 Consolidated Statements of Income. Based on the changes in the total fair value of the Trust’s assets, we recorded deferred compensation adjustments in 2013, 2012 and 2011 of $2.8 million, $0.9 million and $(0.2) million, respectively.
Retiree Medical Coverage
We provide medical, dental and prescription drug coverage to one retired former officer and his spouse, for his life, on the same terms as provided to our active officers, and to the spouse of a former deceased officer for up to 30 years. At December 31, 2013 and 2012, this liability totaled $0.2 million.

Segment_Information_and_Major_

Segment Information and Major Customers	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Segment Information and Major Customers	'
	Note 12 – Segment Information and Major Customers
	We operate in two reportable segments: (1) the Carrier Networks Division and (2) the Enterprise Networks Division. The accounting policies of the segments are the same as those described in the “Nature of Business and Summary of Significant Accounting Policies” (see Note 1) to the extent that such policies affect the reported segment information. 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 each of the years ended December 31, 2013, 2012 and 2011. Asset information by reportable segment is not reported, since we do not produce such information internally.
	Sales and Gross Profit by Market Segment
	(In thousands)		2013				2012				2011
			Sales		Gross Profit		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks		$	500,733	$	233,206	$	492,096	$	247,380	$	569,579	$	327,813
	Enterprise Networks			141,011		75,680		128,518		69,263		147,650		86,505
	Total		$	641,744	$	308,886	$	620,614	$	316,643	$	717,229	$	414,318
	Sales by Product
	Our three major product categories are Carrier Systems, Business Networking and Loop Access.
	Carrier Systems products are used by communications service providers to provide data, voice and video services to consumers and enterprises. This category includes the following product areas and related services:
		•		Broadband Access
		•		Total Access® 5000 Multi-Service Access Node (MSAN)
		•		hiX family of MSANs
		•		Total Access 1100/1200 Series of Fiber to the Node (FTTN) products
		•		Ultra Broadband Ethernet (UBE)
		•		Digital Subscriber Line Access Multiplexer (DSLAM) products
		•		Optical
		•		Optical Networking Edge (ONE)
		•		NetVanta 8000 Series of Fiber Ethernet Access Devices (EAD)
		•		OPTI-6100 and Total Access 3000 optical Multi-Service Provisioning Platforms (MSPP)
		•		Pluggable Optical Products, including SFP, XFP, and SFP+
		•		TDM systems
	Business Networking products provide access to communication services and facilitate the delivery of cloud connectivity and enterprise communications to the small and mid-sized enterprise (SME) market. This category includes the following product areas and related services:
		•		Internetworking products
		•		Total Access IP Business Gateways
		•		Optical Network Terminals (ONTs)
		•		Bluesocket® virtual Wireless LAN (vWLAN®)
		•		NetVanta®
		•		Multiservice Routers
		•		Managed Ethernet Switches
		•		IP Business Gateways
		•		Unified Communications (UC) solutions
		•		Carrier Ethernet Network Terminating Equipment (NTE)
		•		Network Management Solutions
		•		Integrated Access Devices (IADs)
	Loop Access products are used by carrier and enterprise customers for access to copper-based communications networks. The Loop Access category includes the following product areas and related services:
		•		High bit-rate Digital Subscriber Line (HDSL) products
		•		Digital Data Service (DDS)
		•		Integrated Services Digital Network (ISDN) products
		•		T1/E1/T3 Channel Service Units/Data Service Units (CSUs/DSUs)
		•		TRACER fixed-wireless products
	The table below presents sales information by product category for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)		2013		2012		2011
	Carrier Systems		$	427,850	$	399,646	$	420,289
	Business Networking			168,871		149,304		162,186
	Loop Access			45,023		71,664		134,754
	Total		$	641,744	$	620,614	$	717,229
	In addition, we identify subcategories of product revenues, which we divide into core products and legacy products. Our core products consist of Broadband Access and Optical products (included in Carrier Systems), and Internetworking products (included in Business Networking). Our legacy products include HDSL products (included in Loop Access) and other products not included in the aforementioned core products.
	The table below presents subcategory revenues for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)		2013		2012		2011
	Core Products
	Broadband Access (included in Carrier Systems)		$	340,560	$	320,076	$	289,776
	Optical (included in Carrier Systems)			55,615		51,755		82,535
	Internetworking (NetVanta® & Multi-service Access Gateways) (included in Business Networking)			164,422		142,958		151,536
	Subtotal		$	560,597	$	514,789	$	523,847
	Legacy Products
	HDSL (does not include T1) (included in Loop Access)			41,666		66,974		126,976
	Other products (excluding HDSL)			39,481		38,851		66,406
	Subtotal		$	81,147	$	105,825	$	193,382
	Total		$	641,744	$	620,614	$	717,229
	The following table presents sales information by geographic area for the years ended December 31, 2013, 2012 and 2011. International sales correlate to shipments with a non-U.S. destination.
(In thousands)		2013		2012		2011
United States		$	455,996	$	470,369	$	632,795
Germany			97,151		26,918		554
Other international			88,597		123,327		83,880
Total		$	641,744	$	620,614	$	717,229
Customers comprising more than 10% of revenue can change from year to year. Single customers comprising more than 10% of our revenue in 2013 included two customers at 17% and 14%, respectively. Only a single customer comprised more than 10% of our revenue in 2012 at 23%. Single customers comprising more than 10% of our revenue in 2011 included two customers at 25% and 10%, respectively. No other customer accounted for 10% or more of our sales in 2013, 2012 or 2011. Our five largest customers, other than those with more than 10 percent of revenues disclosed above, can change from year to year. These customers represented 22%, 34% and 29% of total revenue in 2013, 2012 and 2011, respectively. Revenues in this disclosure do not include distributor agents who predominately provide fulfillment services to end users. In such cases where known, that revenue is associated with the end user.
As of December 31, 2013, long-lived assets, net totaled $76.7 million, which includes $71.2 million held in the United States and $5.5 million held outside the United States. As of December 31, 2012, long-lived assets, net totaled $80.2 million, which includes $73.9 million held in the United States and $6.3 million held outside the United States.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Note 13 – Commitments and Contingencies
	In the ordinary course of business, we may be subject to various legal proceedings and claims, including employment disputes, patent claims, disputes over contract agreements and other commercial disputes. In some cases, claimants seek damages or other relief, such as royalty payments related to patents, which, if granted, could require significant expenditures. Although the outcome of any claim or litigation can never be certain, it is our opinion that the outcome of all contingencies of which we are currently aware will not materially affect our business, operations, financial condition or cash flows.
	We lease office space and equipment under operating leases which expire at various dates through 2018. As of December 31, 2013, future minimum rental payments under non-cancelable operating leases with original maturities of greater than 12 months are approximately as follows:
	(In thousands)
	2014	$	4,523
	2015		3,556
	2016		2,506
	2017		2,156
	Thereafter		686
	Total	$	13,427
	Rental expense was approximately $4.8 million, $3.9 million and $2.4 million for the years ended December 31, 2013, 2012 and 2011, respectively.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Note 14 – Earnings per Share
	A summary of the calculation of basic and diluted earnings per share (EPS) for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands, except for per share amounts)	2013		2012		2011
	Numerator
	Net Income	$	45,794	$	47,263	$	138,577
	Denominator
	Weighted average number of shares – basic		59,001		63,259		64,145
	Effect of dilutive securities:
	Stock options		390		488		1,236
	Restricted stock and restricted stock units		33		27		35
	Weighted average number of shares – diluted		59,424		63,774		65,416
	Net income per share – basic	$	0.78	$	0.75	$	2.16
	Net income per share – diluted	$	0.77	$	0.74	$	2.12
	For each of the years ended December 31, 2013, 2012 and 2011, 3.2 million, 3.2 million and 1.2 million stock options were outstanding but were not included in the computation of that year’s diluted EPS because the options’ exercise prices were greater than the average market price of the common shares, therefore making them anti-dilutive under the treasury stock method.

Summarized_Quarterly_Financial

Summarized Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Summarized Quarterly Financial Data (Unaudited)	'
	Note 15 – Summarized Quarterly Financial Data (Unaudited)
	The following table presents unaudited quarterly operating results for each of our last eight fiscal quarters. This information has been prepared on a basis consistent with our audited financial statements and includes all adjustments, consisting only of normal recurring adjustments, considered necessary for a fair presentation of the data.
	Unaudited Quarterly Operating Results
	(In thousands, except for per share amounts)
	Three Months Ended		March 31, 2013		June 30, 2013		September 30, 2013		December 31, 2013
	Net sales		$	143,013	$	162,233	$	177,404	$	159,094
	Gross profit		$	69,677	$	79,798	$	82,547	$	76,864
	Operating income		$	6,563	$	14,053	$	17,210	$	10,639
	Net income		$	7,890	$	9,859	$	16,205	$	11,840
	Earnings per common share		$	0.13	$	0.17	$	0.28	$	0.21
	Earnings per common share assuming dilution (1)		$	0.13	$	0.17	$	0.28	$	0.2
	Three Months Ended		31-Mar-12		30-Jun-12		30-Sep-12		31-Dec-12
	Net sales		$	134,735	$	183,998	$	162,125	$	139,756
	Gross profit		$	74,087	$	95,201	$	79,972	$	67,383
	Operating income		$	16,181	$	26,838	$	10,276	$	2,874
	Net income		$	12,960	$	21,070	$	9,272	$	3,961
	Earnings per common share		$	0.2	$	0.33	$	0.15	$	0.06
	Earnings per common share assuming dilution (1)		$	0.2	$	0.33	$	0.15	$	0.06
	(1)	Assumes exercise of dilutive stock options calculated under the treasury stock method.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2013
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Note 16 – 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 years ended 2013, 2012 and 2011, we incurred fees of $10 thousand per month for these legal services.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	Note 17 – Subsequent Events
	On January 21, 2014, the Board declared a quarterly cash dividend of $0.09 per common share to be paid to shareholders of record at the close of business on February 6, 2014. The quarterly dividend payment was $5.1 million and was paid on February 20, 2014. 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.
	In February 2014, we made a decision to make a $16.5 million principal payment on the Amended and Restated Bond. The restricted certificate of deposit included in our long-term investments will be reduced by the amount of the payment. We anticipate this payment will be made during the first quarter of 2014.
	As of February 27, 2014, we have repurchased 0.4 million shares of our common stock through open market purchases at an average cost of $25.13 per share. We currently have the authority to purchase an additional 3.1 million shares of our common stock under the current plan approved by the Board of Directors.

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2013
Valuation And Qualifying Accounts [Abstract]	'
Schedule II - Valuation and Qualifying Accounts	'
	SCHEDULE II
	VALUATION AND QUALIFYING ACCOUNTS
	Column A	Column B		Column C		Column D			Column E		Column F
	(In thousands)	Balance at		Assumed		Charged to			Deductions		Balance at
		Beginning		on		Costs  &					End of
		of Period		Acquisition		Expenses					Period
	Year ended December 31, 2013
	Allowance for Doubtful Accounts	$	6		—		136			12	$	130
	Inventory Reserve	$	11,957		—		11,457			421	$	22,993
	Warranty Liability	$	9,653		—		4,051			4,727	$	8,977
	Deferred Tax Asset Valuation Allowance	$	10,939		—		(1,056	)		1,041	$	8,842
	Year ended December 31, 2012
	Allowance for Doubtful Accounts	$	8		—		38			40	$	6
	Inventory Reserve	$	9,419		—		3,042			504	$	11,957
	Warranty Liability	$	4,118		3,781		5,363			3,609	$	9,653
	Deferred Tax Asset Valuation Allowance	$	7,585		—		3,594			240	$	10,939
	Year ended December 31, 2011
	Allowance for Doubtful Accounts	$	162		—		117			271	$	8
	Inventory Reserve	$	8,932		—		1,137			650	$	9,419
	Warranty Liability	$	3,304		33		2,860			2,079	$	4,118
	Deferred Tax Asset Valuation Allowance	$	5,627		1,462		496			—	$	7,585

Nature_of_Business_and_Summary1

Nature of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Principles of Consolidation	'
	Principles of Consolidation
	Our consolidated financial statements include ADTRAN and its wholly owned subsidiaries. All inter-company accounts and transactions have been eliminated in consolidation.
Changes in Classifications	'
	Changes in Classifications
	Certain balance sheet amounts (including inventory, accounts receivable, unearned revenue and accrued expenses) and related disclosures have been revised to correct immaterial misclassifications in 2012 that were corrected in 2013. The revisions decreased both total assets and total liabilities each by $2.7 million at December 31, 2012. The revisions had no impact on our previously reported stockholders’ equity, income statement, comprehensive income, or earnings per share. Additionally, we corrected immaterial misclassifications between the operating and investing sections of our consolidated statements of cash flows and adjusted our 2012 and 2011 cash flows in these categories by $0.2 million and $0.1 million, respectively, in order to be consistent with the 2013 presentation.
	Additionally, 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 year ended December 31, 2013, we identified two adjustments in the acquired NSN (formerly Nokia Siemens Networks) Broadband Access business (NSN BBA business) relating to customer payment discounts for one customer, and recoverable VAT taxes on certain vendor freight invoices that should have been recorded in prior periods. These adjustments resulted from a $0.4 million understatement of net income in 2012. We evaluated the impact of the adjustments on the results of our previously issued financial statements for the prior period 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 was not material to our results for the year 2013. Accordingly, during the year ended December 31, 2013 we recorded an out of period adjustment to correct these issues.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated working capital adjustments under negotiation related to the NSN BBA business acquisition, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents represent demand deposits, money market funds, and short-term investments classified as available-for-sale with original maturities of three months or less. We maintain depository investments with certain financial institutions. Although these depository investments may exceed government insured depository limits, we have evaluated the credit worthiness of these applicable financial institutions, and determined the risk of material financial loss due to the exposure of such credit risk to be minimal. As of December 31, 2013, $53.5 million of our cash and cash equivalents, primarily certain domestic money market funds and foreign depository accounts, were in excess of government provided insured depository limits.
Financial Instruments	'
	Financial Instruments
	The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the immediate or short-term maturity of these financial instruments. The carrying amount reported for bonds payable was $46.5 million, compared to an estimated fair value of $45.4 million, based on a debt security with a comparable interest rate and maturity and a Standard & Poor’s credit rating of A-.
	Investments with contractual maturities beyond one year, such as our municipal variable rate demand notes, may be classified as short-term based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. Despite the long-term nature of their stated contractual maturities, we routinely buy and sell these securities and we believe we have the ability to quickly sell them to the remarketing agent, tender agent, or issuer at par value plus accrued interest in the event we decide to liquidate our investment in a particular variable rate demand note. All income generated from these investments was recorded as interest income. We have not been required to record any losses relating to municipal variable rate demand notes.
	Long-term investments represent a restricted certificate of deposit held at cost, municipal fixed-rate bonds, corporate bonds, a fixed income bond fund, marketable equity securities, and other equity investments. Marketable equity securities are reported at fair value as determined by the most recently traded price of the securities at the balance sheet date, although the securities may not be readily marketable due to the size of the available market. Unrealized gains and losses, net of tax, are reported as a separate component of stockholders’ equity. Realized gains and losses on sales of securities are computed under the specific identification method and are included in current income. We periodically review our investment portfolio for investments considered to have sustained an other-than-temporary decline in value. Impairment charges for other-than-temporary declines in value are recorded as realized losses in the accompanying consolidated statements of income. All of our investments at December 31, 2013 and 2012 are classified as available-for-sale securities. See Note 4 of Notes to Consolidated Financial Statements for additional information.
Accounts Receivable	'
	Accounts Receivable
	We record accounts receivable at net realizable value. Prior to issuing payment terms to a new customer, we perform a detailed credit review of the customer. Credit limits are established for each new customer based on the results of this credit review. Payment terms are established for each new customer, and collection experience is reviewed periodically in order to determine if the customer’s payment terms and credit limits need to be revised. At December 31, 2013, one customer accounted for 13.1% of our total accounts receivable. At December 31, 2012, one customer accounted for 10.4% of our total accounts receivable.
	We maintain an allowance for doubtful accounts for losses resulting from the inability of our customers to make required payments. We regularly review the allowance for doubtful accounts and consider factors such as the age of accounts receivable balances, the current economic conditions that may affect a customer’s ability to pay, significant one-time events and our historical experience. If the financial condition of a customer deteriorates, resulting in an impairment of their ability to make payments, we may be required to record an allowance for doubtful accounts. If circumstances change with regard to individual receivable balances that have previously been determined to be uncollectible (and for which a specific reserve has been established), a reduction in our allowance for doubtful accounts may be required. Our allowance for doubtful accounts was $130 thousand at December 31, 2013 and $6 thousand at December 31, 2012.
Other Receivables	'
	Other Receivables
	Other receivables are comprised primarily of amounts due from subcontract manufacturers for product component transfers, accrued interest on investments and on a restricted certificate of deposit, and amounts due from employee stock option exercises. At December 31, 2013 and 2012, other receivables also included an estimated receivable due from NSN related to working capital adjustments that are currently under negotiation.
Inventory	'
	Inventory
	Inventory is carried at the lower of cost or market, with cost being determined using the first-in, first-out method. Standard costs for material, labor and manufacturing overhead are used to value inventory. Standard costs are updated at least quarterly; therefore, inventory costs approximate actual costs at the end of each reporting period. 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. When we dispose of excess and obsolete inventories, the related write-downs are charged against the inventory reserve. See Note 6 of Notes to Consolidated Financial Statements for additional information.
Property, Plant and Equipment	'
	Property, Plant and Equipment
	Property, plant and equipment, which is stated at cost, is depreciated using the straight-line method over the estimated useful lives of the assets. We depreciate building and land improvements from five to 39 years, office machinery and equipment from three to seven years, engineering machinery and equipment from three to seven years, and computer software from three to five years. Expenditures for repairs and maintenance are charged to expense as incurred. Betterments that materially prolong the lives of the assets are capitalized. The cost of assets retired or otherwise disposed of and the related accumulated depreciation are removed from the accounts, and the gain or loss on such disposition is included in other income (expense), net in the accompanying consolidated statements of income. See Note 7 of Notes to Consolidated Financial Statements for additional information.
Liability for Warranty	'
	Liability for Warranty
	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 $9.0 million and $9.7 million at December 31, 2013 and 2012, respectively. These liabilities are included in accrued expenses in the accompanying consolidated balance sheets.
	A summary of warranty expense and write-off activity for the years ended December 31, 2013 and 2012 is as follows:
	Year Ended December 31,	2013			2012
	(In thousands)
	Balance at beginning of period	$	9,653		$	4,118
	Plus: Amounts charged to cost and expenses		4,051			5,363
	Amounts assumed on acquisition		—			3,781
	Less: Deductions		(4,727	)		(3,609	)
	Balance at end of period	$	8,977		$	9,653
Pension Benefit Plan Obligations	'
	Pension Benefit Plan Obligations
	As a result of our acquisition of the NSN BBA business, we assumed a defined benefit pension plan covering employees in certain foreign countries. Pension benefit plan obligations are based on various assumptions used by our actuaries in calculating these amounts. These assumptions include discount rates, compensation rate increases, expected return on plan assets, retirement rates and mortality rates. Actual results that differ from the assumptions and changes in assumptions could affect future expenses and obligations.
Stock-Based Compensation	'
	Stock-Based Compensation
	We have two Board and stockholder approved stock option plans from which stock options and other awards are available for grant to employees and directors. All employee and director stock options granted under our stock option plans have an exercise price equal to the fair market value of the award, as defined in the plan, of the underlying common stock on the grant date. There are currently no vesting provisions tied to performance or market conditions for any option awards; vesting for all outstanding option grants is based only on continued service as an employee or director of ADTRAN. All of our outstanding stock option awards are classified as equity awards.
	Under the provisions of our approved plans, we made grants of performance-based restricted stock units to five of our executive officers in 2013, 2012 and 2011. The restricted stock units are subject to a market condition based on the relative total shareholder return of ADTRAN against all the companies in the NASDAQ Telecommunications Index and vest at the end of a three-year performance period. The restricted stock units are converted into shares of common stock upon vesting. Depending on the relative total shareholder return over the performance period, the executive officers may earn from 0% to 150% of the number of restricted stock units granted. The fair value of the award is based on the market price of our common stock on the date of grant, adjusted for the expected outcome of the impact of market conditions using a Monte Carlo Simulation valuation method. The recipients of the restricted stock units also earn dividend credits during the performance period, which will be paid in cash upon the issuance of common stock for the restricted stock units.
	Stock-based compensation expense recognized in 2013, 2012 and 2011 was approximately $9.1 million, $9.3 million and $9.2 million, respectively. As of December 31, 2013, total compensation cost related to non-vested stock options, restricted stock units and restricted stock not yet recognized was approximately $18.8 million, which is expected to be recognized over an average remaining recognition period of 2.7 years. See Note 3 of Notes to Consolidated Financial Statements for additional information.
Impairment of Long-Lived Assets	'
	Impairment of Long-Lived Assets
	We review long-lived assets used in operations for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable and the undiscounted cash flows estimated to be generated by the asset are less than the asset’s carrying value. An impairment loss would be recognized in the amount by which the recorded value of the asset exceeds the fair value of the asset, measured by the quoted market price of an asset or an estimate based on the best information available in the circumstances. There were no impairment losses recognized during 2013, 2012 or 2011.
Goodwill and Purchased Intangible Assets	'
	Goodwill and Purchased Intangible Assets
	We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. When evaluating whether goodwill is impaired, we 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 recognized during 2013, 2012 or 2011. Purchased intangible assets with finite lives are carried at cost, less accumulated amortization. Amortization is recorded over the estimated useful lives of the respective assets, which is 2.5 to 14 years.
Research and Development Costs	'
	Research and Development Costs
	Research and development costs include compensation for engineers and support personnel, outside contracted services, depreciation and material costs associated with new product development, the enhancement of current products, and product cost reductions. We continually evaluate new product opportunities and engage in intensive research and product development efforts. Research and development costs totaled $131.1 million, $126.0 million and $100.3 million for the years ended December 31, 2013, 2012 and 2011, respectively.
Other Comprehensive Income	'
	Other Comprehensive Income
	Other comprehensive income consists of unrealized gains (losses) on available-for-sale securities, reclassification adjustments for amounts included in net income related to impairments of available-for-sale securities and realized gains (losses) on available-for-sale securities, defined benefit plan adjustments and foreign currency translation adjustments.
	The following tables present changes in accumulated other comprehensive income, net of tax, by component for the years ended December 31, 2011, 2012 and 2013:
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains (Losses)			Benefit Plan			Currency
		on Available-			Adjustments			Adjustments
		for-Sale
		Securities
	Balance at December 31, 2010	$	23,852		$	—		$	3,096		$	26,948
	Other comprehensive loss before reclassifications		(6,784	)		—			(154	)		(6,938	)
	Amounts reclassified from accumulated other comprehensive income		(6,908	)		—			—			(6,908	)
	Balance at December 31, 2011	$	10,160		$	—		$	2,942		$	13,102
	Other comprehensive income (loss) before reclassifications		5,426			(1,952	)		170			3,644
	Amounts reclassified from accumulated other comprehensive income		(5,478	)		—			—			(5,478	)
	Balance at December 31, 2012	$	10,108		$	(1,952	)	$	3,112		$	11,268
	Other comprehensive income (loss) before reclassifications		5,508			1,061			(2,205	)		4,364
	Amounts reclassified from accumulated other comprehensive income		(4,879	)		—			—			(4,879	)
	Balance at December 31, 2013	$	10,737		$	(891	)	$	907		$	10,753
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)	2013
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income Is
		Comprehensive Income			Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	8,023		Net realized investment gain
	Impairment expense		(25	)	Net realized investment gain
	Total reclassifications for the period, before tax		7,998
	Tax (expense) benefit		(3,119	)
	Total reclassifications for the period, net of tax	$	4,879
	(In thousands)	2012
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income
		Comprehensive Income			Is Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	9,662		Net realized investment gain
	Impairment expense		(682	)	Net realized investment gain
	Total reclassifications for the period, before tax		8,980
	Tax (expense) benefit		(3,502	)
	Total reclassifications for the period, net of tax	$	5,478
	(In thousands)	2011
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income
		Comprehensive Income			Is Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	11,393		Net realized investment gain
	Impairment expense		(68	)	Net realized investment gain
	Total reclassifications for the period, before tax		11,325
	Tax (expense) benefit		(4,417	)
	Total reclassifications for the period, net of tax	$	6,908
	The following tables present the tax effects related to the change in each component of other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
		2013
	(In thousands)	Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount
					Benefit
	Unrealized gains (losses) on available-for-sale securities	$	9,030		$	(3,522	)	$	5,508
	Reclassification adjustment for amounts included in net income		(7,998	)		3,119			(4,879	)
	Defined benefit plan adjustments		1,061			—			1,061
	Foreign currency translation adjustment		(2,205	)		—			(2,205	)
	Total Other Comprehensive Income (Loss)	$	(112	)	$	(403	)	$	(515	)
		2012
	(In thousands)	Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount
					Benefit
Unrealized gains (losses) on available-for-sale securities	$	8,895		$	(3,469	)	$	5,426
Reclassification adjustment for amounts included in net income		(8,980	)		3,502			(5,478	)
Defined benefit plan adjustments		(1,952	)		—			(1,952	)
Foreign currency translation adjustment		170			—			170
Total Other Comprehensive Income (Loss)	$	(1,867	)	$	33		$	(1,834	)
	2011
(In thousands)	Before-Tax			Tax			Net-of-Tax
	Amount			(Expense)			Amount
				Benefit
Unrealized gains (losses) on available-for-sale securities	$	(11,121	)	$	4,337		$	(6,784	)
Reclassification adjustment for amounts included in net income		(11,325	)		4,417			(6,908	)
Foreign currency translation adjustment		(154	)		—			(154	)
Total Other Comprehensive Income (Loss)	$	(22,600	)	$	8,754		$	(13,846	)
Income Taxes	'
	Income Taxes
	The provision for income taxes has been determined using the asset and liability approach of accounting for income taxes. Under this approach, deferred taxes represent the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. The provision for income taxes represents income taxes paid or payable for the current year plus the change in deferred taxes during the year. Deferred taxes result from the difference between financial and tax bases of our assets and liabilities and are adjusted for changes in tax rates and tax laws when such changes are enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized.
	We establish reserves to remove some or all of the tax benefit of any of our tax positions at the time we determine that the positions become uncertain. We adjust these reserves, including any impact on the related interest and penalties, as facts and circumstances change.
Foreign Currency	'
	Foreign Currency
	We record transactions denominated in foreign currencies on a monthly basis using exchange rates from throughout the year. Assets and liabilities denominated in foreign currencies are translated at the balance sheet dates using the closing rates of exchange between those foreign currencies and the U.S. dollar with any transaction gains or losses reported in other income (expense). Adjustments resulting from translating financial statements of international subsidiaries are recorded as a component of accumulated other comprehensive income (loss).
Revenue Recognition	'
	Revenue Recognition
	Revenue is generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the product price is fixed or determinable, collection of the resulting receivable is reasonably assured, and product returns are reasonably estimable. For product sales, revenue is generally recognized upon shipment of the product to our customer in accordance with the title transfer terms of the sales agreement, generally FOB shipping point. In the case of consigned inventory, revenue is recognized when the end customer assumes ownership of the product. Contracts that contain multiple deliverables are evaluated to determine the units of accounting, and the consideration from the arrangement is allocated to each unit of accounting based on the relative selling price and corresponding terms of the contract. We use vendor-specific objective evidence of selling price. When this evidence is not available, we are generally not able to determine third-party evidence of selling price because of the extent of customization among competing products or services from other companies. We record revenue associated with installation services when all contractual obligations are complete. In instances where customer acceptance is required, revenue is deferred until all acceptance criteria have been met. Contracts that include both installation services and product sales are evaluated for revenue recognition in accordance with contract terms. As a result, depending on contract terms, installation services may be considered a separate deliverable or may be considered a combined single unit of accounting with the delivered product. Generally, either the purchaser, ADTRAN, or a third party can perform the installation of our products. Shipping fees are recorded as revenue and the related cost is included in cost of sales. Sales taxes invoiced to customers are included in revenues, and represent less than one percent of total revenues. The corresponding sales taxes paid are included in cost of goods sold. Value added taxes collected from customers in international jurisdictions are recorded in accrued expenses as a liability. Revenue is recorded net of discounts. Sales returns are accrued based on historical sales return experience, which we believe provides a reasonable estimate of future returns.
	A portion of Enterprise Networks products are sold to a non-exclusive distribution network of major technology distributors in the United States. These large organizations then distribute or provide fulfillment services to an extensive network of value-added resellers and system integrators. Value-added resellers and system integrators may be affiliated with us as a channel partner, or they may purchase from the distributor in an unaffiliated fashion. Additionally, with certain limitations our distributors may return unused and unopened product for stock-balancing purposes when such returns are accompanied by offsetting orders for products of equal or greater value.
	We participate in cooperative advertising and market development programs with certain customers. We use these programs to reimburse customers for certain forms of advertising, and in general, to allow our customers credits up to a specified percentage of their net purchases. Our costs associated with these programs are estimated and included in marketing expenses in our consolidated statements of income. We also participate in rebate programs to provide sales incentives for certain products. Our costs associated with these programs are estimated and accrued at the time of sale, and are recorded as a reduction of sales in our consolidated statements of income.
Unearned Revenue	'
	Unearned Revenue
	Unearned revenue primarily represents customer billings on our maintenance service programs and unearned revenues relating to multiple element contracts where we still have contractual obligations to our customers. We currently offer maintenance contracts ranging from one to five years, primarily on Enterprise Networks Division products sold through distribution channels. Revenue attributable to maintenance contracts is recognized on a straight-line basis over the related contract term. In addition, we provide software maintenance and a variety of hardware maintenance services to Carrier Networks Division customers, which include customers of the acquired NSN BBA business, under contracts with terms up to ten years. At December 31, 2013 and 2012, unearned revenue was as follows:
	(In thousands)	2013			2012
	Current unearned revenue	$	22,205		$	35,326
	Non-current unearned revenue		14,643			22,377
	Total	$	36,848		$	57,703
Other Income (Expense), Net	'
	Other Income (Expense), Net
	Other income (expense), net, is comprised primarily of miscellaneous income and expense, gains and losses on foreign currency transactions, investment account management fees, and gains or losses on the disposal of property, plant and equipment occurring in the normal course of business.
Earnings Per Share	'
	Earnings per Share
	Earnings per common share, and earnings per common share assuming dilution, are based on the weighted average number of common shares and, when dilutive, common equivalent shares outstanding during the year. See Note 14 of Notes to Consolidated Financial Statements for additional information.
Dividends	'
	Dividends
	The Board of Directors presently anticipates that it will declare a regular quarterly dividend as long as the current tax treatment of dividends exists and adequate levels of liquidity are maintained. During the years ended December 31, 2013, 2012 and 2011, we paid $21.4 million, $22.8 million and $23.1 million, respectively, in shareholder dividends. On January 21, 2014, the Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to shareholders of record at the close of business on February 6, 2014. The ex-dividend date was February 4, 2014 and the payment date was February 20, 2014. The quarterly dividend payment was $5.1 million.
Business Combinations	'
	Business Combinations
	We use the acquisition method to account for business combinations. Under the acquisition method of accounting, we recognize the assets acquired and liabilities assumed at their fair value on the acquisition date. Goodwill is measured as the excess of the consideration transferred over the net assets acquired. Costs incurred to complete the business combination, such as legal, accounting or other professional fees, are charged to general and administrative expenses as they are incurred.
Recently Issued Accounting Standards	'
	Recently Issued Accounting Standards
	During 2013, we adopted the following accounting standards, 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 years ended December 31, 2013, 2012 and 2011 in Note 1 of Notes to Consolidated Financial Statements.

Nature_of_Business_and_Summary2

Nature of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Summary of Warranty Expense and Write-Off Activity	'
	A summary of warranty expense and write-off activity for the years ended December 31, 2013 and 2012 is as follows:
	Year Ended December 31,	2013			2012
	(In thousands)
	Balance at beginning of period	$	9,653		$	4,118
	Plus: Amounts charged to cost and expenses		4,051			5,363
	Amounts assumed on acquisition		—			3,781
	Less: Deductions		(4,727	)		(3,609	)
	Balance at end of period	$	8,977		$	9,653
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 years ended December 31, 2011, 2012 and 2013:
	(In thousands)	Unrealized			Defined			Foreign			Total
		Gains (Losses)			Benefit Plan			Currency
		on Available-			Adjustments			Adjustments
		for-Sale
		Securities
	Balance at December 31, 2010	$	23,852		$	—		$	3,096		$	26,948
	Other comprehensive loss before reclassifications		(6,784	)		—			(154	)		(6,938	)
	Amounts reclassified from accumulated other comprehensive income		(6,908	)		—			—			(6,908	)
	Balance at December 31, 2011	$	10,160		$	—		$	2,942		$	13,102
	Other comprehensive income (loss) before reclassifications		5,426			(1,952	)		170			3,644
	Amounts reclassified from accumulated other comprehensive income		(5,478	)		—			—			(5,478	)
	Balance at December 31, 2012	$	10,108		$	(1,952	)	$	3,112		$	11,268
	Other comprehensive income (loss) before reclassifications		5,508			1,061			(2,205	)		4,364
	Amounts reclassified from accumulated other comprehensive income		(4,879	)		—			—			(4,879	)
	Balance at December 31, 2013	$	10,737		$	(891	)	$	907		$	10,753
Reclassifications Out of Accumulated Other Comprehensive Income	'
	The following tables present the details of reclassifications out of accumulated other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)	2013
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income Is
		Comprehensive Income			Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	8,023		Net realized investment gain
	Impairment expense		(25	)	Net realized investment gain
	Total reclassifications for the period, before tax		7,998
	Tax (expense) benefit		(3,119	)
	Total reclassifications for the period, net of tax	$	4,879
	(In thousands)	2012
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income
		Comprehensive Income			Is Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	9,662		Net realized investment gain
	Impairment expense		(682	)	Net realized investment gain
	Total reclassifications for the period, before tax		8,980
	Tax (expense) benefit		(3,502	)
	Total reclassifications for the period, net of tax	$	5,478
	(In thousands)	2011
	Details about Accumulated Other Comprehensive	Amount Reclassified			Affected Line Item in the
	Income Components	from Accumulated Other			Statement Where Net Income
		Comprehensive Income			Is Presented
	Unrealized gains (losses) on available-for-sale securities:
	Net realized gain on sales of securities	$	11,393		Net realized investment gain
	Impairment expense		(68	)	Net realized investment gain
	Total reclassifications for the period, before tax		11,325
	Tax (expense) benefit		(4,417	)
	Total reclassifications for the period, net of tax	$	6,908
Other Comprehensive Income	'
	The following tables present the tax effects related to the change in each component of other comprehensive income for the years ended December 31, 2013, 2012 and 2011:
		2013
	(In thousands)	Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount
					Benefit
	Unrealized gains (losses) on available-for-sale securities	$	9,030		$	(3,522	)	$	5,508
	Reclassification adjustment for amounts included in net income		(7,998	)		3,119			(4,879	)
	Defined benefit plan adjustments		1,061			—			1,061
	Foreign currency translation adjustment		(2,205	)		—			(2,205	)
	Total Other Comprehensive Income (Loss)	$	(112	)	$	(403	)	$	(515	)
		2012
	(In thousands)	Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount
					Benefit
	Unrealized gains (losses) on available-for-sale securities	$	8,895		$	(3,469	)	$	5,426
	Reclassification adjustment for amounts included in net income		(8,980	)		3,502			(5,478	)
	Defined benefit plan adjustments		(1,952	)		—			(1,952	)
	Foreign currency translation adjustment		170			—			170
	Total Other Comprehensive Income (Loss)	$	(1,867	)	$	33		$	(1,834	)
		2011
	(In thousands)	Before-Tax			Tax			Net-of-Tax
		Amount			(Expense)			Amount
					Benefit
	Unrealized gains (losses) on available-for-sale securities	$	(11,121	)	$	4,337		$	(6,784	)
	Reclassification adjustment for amounts included in net income		(11,325	)		4,417			(6,908	)
	Foreign currency translation adjustment		(154	)		—			(154	)
	Total Other Comprehensive Income (Loss)	$	(22,600	)	$	8,754		$	(13,846	)
Unearned Revenue	'
	At December 31, 2013 and 2012, unearned revenue was as follows:
	(In thousands)	2013			2012
	Current unearned revenue	$	22,205		$	35,326
	Non-current unearned revenue		14,643			22,377
	Total	$	36,848		$	57,703

Business_Combinations_Tables

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2013
Supplemental Pro Forma Information	'
	This supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition of the NSN BBA business been completed on January 1, 2011, nor are they indicative of any future results.
	(In thousands) (Unaudited)	2012			2011
	Pro forma revenue	$	119,600		$	196,256
	Pro forma pre-tax loss	$	(23,621	)	$	(36,980	)
	Weighted average exchange rate during the period (EURO/USD)	€	1.00/$1.29		€	1.00/$1.38
Nokia Siemens Networks [Member]	'
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		(3,361	)
	Accrued wages and benefits		(2,251	)
	Deferred tax liability		(788	)
	Non-current unearned revenue		(19,886	)
	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	)
Bluesocket [Member]	'
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)
	Cash	$	1,027
	Accounts receivable		298
	Inventory		792
	Prepaid expenses		357
	Property, plant and equipment		173
	Deferred tax assets, net		12,962
	Accounts payable		(441	)
	Unearned revenue		(600	)
	Accrued expenses		(332	)
	Net assets acquired		14,236
	Customer relationships		1,530
	Developed technology		3,230
	Intellectual property		930
	Trade names		270
	Goodwill		3,492
	Total purchase price	$	23,688

Stock_Incentive_Plans_Tables

Stock Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2013
Summary of Stock Options Outstanding	'
	The following table is a summary of our stock options outstanding as of December 31, 2012 and 2013 and the changes that occurred during 2013:
	(In thousands, except per share amounts)	Number of			Weighted			Weighted Avg.			Aggregate
		Options			Average			Remaining			Intrinsic Value
					Exercise Price			Contractual Life
								in Years
	Options outstanding, December 31, 2012		6,035		$	24.81			6.69		$	5,154
	Options granted		1,005		$	23.64
	Options cancelled/forfeited		(491	)	$	29.6
	Options exercised		(191	)	$	19.07
	Options outstanding, December 31, 2013		6,358		$	24.43			6.6		$	25,878
	Options exercisable, December 31, 2013		3,911		$	24.75			5.19		$	15,336
Stock Options Outstanding	'
	The following table further describes our stock options outstanding as of December 31, 2013:
		Options Outstanding									Options Exercisable
	Range of	Options			Weighted Avg.			Weighted			Options		Weighted
	Exercise Prices	Outstanding at			Remaining			Average			Exercisable at		Average
		12/31/13			Contractual Life			Exercise			12/31/13		Exercise
		(In thousands)			in Years			Price			(In thousands)		Price
	$14.88 – 18.07		1,456			7.42		$	16.37			742	$	15.79
	$18.08 – 23.36		1,002			3.04		$	22.59			1,001	$	22.59
	$23.37 – 26.06		1,745			8.1		$	23.6			745	$	23.54
	$26.07 – 30.04		466			3.59		$	29.39			383	$	29.71
	$30.05 – 30.36		905			7.67		$	30.36			454	$	30.36
	$30.37 – 41.92		784			6.84		$	33.78			586	$	33.76
			6,358									3,911
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 2013 and the changes that occurred during 2013:
	(In thousands, except per share amounts)	Number of			Weighted
		shares			Average Grant
					Date Fair Value
	Unvested RSUs and restricted stock outstanding, December 31, 2012		103		$	29.25
	RSUs and restricted stock granted		41		$	27.47
	RSUs and restricted stock vested		(39	)	$	29.42
	Adjustments to shares granted due to shares earned at vesting		(10	)	$	39.21
	Unvested RSUs and restricted stock outstanding, December 31, 2013		95		$	28.38
Stock-Based Compensation Expense Related to Stock Options, RSUs and Restricted Stock	'
	The following table summarizes stock-based compensation expense related to stock options, RSUs and restricted stock for the years ended December 31, 2013, 2012 and 2011, which was recognized as follows:
	(In thousands)	2013			2012			2011
	Stock-based compensation expense included in cost of sales	$	465		$	422		$	412
	Selling, general and administrative expense		4,443			4,351			4,316
	Research and development expense		4,165			4,491			4,441
	Stock-based compensation expense included in operating expenses		8,608			8,842			8,757
	Total stock-based compensation expense		9,073			9,264			9,169
	Tax benefit for expense associated with non-qualified options		(1,298	)		(1,234	)		(1,321	)
	Total stock-based compensation expense, net of tax	$	7,775		$	8,030		$	7,848
Stock Options [Member]	'
Summary of Weighted-Average Assumptions and Value of Options Granted	'
	The weighted-average estimated fair value of stock options granted to employees and directors during the years ended December 31, 2013, 2012 and 2011 was $8.35 per share, $5.60 per share and $9.53 per share, respectively, with the following weighted-average assumptions:
		2013			2012			2011
	Expected volatility		39.92	%		39.46	%		38.32	%
	Risk-free interest rate		1.71	%		0.96	%		1.01	%
	Expected dividend yield		1.52	%		2.05	%		1.19	%
	Expected life (in years)		6.36			6.18			5.15
Restricted Stock Units (RSUs) [Member]	'
Summary of Weighted-Average Assumptions and Value of Options Granted	'
	The RSU pricing model also requires the use of several significant assumptions that impact the fair value estimate. The estimated fair value of the RSUs granted to employees during the years ended December 31, 2013, 2012 and 2011 was $27.72 per share, $19.46 per share and $38.73 per share, respectively, with the following assumptions:
		2013			2012			2011
	Expected volatility		38.83	%		37.75	%		39.32	%
	Risk-free interest rate		0.61	%		0.38	%		0.37	%
	Expected dividend yield		1.52	%		2.12	%		1.08	%

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]	'
Securities and Investments, Recorded at Either Fair Value or Cost	'
	At December 31, 2013, we held the following securities and investments, recorded at either fair value or cost:
		Amortized			Gross Unrealized						Fair Value /
		Cost									Carrying
	(In thousands)				Gains			Losses			Value
	Deferred compensation plan assets	$	12,300		$	2,847		$	(24	)	$	15,123
	Corporate bonds		166,370			534			(45	)		166,859
	Municipal fixed-rate bonds		135,773			583			(54	)		136,302
	Municipal variable rate demand notes		8,310			—			—			8,310
	Marketable equity securities		24,654			13,975			(177	)		38,452
	Available-for-sale securities held at fair value	$	347,407		$	17,939		$	(300	)	$	365,046
	Restricted investment held at cost											48,250
	Other investments held at cost											1,689
	Total carrying value of available-for-sale investments										$	414,985
	At December 31, 2012, we held the following securities and investments, recorded at either fair value or cost:
		Amortized			Gross Unrealized						Fair Value /
		Cost									Carrying
	(In thousands)				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 December 31, 2013, corporate and municipal fixed-rate bonds had the following contractual maturities:
	(In thousands)	Corporate			Municipal
		bonds			fixed-rate bonds
	Less than one year	$	55,396		$	46,606
	One to two years		37,838			25,284
	Two to three years		70,447			55,358
	Three to five years		3,178			9,054
	Total	$	166,859		$	136,302
Gross Realized Gains and Losses on Sale of Securities	'
	The following table presents gross realized gains and losses related to our investments for the years ended December 31, 2013, 2012 and 2011:
	Year Ended December 31,	2013			2012			2011
	(In thousands)
	Gross realized gains	$	8,932		$	11,006		$	13,641
	Gross realized losses	$	(318	)	$	(1,456	)	$	(1,187	)
Breakdown of Investments with Unrealized Losses	'
	The following table presents the breakdown of investments with unrealized losses at December 31, 2013:
	(In thousands)	Continuous Unrealized						Continuous Unrealized						Total
		Loss Position for Less						Loss Position for 12
		than 12 Months						Months or Greater
		Fair Value			Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
	Deferred compensation plan assets	$	48		$	(6	)	$	409		$	(18	)	$	457	$	(24	)
	Corporate bonds		20,697			(45	)		—			—			20,697		(45	)
	Municipal fixed-rate bonds		13,733			(54	)		—			—			13,733		(54	)
	Marketable equity securities		2,758			(173	)		31			(4	)		2,789		(177	)
	Total	$	37,236		$	(278	)	$	440		$	(22	)	$	37,676	$	(300	)
	The following table presents the breakdown of investments with unrealized losses at December 31, 2012.
	(In thousands)	Continuous Unrealized						Continuous Unrealized						Total
		Loss Position for Less						Loss Position for 12
		than 12 Months						Months or Greater
		Fair Value			Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
	Deferred compensation plan assets	$	915		$	(7	)	$	—		$	—		$	915	$	(7	)
	Corporate bonds		20,204			(17	)		1,600			(1	)		21,804		(18	)
	Municipal fixed-rate bonds		34,297			(73	)		—			—			34,297		(73	)
	Marketable equity securities		6,171			(355	)		230			(37	)		6,401		(392	)
	Total	$	61,587		$	(452	)	$	1,830		$	(38	)	$	63,417	$	(490	)
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 for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
		Fair Value Measurements at December 31, 2013 Using
	(In thousands)	Fair Value			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Markets for			Observable			Inputs
					Identical Assets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Cash equivalents
	Money market funds	$	3,949		$	3,949		$	—		$	—
	Available-for-sale securities
	Deferred compensation plan assets		15,123			15,123			—			—
	Available-for-sale debt securities
	Corporate bonds		166,859			—			166,859			—
	Municipal fixed-rate bonds		136,302			—			136,302			—
	Municipal variable rate demand notes		8,310			—			8,310			—
	Available-for-sale marketable equity securities
	Marketable equity securities – technology industry		11,398			11,398			—			—
	Marketable equity securities – other		27,054			27,054			—			—
	Available-for-sale securities		365,046			53,575			311,471			—
	Total	$	368,995		$	57,524		$	311,471		$	—
		Fair Value Measurements at December 31, 2012 Using
	(In thousands)	Fair Value			Quoted Prices			Significant			Significant
					in Active			Other			Unobservable
					Markets for			Observable			Inputs
					Identical Assets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	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
	Marketable equity securities – technology industry		14,099			14,099			—			—
	Marketable 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)	12 Months Ended
	Dec. 31, 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 December 31, 2013 were as follows:
		December 31, 2013
	(In thousands)	Balance Sheet	Fair Value
		Location
	Derivatives Not Designated as Hedging Instruments (Level 2):
	Foreign exchange contracts – asset derivatives	Other receivables	$	18
	Foreign exchange contracts – liability derivatives	Accounts payable	$	(15	)
Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income	'
	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the year ended December 31, 2013 were as follows:
	(In thousands)	Income Statement	2013
		Location
	Derivatives Not Designated as Hedging Instruments:
	Foreign exchange contracts	Other income (expense)	$	750

Inventory_Tables

Inventory (Tables)	12 Months Ended
	Dec. 31, 2013
Inventory Disclosure [Abstract]	'
Components of Inventory	'
	At December 31, 2013 and 2012, inventory was comprised of the following:
	(In thousands)	2013		2012
	Raw materials	$	44,093	$	47,054
	Work in process		3,484		3,262
	Finished goods		42,534		51,061
	Total Inventory, net	$	90,111	$	101,377

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Property, Plant and Equipment	'
	At December 31, 2013 and 2012, property, plant and equipment were comprised of the following:
	(In thousands)	2013			2012
	Land	$	4,263		$	4,263
	Building and land improvements		21,776			20,915
	Building		68,479			68,479
	Furniture and fixtures		16,465			16,631
	Computer hardware and software		70,468			68,596
	Engineering and other equipment		104,584			99,081
	Total Property, Plant and Equipment		286,035			277,965
	Less accumulated depreciation		(209,296	)		(197,719	)
	Total Property, Plant and Equipment, net	$	76,739		$	80,246

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Changes in Carrying Value of Goodwill	'
	The changes in the carrying value of goodwill, all of which is included in our Enterprise Networks division, for the year ended December 31, 2013 are as follows:
	(In thousands)
	Balance, December 31, 2012	$	3,492
	Acquisitions		—
	Impairment losses		—
	Balance, December 31, 2013	$	3,492
	Balance as of December 31, 2013:
	Goodwill	$	3,492
	Accumulated impairment losses		—
	Total goodwill	$	3,492
Summary of Intangible Assets	'
	The following table presents our intangible assets as of December 31, 2013 and 2012:
	(In thousands)	2013							2012
		Gross Value		Accumulated			Net Value		Gross		Accumulated			Net Value
				Amortization					Value		Amortization
	Customer relationships	$	6,996	$	(1,555	)	$	5,441	$	6,769	$	(766	)	$	6,003
	Developed technology		6,537		(2,692	)		3,845		6,397		(1,354	)		5,043
	Intellectual property		2,340		(1,185	)		1,155		2,340		(851	)		1,489
	Trade names		270		(145	)		125		270		(85	)		185
	Other		14		(8	)		6		13		(3	)		10
	Total	$	16,157	$	(5,585	)	$	10,572	$	15,789	$	(3,059	)	$	12,730
Estimated Future Amortization Expense Related to Intangible Assets	'
	As of December 31, 2013, the estimated future amortization expense of intangible assets is as follows:
	(In thousands)	Amount
	2014	$	2,335
	2015		2,199
	2016		1,925
	2017		1,302
	2018		784
	Thereafter		2,027
	Total	$	10,572

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Summary of Components of Provision for Income Taxes	'
	A summary of the components of the provision for income taxes for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands)	2013			2012			2011
	Current
	Federal	$	15,641		$	26,225		$	59,382
	State		2,041			3,766			7,177
	International		1,437			(504	)		431
	Total Current		19,119			29,487			66,990
	Deferred
	Federal		(3,606	)		(3,395	)		527
	State		(412	)		(388	)		60
	International		(40	)		(2	)		(12	)
	Total Deferred		(4,058	)		(3,785	)		575
	Total Provision for Income Taxes	$	15,061		$	25,702		$	67,565
Effective Income Tax Rate Differs from Federal Statutory Rate	'
	Our effective income tax rate differs from the federal statutory rate due to the following:
		2013			2012			2011
	Tax provision computed at the federal statutory rate		35	%		35	%		35	%
	State income tax provision, net of federal benefit		3.98			3.78			3.19
	Federal research credits		(9.24	)		—			(2.50	)
	International		(2.93	)		3.8			—
	Tax-exempt income		(1.11	)		(1.01	)		(0.27	)
	State tax incentives		(2.19	)		(4.46	)		(0.90	)
	Stock-based compensation		2.97			2.36			0.03
	Domestic production activity deduction		(1.80	)		(3.21	)		(1.84	)
	Other, net		0.07			(1.03	)		0.07
	Effective Tax Rate		24.75	%		35.23	%		32.78	%
Income Before Provision for Income Taxes	'
	Income before provision for income taxes for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands)	2013			2012			2011
	U.S. entities	$	51,752		$	80,926		$	204,652
	International entities		9,103			(7,961	)		1,490
	Total	$	60,855		$	72,965		$	206,142
Principal Components of Current and Non-current Deferred Taxes	'
	Deferred income taxes on the balance sheet result from temporary differences between the amount of assets and liabilities recognized for financial reporting and tax purposes. The principal components of our current and non-current deferred taxes are as follows:
	(In thousands)	2013			2012
	Current deferred tax assets
	Accounts receivable	$	51		$	2
	Inventory		9,877			7,507
	Accrued expenses		7,155			5,546
	Total Current Deferred Tax Assets		17,083			13,055
	Non-current deferred tax assets
	Accrued expenses		140			116
	Deferred compensation		5,972			4,456
	Stock-based compensation		5,331			4,569
	Uncertain tax positions related to state taxes and related interest		1,107			1,005
	Pensions		301			605
	Foreign losses		5,702			6,978
	State losses and credit carry-forwards		3,737			4,349
	Federal loss and research carry-forwards		8,322			12,210
	Valuation allowance		(8,842	)		(10,939	)
	Total Non-current Deferred Tax Assets		21,770			23,349
	Total Deferred Tax Assets	$	38,853		$	36,404
	Non-current deferred tax liabilities
	Property, plant and equipment	$	(5,499	)	$	(6,405	)
	Intellectual property		(1,006	)		(1,839	)
	Investments		(5,643	)		(4,844	)
	Total Non-current Deferred Tax Liabilities	$	(12,148	)	$	(13,088	)
	Net Deferred Tax Assets	$	26,705		$	23,316
Change in Unrecognized Income Tax Benefits	'
	The change in the unrecognized income tax benefits for 2013, 2012 and 2011 is reconciled below:
	(In thousands)	2013			2012			2011
	Balance at beginning of period	$	2,926		$	2,970		$	2,593
	Increases for tax position related to:
	Prior years		89			965			—
	Current year		549			302			840
	Decreases for tax positions related to:
	Prior years		—			(49	)		(92	)
	Settlements with taxing authorities		(141	)		(507	)		(354	)
	Expiration of applicable statute of limitations		(183	)		(755	)		(17	)
	Balance at end of period	$	3,240		$	2,926		$	2,970

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]	'
Schedule of Pension Benefit Plan Obligations and Funded Status	'
	The pension benefit plan obligations and funded status at December 31, 2013 and 2012, are as follows:
	(In thousands)	2013			2012
	Change in projected benefit obligation:
	Projected benefit obligation at beginning of period	$	(21,181	)	$	—
	Business combination		—			(18,063	)
	Service cost		(1,198	)		(766	)
	Interest cost		(745	)		(494	)
	Actuarial gain (loss)		779			(1,862	)
	Benefit payments		(1	)		—
	Foreign currency exchange rate changes		(1,008	)		4
	Projected benefit obligation at end of period	$	(23,354	)	$	(21,181	)
	Change in plan assets:
	Fair value of plan assets at beginning of period	$	18,620		$	—
	Business combination		—			18,063
	Actual return on plan assets		1,281			592
	Foreign currency exchange rate changes		872			(35	)
	Fair value of plan assets at end of period	$	20,773		$	18,620
	Funded status at end of period	$	(2,581	)	$	(2,561	)
Summary of Net Amounts Recognized Balance Sheet for the Unfunded Pension Liability	'
	The net amounts recognized in the balance sheet for the unfunded pension liability as of December 31, 2013 and 2012 are as follows:
	(In thousands)	2013			2012
	Current liability	$	—		$	(609	)
	Non-current liability		(2,581	)		(1,952	)
	Total	$	(2,581	)	$	(2,561	)
Components of Net Periodic Pension Cost and Amounts Recognized Other Comprehensive Income	'
	The components of net periodic pension cost and amounts recognized in other comprehensive income for the year ended December 31, 2013 and the period May 4, 2012 to December 31, 2012 are as follows:
	(In thousands)	Year Ended			May 4, 2012 to
		December 31, 2013			December 31, 2012
	Net periodic benefit cost:
	Service cost	$	1,198		$	766
	Interest cost		745			494
	Expected return on plan assets		(1,010	)		(674	)
	Net periodic benefit cost		933			586
	Other changes in plan assets and benefit obligations recognized in other comprehensive income:
	Net actuarial (gain) loss		(779	)		1,862
	Net unrealized (gain) loss on plan assets		(282	)		90
	Other comprehensive (income) loss		(1,061	)		1,952
	Total recognized in net periodic benefit cost and other comprehensive income	$	(128	)	$	2,538
Accumulated Other Comprehensive Income	'
	The amounts recognized in accumulated other comprehensive income as of December 31, 2013 and 2012 are as follows:
	(In thousands)	2013			2012
	Net actuarial (gain) loss	$	1,083		$	1,862
	Net unrealized (gain) loss on plan assets		(192	)		90
	Total	$	891		$	1,952
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost	'
	The weighted-average assumptions that were used to determine the net periodic benefit cost for the year ended December 31, 2013 and the period May 4, 2012 to December 31, 2012 are as follows:
		Year Ended			May 4, 2012 to
		December 31, 2013			December 31, 2012
	Discount rates		3.5	%		3.96	%
	Rate of compensation increase		2.25	%		2.25	%
	Expected long-term rates of return		5.4	%		5.4	%
Weighted-Average Assumptions Used to Determine Benefit Obligation	'
	The weighted-average assumptions that were used to determine the benefit obligation at December 31, 2013 and 2012:
		2013			2012
	Discount rates		3.7	%		3.5	%
	Rate of compensation increase		2.25	%		2.25	%
Schedule of Pension Benefit Payments Expected Future Service	'
	The following pension benefit payments, which reflect expected future service, as appropriate, are expected to be paid to participants:
	(In thousands)
	2014	$	357
	2015		312
	2016		223
	2017		390
	2018		650
	2019 – 2023		4,427
	Total	$	6,359
Schedule of Cash Equivalents and Investments Held at Fair Value	'
	We have categorized our cash equivalents and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1—Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2—Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3—Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees.
					Fair Value Measurements at December 31, 2013 Using
	(In thousands)	Fair Value			Quoted Prices			Significant		Significant
					in Active			Other		Unobservable
					Markets for			Observable		Inputs
					Identical Assets			Inputs		(Level 3)
					(Level 1)			(Level 2)
	Cash equivalents	$	4		$	4		$	—	$	—
	Available-for-sale securities
	Bond funds:
	Corporate bonds		12,976			12,976			—		—
	Government bonds		1,915			1,915			—		—
	Equity funds:
	Large cap blend		4,720			4,720			—		—
	Large cap value		287			287			—		—
	Balanced fund		871			871			—		—
	Available-for-sale securities		20,769			20,769			—		—
	Total	$	20,773		$	20,773		$	—	$	—
					Fair Value Measurements at December 31, 2012 Using
	(In thousands)	Fair Value			Quoted Prices			Significant		Significant
					in Active			Other		Unobservable
					Markets for			Observable		Inputs
					Identical Assets			Inputs		(Level 3)
					(Level 1)			(Level 2)
	Cash equivalents	$	6		$	6		$	—	$	—
	Available-for-sale securities
	Bond funds:
	Corporate bonds		12,041			12,041			—		—
	Government bonds		1,839			1,839			—		—
	Equity funds:
	Large cap blend		3,740			3,740			—		—
	Large cap value		235			235			—		—
	Balanced fund		759			759			—		—
	Available-for-sale securities		18,614			18,614			—		—
	Total	$	18,620		$	18,620		$	—	$	—
Fair Value of Assets Held by Trust and Amounts Payable to Plan Participants	'
	The fair value of the assets held by the Trust and the amounts payable to the plan participants are as follows:
	(In thousands)	2013			2012
	Fair Value of Plan Assets
	Long-term Investments	$	15,123		$	11,527
	Total Fair Value of Plan Assets	$	15,123		$	11,527
	Amounts Payable to Plan Participants
	Non-current Liabilities	$	15,123		$	11,527
	Total Amounts Payable to Plan Participants	$	15,123		$	11,527

Segment_Information_and_Major_1

Segment Information and Major Customers (Tables)	12 Months Ended
	Dec. 31, 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 each of the years ended December 31, 2013, 2012 and 2011. Asset information by reportable segment is not reported, since we do not produce such information internally.
	Sales and Gross Profit by Market Segment
	(In thousands)	2013				2012				2011
		Sales		Gross Profit		Sales		Gross Profit		Sales		Gross Profit
	Carrier Networks	$	500,733	$	233,206	$	492,096	$	247,380	$	569,579	$	327,813
	Enterprise Networks		141,011		75,680		128,518		69,263		147,650		86,505
	Total	$	641,744	$	308,886	$	620,614	$	316,643	$	717,229	$	414,318
Sales Information by Product Category	'
	The table below presents sales information by product category for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)	2013		2012		2011
	Carrier Systems	$	427,850	$	399,646	$	420,289
	Business Networking		168,871		149,304		162,186
	Loop Access		45,023		71,664		134,754
	Total	$	641,744	$	620,614	$	717,229
Subcategory Revenues	'
	The table below presents subcategory revenues for the years ended December 31, 2013, 2012 and 2011:
	(In thousands)	2013		2012		2011
	Core Products
	Broadband Access (included in Carrier Systems)	$	340,560	$	320,076	$	289,776
	Optical (included in Carrier Systems)		55,615		51,755		82,535
	Internetworking (NetVanta® & Multi-service Access Gateways) (included in Business Networking)		164,422		142,958		151,536
	Subtotal	$	560,597	$	514,789	$	523,847
	Legacy Products
	HDSL (does not include T1) (included in Loop Access)		41,666		66,974		126,976
	Other products (excluding HDSL)		39,481		38,851		66,406
	Subtotal	$	81,147	$	105,825	$	193,382
	Total	$	641,744	$	620,614	$	717,229
Sales Information by Geographic Area	'
	The following table presents sales information by geographic area for the years ended December 31, 2013, 2012 and 2011. International sales correlate to shipments with a non-U.S. destination.
	(In thousands)	2013		2012		2011
	United States	$	455,996	$	470,369	$	632,795
	Germany		97,151		26,918		554
	Other international		88,597		123,327		83,880
	Total	$	641,744	$	620,614	$	717,229

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Future Minimum Rental Payments under Non-Cancelable Operating Leases with Original Maturities of Greater than 12 Months	'
	As of December 31, 2013, future minimum rental payments under non-cancelable operating leases with original maturities of greater than 12 months are approximately as follows:
	(In thousands)
	2014	$	4,523
	2015		3,556
	2016		2,506
	2017		2,156
	Thereafter		686
	Total	$	13,427

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Summary of Calculation of Basic and Diluted Earnings Per Share	'
	A summary of the calculation of basic and diluted earnings per share (EPS) for the years ended December 31, 2013, 2012 and 2011 is as follows:
	(In thousands, except for per share amounts)	2013		2012		2011
	Numerator
	Net Income	$	45,794	$	47,263	$	138,577
	Denominator
	Weighted average number of shares – basic		59,001		63,259		64,145
	Effect of dilutive securities:
	Stock options		390		488		1,236
	Restricted stock and restricted stock units		33		27		35
	Weighted average number of shares – diluted		59,424		63,774		65,416
	Net income per share – basic	$	0.78	$	0.75	$	2.16
	Net income per share – diluted	$	0.77	$	0.74	$	2.12

Summarized_Quarterly_Financial1

Summarized Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Operating Results	'
	The following table presents unaudited quarterly operating results for each of our last eight fiscal quarters.
	Unaudited Quarterly Operating Results
	(In thousands, except for per share amounts)
	Three Months Ended		March 31, 2013		June 30, 2013		September 30, 2013		December 31, 2013
	Net sales		$	143,013	$	162,233	$	177,404	$	159,094
	Gross profit		$	69,677	$	79,798	$	82,547	$	76,864
	Operating income		$	6,563	$	14,053	$	17,210	$	10,639
	Net income		$	7,890	$	9,859	$	16,205	$	11,840
	Earnings per common share		$	0.13	$	0.17	$	0.28	$	0.21
	Earnings per common share assuming dilution (1)		$	0.13	$	0.17	$	0.28	$	0.2
	Three Months Ended		31-Mar-12		30-Jun-12		30-Sep-12		31-Dec-12
	Net sales		$	134,735	$	183,998	$	162,125	$	139,756
	Gross profit		$	74,087	$	95,201	$	79,972	$	67,383
	Operating income		$	16,181	$	26,838	$	10,276	$	2,874
	Net income		$	12,960	$	21,070	$	9,272	$	3,961
	Earnings per common share		$	0.2	$	0.33	$	0.15	$	0.06
	Earnings per common share assuming dilution (1)		$	0.2	$	0.33	$	0.15	$	0.06
	(1)	Assumes exercise of dilutive stock options calculated under the treasury stock method.

Nature_of_Business_and_Summary3

Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2008

Jan. 13, 1995

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jan. 21, 2014

Feb. 20, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Dec. 31, 2011

Customer

Customer

Employees

Minimum [Member]

Maximum [Member]

Building and Land Improvements [Member]

Building and Land Improvements [Member]

Office Machinery and Equipment [Member]

Office Machinery and Equipment [Member]

Engineering Machinery and Equipment [Member]

Engineering Machinery and Equipment [Member]

Computer Software [Member]

Computer Software [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Credit Concentration Risk [Member]

Credit Concentration Risk [Member]

Immaterial Corrections [Member]

Adjustments to Assets [Member]

Adjustments to Liabilities [Member]

Adjustments to Operating Activities [Member]

Adjustments to Operating Activities [Member]

Adjustments to Investing Activities [Member]

Adjustments to Investing Activities [Member]

Employees

Employees

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

OptionPlans

Summary of Significant Accounting Policy [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prior period reclassification adjustment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

($2,700,000)

($2,700,000)

$200,000

($100,000)

($200,000)

$100,000

Understatement of net income of previous year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000

'

'

'

'

'

'

Original maturity period of cash and cash equivalents

'Three months or less

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash, uninsured amount

53,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Bonds payable, carrying amount

46,500,000

'

'

50,000,000

20,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Bonds payable, fair value

45,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of customers accounting for 13.1 and 10.4 percent of accounts receivable

1

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of accounts receivable accounted by each customers

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13.10%

10.40%

'

'

'

'

'

'

'

Allowance for doubtful accounts

130,000

6,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property, plant and equipment, estimated useful lives

'

'

'

'

'

'

'

'5 years

'39 years

'3 years

'7 years

'3 years

'7 years

'3 years

'5 years

'

'

'

'

'

'

'

'

'

'

'

Period of warranty for product defects

'90 days to ten years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Liability for warranty obligations

8,977,000

9,653,000

4,118,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of stock option plans

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of executive officers

5

5

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Performance period

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of restricted stock units granted

'

'

'

'

'

0.00%

150.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation expense

9,100,000

9,300,000

9,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total compensation cost related to non-vested stock options, restricted stock units and restricted stock not yet recognized

18,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recognition period of non-vested compensation cost

'2 years 8 months 12 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment losses recognized on long-lived assets

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment losses recognized on goodwill and other intangible assets

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amortization, estimated useful lives

'

'

'

'

'

'2 years 6 months

'14 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Research and development costs

131,055,000

125,951,000

100,301,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of sales taxes collected from customers

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maintenance contract period

'

'

'

'

'

'1 year

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividend payments

21,400,000

22,800,000

23,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock dividends per share declared

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$0.09

'

'

'

'

'

'

'

'

'

'

Quarterly dividend payable subsequent to balance sheet date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5,100,000

'

'

'

'

'

'

'

'

'

Dividends payable, date declared

21-Jan-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Record date for dividend payments

6-Feb-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash dividend payment date

20-Feb-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ex-dividend date

4-Feb-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nature_of_Business_and_Summary4

Nature of Business and Summary of Significant Accounting Policies - Summary of Warranty Expense and Write-Off Activity (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]	'	'
Balance at beginning of period	$9,653	$4,118
Plus: Amounts charged to cost and expenses	4,051	5,363
Amounts assumed on acquisition	'	3,781
Less: Deductions	-4,727	-3,609
Balance at end of period	$8,977	$9,653

Nature_of_Business_and_Summary5

Nature of Business and Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning balance	$11,268	$13,102	$26,948
Other comprehensive income (loss) before reclassifications	4,364	3,644	-6,938
Amounts reclassified from accumulated other comprehensive income	-4,879	-5,478	-6,908
Ending balance	10,753	11,268	13,102
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning balance	10,108	10,160	23,852
Other comprehensive income (loss) before reclassifications	5,508	5,426	-6,784
Amounts reclassified from accumulated other comprehensive income	-4,879	-5,478	-6,908
Ending balance	10,737	10,108	10,160
Defined Benefit Plan Adjustments [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning balance	-1,952	'	'
Other comprehensive income (loss) before reclassifications	1,061	-1,952	'
Ending balance	-891	-1,952	'
Foreign Currency Adjustments [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning balance	3,112	2,942	3,096
Other comprehensive income (loss) before reclassifications	-2,205	170	-154
Ending balance	$907	$3,112	$2,942

Nature_of_Business_and_Summary6

Nature of Business and Summary of Significant Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized gain on sales of securities	'	'	'	'	'	'	'	'	$8,614	$9,550	$12,454
Total reclassifications for the period, before tax	'	'	'	'	'	'	'	'	60,855	72,965	206,142
Tax (expense) benefit	'	'	'	'	'	'	'	'	-15,061	-25,702	-67,565
Total reclassifications for the period, net of tax	11,840	16,205	9,859	7,890	3,961	9,272	21,070	12,960	45,794	47,263	138,577
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	'	'	'	'	'	'	'	'	7,998	8,980	11,325
Tax (expense) benefit	'	'	'	'	'	'	'	'	-3,119	-3,502	-4,417
Total reclassifications for the period, net of tax	'	'	'	'	'	'	'	'	4,879	5,478	6,908
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 gain on sales of securities	'	'	'	'	'	'	'	'	8,023	9,662	11,393
Impairment Expense [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]	'	'	'	'	'	'	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized gain on sales of securities	'	'	'	'	'	'	'	'	($25)	($682)	($68)

Nature_of_Business_and_Summary7

Nature of Business and Summary of Significant Accounting Policies - Other Comprehensive Income (Detail) (USD $)	8 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounting Policies [Abstract]	'	'	'	'
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	'	$9,030	$8,895	($11,121)
Reclassification adjustment for amounts included in net income, Before-Tax Amount	'	-7,998	-8,980	-11,325
Defined benefit plan adjustments, Before-Tax Amount	'	1,061	-1,952	'
Foreign currency translation adjustment, Before-Tax Amount	'	-2,205	170	-154
Total Other Comprehensive Income (Loss), Before-Tax Amount	'	-112	-1,867	-22,600
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	'	-3,522	-3,469	4,337
Reclassification adjustment for amounts included in net income, Tax (Expense) Benefit	'	3,119	3,502	4,417
Defined benefit plan adjustments, Tax (Expense) Benefit	'	'	'	'
Foreign currency translation adjustment, Tax (Expense) Benefit	'	'	'	'
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	'	-403	33	8,754
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	'	5,508	5,426	-6,784
Reclassification adjustment for amounts included in net income, Net-of-Tax Amount	'	-4,879	-5,478	-6,908
Defined benefit plan adjustments, Net-of-Tax Amount	-1,952	1,061	-1,952	'
Foreign currency translation adjustment, Net-of-Tax Amount	'	-2,205	170	-154
Other Comprehensive Income (Loss), net of tax	'	($515)	($1,834)	($13,846)

Nature_of_Business_and_Summary8

Nature of Business and Summary of Significant Accounting Policies - Unearned Revenue (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Current unearned revenue	$22,205	$35,326
Non-current unearned revenue	14,643	22,377
Total	$36,848	$57,703

Business_Combinations_Addition

Business Combinations - Additional Information (Detail) (USD $)

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2012

Dec. 31, 2013

4-May-12

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Aug. 04, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Customer Relationships [Member]

Developed Technology [Member]

Customer Relationships [Member]

Developed Technology [Member]

Intellectual Property [Member]

Trade Names [Member]

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase price, net of consideration

'

'

($7,496,000)

'

'

'

'

$23,688,000

'

'

'

'

'

'

'

Bargain purchase gain, net of tax

1,753,000

'

1,800,000

'

'

'

'

'

'

'

'

'

'

'

'

Average estimated useful life

'

'

'

'

'

'13 years

'5 years

'

'

'

'

'7 years

'4 years 6 months

'7 years

'4 years 6 months

Acquisition and integration related expenses and amortization of acquired intangibles

'

'

'

2,900,000

7,900,000

'

'

'

'

'

'

'

'

'

'

Acquisition cost

'

'

'

'

'

'

'

23,700,000

'

'

'

'

'

'

'

Goodwill

3,492,000

3,492,000

'

'

'

'

'

3,492,000

3,500,000

'

'

'

'

'

'

Acquisition and integration related expenses and amortization of acquired intangibles

'

'

'

'

'

'

'

'

$1,100,000

$1,500,000

$1,700,000

'

'

'

'

Business_Combinations_Allocati

Business Combinations - Allocation of Purchase Price to Estimated Fair Value of Assets Acquired and Liabilities Assumed at Acquisition Date (Detail) (USD $)

Dec. 31, 2013

Dec. 31, 2012

4-May-12

4-May-12

4-May-12

4-May-12

Dec. 31, 2013

Aug. 04, 2011

Aug. 04, 2011

Aug. 04, 2011

Aug. 04, 2011

Aug. 04, 2011

In Thousands, unless otherwise specified

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Nokia Siemens Networks [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Bluesocket [Member]

Customer Relationships [Member]

Developed Technology [Member]

Other [Member]

Customer Relationships [Member]

Developed Technology [Member]

Intellectual Property [Member]

Trade Names [Member]

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Cash

'

'

'

'

'

'

'

$1,027

'

'

'

'

Goodwill

3,492

3,492

'

'

'

'

3,500

3,492

'

'

'

'

Accounts receivable

'

'

9,486

'

'

'

'

298

'

'

'

'

Inventory

'

'

21,068

'

'

'

'

792

'

'

'

'

Prepaid expenses

'

'

'

'

'

'

'

357

'

'

'

'

Property, plant and equipment

'

'

5,035

'

'

'

'

173

'

'

'

'

Deferred tax assets, net

'

'

'

'

'

'

'

12,962

'

'

'

'

Accounts payable

'

'

-5,194

'

'

'

'

-441

'

'

'

'

Unearned revenue

'

'

-18,203

'

'

'

'

-600

'

'

'

'

Accrued expenses

'

'

-3,361

'

'

'

'

-332

'

'

'

'

Accrued wages and benefits

'

'

-2,251

'

'

'

'

'

'

'

'

'

Net assets acquired

'

'

'

'

'

'

'

14,236

'

'

'

'

Deferred tax liability

'

'

-788

'

'

'

'

'

'

'

'

'

Non-current unearned revenue

'

'

-19,886

'

'

'

'

'

'

'

'

'

Net liabilities assumed

'

'

-14,094

'

'

'

'

'

'

'

'

'

Intangible assets

'

'

'

5,162

3,176

13

'

'

1,530

3,230

930

270

Gain on bargain purchase of a business, net of tax

'

'

-1,753

'

'

'

'

'

'

'

'

'

Net consideration received from seller

'

'

($7,496)

'

'

'

'

$23,688

'

'

'

'

Business_Combinations_Suppleme

Business Combinations - Supplemental Pro Forma Information (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011
	USD ($)	EUR (€)	USD ($)	EUR (€)
Business Combinations [Abstract]	'	'	'	'
Pro forma revenue	$119,600,000	'	$196,256,000	'
Pro forma pre-tax loss	-23,621,000	'	-36,980,000	'
Weighted average exchange rate during the period (EURO/USD)	$1.29	€ 1	$1.38	€ 1

Stock_Incentive_Plans_Addition

Stock Incentive Plans - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

In Millions, except Per Share data, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Nov. 06, 2008

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

2006 Employee Stock Incentive Plan other than Options [Member]

2006 Employee Stock Incentive Plan other than Options [Member]

1996 Employee Incentive Stock Option Plan [Member]

1996 Employee Incentive Stock Option Plan [Member]

1996 Employee Incentive Stock Option Plan [Member]

2006 Employee Stock Incentive Plan [Member]

2006 Employee Stock Incentive Plan [Member]

2006 Employee Stock Incentive Plan [Member]

2010 Directors Stock Plan [Member]

2010 Directors Stock Plan [Member]

2010 Directors Stock Plan [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

RSUs and Restricted Stock [Member]

Restricted Stock [Member]

Non Vested Stock Options [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares of common stock authorized

'

'

'

'

'

17

'

'

13

'

'

0.5

'

'

'

'

'

'

'

'

Vesting period

'

'

'

'

'

'

'4 years

'5 years

'4 years

'

'

'

'

'

'3 years

'

'

'

'

'

Contractual term

'10 years

'

'

'

'

'10 years

'

'

'10 years

'

'

'10 years

'

'

'

'

'

'

'

'

Expiration date of options

'

'

'

'

'

'

'2014

'2015

'

'2016

'2023

'

'2014

'2019

'

'

'

'

'

'

Number of shares available for grant

6

'

'

3.3

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total pre-tax intrinsic value of options exercised

$1.10

$4.50

$39.80

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of options fully vested

7.7

7.7

7.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares granted for issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13

'

'

'

'

'

Minimum earn out percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

'

'

'

'

'

Maximum earn out percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

150.00%

'

'

'

'

'

Unamortized compensation cost

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.7

'

'

Recognition period of non-vested compensation cost

'2 years 8 months 12 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'1 year 10 months 24 days

'2 years 9 months 18 days

Total stock-based compensation cost not yet recognized

$18.80

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$17.10

Weighted-average estimated value

$8.35

$5.60

$9.53

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average grant date fair value, RSUs granted

$27.47

'

'

'

'

'

'

'

'

'

'

'

'

'

$27.72

$19.46

$38.73

'

'

'

Estimated forfeitures for stock options

2.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Forfeitures rate for RSUs and restricted stock units

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

'

'

Stock_Incentive_Plans_Summary_

Stock Incentive Plans - Summary of Stock Options Outstanding (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Number of Options, outstanding, Beginning Balance	6,035	'
Number of Options, granted	1,005	'
Number of Options, cancelled/forfeited	-491	'
Number of Options, exercised	-191	'
Number of Options, outstanding, Ending Balance	6,358	6,035
Number of Options, Options exercisable	3,911	'
Weighted Average Exercise Price, outstanding, Beginning Balance	$24.81	'
Weighted Average Exercise Price, granted	$23.64	'
Weighted Average Exercise Price, cancelled/forfeited	$29.60	'
Weighted Average Exercise Price, exercised	$19.07	'
Weighted Average Exercise Price, outstanding, Ending Balance	$24.43	$24.81
Weighted Average Exercise Price, Options Exercisable	$24.75	'
Weighted Average Remaining Contractual Life In Years, Options outstanding	'6 years 7 months 6 days	'6 years 8 months 9 days
Weighted Average Remaining Contractual Life In Years, Options exercisable	'5 years 2 months 9 days	'
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$5,154	'
Aggregate Intrinsic Value, Options outstanding, Ending Balance	25,878	5,154
Aggregate Intrinsic Value, Options exercisable	$15,336	'

Stock_Incentive_Plans_Stock_Op

Stock Incentive Plans - Stock Options Outstanding (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified			$14.88 - 18.07 [Member]	$18.08 - 23.36 [Member]	$23.37 - 26.06 [Member]	$26.07 - 30.04 [Member]	$30.05 - 30.36 [Member]	$30.37 - 41.92 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'	'	'	'	'
Lower Range Limit	'	'	$14.88	$18.08	$23.37	$26.07	$30.05	$30.37
Upper Range Limit	'	'	$18.07	$23.36	$26.06	$30.04	$30.36	$41.92
Options Outstanding at 12/31/13	6,358	6,035	1,456	1,002	1,745	466	905	784
Weighted Avg. Remaining Contractual Life In Years, Options Outstanding	'	'	'7 years 5 months 1 day	'3 years 15 days	'8 years 1 month 6 days	'3 years 7 months 2 days	'7 years 8 months 1 day	'6 years 10 months 2 days
Weighted Average Exercise Price, Options Outstanding	'	'	$16.37	$22.59	$23.60	$29.39	$30.36	$33.78
Options Exercisable at 12/31/13	3,911	'	742	1,001	745	383	454	586
Weighted Average Exercise Price, Options Exercisable	$24.75	'	$15.79	$22.59	$23.54	$29.71	$30.36	$33.76

Stock_Incentive_Plans_Summary_1

Stock Incentive Plans - Summary of RSUs and Restricted Stock Outstanding (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 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	41
Number of RSUs and restricted stock vested	-39
Number of Unvested RSUs and restricted stock outstanding, Adjustments to shares granted due to shares earned at vesting	-10
Number of Unvested RSUs and restricted stock outstanding, ending balance	95
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	$27.47
Weighted Average Grant Date Fair Value, RSUs and restricted stock vested	$29.42
Weighted Average Grant Date Fair Value, Adjustments to shares granted due to shares earned at vesting	$39.21
Weighted Average Grant Date Fair Value, Unvested RSUs and restricted stock outstanding, Ending balance	$28.38

Stock_Incentive_Plans_StockBas

Stock Incentive Plans - Stock-Based Compensation Expense Related to Stock Options, RSUs and Restricted Stock (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	$9,073	$9,264	$9,169
Tax benefit for expense associated with non-qualified options	-1,298	-1,234	-1,321
Total stock-based compensation expense, net of tax	7,775	8,030	7,848
Cost of Sales [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	465	422	412
Selling, General and Administrative Expense [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	4,443	4,351	4,316
Research and Development Expense [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	4,165	4,491	4,441
Operating Expenses [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	$8,608	$8,842	$8,757

Stock_Incentive_Plans_Summary_2

Stock Incentive Plans - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Options [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Expected volatility	39.92%	39.46%	38.32%
Risk-free interest rate	1.71%	0.96%	1.01%
Expected dividend yield	1.52%	2.05%	1.19%
Expected life (in years)	'6 years 4 months 10 days	'6 years 2 months 5 days	'5 years 1 month 24 days
Restricted Stock Units (RSUs) [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Expected volatility	38.83%	37.75%	39.32%
Risk-free interest rate	0.61%	0.38%	0.37%
Expected dividend yield	1.52%	2.12%	1.08%

Investments_Securities_and_Inv

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$347,407	$426,467
Gross Unrealized Gains	17,939	17,081
Gross Unrealized Losses	-300	-490
Available-for-sale-securities, Fair Value/Carrying Value	365,046	443,058
Restricted investment held at cost	48,250	48,250
Other investments held at cost	1,689	1,902
Total carrying value of available-for-sale investments	414,985	493,210
Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	12,300	10,688
Gross Unrealized Gains	2,847	846
Gross Unrealized Losses	-24	-7
Available-for-sale-securities, Fair Value/Carrying Value	15,123	11,527
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	166,370	185,464
Gross Unrealized Gains	534	966
Gross Unrealized Losses	-45	-18
Available-for-sale-securities, Fair Value/Carrying Value	166,859	186,412
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	135,773	174,530
Gross Unrealized Gains	583	627
Gross Unrealized Losses	-54	-73
Available-for-sale-securities, Fair Value/Carrying Value	136,302	175,084
Municipal Variable Rate Demand Notes [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	8,310	34,375
Available-for-sale-securities, Fair Value/Carrying Value	8,310	34,375
Fixed Income Bond Fund [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	'	444
Gross Unrealized Gains	'	12
Available-for-sale-securities, Fair Value/Carrying Value	'	456
Marketable Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	24,654	20,966
Gross Unrealized Gains	13,975	14,630
Gross Unrealized Losses	-177	-392
Available-for-sale-securities, Fair Value/Carrying Value	$38,452	$35,204

Investments_Contractual_Maturi

Investments - Contractual Maturities of Corporate and Municipal Fixed-Rate Bonds (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale-securities, Fair Value/Carrying Value	$365,046	$443,058
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	55,396	'
One to two years	37,838	'
Two to three years	70,447	'
Three to five years	3,178	'
Available-for-sale-securities, Fair Value/Carrying Value	166,859	186,412
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year	46,606	'
One to two years	25,284	'
Two to three years	55,358	'
Three to five years	9,054	'
Available-for-sale-securities, Fair Value/Carrying Value	$136,302	$175,084

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
		Securities
Schedule of Investments [Line Items]	'	'	'	'
Identification of potential other-than-temporary impairments	'	25.00%	'	'
Impairment of investments	$11	$25	$700	$68
Number of marketable equity securities in an unrealized loss position	'	168	'	'
Investment [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Investment concentration risk percentage	'	5.00%	'	'

Investments_Gross_Realized_Gai

Investments - Gross Realized Gains and Losses on Sale of Securities (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Debt And Equity Securities [Abstract]	'	'	'
Gross realized gains	$8,932	$11,006	$13,641
Gross realized losses	($318)	($1,456)	($1,187)

Investments_Breakdown_of_Inves

Investments - Breakdown of Investments with Unrealized Losses (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	$37,236	$61,587
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	-278	-452
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	440	1,830
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	-22	-38
Total Fair Value	37,676	63,417
Total Unrealized Losses	-300	-490
Deferred Compensation Plan Assets [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	48	915
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	-6	-7
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	409	'
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	-18	'
Total Fair Value	457	915
Total Unrealized Losses	-24	-7
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	20,697	20,204
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	-45	-17
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	'	1,600
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	'	-1
Total Fair Value	20,697	21,804
Total Unrealized Losses	-45	-18
Municipal Fixed-Rate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	13,733	34,297
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	-54	-73
Total Fair Value	13,733	34,297
Total Unrealized Losses	-54	-73
Marketable Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	2,758	6,171
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	-173	-355
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	31	230
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	-4	-37
Total Fair Value	2,789	6,401
Total Unrealized Losses	($177)	($392)

Investments_Fair_Value_Measure

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	$365,046	$443,058
Fair Value, Measurements, Recurring [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	365,046	443,058
Total	368,995	471,129
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	53,575	47,187
Total	57,524	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	311,471	395,871
Total	311,471	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	3,949	28,071
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Cash equivalents	3,949	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	15,123	11,527
Fair Value, Measurements, Recurring [Member] | Deferred Compensation Plan Assets [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	15,123	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	166,859	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	166,859	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	136,302	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	136,302	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	8,310	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	8,310	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 Markets 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] | Marketable Equity Securities - Technology Industry [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	11,398	14,099
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	11,398	14,099
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Technology Industry [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	27,054	21,105
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	27,054	21,105
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities - Other [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale securities	'	'

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities - Additional Information (Detail)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
		Forward Contracts [Member]	Forward Contracts [Member]
		USD ($)	EUR (€)
Derivative [Line Items]	'	'	'
Maximum contractual period for derivatives	'12 months	'	'
Derivative, notional amount	'	$25.50	€ 18.50
Derivative maturity year	'	'2014	'2014

Derivative_Instruments_and_Hed3

Derivative Instruments and Hedging Activities - Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) (Significant Other Observable Inputs (Level 2) [Member], Foreign Exchange Contracts [Member], USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Receivables [Member]	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'
Derivatives asset, fair value	$18
Accounts Payable [Member]	'
Derivatives Not Designated as Hedging Instruments (Level 2):	'
Derivatives liability, fair value	($15)

Derivative_Instruments_and_Hed4

Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail) (Foreign Exchange Contracts [Member], Other Income (Expense) [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]	'
Derivatives Not Designated as Hedging Instruments:	'
Derivative instrument, gain or loss	$750

Inventory_Components_of_Invent

Inventory - Components of Inventory (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials	$44,093	$47,054
Work in process	3,484	3,262
Finished goods	42,534	51,061
Total Inventory, net	$90,111	$101,377

Inventory_Additional_Informati

Inventory - Additional Information (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials reserves, total	$16.90	$9.90
Finished goods inventory reserves, total	$6.10	$2.10

Property_Plant_and_Equipment_P

Property, Plant and Equipment - Property, Plant and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property Plant And Equipment [Abstract]	'	'
Land	$4,263	$4,263
Building and land improvements	21,776	20,915
Building	68,479	68,479
Furniture and fixtures	16,465	16,631
Computer hardware and software	70,468	68,596
Engineering and other equipment	104,584	99,081
Total Property, Plant and Equipment	286,035	277,965
Less accumulated depreciation	-209,296	-197,719
Total Property, Plant and Equipment, net	$76,739	$80,246

Property_Plant_and_Equipment_A

Property, Plant and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property Plant And Equipment [Abstract]	'	'	'
Depreciation	$12.20	$12.10	$10.80

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Changes in Carrying Value of Goodwill (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Goodwill, Beginning balance	$3,492,000	'
Acquisitions	'	'
Impairment losses	0	0
Accumulated impairment losses	'	'
Goodwill, Ending balance	$3,492,000	$3,492,000

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill And Intangible Assets Disclosure [Abstract]	'	'	'
Impairment losses	$0	$0	'
Amortization expense	$2.40	$2	$0.70

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill [Line Items]	'	'
Gross Value	$16,157	$15,789
Accumulated Amortization	-5,585	-3,059
Net Value	10,572	12,730
Customer Relationships [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,996	6,769
Accumulated Amortization	-1,555	-766
Net Value	5,441	6,003
Developed Technology [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	6,537	6,397
Accumulated Amortization	-2,692	-1,354
Net Value	3,845	5,043
Intellectual Property [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	2,340	2,340
Accumulated Amortization	-1,185	-851
Net Value	1,155	1,489
Trade Names [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	270	270
Accumulated Amortization	-145	-85
Net Value	125	185
Other [Member]	'	'
Goodwill [Line Items]	'	'
Gross Value	14	13
Accumulated Amortization	-8	-3
Net Value	$6	$10

Goodwill_and_Intangible_Assets5

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
2014	$2,335	'
2015	2,199	'
2016	1,925	'
2017	1,302	'
2018	784	'
Thereafter	2,027	'
Net Value	$10,572	$12,730

Alabama_State_Industrial_Devel1

Alabama State Industrial Development Authority Financing and Economic Incentives - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2008	Jan. 13, 1995
Debt Instrument [Line Items]	'	'	'	'	'
Proceeds from state industrial development authority issued taxable bonds loaned to ADTRAN	$46,500,000	'	'	$50,000,000	$20,000,000
Percentage of interest on amended and restated bond	5.00%	'	'	'	'
Maturity date of amended and restated bond	1-Jan-20	'	'	'	'
Restricted certificate of deposit held	48,250,000	48,250,000	'	'	'
Total realized economic incentives	1,300,000	1,400,000	1,900,000	'	'
Bond debt outstanding classified as current liability	300,000	500,000	'	'	'
Payments on long-term debt	'	500,000	1,000,000	'	'
Significant Other Observable Inputs (Level 2) [Member] | US States and Political Subdivisions Debt Securities [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Estimated fair value of bond	$45,400,000	'	'	'	'

Income_Taxes_Summary_of_Compon

Income Taxes - Summary of Components of Provision for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current	'	'	'
Federal	$15,641	$26,225	$59,382
State	2,041	3,766	7,177
International	1,437	-504	431
Total Current	19,119	29,487	66,990
Deferred	'	'	'
Federal	-3,606	-3,395	527
State	-412	-388	60
International	-40	-2	-12
Total Deferred	-4,058	-3,785	575
Total Provision for Income Taxes	$15,061	$25,702	$67,565

Income_Taxes_Effective_Income_

Income Taxes - Effective Income Tax Rate Differs from Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Tax provision computed at the federal statutory rate	35.00%	35.00%	35.00%
State income tax provision, net of federal benefit	3.98%	3.78%	3.19%
Federal research credits	-9.24%	'	-2.50%
International	-2.93%	3.80%	'
Tax-exempt income	-1.11%	-1.01%	-0.27%
State tax incentives	-2.19%	-4.46%	-0.90%
Stock-based compensation	2.97%	2.36%	0.03%
Domestic production activity deduction	-1.80%	-3.21%	-1.84%
Other, net	0.07%	-1.03%	0.07%
Effective Tax Rate	24.75%	35.23%	32.78%

Income_Taxes_Income_Before_Pro

Income Taxes - Income Before Provision for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
U.S. entities	$51,752	$80,926	$204,652
International entities	9,103	-7,961	1,490
Income before provision for income taxes	$60,855	$72,965	$206,142

Income_Taxes_Principal_Compone

Income Taxes - Principal Components of Current and Non-current Deferred Taxes (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'
Accounts receivable	$51	$2
Inventory	9,877	7,507
Accrued expenses	7,155	5,546
Total Current Deferred Tax Assets	17,083	13,055
Accrued expenses	140	116
Deferred compensation	5,972	4,456
Stock-based compensation	5,331	4,569
Uncertain tax positions related to state taxes and related interest	1,107	1,005
Pensions	301	605
Foreign losses	5,702	6,978
State losses and credit carry-forwards	3,737	4,349
Federal loss and research carry-forwards	8,322	12,210
Valuation allowance	-8,842	-10,939
Total Non-current Deferred Tax Assets	21,770	23,349
Total Deferred Tax Assets	38,853	36,404
Property, plant and equipment	-5,499	-6,405
Intellectual property	-1,006	-1,839
Investments	-5,643	-4,844
Total Non-current Deferred Tax Liabilities	-12,148	-13,088
Net Deferred Tax Assets	$26,705	$23,316

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components Of Income Before Taxes [Line Items]	'	'	'	'
Deferred tax expense (benefit) provision recorded as an adjustment to other comprehensive income	$400,000	$33,000	'	'
Foreign and domestic loss, unamortized research and development cost and state credit carry-forwards	19,000,000	'	'	'
Income tax benefit from exercise of stock options	169,000	1,905,000	10,525,000	'
Unrecognized tax benefits	3,240,000	2,926,000	2,970,000	2,593,000
Unrecognized tax benefits, effective tax rate	2,500,000	2,200,000	2,400,000	'
Accrued interest and penalties	$1,000,000	$800,000	$1,200,000	'
Minimum [Member]	'	'	'	'
Components Of Income Before Taxes [Line Items]	'	'	'	'
Operating loss carry forwards expiration year	'2014	'	'	'
Maximum [Member]	'	'	'	'
Components Of Income Before Taxes [Line Items]	'	'	'	'
Operating loss carry forwards expiration year	'2030	'	'	'

Income_Taxes_Change_in_Unrecog

Income Taxes - Change in Unrecognized Income Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Balance at beginning of period	$2,926	$2,970	$2,593
Increases for tax position related to, Prior years	89	965	'
Increases for tax position related to, Current year	549	302	840
Decreases for tax positions related to, Prior years	'	-49	-92
Settlements with taxing authorities	-141	-507	-354
Expiration of applicable statute of limitations	-183	-755	-17
Balance at end of period	$3,240	$2,926	$2,970

Employee_Benefit_Plans_Schedul

Employee Benefit Plans - Schedule of Pension Benefit Plan Obligations and Funded Status (Detail) (USD $)	8 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Change in projected benefit obligation:	'	'	'
Projected benefit obligation at beginning of period	'	($21,181)	'
Business combination	'	'	-18,063
Service cost	-766	-1,198	-766
Interest cost	-494	-745	-494
Actuarial gain (loss)	'	779	-1,862
Benefit payments	'	-1	'
Foreign currency exchange rate changes	'	-1,008	4
Projected benefit obligation at end of period	-21,181	-23,354	-21,181
Change in plan assets:	'	'	'
Fair value of plan assets at beginning of period	'	18,620	'
Business combination	'	'	18,063
Actual return on plan assets	'	1,281	592
Foreign currency exchange rate changes	'	872	-35
Fair value of plan assets at end of period	18,620	20,773	18,620
Funded status at end of period	($2,561)	($2,581)	($2,561)

Employee_Benefit_Plans_Additio

Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Accumulated benefit obligation	$22,900,000	$20,800,000	'
Criteria of employer to contribute in employee saving plan	'100% of an employee's first 3% of contributions and 50% of their next 2% of contributions	'	'
Upper limit of employer match	4.00%	'	'
Maximum statutory compensation under code	255,000	'	'
Percentage contributions under the Savings Plan, vested	100.00%	'	'
Contributions and plan administration costs for savings plan	4,500,000	4,600,000	4,300,000
Maximum percentage of cash compensation allowed to be deferred under the deferred compensation plan	25.00%	'	'
Criteria for benefit distribution	'Six months after termination of employment in a single lump sum payment or annual installments paid over a three or ten year term.	'	'
Deferred compensation adjustments due to fair value of the trust assets	2,800,000	900,000	-200,000
Maximum number of years medical, dental and prescription drug coverage to spouse of deceased officer	'30 years	'	'
Total liability recorded to provide medical, dental and prescription drug coverage	200,000	200,000	'
Scenario, Forecast [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Amortization from accumulated other comprehensive income	$0	'	'
First Contributions [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of employer match to employee's contribution	100.00%	'	'
Second Contributions [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of employer match to employee's contribution	50.00%	'	'
Bond Funds [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of target allocation ranges by asset class	75.00%	'	'
Equity Funds [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of target allocation ranges by asset class	25.00%	'	'

Employee_Benefit_Plans_Summary

Employee Benefit Plans - Summary of Net Amounts Recognized Balance Sheet for the Unfunded Pension Liability (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Compensation And Retirement Disclosure [Abstract]	'	'
Current liability	'	($609)
Non-current liability	-2,581	-1,952
Total	($2,581)	($2,561)

Employee_Benefit_Plans_Compone

Employee Benefit Plans - Components of Net Periodic Pension Cost and Amounts Recognized Other Comprehensive Income (Detail) (USD $)	8 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Net periodic benefit cost:	'	'	'
Service cost	$766	$1,198	$766
Interest cost	494	745	494
Expected return on plan assets	-674	-1,010	'
Net periodic benefit cost	586	933	'
Other changes in plan assets and benefit obligations recognized in other comprehensive income:	'	'	'
Other comprehensive (income) loss	1,952	-1,061	1,952
Total recognized in net periodic benefit cost and other comprehensive income	2,538	-128	2,538
Net Actuarial (Gain) Loss [Member]	'	'	'
Other changes in plan assets and benefit obligations recognized in other comprehensive income:	'	'	'
Net (gain) loss	1,862	-779	1,862
Net Unrealized (Gain) Loss on Plan Assets [Member]	'	'	'
Other changes in plan assets and benefit obligations recognized in other comprehensive income:	'	'	'
Net (gain) loss	$90	($282)	$90

Employee_Benefit_Plans_Accumul

Employee Benefit Plans - Accumulated Other Comprehensive Income (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Compensation And Retirement Disclosure [Abstract]	'	'
Net actuarial (gain) loss	$1,083	$1,862
Net unrealized (gain) loss on plan assets	-192	90
Total	$891	$1,952

Employee_Benefit_Plans_Weighte

Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)	8 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]	'	'
Discount rates	3.96%	3.50%
Rate of compensation increase	2.25%	2.25%
Expected long-term rates of return	5.40%	5.40%

Employee_Benefit_Plans_Weighte1

Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Benefit Obligation (Detail)	Dec. 31, 2013	Dec. 31, 2012
Compensation And Retirement Disclosure [Abstract]	'	'
Discount rates	3.70%	3.50%
Rate of compensation increase	2.25%	2.25%

Employee_Benefit_Plans_Schedul1

Employee Benefit Plans - Schedule of Pension Benefit Payments Expected Future Service (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Compensation And Retirement Disclosure [Abstract]	'
2014	$357
2015	312
2016	223
2017	390
2018	650
2019 - 2023	4,427
Total	$6,359

Employee_Benefit_Plans_Schedul2

Employee Benefit Plans - Schedule of Cash Equivalents and Investments Held at Fair Value (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	$20,773	$18,620
Fair Value [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	20,773	18,620
Fair Value [Member] | Cash Equivalents [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	4	6
Fair Value [Member] | Bond Funds [Member] | Corporate Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	12,976	12,041
Fair Value [Member] | Bond Funds [Member] | Government Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	1,915	1,839
Fair Value [Member] | Equity Funds [Member] | Large Cap Blend [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	4,720	3,740
Fair Value [Member] | Equity Funds [Member] | Large Cap Value [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	287	235
Fair Value [Member] | Balanced Fund [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	871	759
Fair Value [Member] | Available-for-Sale Securities [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	20,769	18,614
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	20,773	18,620
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash Equivalents [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	4	6
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Bond Funds [Member] | Corporate Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	12,976	12,041
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Bond Funds [Member] | Government Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	1,915	1,839
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Funds [Member] | Large Cap Blend [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	4,720	3,740
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Funds [Member] | Large Cap Value [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	287	235
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Balanced Fund [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	871	759
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Available-for-Sale Securities [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	20,769	18,614
Significant Other Observable Inputs (Level 2) [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Cash Equivalents [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Bond Funds [Member] | Corporate Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Bond Funds [Member] | Government Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Equity Funds [Member] | Large Cap Blend [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Equity Funds [Member] | Large Cap Value [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Balanced Fund [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Other Observable Inputs (Level 2) [Member] | Available-for-Sale Securities [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Cash Equivalents [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Bond Funds [Member] | Corporate Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Bond Funds [Member] | Government Bonds [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Equity Funds [Member] | Large Cap Blend [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Equity Funds [Member] | Large Cap Value [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Balanced Fund [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Available-for-Sale Securities [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Available-for-sale securities	'	'

Employee_Benefit_Plans_Fair_Va

Employee Benefit Plans - Fair Value of Assets Held by Trust and Amounts Payable to Plan Participants (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]	'	'
Long-term Investments	$15,123	$11,527
Amounts Payable to Plan Participants Non-current Liabilities	15,123	11,527
Long-Term Investments [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Long-term Investments	15,123	11,527
Non-Current Liabilities [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Amounts Payable to Plan Participants Non-current Liabilities	$15,123	$11,527

Segment_Information_and_Major_2

Segment Information and Major Customers - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Product_Category	Customer	Customer
	Customer
	Segment
Segment Reporting Information [Line Items]	'	'	'
Number of operating reportable segments	2	'	'
Number of product categories	3	'	'
Number of other customers who accounted for more than threshold percentage of revenue	0	0	0
Number of single customer comprising more than 10% of revenue	2	1	2
Long-lived assets	$76,700,000	$80,200,000	'
Customer Concentration Risk [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Concentration risk, percentage	17.00%	23.00%	25.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | The Five Largest Customers Other Than Those With More Than 10% Of Revenues [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Concentration risk, percentage	22.00%	34.00%	29.00%
Customer Two Concentration Risk [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Concentration risk, percentage	14.00%	'	10.00%
Inter-Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Inter-segment revenues	0	'	'
United States [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Long-lived assets	71,200,000	73,900,000	'
Outside United States [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Long-lived assets	$5,500,000	$6,300,000	'

Segment_Information_and_Major_3

Segment Information and Major Customers - Sales and Gross Profit of Reportable Segments (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	$159,094	$177,404	$162,233	$143,013	$139,756	$162,125	$183,998	$134,735	$641,744	$620,614	$717,229
Gross profit	76,864	82,547	79,798	69,677	67,383	79,972	95,201	74,087	308,886	316,643	414,318
Carrier Networks [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	500,733	492,096	569,579
Gross profit	'	'	'	'	'	'	'	'	233,206	247,380	327,813
Enterprise Networks [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	141,011	128,518	147,650
Gross profit	'	'	'	'	'	'	'	'	$75,680	$69,263	$86,505

Segment_Information_and_Major_4

Segment Information and Major Customers - Sales Information by Product Category (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	$159,094	$177,404	$162,233	$143,013	$139,756	$162,125	$183,998	$134,735	$641,744	$620,614	$717,229
Carrier Systems [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	427,850	399,646	420,289
Business Networking [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	168,871	149,304	162,186
Loop Access [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	$45,023	$71,664	$134,754

Segment_Information_and_Major_5

Segment Information and Major Customers - Subcategory Revenues (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	$159,094	$177,404	$162,233	$143,013	$139,756	$162,125	$183,998	$134,735	$641,744	$620,614	$717,229
Core Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	560,597	514,789	523,847
Legacy Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	81,147	105,825	193,382
Broadband Access (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	340,560	320,076	289,776
Optical (Included in Carrier Systems) [Member] | Core Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	55,615	51,755	82,535
Internetworking (NetVanta & Multi-Service Access Gateways) (Included in Business Networking) [Member] | Core Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	164,422	142,958	151,536
HDSL (Does not Include T1) (Included in Loop Access) [Member] | Legacy Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	41,666	66,974	126,976
Other Products (Excluding HDSL) [Member] | Legacy Products [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	$39,481	$38,851	$66,406

Segment_Information_and_Major_6

Segment Information and Major Customers - Sales Information by Geographic Area (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	$159,094	$177,404	$162,233	$143,013	$139,756	$162,125	$183,998	$134,735	$641,744	$620,614	$717,229
United States [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	455,996	470,369	632,795
Germany [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	97,151	26,918	554
Other International [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Sales	'	'	'	'	'	'	'	'	$88,597	$123,327	$83,880

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments And Contingencies Disclosure [Abstract]	'	'	'
Operating leases expiration year	'2018	'	'
Rental expense	$4.80	$3.90	$2.40

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Rental Payments under Non-Cancelable Operating Leases with Original Maturities of Greater than 12 Months (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014	$4,523
2015	3,556
2016	2,506
2017	2,156
Thereafter	686
Total	$13,427

Earnings_Per_Share_Summary_of_

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator	'	'	'	'	'	'	'	'	'	'	'
Net Income	$11,840	$16,205	$9,859	$7,890	$3,961	$9,272	$21,070	$12,960	$45,794	$47,263	$138,577
Denominator	'	'	'	'	'	'	'	'	'	'	'
Weighted average number of shares - basic	'	'	'	'	'	'	'	'	59,001	63,259	64,145
Effect of dilutive securities:	'	'	'	'	'	'	'	'	'	'	'
Stock options	'	'	'	'	'	'	'	'	390	488	1,236
Restricted stock and restricted stock units	'	'	'	'	'	'	'	'	33	27	35
Weighted average number of shares - diluted	'	'	'	'	'	'	'	'	59,424	63,774	65,416
Net income per share - basic	$0.21	$0.28	$0.17	$0.13	$0.06	$0.15	$0.33	$0.20	$0.78	$0.75	$2.16
Net income per share - diluted	$0.20	$0.28	$0.17	$0.13	$0.06	$0.15	$0.33	$0.20	$0.77	$0.74	$2.12

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'
Anti dilutive options, Total	3.2	3.2	1.2

Summarized_Quarterly_Financial2

Summarized Quarterly Financial Data (Unaudited) - Quarterly Operating Results (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Net sales	$159,094	$177,404	$162,233	$143,013	$139,756	$162,125	$183,998	$134,735	$641,744	$620,614	$717,229
Gross profit	76,864	82,547	79,798	69,677	67,383	79,972	95,201	74,087	308,886	316,643	414,318
Operating income	10,639	17,210	14,053	6,563	2,874	10,276	26,838	16,181	48,465	56,169	189,138
Net Income	$11,840	$16,205	$9,859	$7,890	$3,961	$9,272	$21,070	$12,960	$45,794	$47,263	$138,577
Earnings per common share	$0.21	$0.28	$0.17	$0.13	$0.06	$0.15	$0.33	$0.20	$0.78	$0.75	$2.16
Earnings per common share assuming dilution	$0.20	$0.28	$0.17	$0.13	$0.06	$0.15	$0.33	$0.20	$0.77	$0.74	$2.12

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transactions [Abstract]	'	'	'
Related party legal fees per month	$10	$10	$10

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended		1 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 27, 2014	Jan. 21, 2014	Feb. 28, 2014	Feb. 20, 2014
				Subsequent Events [Member]	Subsequent Events [Member]	Subsequent Events [Member]	Subsequent Events [Member]
Subsequent Event [Line Items]	'	'	'	'	'	'	'
Dividend declaration date	21-Jan-14	'	'	'	'	'	'
Cash dividend per common share	'	'	'	'	$0.09	'	'
Dividend record date	6-Feb-14	'	'	'	'	'	'
Dividend payment date	20-Feb-14	'	'	'	'	'	'
Principal payment	'	'	'	'	'	$16.50	'
Cash dividend	'	'	'	'	'	'	$5.10
Stock repurchased, shares	5,608,000	1,786,000	1,112,000	400,000	'	'	'
Shares repurchased, average price per share	'	'	'	$25.13	'	'	'
Additional shares authorized for purchase	'	'	'	3,100,000	'	'	'

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Doubtful Accounts [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at beginning of period	$6	$8	$162
Charged to costs & expenses	136	38	117
Deductions	12	40	271
Balance at end of period	130	6	8
Inventory Reserve [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at beginning of period	11,957	9,419	8,932
Charged to costs & expenses	11,457	3,042	1,137
Deductions	421	504	650
Balance at end of period	22,993	11,957	9,419
Warranty Liability [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at beginning of period	9,653	4,118	3,304
Assumed on acquisition	'	3,781	33
Charged to costs & expenses	4,051	5,363	2,860
Deductions	4,727	3,609	2,079
Balance at end of period	8,977	9,653	4,118
Deferred Tax Asset Valuation Allowance [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at beginning of period	10,939	7,585	5,627
Assumed on acquisition	'	'	1,462
Charged to costs & expenses	-1,056	3,594	496
Deductions	1,041	240	'
Balance at end of period	$8,842	$10,939	$7,585