ADTRAN (ADTN) 10-K 25 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	ADTN
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 Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		48,086,618
Entity Public Float			$ 724,323,806
Entity Interactive Data Current	Yes
Entity File Number	000-24612
Entity Tax Identification Number	63-0918200
Entity Address, Address Line One	901 Explorer Boulevard
Entity Address, City or Town	Huntsville
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35806-2807
City Area Code	256
Local Phone Number	963-8000
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, Par Value $0.01
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Proxy Statement for the Annual Meeting of Stockholders to be held on May 13, 2020 are incorporated herein by reference in Part III.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 73,773	$ 105,504
Short-term investments	33,243	3,246
Accounts receivable, less allowance for doubtful accounts of $38 and $128 as of December 31, 2019 and 2018, respectively	90,531	99,385
Other receivables	16,566	36,699
Inventory, net	98,305	99,848
Prepaid expenses and other current assets	7,892	10,744
Total Current Assets	320,310	355,426
Property, plant and equipment, net	73,708	80,635
Deferred tax assets, net	7,561	37,187
Goodwill	6,968	7,106
Intangibles, net	27,821	33,183
Other assets	14,261	5,668
Long-term investments	94,489	108,822
Total Assets	545,118	628,027
Current Liabilities
Accounts payable	44,870	60,054
Bonds payable	24,600	1,000
Unearned revenue	11,963	17,940
Accrued expenses and other current liabilities	13,876	11,746
Accrued wages and benefits	13,890	14,752
Income tax payable, net	3,512	12,518
Total Current Liabilities	112,711	118,010
Non-current unearned revenue	6,012	5,296
Pension liability	15,886	13,086
Deferred compensation liability	21,698	18,256
Other non-current liabilities	8,385	2,500
Bonds payable		24,600
Total Liabilities	164,692	181,748
Commitments and contingencies (see Note 16)
Stockholders' Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 48,020 shares outstanding as of December 31, 2019 and 79,652 shares issued and 47,751 shares outstanding as of December 31, 2018	797	797
Additional paid-in capital	274,632	267,670
Accumulated other comprehensive loss	(16,417)	(14,416)
Retained earnings	806,702	883,975
Less treasury stock at cost: 31,638 and 31,901 shares as of December 31, 2019 and 2018, respectively	(685,288)	(691,747)
Total Stockholders' Equity	380,426	446,279
Total Liabilities and Stockholders' Equity	$ 545,118	$ 628,027

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 38	$ 128
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,652,000	79,652,000
Common stock, shares outstanding	48,020,000	47,751,000
Treasury stock, shares	31,638,000	31,901,000

Consolidated Statements of Inco

Consolidated Statements of Income (Loss) - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sales
Total Sales	$ 530,061,000	$ 529,277,000	$ 666,900,000
Cost of Sales
Total Cost of Sales	310,894,000	325,712,000	363,265,000
Gross Profit	219,167,000	203,565,000	303,635,000
Selling, general and administrative expenses	130,288,000	124,440,000	135,583,000
Research and development expenses	126,200,000	124,547,000	130,666,000
Asset impairments	3,872,000	0	0
Gain on contingency	(1,230,000)
Operating Income (Loss)	(39,963,000)	(45,422,000)	37,386,000
Interest and dividend income	2,765,000	4,026,000	4,380,000
Interest expense	(511,000)	(533,000)	(556,000)
Net investment gain (loss)	11,434,000	(4,050,000)	4,685,000
Other income (expense), net	1,498,000	1,286,000	(1,208,000)
Gain on bargain purchase of a business		11,322,000
Income (Loss) Before Income Taxes	(24,777,000)	(33,371,000)	44,687,000
Income tax (expense) benefit	(28,205,000)	14,029,000	(20,847,000)
Net Income (Loss)	$ (52,982,000)	$ (19,342,000)	$ 23,840,000
Weighted average shares outstanding – basic	47,836	47,880	48,153
Weighted average shares outstanding – diluted	47,836	47,880	48,699
Earnings (loss) per common share – basic	$ (1.11)	$ (0.40)	$ 0.50
Earnings (loss) per common share – diluted	$ (1.11)	$ (0.40)	$ 0.49
Network Solutions [Member]
Sales
Total Sales	$ 455,226,000	$ 458,232,000	$ 540,396,000
Cost of Sales
Total Cost of Sales	263,677,000	278,929,000	279,563,000
Gross Profit	191,549,000	179,303,000	260,833,000
Services & Support [Member]
Sales
Total Sales	74,835,000	71,045,000	126,504,000
Cost of Sales
Total Cost of Sales	47,217,000	46,783,000	83,702,000
Gross Profit	$ 27,618,000	$ 24,262,000	$ 42,802,000

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income (loss)	$ (52,982)	$ (19,342)	$ 23,840
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	279	(3,130)	2,163
Defined benefit plan adjustments	(1,185)	(3,755)	731
Foreign currency translation	(1,480)	(4,236)	5,999
Other Comprehensive Income (Loss), net of tax	(2,386)	(11,121)	8,893
Comprehensive Income (Loss), net of tax	$ (55,368)	$ (30,463)	$ 32,733

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2016	$ 479,517	$ 797	$ 252,957	$ 921,942	$ (683,991)	$ (12,188)
Beginning Balance, Shares at Dec. 31, 2016		79,652
Net income (loss)	23,840			23,840
Other comprehensive income (loss), net of tax	8,893					8,893
Dividend payments ($0.09 per share)	(17,368)			(17,368)
Dividends accrued on unvested restricted stock units	(37)			(37)
Stock options exercised	13,412			(2,827)	16,239
PSUs, RSUs and restricted stock vested	(441)			(3,257)	2,816
Purchase of treasury stock	(17,348)				(17,348)
Stock-based compensation expense	7,433		7,433
ASU 2016-09 adoption	10		125	(115)
Ending Balance at Dec. 31, 2017	497,911	$ 797	260,515	922,178	(682,284)	(3,295)
Ending Balance, Shares at Dec. 31, 2017		79,652
Net income (loss)	(19,342)			(19,342)
ASU adoption (see Note 1) | ASU 2014-09 [member]	278			278
ASU adoption (see Note 1) | ASU 2016-01 [Member]	3,220			3,220
Other comprehensive income (loss), net of tax	(11,121)					(11,121)
Dividend payments ($0.09 per share)	(17,267)			(17,267)
Dividends accrued on unvested restricted stock units	(7)			(7)
Stock options exercised	1,483			(603)	2,086
PSUs, RSUs and restricted stock vested	(499)			(4,482)	3,983
Purchase of treasury stock	(15,532)				(15,532)
Stock-based compensation expense	7,155		7,155
Ending Balance at Dec. 31, 2018	$ 446,279	$ 797	267,670	883,975	(691,747)	(14,416)
Ending Balance, Shares at Dec. 31, 2018	79,652	79,652
Net income (loss)	$ (52,982)			(52,982)
ASU adoption (see Note 1) | ASU 2016-02 [member]	4			4
ASU adoption (see Note 1) | ASU 2018-02 [Member]				(385)		385
Other comprehensive income (loss), net of tax	(2,386)					(2,386)
Dividend payments ($0.09 per share)	(17,212)			(17,212)
Dividends accrued on unvested restricted stock units	(10)			(10)
Stock options exercised	526			(208)	734
PSUs, RSUs and restricted stock vested	(571)			(6,480)	5,909
Purchase of treasury stock	(184)				(184)
Stock-based compensation expense	6,962		6,962
Ending Balance at Dec. 31, 2019	380,426	$ 797	$ 274,632	$ 806,702	$ (685,288)	$ (16,417)
Ending Balance (ASU 2018-02 [Member]) at Dec. 31, 2019	$ 385
Ending Balance, Shares at Dec. 31, 2019	79,652	79,652

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Dividend payments	$ 0.09	$ 0.09	$ 0.09

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ (52,982,000)	$ (19,342,000)	$ 23,840,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,771,000	15,891,000	15,692,000
Asset impairments	3,872,000	0	0
Amortization of net premium (discount) on available-for-sale investments	(100,000)	(50,000)	425,000
Net (gain) loss on long-term investments	(11,434,000)	4,050,000	(4,685,000)
Net (gain) loss on disposal of property, plant and equipment	67,000	67,000	(145,000)
Gain on bargain purchase of a business		(11,322,000)
Gain on contingency payment	(1,230,000)
Gain on life insurance proceeds	(1,000,000)
Stock-based compensation expense	6,962,000	7,155,000	7,433,000
Deferred income taxes	30,070,000	(17,257,000)	14,073,000
Change in operating assets and liabilities:
Accounts receivable, net	8,282,000	49,200,000	(49,103,000)
Other receivables	20,046,000	(8,522,000)	(10,222,000)
Inventory, net	1,252,000	24,192,000	(15,518,000)
Prepaid expenses and other assets	2,749,000	10,727,000	(4,830,000)
Accounts payable, net	(13,494,000)	(3,799,000)	(17,742,000)
Accrued expenses and other liabilities	(4,598,000)	(3,226,000)	(5,455,000)
Income taxes payable	(8,705,000)	7,690,000	3,858,000
Net cash provided by (used in) operating activities	(2,472,000)	55,454,000	(42,379,000)
Cash flows from investing activities:
Purchases of property, plant and equipment	(9,494,000)	(8,110,000)	(14,720,000)
Proceeds from disposals of property, plant and equipment			151,000
Proceeds from sales and maturities of available-for-sale investments	47,268,000	153,649,000	173,752,000
Purchases of available-for-sale investments	(48,578,000)	(123,209,000)	(93,141,000)
Life insurance proceeds received	1,000,000
Acquisition of business, net of cash acquired	13,000	(22,045,000)
Net cash provided by (used in) investing activities	(9,791,000)	285,000	66,042,000
Cash flows from financing activities:
Proceeds from stock option exercises	526,000	1,483,000	13,412,000
Purchases of treasury stock	(184,000)	(15,532,000)	(17,348,000)
Dividend payments	(17,212,000)	(17,267,000)	(17,368,000)
Payments on long-term debt	(1,000,000)	(1,100,000)	(1,100,000)
Net cash used in financing activities	(17,870,000)	(32,416,000)	(22,404,000)
Net increase (decrease) in cash and cash equivalents	(30,133,000)	23,323,000	1,259,000
Effect of exchange rate changes	(1,598,000)	(4,252,000)	5,279,000
Cash and cash equivalents, beginning of year	105,504,000	86,433,000	79,895,000
Cash and cash equivalents, end of year	73,773,000	105,504,000	86,433,000
Supplemental disclosure of cash flow information
Cash paid during the year for interest	512,000	534,000	555,000
Cash paid during the year for income taxes	9,357,000	4,104,000	2,988,000
Supplemental disclosure of non-cash investing activities
Purchases of property, plant and equipment included in accounts payable	$ 90,000	62,000	$ 408,000
Contingent payment		$ 1,230,000

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	Note 1 – Nature of Business ADTRAN, Inc. (“ADTRAN” or the “Company”) is a leading global provider of networking and communications solutions. Our vision is to enable a fully connected world where the power to communicate is available to everyone, everywhere. Our unique approach, unmatched industry expertise and innovative solutions enable us to address almost any customer need. Our products and services are utilized by a diverse global customer base of network operators that range from those having national or regional reach, operating as telephone or cable television network operators, to alternative network providers such as municipalities or utilities, as well as managed service providers who serve small- and medium-sized businesses and distributed enterprises. Principles of Consolidation The accompanying Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the U.S. (“U.S. GAAP”) and include the financial position, results of operations, comprehensive income (loss), changes in equity and cash flows of ADTRAN and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP 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 expenses during the reporting period. Our more significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues and network installations, estimated income tax provision and income tax contingencies, fair value of stock-based compensation, assessment of goodwill and other intangibles for impairment, estimated lives of intangible assets, estimated pension liability, fair value of investments and evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates. Correction of Immaterial Misstatement During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserves and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in the Company’s excess and obsolete inventory reserves and cost of goods sold. Summary of Significant Accounting Policies 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, 2019, $71.6 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 $24.6 million, which was its fair value as of December 31, 2019. Investments with contractual maturities beyond one year 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 recorded any losses relating to variable rate demand notes. Long-term investments is comprised of deferred compensation plan assets, corporate bonds, municipal fixed-rate bonds, asse t-backed bonds, mortgage/agency- backed bonds, U.S. and foreign government bonds, m arketable 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. Any changes in fair value are recognized in net investment gain (loss). Realized gains and losses on sales of debt securities are computed under the specific identification method and are included in other income (expense) . See Note 5 for additional information. Accounts Receivable We record accounts receivable at net realizable value. Prior to establishing payment terms for a new customer, we evaluate the credit risk of the customer. Credit limits and payment terms established for new customers are re-evaluated periodically based on customer collection experience and other financial factors. As of December 31, 2019, single customers comprising more than 10% of our total accounts receivable balance included four customers, which accounted for 53.2% of our total accounts receivable. As of December 31, 2018, single customers comprising more than 10% of our total accounts receivable balance included two customers, which accounted for 36.9% of our total accounts receivable. We regularly review the need to maintain an 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 impacting these customers 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 $38 thousand and $0.1 million as of December 31, 2019 and December 31, 2018, respectively. Inventory Inventory is carried at the lower of cost and estimated net realizable value, with cost being determined using the first-in, first-out method. Standard costs for material, labor and manufacturing overhead are used to value inventory and are updated at least quarterly. We establish reserves for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on estimated reserve percentages, which consider historical usage, known trends, inventory age and market conditions. When we dispose of excess and obsolete inventories, the related disposals are charged against the inventory reserve. See Note 7 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. Major improvements that materially prolong the lives of the assets are capitalized. Gains and losses on the disposal of property, plant and equipment are recorded in operating income (loss). See Note 8 for additional information. Intangible Assets 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 two to 14 years . Impairment of Long-Lived Assets and Intangibles Long-lived assets used in operations and intangible assets are reviewed 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. During the year ended December 31, 2019, we recognized an impairment loss of approximately $3.9 million related to the abandonment of certain information technology implementation projects which we had previously capitalized expenses related to these projects. There were no impairment losses for long-lived assets during the years ended December 31, 2018 or 2017, or for intangible assets recognized during the years ended December 31, 2019, 2018 or 2017. Goodwill Goodwill represents the excess purchase price over the fair value of net assets acquired. We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. We have elected to by-pass a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount and, in turn, performed a step-1 analysis of goodwill. Based on the results of our step-1 analysis, no impairment charges on goodwill were recognized during the years ended December 31, 2019, 2018 and 2017. Liability for Warranty Our products generally include warranties of 90 days to five years for product defects. We accrue for warranty returns at the time revenue is recognized based on our historical return rate and 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. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $8.4 million and $8.6 million as of December 31, 2019 and 2018, respectively. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets. During 2017, we recorded a reduction in warranty expense related to a settlement with a third-party supplier for a defective component, the impact of which is reflected in the following table. A summary of warranty expense and write-off activity for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 Year Ended December 31, Balance at beginning of period $ 8,623 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses 4,569 7,392 6,951 Less: Deductions (4,798 ) (8,493 ) (5,775 ) Balance at end of period $ 8,394 $ 8,623 $ 9,724 Pension Benefit Plan Obligations We maintain 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. Our net pension liability totaled $15.9 million and $13.1 million as of December 31, 2019 and 2018, respectively. Stock-Based Compensation We have two stock incentive plans from which stock options, performance stock units (“PSUs”), restricted stock units (“RSUs”) and restricted stock are available for grant to employees and directors. Costs related to these awards are recognized over their vesting periods. 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. All of our outstanding stock option awards are classified as equity awards and therefore are measured at fair value on their grant date. Stock-based compensation expense recognized for the years ended December 31, 2019, 2018 and 2017 was approximately $7.0 million, $7.2 million and $7.4 million, respectively. As of December 31, 2019, total unrecognized compensation cost related to non-vested stock options, PSUs, RSUs and restricted stock was approximately $17.2 million, which is expected to be recognized over an average remaining recognition period of 3.0 years. See Note 4 for additional information. 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, 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 $126.2 million, $124.5 million and $130.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. Other Comprehensive Income (Loss) The following table presents changes in accumulated other comprehensive income (loss), net of tax, by components of accumulated other comprehensive income (loss) for the years ended December 31, 2019 2018 and 2017: (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (2) Total Balance as of December 31, 2016 $ 404 $ — $ (5,017 ) $ (7,575 ) $ — $ (12,188 ) Other comprehensive income before reclassifications 5,020 (619 ) 451 5,999 — 10,851 Amounts reclassified from accumulated other comprehensive loss (2,857 ) 619 280 — — (1,958 ) Balance as of December 31, 2017 2,567 — (4,286 ) (1,576 ) — (3,295 ) Other comprehensive loss before reclassifications 685 — (3,890 ) (4,236 ) — (7,441 ) Amounts reclassified to retained earnings (1) (3,220 ) — — — — (3,220 ) Amounts reclassified from accumulated other comprehensive loss (595 ) — 135 — — (460 ) Balance as of December 31, 2018 (563 ) — (8,041 ) (5,812 ) — (14,416 ) Other comprehensive loss before reclassifications 573 — (1,717 ) (1,480 ) — (2,624 ) Amounts reclassified to retained earnings (1) — — — — 385 385 Amounts reclassified from accumulated other comprehensive loss (294 ) — 532 — — 238 Balance as of December 31, 2019 $ (284 ) $ — $ (9,226 ) $ (7,292 ) $ 385 $ (16,417 ) (1) With the adoption of ASU 2016-01, the unrealized gains on our equity investments were reclassified to retained earnings. See Recently Issued Accounting Standards below for more information. (2) With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 13 for additional information. The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 397 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (771 ) (1) Total reclassifications for the period, before tax (374 ) Tax benefit 136 Total reclassifications for the period, net of tax $ (238 ) (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2018 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 804 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (196 ) (1) Total reclassifications for the period, before tax 608 Tax expense (148 ) Total reclassifications for the period, net of tax $ 460 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 4,864 Net investment gain (loss) Impairment expense (180 ) Net investment gain (loss) Net losses on derivatives designated as hedging instruments (897 ) Cost of sales Defined benefit plan adjustments – actuarial losses (406 ) (1) Total reclassifications for the period, before tax 3,381 Tax expense (1,423 ) Total reclassifications for the period, net of tax $ 1,958 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. The following tables present the tax effects related to the change in each component of other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 774 $ (201 ) $ 573 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (397 ) 103 (294 ) Defined benefit plan adjustments (2,488 ) 771 (1,717 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 771 (239 ) 532 Foreign currency translation adjustment (1,480 ) — (1,480 ) Total Other Comprehensive Income (Loss) $ (2,820 ) $ 434 $ (2,386 ) 2018 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 926 $ (241 ) $ 685 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (804 ) 209 (595 ) Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01 (4,351 ) 1,131 (3,220 ) Defined benefit plan adjustments (5,638 ) 1,748 (3,890 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 196 (61 ) 135 Foreign currency translation adjustment (4,236 ) — (4,236 ) Total Other Comprehensive Income (Loss) $ (13,907 ) $ 2,786 $ (11,121 ) 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 8,230 $ (3,210 ) $ 5,020 Reclassification adjustment for amounts related to available-for-sale investments included in net income (4,684 ) 1,827 (2,857 ) Unrealized gains (losses) on cash flow hedges (897 ) 278 (619 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 897 (278 ) 619 Defined benefit plan adjustments 654 (203 ) 451 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 406 (126 ) 280 Foreign currency translation adjustment 5,999 — 5,999 Total Other Comprehensive Income (Loss) $ 10,605 $ (1,712 ) $ 8,893 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 using appropriate exchange rates from throughout the year. Assets and liabilities denominated in foreign currencies are remeasured at the balance sheet dates using the closing rates of exchange between those foreign currencies and the functional currency with any transaction gains or losses reported in other income (expense). Our primary exposures to foreign currency exchange rate movements are with our German subsidiary, whose functional currency is the Euro, our Australian subsidiary, whose functional currency is the Australian dollar and our Mexican subsidiary, whose functional currency is the U.S. dollar as most invoices are paid in Mexican Pesos. Adjustments resulting from translating financial statements of international subsidiaries are recorded as a component of accumulated other comprehensive income (loss). Revenue On January 1, 2018, we adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), Revenue Recognition. Accounting Policy under Topic 606 Revenue is measured based on the consideration we expect to receive in exchange for transferring goods or providing services to a customer and as performance obligations under the terms of the contract are satisfied. Generally, this occurs with the transfer of control of a product to the customer. Review of contracts with customers, for both direct customers and distributors, are performed and assessment made regarding principal versus agent considerations to determine primary responsibility for delivery of performance obligation, presumed inventory risk, and discretion in establishing pricing. For transactions where there are multiple performance obligations, we account for individual products and services separately if they are distinct (if a product or service is separately identifiable from other items and if a customer can benefit from it on its own or with other resources that are readily available to the customer). The consideration, including any discounts, is allocated between separate products and services based on their stand-alone selling prices. Stand-alone selling prices are determined based on the prices at which we sell the separate products and services and are allocated based on each item’s relative value to the total value of the products and services in the arrangement. For items that are not sold separately, we estimate stand-alone selling prices primarily using the “expected cost plus a margin” approach. Payment terms are generally 30 days in the U.S. and typically longer in many geographic markets outside the U.S. The following is a description of the principal activities from which we generate our revenue by reportable segment. Network Solutions Segment Network Solutions includes hardware products and software defined next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. The majority of the revenue from this segment is from hardware sales. Hardware and Software Revenue Revenue from hardware sales is recognized when control is transferred to our customers, which is generally when we ship the products. Shipping terms are generally FOB shipping point. This segment also includes revenues from software license sales which is recognized at delivery and transfer of control to the customer. Revenue is recorded net of estimated discounts and rebates using historical trends. Customers are typically invoiced when control is transferred and revenue is recognized. Our products generally include assurance-based warranties of 90 days to five years for product defects, which are accrued at the time revenue is recognized. In certain transactions, we are also the lessor in sales-type lease arrangements for network equipment that have terms of 18 months to five years. These arrangements typically include network equipment, network implementation services and maintenance services. Services & Support Segment To complement our Network Solutions segment, we offer a complete portfolio of maintenance, network implementation and solutions integration and managed services, which include hosted cloud services and subscription services. Maintenance Revenue Our maintenance service periods range from one month to five years. Customers are typically invoiced and pay for maintenance services at the beginning of the maintenance period. We recognize revenue for maintenance services on a straight-line basis over the maintenance period as our customers benefit evenly throughout the contract term and deferred revenues, when applicable, are recorded in current and non-current unearned revenue. Network Implementation Revenue We recognize revenue for network implementation, which primarily consists of engineering, execution and enablement services at a point in time when each performance obligation is complete. If we have recognized revenue but have not billed the customer, the right to consideration is recognized as a contract asset that is included in other receivables on the Consolidated Balance Sheet. The contract asset is transferred to accounts receivable when the completed performance obligation is invoiced to the customer. Accounting Policy under Topic 605 Revenue was generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the product price was fixed or determinable, collection of the resulting receivable was reasonably assured, and product returns were reasonably estimable. For product sales, revenue was generally recognized upon shipment of the product to our customer in accordance with the title transfer terms of the sales agreement, generally Ex Works, per International Commercial Terms. In the case of consigned inventory, revenue was recognized when the end customer assumes ownership of the product. Contracts that contained multiple deliverables were evaluated to determine the units of accounting, and the consideration from the arrangement was allocated to each unit of accounting based on the relative selling price and corresponding terms of the contract. When this was not available, we were 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. In these instances, we used best estimates to allocate consideration to each respective unit of accounting. These estimates included analysis of respective bills of material and review and analysis of similar product and service offerings. We recorded revenue associated with installation services when respective contractual obligations are complete. In instances where customer acceptance was required, revenue was deferred until respective acceptance criteria were met. Contracts that included both installation services and product sales were evaluated for revenue recognition in accordance with contract terms. As a result, installation services may have been considered a separate deliverable or may have been considered a combined single unit of accounting with the delivered product. Generally, either the purchaser, ADTRAN, or a third party would perform the installation of our products. Shipping fees were recorded as revenue and the related costs were included in cost of sales. Sales taxes invoiced to customers were included in revenues and represented less than one percent of total revenues. The corresponding sales taxes paid were included in cost of goods sold. Value-added taxes collected from customers in international jurisdictions were recorded in accrued expenses as a liability. Revenue was recorded net of discounts. Sales returns were recorded as a reduction of revenue and accrued based on historical sales return experience, which we believed provided a reasonable estimate of future returns. Unearned Revenue Unearned revenue primarily represents customer billings on our maintenance service programs and unearned revenues related to multiple element contracts where we still have contractual obligations to our customers. We currently offer maintenance contracts ranging from one month to five years. 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 customers under contracts with terms up to ten years. When we defer revenue related to multiple performance obligations where we still have contractual obligations, we also defer the related costs. Current deferred costs are included in prepaid expenses and other current assets on the accompanying Consolidated Balance Sheets and totaled $1.6 million and $2.4 million as of December 31, 2019 and 2018, respectively. Non-current deferred costs are included in other assets on the accompanying Consolidated Balance Sheets and totaled $0.1 million and $0.8 million as of December 31, 2019 and 2018, respectively. Earnings (Loss) per Share Earnings (loss) per common share and earnings (loss) 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 17 for additional information. Business Combinations The Company records assets acquired, liabilities assumed, contractual contingencies, when applicable, and intangible assets recognized as part of business combinations based on their fair values on the date of acquisition. The excess of the purchase price over the estimated fair values of the net tangible and intangible assets and liabilities assumed acquired is recorded as goodwill. If the estimated fair values of net tangible and intangible assets acquired and liabilities assumed exceed the purchase price, a bargain purchase gain is recorded. The Company’s estimates of fair value are based on historical experience, industry knowledge, certain information obtained from the management of the acquired company and, in some cases, valuations performed by independent third-party firms. The results of operations of acquired companies are included in the accompanying Consolidated Statements of Operations since their dates of acquisition. Costs incurred to complete the business combination, such as legal, accounting or other professional fees are charged to selling, general and administrative expenses as incurred. Derivative Instruments and Hedging Activities Histor

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Business Combinations	Note 2 – Business Combinations In November 2018, we acquired SmartRG, Inc., a provider of carrier-class, open-source connected home platforms and cloud services for broadband service providers for cash consideration. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. These revenues are included in the Subscriber Solutions & Experience category within the Network Solutions and Services & Support reportable segments. Contingent liabilities with a fair value totaling $1.2 million were recognized at the acquisition date, the payments of which were dependent upon SmartRG achieving future revenue, EBIT or customer purchase order milestones during the first half of 2019. The required milestones were not achieved and therefore, we recognized a gain of $1.2 million upon the reversal of these liabilities during the second quarter of 2019. An escrow in the amount of $2.8 million was set up at the acquisition date to fund post-closing working capital settlements and to satisfy indemnity obligations to the Company arising from any inaccuracy or breach of representations, warranties, covenants, agreements or obligations of the sellers. The escrow is subject to arbitration. In December 2019, $1.3 million of the $2.8 million was released from the escrow account pursuant to the agreement, with the final settlement of the remaining balance expected during the fourth quarter of 2020. The remaining minimum and maximum potential release of funds to the seller ranges from no payment to $1.5 million. We recorded goodwill of $3.5 million as a result of this acquisition, which represents the excess of the purchase price over the fair value of net assets acquired and liabilities assumed. We assessed the recognition and measurement of the assets acquired and liabilities assumed based on historical and forecasted data for future periods and concluded that our valuation procedures and resulting measures were appropriate. On March 19, 2018, we acquired Sumitomo Electric Lightwave Corp.’s (SEL) North American EPON business and entered into a technology license and OEM supply agreement with Sumitomo Electric Industries, Ltd. (SEI). This acquisition establishes ADTRAN as the North American market leader for EPON solutions for the cable MSO industry and it will accelerate the MSO market’s adoption of our open, programmable and scalable architectures. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. These revenues are included in the Access & Aggregation and Subscriber Solutions & Experience categories within the Network Solutions reportable segment. We recorded a bargain purchase gain of $11.3 million during the first quarter of 2018, net of income taxes, which is subject to customary working capital adjustments between the parties. The bargain purchase gain of $11.3 million represents the difference between the fair-value of the net assets acquired over the cash paid. SEI, an OEM supplier based in Japan, is the global market leader in EPON. SEI’s Broadband Networks Division, through its SEL subsidiary, operated a North American EPON business that included sales, marketing, support, and region-specific engineering development. The North American EPON market is primarily driven by the Tier 1 cable MSO operators and has developed more slowly than anticipated. Through the transaction, SEI divested its North American EPON assets and established a relationship with ADTRAN. The transfer of these assets to ADTRAN, which included key customer relationships and a required assumption by ADTRAN of relatively low incremental expenses, along with the value of the technology license and OEM supply agreement, resulted in the bargain purchase gain. We have assessed the recognition and measurement of the assets acquired and liabilities assumed based on historical and forecasted data for future periods and we 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 2018 Consolidated Statements of Income. The final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for SmartRG and the final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for Sumitomo are as follows: (In thousands) Sumitomo SmartRG Assets Tangible assets acquired $ 1,006 $ 8,594 Intangible assets 22,100 9,960 Goodwill — 3,476 Total assets acquired 23,106 22,030 Liabilities Liabilities assumed (3,978 ) (6,001 ) Total liabilities assumed (3,978 ) (6,001 ) Total net assets 19,128 16,029 Gain on bargain purchase of a business, net of tax (11,322 ) — Total purchase price $ 7,806 $ 16,029 Our Consolidated Statements of Income include the following revenue and net loss attributable to SmartRG and Sumitomo since the date of acquisition: (In thousands) March 19, 2018 to December 31, 2018 Revenue $ 9,186 Net loss $ (1,297 ) The details of the acquired intangible assets from the SmartRG and Sumitomo acquisitions are as follows: (In thousands) Value Life (in years) Customer relationships $ 15,190 3 - 12 Developed technology 7,400 7 Licensed technology 5,900 9 Supplier relationship 2,800 2 Licensing agreements 560 5 - 10 Trade name 210 3 Total $ 32,060 The following unaudited supplemental pro forma information presents the financial results as if the acquisition of SmartRG and Sumitomo had occurred on January 1, 2017. This unaudited supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition been completed on January 1, 2017, nor is it indicative of any future results. Aside from revising the 2017 net income for the effect of the bargain purchase gains, there were no material, non-recurring adjustments to this unaudited pro-forma information. (In thousands) 2018 2017 Pro forma revenue $ 559,050 $ 702,573 Pro forma net loss $ (33,862 ) $ 33,206 For the years ended December 31, 2019 and 2018, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $5.0 million and $2.9 million, respectively, related to the SmartRG and Sumitomo acquisitions. No acquisition expenses related to the SmartRG and Sumitomo acquisitions were recorded during the year ended December 31, 2017.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Revenue	Note 3 - Revenue The following table disaggregates our revenue by major source for the year ended December 31, 2019: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 (1) The following table disaggregates our revenue by major source for the year ended December 31, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 (1) Revenue allocated to remaining performance obligations represents contract revenues that have not yet been recognized for contracts with a duration greater than one year. As of December 31, 2019, we did not have any significant performance obligations related to customer contracts that had an original expected duration of one year or more, other than maintenance services, which are satisfied over time. As a practical expedient, for certain contracts recognize revenue equal to the amounts we are entitled to invoice which correspond to the value of completed performance obligations to date. The amount related to these performance obligations was $13.3 million as of December 31, 2018. The amount related to these performance obligations was $13.6 million as of December 31, 2019, and the Company expects to recognize 64% of such revenue over the next 12 months with the remainder thereafter. The following table provides information about accounts receivables, contract assets and unearned revenue from contracts with customers: (In thousands) December 31, 2019 December 31, 2018 Accounts receivable $ 90,531 $ 99,385 Contract assets (1) $ 2,812 $ 3,766 Unearned revenue $ 11,963 $ 17,940 Non-current unearned revenue $ 6,012 $ 5,296 (1) Of the outstanding unearned revenue balance as of December 31, 2018, $12.7 million was recognized as revenue during the year ended December 31, 2019.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 4 – Stock-Based Compensation Stock Incentive Program Descriptions In January 2006, the Board of Directors adopted the ADTRAN, Inc. 2006 Employee Stock Incentive Plan (the “2006 Plan”), which authorized 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, RSUs and restricted stock. The 2006 Plan was adopted by stockholder approval at our annual meeting of stockholders held in May 2006. Options granted under the 2006 Plan typically become exercisable beginning after one year of continued employment, normally pursuant to a four-year ten-year In January 2015, the Board of Directors adopted the 2015 Plan, which authorized 7.7 million shares of common stock for issuance to certain employees and officers through incentive stock options and non-qualified stock options, stock appreciation rights, PSUs, RSUs and restricted stock. The 2015 Plan was adopted by stockholder approval at our annual meeting of stockholders held in May 2015. PSUs, RSUs and restricted stock granted under the 2015 Plan reduce the shares authorized for issuance under the 2015 Plan by 2.5 shares of common stock for each share underlying the award. Options granted under the 2015 Plan typically become exercisable beginning after one year of continued employment, normally pursuant to a four-year ten-year Our stockholders approved the 2010 Directors Stock Plan (the “2010 Directors Plan”) in May 2010, under which 0.5 million shares of common stock have been reserved for issuance. This plan replaced the 2005 Directors Stock Option Plan. Under the 2010 Directors Plan, the Company may issue stock options, restricted stock and RSUs to our non-employee directors. Stock awards issued under the 2010 Directors Plan become vested in full on the first anniversary of the grant date. Options issued under the 2010 Directors Plan had a ten-year The following table summarizes stock-based compensation expense related to stock options, PSUs, RSUs and restricted stock for the years ended December 31, 2019, 2018 and 2017, which was recognized as follows: (In thousands) 2019 2018 2017 Stock-based compensation expense included in cost of sales $ 369 $ 418 $ 379 Selling, general and administrative expense 3,889 3,989 4,063 Research and development expense 2,704 2,748 2,991 Stock-based compensation expense included in operating expenses 6,593 6,737 7,054 Total stock-based compensation expense 6,962 7,155 7,433 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (1,659 ) (1,432 ) (1,699 ) Total stock-based compensation expense, net of tax $ 5,303 $ 5,723 $ 5,734 PSUs, RSUs and restricted stock Under the 2015 Plan, awards other than stock options, including PSUs, RSUs and restricted stock, may be granted to certain employees and officers. Under our market-based PSU program, the number of shares of common stock earned by a recipient 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 During the first quarter of 2017, the Compensation Committee of the Board of Directors approved a one-time PSU grant of 0.5 million shares that contained performance conditions and would have vested at the end of a three-year period if such performance conditions were met. The fair value of these performance-based PSU awards was equal to the closing price of our stock on the date of grant. These awards were forfeited during the first quarter of 2020 as the performance conditions were not achieved. The fair value of RSUs and restricted stock is equal to the closing price of our stock on the business day immediately preceding the grant date. RSUs and restricted stock vest ratably over four-year one-year 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 is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2018 and 2019 and the changes that occurred during 2019: (In thousands, except per share amounts) Number of shares Weighted Average Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2018 1,570 $ 18.52 PSUs, RSUs and restricted stock granted 897 $ 9.63 PSUs, RSUs and restricted stock vested (368 ) $ 17.23 PSUs, RSUs and restricted stock forfeited (208 ) $ 18.24 Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2019 1,891 $ 14.58 As of December 31, 2019, total unrecognized compensation expense related to the non-vested portion of market-based PSUs, RSUs and restricted stock was approximately $17.2 million, which is expected to be recognized over an average remaining recognition period of 2.9 years and adjusted for actual forfeitures as they occur. The following table details the significant assumptions that impact the fair value estimate of the market-based PSUs: 2019 2018 2017 Estimated fair value per share $9.53 to $18.05 $ 16.59 $ 24.17 Expected volatility 32.7% to 38.9% 27.98% to 31.58% 27.03 % Risk-free interest rate 1.6% to 2.46% 2.11% to 2.99% 1.78 % Expected dividend yield 2.3% to 4.09% 1.83% to 2.49% 1.74 % As of December 31, 2019, 1.0 million shares were available for issuance under shareholder-approved equity plans in connection with the grant and exercise of stock options, PSU’s, RSU’s or restricted stock. Stock Options The following table is a summary of our stock options outstanding as of December 31, 2019 and 2018 and the changes that occurred during 2019: Number of Options (in thousands) Weighted Average Exercise Price (per share) Weighted Avg. Remaining Contractual Life in Years Aggregate Intrinsic (in thousands) Stock options outstanding, December 31, 2018 4,382 $ 22.91 4.10 $ — Stock options granted — $ — Stock options exercised (34 ) $ 15.53 Stock options forfeited (32 ) $ 15.56 Stock options expired (744 ) $ 23.72 Stock options outstanding, December 31, 2019 3,572 $ 22.88 3.40 $ — Stock options exercisable, December 31, 2019 3,570 $ 22.89 3.40 $ — All of the options above were issued at exercise prices that approximated fair market value at the date of grant. As of December 31, 2019, total unrecognized compensation expense related to non-vested stock options was approximately $11 thousand, which is expected to be recognized over an average remaining recognition period of one year and will be adjusted for actual forfeitures as they occur. 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 2019 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, 2019. The amount of aggregate intrinsic value will change based on the fair market value of ADTRAN’s stock and was $0 as of December 31, 2019. The total pre-tax intrinsic value of options exercised during 2019, 2018 and 2017 was $0.1 million, $0.2 million and $3.4 million, respectively. The fair value of options fully vesting during 2019, 2018 and 2017 was $0.9 million, $2.5 million and $4.3 million, respectively. The following table further describes our stock options outstanding as of December 31, 2019: Options Outstanding Options Exercisable Range of Exercise Prices Options Outstanding at December 31, 2019 (In thousands) Weighted Avg. Remaining Contractual Life in Years Weighted Average Exercise Price Options Exercisable at December 31, 2019 (In thousands) Weighted Average Exercise Price $14.88 – $18.96 1,135 4.90 $ 15.89 1,133 $ 15.89 $18.97 – $23.45 685 4.70 $ 19.10 685 $ 19.10 $23.46 – $30.35 686 3.67 $ 24.17 686 $ 24.17 $30.36 – $41.92 1,066 1.29 $ 31.93 1,066 $ 31.93 3,572 3,570 The Black-Scholes option pricing model (the “Black-Scholes Model”) is used to determine 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. 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 stock options granted in during the years ended December 31, 2019, 2018 or 2017.

Investments

Investments	12 Months Ended
	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Investments	Note 5 – Investments Debt Securities and Other Investments As of December 31, 2019, we held the following debt securities and other investments, recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,304 $ 80 $ — $ 9,384 Municipal fixed-rate bonds 930 — — 930 Asset-backed bonds 6,867 26 (3 ) 6,890 Mortgage/Agency-backed bonds 6,944 26 (8 ) 6,962 U.S. government bonds 12,311 21 (9 ) 12,323 Foreign government bonds 372 — (1 ) 371 Variable rate demand notes 800 — — 800 Available-for-sale debt securities held at fair value $ 37,528 $ 153 $ (21 ) $ 37,660 As of December 31, 2018, we held the following debt securities and other investments, recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 20,777 $ 19 $ (112 ) $ 20,684 Municipal fixed-rate bonds 1,339 — (26 ) 1,313 Asset-backed bonds 5,230 5 (14 ) 5,221 Mortgage/Agency-backed bonds 3,833 2 (44 ) 3,791 U.S. government bonds 9,271 1 (66 ) 9,206 Foreign government bonds 592 — (8 ) 584 Available-for-sale debt securities held at fair value $ 41,042 $ 27 $ (270 ) $ 40,799 As of December 31, 2019, our debt securities had the following contractual maturities: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset-backed bonds Mortgage / Agency-backed bonds U.S. government bonds Foreign government bonds Less than one year $ 4,005 $ — $ 396 $ — $ — $ — One to two years 4,120 930 760 213 1,347 — Two to three years 967 — 1,632 1,424 9,344 — Three to five years 292 — 2,092 494 1,632 371 Five to ten years — — 1,719 792 — — More than ten years — — 291 4,039 — — Total $ 9,384 $ 930 $ 6,890 $ 6,962 $ 12,323 $ 371 Actual maturities may differ from contractual maturities as some borrowers have the right to call or prepay obligations with or without call or prepayment penalties. 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 debt securities for the years ended December 31, 2019, 2018 and 2017: (In thousands) Year Ended December 31, 2019 2018 2017 Gross realized gains on debt securities $ 108 $ 57 $ 169 Gross realized losses on debt securities (50 ) (592 ) (226 ) Total gain (loss) recognized, net $ 58 $ (535 ) $ (57 ) 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. The following table presents the breakdown of debt securities and other investments with unrealized losses as of December 31, 2019: Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 203 — — — 203 — Municipal fixed-rate bonds 930 — — — 930 — Asset-backed bonds 797 (3 ) — — 797 (3 ) Mortgage/Agency-backed bonds 2,594 (6 ) 136 (2 ) 2,730 (8 ) U.S. government bonds 4,070 (9 ) — — 4,070 (9 ) Marketable equity securities 371 (1 ) — — 371 (1 ) Total $ 8,965 $ (19 ) $ 136 $ (2 ) $ 9,101 $ (21 ) The following table presents the breakdown of debt securities and other investments with unrealized losses as of December 31, 2018: Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds $ 11,129 $ (60 ) $ 3,608 $ (52 ) $ 14,737 $ (112 ) Municipal fixed-rate bonds — — 1,136 (26 ) 1,136 (26 ) Asset-backed bonds 1,874 (2 ) 1,257 (12 ) 3,131 (14 ) Mortgage/Agency-backed bonds 1,021 (5 ) 1,918 (39 ) 2,939 (44 ) U.S. government bonds 6,527 (48 ) 537 (18 ) 7,064 (66 ) Foreign government bonds 584 (8 ) — — 584 (8 ) Total $ 21,135 $ (123 ) $ 8,456 $ (147 ) $ 29,591 $ (270 ) The decrease in unrealized losses during 2019, as reflected in the table above, results from changes in market positions associated with our fixed income portfolio. Marketable Equity Securities Our marketable equity securities consist of publicly traded stocks or funds measured at fair value. Prior to January 1, 2018, our marketable equity securities were classified as available-for-sale. Realized gains and losses on marketable equity securities were included in net investment gain (loss). Unrealized gains and losses were recognized in accumulated other comprehensive income (loss), net of deferred taxes, on the balance sheet. On January 1, 2018, we adopted ASU 2016-01, which requires us to measure all equity investments that do not result in consolidation and are not accounted for under the equity method at fair value, with any changes in fair value recognized in net investment gain (loss). Upon adoption, we reclassified $3.2 million of net unrealized gains related to marketable equity securities from accumulated other comprehensive income (loss) to opening retained earnings. ASU 2016-01 also provides a measurement alternative for equity investments that do not have a readily determinable fair value in which investments can be recorded at cost less impairment, if any, adjusted for observable price changes for an identical or similar investment. We elected to record our equity investment that does not have a readily determinable fair value using the measurement alternative method. As of December 31, 2018, the Company had a note receivable of approximately $4.3 million, which was included in other receivables on the Consolidated Balance Sheets. During the three months ended March 31, 2019, this amount was repaid and reissued in the form of debt and equity. Approximately $3.4 million was issued as an equity investment, which represented a non-cash investing activity. The carrying value of this investment under the measurement alternative was $3.4 million as of December 31, 2019. The remaining amount, approximately $0.9 million, was converted into a new note receivable, which is included in other receivables on the Consolidated Balance Sheets and represents a non-cash operating activity. Realized and unrealized gains and losses for our marketable equity securities for the twelve months ended December 31, 2019 were as follows: (In thousands) 2019 2018 Realized gains (losses) on equity securities sold $ (96 ) $ 1,306 Unrealized gains (losses) on equity securities held 11,472 (4,821 ) Total gain (loss) recognized, net $ 11,376 $ (3,515 ) As of December 31, 2019 and 2018, gross unrealized losses related to individual investments in a continuous loss position for twelve months or longer were not material. U.S. GAAP establishes a three-level valuation hierarchy based upon observable and unobservable inputs for fair value measurement of financial instruments: • Level 1 – Observable outputs; values based on unadjusted quoted prices for identical assets or liabilities in an active market; • Level 2 – Significant inputs that are observable; values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; • Level 3 – Significant unobservable inputs; values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs could include information supplied by investees. We have categorized our cash equivalents and our investments held at fair value into this hierarchy as follows: Fair Value Measurements as of December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,309 $ 1,309 $ — $ — Available-for-sale debt securities Corporate bonds 9,384 — 9,384 — Municipal fixed-rate bonds 930 — 930 — Asset-backed bonds 6,890 — 6,890 — Mortgage/Agency-backed bonds 6,962 — 6,962 — U.S. government bonds 12,323 12,323 — — Foreign government bonds 371 — 371 — Variable rate demand notes 800 — 800 — Marketable equity securities Marketable equity securities – various industries 35,501 35,501 — — Equity in escrow 298 298 — — Deferred compensation plan assets 21,698 21,698 — — Other investments 2,442 2,442 — — Total $ 98,908 $ 73,571 $ 25,337 $ — Fair Value Measurements as of December 31, 2018 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,554 $ 1,554 $ — $ — Available-for-sale debt securities Corporate bonds 20,684 — 20,684 — Municipal fixed-rate bonds 1,313 — 1,313 — Asset-backed bonds 5,221 — 5,221 — Mortgage/Agency-backed bonds 3,791 — 3,791 — U.S. government bonds 9,206 9,206 — — Foreign government bonds 584 — 584 — Marketable equity securities Marketable equity securities – various industries 26,763 26,763 — — Equity in escrow 253 253 — — Deferred compensation plan assets 18,256 18,256 — — Total $ 87,625 $ 56,032 $ 31,593 $ — 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 variable rate demand notes have a structure that implies a standard expected market price. The frequent interest rate resets make it reasonable to expect the price to stay at par. These securities are priced at the expected market price.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	Note 6 – Derivative Instruments and Hedging Activities As of December 31, 2019 and 2018, we had no foreign exchange forward contracts. The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income (Loss) during the years ended December 31, 2019, 2018 and 2017 were as follows: (In thousands) Income Statement Location 2019 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ — $ 13 $ (754 ) The change in our derivatives designated as hedging instruments recorded in other comprehensive income and reclassified to income, net of tax, during the twelve months ended December 31, 2019, 2018 and 2017 were as follows: Location of Amount of Losses Reclassified Losses Reclassified from AOCI into Income (In thousands) from AOCI into Income 2019 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts Cost of Sales $ — $ — $ (897 )

Inventory

Inventory	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory	Note 7 – Inventory As of December 31, 2019 and 2018, inventory was comprised of the following: (In thousands) 2019 2018 Raw materials $ 36,987 $ 45,333 Work in process 1,085 1,638 Finished goods 60,233 52,877 Total Inventory, net $ 98,305 $ 99,848 Inventory reserves are established for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on estimated reserve percentages, which consider historical usage, known trends, inventory age and market conditions. As of December 31, 2019 and 2018, our inventory reserve was $34.1 million and $30.0 million, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	Note 8 – Property, Plant and Equipment As of December 31, 2019 and 2018, property, plant and equipment was comprised of the following: (In thousands) 2019 2018 Land $ 4,575 $ 4,575 Building and land improvements 34,797 34,379 Building 68,157 68,183 Furniture and fixtures 19,959 19,831 Computer hardware and software 74,399 92,071 Engineering and other equipment 130,430 127,060 Total Property, Plant and Equipment 332,317 346,099 Less accumulated depreciation (258,609 ) (265,464 ) Total Property, Plant and Equipment, net $ 73,708 $ 80,635 Depreciation expense was $12.5 million, $12.7 million and $12.8 million for the years ended December 31, 2019, 2018 and 2017, respectively, which is recorded in cost of sales, selling, general and administrative expense and research and development expense in the consolidated statements of income. We assess long-lived assets used in operations for potential 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. During the year ended December 31, 2019, the Company recognized impairment charges of $3.9 million related to the abandonment of certain information technology projects in which we had previously capitalized expenses related to these projects. The impairment charges were determined based on actual costs incurred as part of the projects. No impairment charges were recognized during the years ended December 31, 2018 and 2017.

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Note 9 – Leases We have operating leases for office space, automobiles and various other equipment in the U.S. and in certain international locations. We also reviewed other contracts, such as manufacturing agreements and service agreements, for potential embedded leases. We specifically reviewed these other contracts to determine whether we have the right to substantially all of the economic benefit from the use of any specified assets or the right to direct the use of any specified assets, either of which would indicate the existence of a lease. As of December 31, 2019, our operating leases had remaining lease terms of one month to six years, some of which included options to extend the leases for up to nine years, and some of which included options to terminate the leases within three months Supplemental balance sheet information related to operating leases is as follows: December 31, January 1, (In thousands) Classification 2019 2019 (1) Assets Right of use lease assets Other assets $ 8,452 $ 10,322 Total lease asset $ 8,452 $ 10,322 Liabilities Current lease liability Accrued expenses $ 2,676 $ 2,948 Non-current lease liability Other non-current liabilities 5,818 7,374 Total lease liability $ 8,494 $ 10,322 (1) The components of lease expense included in the Consolidated Statements of Income for the twelve months ended December 31, 2019 were as follows: For the Year Ended December 31, (In thousands) 2019 Research and development expenses $ 2,417 Selling, general and administrative expenses 1,400 Cost of sales 64 Total operating lease expense $ 3,881 As of December 31, 2019, operating lease liabilities included on the Consolidated Balance Sheet by future maturity were as follows: (In thousands) Amount 2020 $ 2,856 2021 2,412 2022 1,705 2023 1,160 2024 482 Thereafter 264 Total lease payments 8,879 Less: Interest (385 ) Present value of lease liabilities $ 8,494 Future o perating lease payments include $0.7 million related to options to extend lease terms that are reasonably certain of being exercised. There are no legally binding leases that have not yet commenced A s of December 31, 2018, future minimum rental payments under non-cancelable operating leases, including renewals determined to be reasonably assured as of December 31, 2018, with original maturities of greater than 12 months, were as follows: (In thousands) Amount (1) 2019 $ 3,873 2020 3,580 2021 2,771 2022 2,053 2023 1,317 Thereafter 762 Total $ 14,356 (1) Certain renewal options were subsequently determined to not be reasonably assured of renewal upon the Company’s adoption of the new lease accounting standard on January 1, 2019. Our leases do not provide an implicit rate and therefore we use an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We used the incremental borrowing rate on January 1, 2019, for operating leases that commenced on or prior to that date. The incremental borrowing rate was determined on a portfolio basis by grouping leases with similar terms as well as grouping leases based on a U.S. dollar or Euro functional currency. The actual rate was then determined based on a credit spread over LIBOR as well as the Bloomberg Curve Matrix for the U.S. Communications section. The following table provides information about our weighted average lease terms and weighted average discount rates as of December 31, 2019: As of December 31, 2019 Weighted average remaining lease term (years) Operating leases with USD functional currency 2.6 Operating leases with Euro functional currency 4.4 Weighted average discount rate Operating leases with USD functional currency 4.02 % Operating leases with Euro functional currency 1.84 % Supplemental cash flow information related to operating leases is as follows: As of December 31, (In thousands) 2019 Cash paid for amounts included in the measurement of operating lease assets / liabilities Cash used in operating activities related to operating leases $ 3,439 Right-of-use assets obtained in exchange for lease obligations $ 11,615 Sales-Type Leases We are the lessor in sales-type lease arrangements for network equipment, which have initial terms of up to five years. Our sales-type lease arrangements contain either a provision whereby the network equipment reverts back to us upon the expiration of the lease or a provision that allows the lessee to purchase the network equipment at a bargain purchase amount at the end of the lease. In addition, our sales-type lease arrangements do not contain any residual value guarantees or material restrictive covenants. The allocation of the consideration between lease and nonlease components is determined by stand-alone selling price by component. The net investment in sales-type leases consists of lease receivables less unearned income. Collectability of sales-type leases is evaluated periodically at an individual customer level. The Company has elected to exclude taxes related to sales-type leases from revenue and the associated expense of such taxes. As of December 31, 2019 and 2018, we did not have an allowance for credit losses for our net investment in sales-type leases. As of December 31, 2019 and 2018, the components of the net investment in sales-type leases were as follows: December 31, December 31, (In thousands) 2019 2018 Current minimum lease payments receivable (1) $ 1,201 $ 11,339 Non-current minimum lease payments receivable (2) 889 1,670 Total minimum lease payments receivable 2,090 13,009 Less: Current unearned revenue (1) 365 631 Less: Non-current unearned revenue (2) 163 473 Net investment in sales-type leases $ 1,562 $ 11,905 (1) Included in other receivables on the Consolidated Balance Sheet. (2) Included in other assets on the Consolidated Balance Sheet. The components of sales-type lease gross profit recognized at the lease commencement date and interest and dividend income, included in the Consolidated Statements of Income for the twelve months ended December 31, 2019 were as follows: (In thousands) For the Year Ended December 31, 2019 Sales - Network Solutions $ 1,723 Cost of sales - Network Solutions 675 Gross profit $ 1,048 Interest and dividend income $ 357 As of December 31, 2019 future minimum lease payments to be received from sales-type leases were as follows: (In thousands) Amount 2020 $ 1,201 2021 565 2022 232 2023 86 2024 6 Total $ 2,090

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2019
Goodwill Disclosure [Abstract]
Goodwill	Note 10 – Goodwill Goodwill, all of which relates to our acquisitions of Bluesocket, Inc. in 2011 and SmartRG in 2018, was $7.0 million as of December 31, 2019 and $7.1 million as of December 31, 2018 of which $6.6 million and $0.4 million was allocated to our Network Solutions and Services & Support reportable segments, respectively, for the year ended December 31, 2019, and of which $6.7 million and $0.4 million was allocated to our Network Solutions and Services & Support reportable segments, respectively, for the year ended December 31, 2018. Goodwill related to our SmartRG acquisition was reduced by $0.1 million during the twelve months ended December 31, 2019 as a result of a measurement period adjustment. We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. We have elected to first assess the qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step impairment test. If we determine that it is more likely than not that its fair value is less than its carrying amount, then the two-step impairment test will be performed. Based on the results of our qualitative assessment for the years ended December 31, 2019 , 2018 and 2017, there were no events or circumstances that occurred that would more likely than not reduce the fair value of goodwill below its carrying value .

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2019
Intangible Assets Net Excluding Goodwill [Abstract]
Intangible Assets	Note 11 – Intangible Assets As of December 31, 2019 and 2018, our intangible assets were comprised of the following: 2019 2018 (In thousands) Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 22,356 $ (7,233 ) $ 15,123 $ 22,455 $ (5,380 ) $ 17,075 Developed technology 10,170 (3,379 ) 6,791 12,801 (4,867 ) 7,934 Licensed technology 5,900 (1,174 ) 4,726 5,900 (520 ) 5,380 Supplier relationships 2,800 (2,508 ) 292 2,800 (1,108 ) 1,692 Intellectual property — — — 930 (930 ) — Licensing agreements 560 (79 ) 481 560 (5 ) 555 Patents 500 (226 ) 274 500 (157 ) 343 Trade names 310 (176 ) 134 310 (106 ) 204 Non-compete — — — 200 (200 ) — Total $ 42,596 $ (14,775 ) $ 27,821 $ 46,456 $ (13,273 ) $ 33,183 Amortization expense was $5.3 million, $2.3 million and $2.9 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, the estimated future amortization expense of intangible assets is as follows: (In thousands) Amount 2020 $ 4,444 2021 4,095 2022 3,471 2023 3,320 2024 3,226 Thereafter 9,265 Total $ 27,821

Alabama State Industrial Develo

Alabama State Industrial Development Authority Financing and Economic Incentives	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
Alabama State Industrial Development Authority Financing and Economic Incentives	Note 12 – Alabama State Industrial Development Authority Financing and Economic Incentives In conjunction with the 1995 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 (the “Taxable Revenue Bonds”) and loaned the proceeds from the sale of the Taxable Revenue Bonds to ADTRAN. Further advances on the Taxable Revenue Bonds were made by the Authority, bringing the total amount outstanding to $50.0 million. The Taxable Revenue Bonds bore interest, payable monthly with an interest rate of 2% per annum. The Taxable Revenue Bond’s outstanding aggregate principal amount of $24.6 million matured on January 1, 2020 and was repaid in full on January 2, 2020. In conjunction with this program, we were eligible to receive certain economic incentives from the state of Alabama that reduce the amount of payroll withholdings that we were required to remit to the state for those employment positions that qualify under the program. We realized economic incentives related to payroll withholdings totaling $1.2 million, $1.4 million and $1.5 million for the years ended December 31, 2019, 2018 and 2017, respectively. This program concluded on January 2, 2020 following the maturity of the Taxable Revenue Bonds. No additional benefits will be received in future periods. We made principal payments of $1.0 million and $1.1 million for the years ended December 31, 2019 and 2018. No additional principal payments will be made in future periods.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Note 13 – Income Taxes A summary of the components of the expense (benefit) for income taxes for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 Current Federal $ (518 ) $ (8,001 ) $ 466 State (1,065 ) (476 ) (150 ) International (282 ) 11,705 6,458 Total Current (1,865 ) 3,228 6,774 Deferred Federal 24,801 (14,448 ) 8,024 State 5,815 (3,390 ) 1,882 International (546 ) 581 4,167 Total Deferred 30,070 (17,257 ) 14,073 Total Income Tax Expense (Benefit) $ 28,205 $ (14,029 ) $ 20,847 Our effective income tax rate differs from the federal statutory rate due to the following: 2019 2018 2017 Tax provision computed at the federal statutory rate 21.00 % 21.00 % 35.00 % State income tax provision, net of federal benefit 6.97 14.53 2.17 Federal research credits 15.53 14.23 (11.88 ) Foreign taxes 2.83 (11.45 ) (2.27 ) Tax-exempt income 0.49 0.45 (0.75 ) State tax incentives 3.85 3.15 (2.71 ) Change in valuation allowance (172.82 ) — — Foreign tax credits 16.69 — — Stock-based compensation (6.01 ) (2.87 ) 1.43 Domestic production activity deduction — — (1.13 ) Bargain purchase — 8.82 — Impact of U.S. tax reform — 12.00 26.70 Global intangible low-taxed income ("GILTI") (1.87 ) (17.48 ) — Other, net (0.49 ) (0.34 ) 0.09 Effective Tax Rate (113.83 )% 42.04 % 46.65 % Income (loss) before expense (benefit) for income taxes for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 U.S. entities $ (29,829 ) $ (74,131 ) $ 26,552 International entities 5,052 40,760 18,135 Total $ (24,777 ) $ (33,371 ) $ 44,687 Income (loss) before expense (benefit) for income taxes for international entities reflects income (loss) based on statutory transfer pricing agreements. This amount does not correlate to consolidated international revenue, many of which occur from our U.S. entity. Deferred income taxes on the Consolidated Balance Sheets 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 were as follows: (In thousands) 2019 2018 Deferred tax assets Inventory $ 7,144 $ 6,609 Accrued expenses 2,330 2,850 Investments — 1,122 Deferred compensation 5,660 4,779 Stock-based compensation 2,451 3,069 Uncertain tax positions related to state taxes and related interest 241 326 Pensions 7,074 5,538 Foreign losses 2,925 3,097 State losses and credit carry-forwards 3,995 8,164 Federal loss and research carry-forwards 12,171 17,495 Lease liabilities 2,496 — Capitalized research and development expenditures 22,230 — Valuation allowance (48,616 ) (5,816 ) Total Deferred Tax Assets 20,101 47,233 Deferred tax liabilities Property, plant and equipment (2,815 ) (3,515 ) Intellectual property (5,337 ) (6,531 ) Right of use lease assets (2,496 ) — Investments (1,892 ) — Total Deferred Tax Liabilities (12,540 ) (10,046 ) Net Deferred Tax Assets $ 7,561 $ 37,187 In December 2017, the Tax Cuts and Jobs Act (“the Act”) was signed into law. As a result of the Act, we recognized an estimated expense of $11.9 million in the fourth quarter of 2017, of which $9.2 million related to the write-down of deferred tax assets and $2.7 million related to tax on unrepatriated foreign earnings. We calculated our best estimate of the impact of the Act in our 2017 year-end income tax provision in accordance with Staff Accounting Bulletin No. 118, which was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed to finalize the accounting for certain income tax effects of the Act. Additional work to complete a more detailed analysis of historical foreign earnings, as well as the full impact relating to the write-down of deferred tax assets, was completed in the third quarter of 2018 and resulted in a tax benefit of $4.0 million for the year ended December 31, 2018. As of December 31, 2019 and 2018, non-current deferred taxes related to our investments and our defined benefit pension plan reflect deferred taxes on the net unrealized gains and losses on available-for-sale investments and deferred taxes on unrealized losses in our pension plan. The net change in non-current deferred taxes associated with these items, which resulted in a deferred tax benefit of $0.4 million and $2.8 million in 2019 and 2018, respectively, was recorded as an adjustment to other comprehensive income (loss), presented in the Consolidated Statements of Comprehensive Income (Loss). The Company continually reviews the adequacy of our valuation allowance and recognizes the benefits of deferred tax assets only as the reassessment indicates that it is more likely than not that the deferred tax assets will be realized in accordance with ASC 740, Income Taxes As of December 31, 2019, the Company had gross deferred tax assets totaling $56.2 million offset by a valuation allowance totaling $48.6 million. Of the valuation allowance, $42.8 million was established in the current year primarily related to our domestic deferred tax assets. The remaining $5.8 million established in prior periods related to state research and development credit carryforwards and foreign net operating loss and research and development credit carryforwards where we lack sufficient activity to realize those deferred tax assets. The remaining $7.6 million in deferred tax assets that were not offset by a valuation allowance are located in various foreign jurisdictions where the Company believes it is more likely than not we will realize these deferred tax assets. Supplemental balance sheet information related to deferred tax assets is as follows: December 31, 2019 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 46,266 $ (46,266 ) $ — International 9,911 (2,350 ) 7,561 Total $ 56,177 $ (48,616 ) $ 7,561 As of December 31, 2019 and 2018, the deferred tax assets for foreign and domestic loss carry-forwards, research and development tax credits, unamortized research and development costs and state credit carry-forwards totaled $41.3 million and $28.8 million, respectively. As of December 31, 2019, $19.1 million of these deferred tax assets will expire at various times between 2020 and 2039. The remaining deferred tax assets will either amortize through 2029 or carryforward indefinitely. As of December 31, 2019 and 2018, respectively, our cash and cash equivalents were $73.8 million and $105.5 million and short-term investments were $33.2 million and $3.2 million, which provided available short-term liquidity of $107.0 million and $108.7 million. Of these amounts, our foreign subsidiaries held cash of $52.3 million and $87.1 million, respectively, representing approximately 48.9% and 80.1% of available short-term liquidity, which is used to fund on-going liquidity needs of these subsidiaries. We intend to permanently reinvest these funds outside the U.S. except to the extent any of these funds can be repatriated without withholding tax and our current business plans do not indicate a need to repatriate to fund domestic operations. However, if all of these funds were repatriated to the U.S. or used for U.S. operations, certain amounts could be subject to tax. Due to the timing and circumstances of repatriation of such earnings, if any, it is not practical to determine the amount of funds subject to unrecognized deferred tax liability. During 2019, 2018 and 2017, no income tax benefit or expense was recorded for stock options exercised as an adjustment to equity. The change in the unrecognized income tax benefits for the years ended December 31, 2019, 2018 and 2017 is reconciled below: (In thousands) 2019 2018 2017 Balance at beginning of period $ 1,868 $ 2,366 $ 2,226 Increases for tax position related to: Prior years — 3 465 Current year 161 254 285 Decreases for tax positions related to: Prior years (71 ) — (14 ) Expiration of applicable statute of limitations (471 ) (755 ) (596 ) Balance at end of period $ 1,487 $ 1,868 $ 2,366 As of December 31, 2019, 2018 and 2017, our total liability for unrecognized tax benefits was $1.5 million, $1.9 million and $2.4 million, respectively, of which $1.4 million, $1.7 million and $2.2 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, 2019, 2018 and 2017, the balances of accrued interest and penalties were $0.5 million, $0.7 million and $0.8 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. for federal and various state jurisdictions and several foreign jurisdictions. We are not currently under audit by the Internal Revenue Service. Generally, we are not subject to changes in income taxes by any taxing jurisdiction for the years prior to 2016.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	Note 14 – Employee Benefit Plans Pension Benefit Plan We maintain a defined benefit pension plan covering employees in certain foreign countries. The pension benefit plan obligations and funded status as of December 31, 2019 and 2018, were as follows: (In thousands) 2019 2018 Change in projected benefit obligation: Projected benefit obligation at beginning of period $ 37,245 $ 34,893 Service cost 1,471 1,193 Interest cost 634 727 Actuarial loss - experience 453 38 Actuarial loss - assumptions 5,091 2,139 Benefit payments (166 ) (138 ) Effects of foreign currency exchange rate changes (826 ) (1,607 ) Projected benefit obligation at end of period 43,902 37,245 Change in plan assets: Fair value of plan assets at beginning of period 24,159 26,624 Actual gain (loss) on plan assets 4,392 (2,024 ) Contributions — 688 Effects of foreign currency exchange rate changes (535 ) (1,129 ) Fair value of plan assets at end of period 28,016 24,159 Unfunded status at end of period $ (15,886 ) $ (13,086 ) The accumulated benefit obligation was $43.9 million and $37.2 million as of December 31, 2019 and 2018, respectively. The increase in the accumulated benefit obligation and the actuarial loss was primarily attributable to a decrease in the discount rate during 2019. The net amounts recognized in the balance sheet for the unfunded pension liability as of December 31, 2019 and 2018 were as follows: (In thousands) 2019 2018 Current liability $ — $ — Pension liability 15,886 13,086 Total $ 15,886 $ 13,086 The components of net periodic pension cost, other than the service cost component, are included in other income (expense), net in the Consolidated Statements of Income (Loss). The components of net periodic pension cost and amounts recognized in other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017 were as follows: (In thousands) 2019 2018 2017 Net periodic benefit cost: Service cost $ 1,471 $ 1,193 $ 1,260 Interest cost 634 727 607 Expected return on plan assets (1,392 ) (1,548 ) (1,267 ) Amortization of actuarial losses 795 247 309 Net periodic benefit cost 1,508 619 909 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Net actuarial (gain) loss 2,488 5,638 (654 ) Amortization of actuarial losses (771 ) (196 ) (406 ) Amount recognized in other comprehensive income (loss) 1,717 5,442 (1,060 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 3,225 $ 6,061 $ (151 ) The amounts recognized in accumulated other comprehensive income (loss) as of December 31, 2019 and 2018 were as follows: (In thousands) 2019 2018 Net actuarial loss $ (12,973 ) $ (11,256 ) The defined benefit pension plan is accounted for on an actuarial basis, which requires the use 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. 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 years ended December 31, 2019, 2018 and 2017 were as follows: 2019 2018 2017 Discount rate 1.75 % 2.13 % 1.90 % Rate of compensation increase 2.00 % 2.00 % 2.00 % Expected long-term rates of return 5.90 % 5.90 % 5.90 % The weighted-average assumptions that were used to determine the benefit obligation as of December 31, 2019 and 2018: 2019 2018 Discount rate 1.00 % 1.75 % Rate of compensation increase 2.00 % 2.00 % Actuarial gains and losses are recorded in accumulated other comprehensive income (loss). To the extent unamortized gains and losses exceed 10% of the higher of the market-related value of assets or the projected benefit obligation, the excess is amortized as a component of net periodic pension cost over the remaining service period of active participants. We estimate that $0.8 million will be amortized from accumulated other comprehensive income (loss) into net periodic pension cost in 2020 for the net actuarial loss. We do not anticipate making any contributions to the pension plan in 2020. The following pension benefit payments, which reflect expected future service, as appropriate, are expected to be paid to participants: (In thousands) 2020 $ 515 2021 582 2022 619 2023 706 2024 789 Thereafter 4,872 Total $ 8,083 U.S. GAAP establishes a three-level valuation hierarchy based upon observable and unobservable inputs for fair value measurement of financial instruments: • Level 1 – Observable outputs; values based on unadjusted quoted prices for identical assets or liabilities in an active market; • Level 2 – Significant inputs that are observable; values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; • Level 3 – Significant unobservable inputs; values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs could include information supplied by investees. We have categorized our cash equivalents and our investments held at fair value into this hierarchy as follows: Fair Value Measurements at December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and cash equivalents $ 691 $ 691 $ — $ — Available-for-sale securities Bond funds: Government bonds 6,645 6,645 — — Corporate bonds 5,514 5,514 — — Emerging markets bonds 531 531 — — Equity funds: Global equity 11,071 11,071 — — Emerging markets 956 956 — — Balanced fund 863 863 — — Large cap value 312 312 — — Global real estate fund 902 902 — — Managed futures fund 531 531 — — Available-for-sale securities 27,325 27,325 — — Total $ 28,016 $ 28,016 $ — $ — Fair Value Measurements at December 31, 2018 Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and cash equivalents $ 1,010 $ 1,010 $ — $ — Available-for-sale securities Bond funds: Government bonds 6,268 6,268 — — Corporate bonds 4,840 4,840 — — Emerging markets bonds 443 443 — — Equity funds: Global equity 7,743 7,743 — — Emerging markets 1,188 1,188 — — Balanced fund 815 815 — — Large cap value 262 262 — — Global real estate fund 926 926 — — Managed futures fund 664 664 — — Available-for-sale securities 23,149 23,149 — — Total $ 24,159 $ 24,159 $ — $ — 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 and consider a broad range of economic conditions. Central to the policy are target allocation ranges by asset class, which is currently 50% for bond funds, 40% for equity funds and 10% cash, real estate and managed futures. 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 (the “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 (the “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 ($280,000 for 2019). All matching contributions under the Savings Plan vest immediately. Employer contribution expense and plan administration costs for the Savings Plan amounted to approximately $4.4 million, $4.4 million and $4.6 million in 2019, 2018 and 2017, respectively. Deferred Compensation Plans We maintain four deferred compensation programs for certain executive management employees and our Board of Directors. For our executive management employees, the ADTRAN, Inc. Deferred Compensation Program for Employees 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. This 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. Under this plan, participants may elect to defer all or a portion of their vested PSUs and RSUs 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. For our Board of Directors, we maintain the ADTRAN, Inc. Deferred Compensation Program for Directors. This program allows our Board of Directors to defer all or a portion of monetary remuneration paid to the Director, including, but not limited to, meeting fees and annual retainers. We also maintain the ADTRAN, Inc. Equity Deferral Program for Directors. Under this plan, participants may elect to defer all or a portion of their vested restricted stock awards. 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 director. We have set aside the plan assets for all plans in a rabbi trust (the “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 based on the participant’s election. 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 a s of December 31, 2019 and 2018 wer e as follows: (In thousands) 2019 2018 Fair Value of Plan Assets Long-term investments $ 21,698 $ 18,256 Total Fair Value of Plan Assets $ 21,698 $ 18,256 Amounts Payable to Plan Participants Deferred compensation liability $ 21,698 $ 18,256 Total Amounts Payable to Plan Participants $ 21,698 $ 18,256 Interest and dividend income of the Trust are included in interest and dividend income in the accompanying 2019, 2018 and 2017 Consolidated Statements of Income (Loss). Changes in the fair value of the plan assets held by the Trust have been included in other income (expense) in the accompanying 2019, 2018 and 2017 Consolidated Statements of Income (Loss). Changes in the fair value of the deferred compensation liability are included as selling, general and administrative expense in the accompanying 2019, 2018 and 2017 Consolidated Statements of Income (Loss). Based on the changes in the total fair value of the Trust’s assets, we recorded deferred compensation income (expense) in 2019, 2018 and 2017 of $3.6 million, $(2.1) million and $(2.6) million, respectively. Retiree Medical Coverage We provided medical, dental and prescription drug coverage to two spouses of retired former officers on the same terms as provided to our active officers for up to 30 years. As of December 31, 2019 and 2018, this liability totaled $0.1 million.

Segment Information and Major C

Segment Information and Major Customers	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information and Major Customers	Note 15 – Segment Information and Major Customers Our chief operating decision maker regularly reviews our financial performance based on two reportable segments across our segments– (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware and software products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes a portfolio of maintenance, network implementation and solutions integration services, which include hosted cloud services and subscription services. We evaluate the performance of our segments based on gross profit. Selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment gain (loss), other income (expense) and income tax (expense) benefit are reported on a company-wide, functional 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, 2019, 2018 and 2017. Asset information by reportable segment is not reported, since we do not produce such information internally. (In thousands) 2019 2018 2017 Sales Gross Profit Sales Gross Profit Sales Gross Profit Network Solutions $ 455,226 $ 191,549 $ 458,232 $ 179,303 $ 540,396 $ 260,833 Services & Support 74,835 27,618 71,045 24,262 126,504 42,802 Total $ 530,061 $ 219,167 $ 529,277 $ 203,565 $ 666,900 $ 303,635 Sales by Category In addition to the above reporting segments, we also report revenue for the following three categories – (1) Access & Aggregation, (2) Subscriber Solutions & Experience and (3) Traditional & Other Products. The following tables disaggregates our revenue by major source for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 2018 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 2017 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 361,955 $ 111,989 $ 473,944 Subscriber Solutions & Experience (1) 132,294 6,162 138,456 Traditional & Other Products 46,147 8,353 54,500 Total $ 540,396 $ 126,504 $ 666,900 (1) Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category. Additional Information The following table presents sales information by geographic area for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 United States $ 300,853 $ 288,843 $ 508,178 Mexico 90,795 12,186 2,246 Germany 78,062 167,251 119,502 Other international 60,351 60,997 36,974 Total $ 530,061 $ 529,277 $ 666,900 Customers comprising more than 10% of revenue can change from year to year. Single customers comprising more than 10% of our revenue in 2019 included three customers at 19%, 17% and 13%. Single customers comprising more than 10% of our revenue in 2018 included two customers at 27% and 17%. Single customers comprising more than 10% of our revenue in 2017 included two customers at 40% and 16%. Other than those with more than 10% of revenues disclosed above, and excluding distributors, our next five largest customers can change, and has historically changed, from year-to-year. These combined customers represented 15%, 18% and 15% of total revenue in 2019, 2018 and 2017, respectively. As of December 31, 2019, property, plant and equipment, net totaled $73.7 million, which included $69.9 million held in the U.S. and $3.9 million held outside the U.S. As of December 31, 2018, property, plant and equipment, net totaled $80.6 million, which included $77.3 million held in the U.S. and $3.3 million held outside the U.S. Property, plant and equipment, net is reported on a company-wide, functional basis only.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 16 – Commitments and Contingencies Securities Class Action Lawsuit On October 17, 2019, a purported stockholder class action lawsuit, captioned Burbridge v. ADTRAN, Inc. et al., Docket No. 19-cv-09619, was filed in the United States District Court for the Southern District of New York against the Company, two of its current executive officers and one of its former executive officers. The complaint alleges violations of federal securities laws and seeks unspecified compensatory damages on behalf of purported purchasers of ADTRAN securities between February 28, 2019 and October 9, 2019. The lawsuit claims that the defendants made materially false and misleading statements regarding, and/or failed to disclose material adverse facts about, the Company’s business, operations and prospects, specifically relating to the Company’s internal control over financial reporting, excess and obsolete inventory reserves, financial results and shipments to a Latin American customer. Investors in ADTRAN securities had until December 16, 2019 to move the court to serve as lead plaintiff in this action. On December 16, 2019, two purported investors in ADTRAN securities filed motions seeking to be appointed lead plaintiff in the case. On January 6, 2020, the United States District Court for the Southern District of New York granted Defendants’ unopposed request to transfer the case to the United States District Court for the Northern District of Alabama, where the case is now pending as Burbridge v. ADTRAN, Inc. et al., Docket No. 5:20-cv-00050-LCB. On January 27, 2020, the two prospective lead plaintiff movants filed a stipulation among plaintiffs seeking to be appointed as co-lead plaintiffs in the case. We disagree with the claims made in the complaint and intend to vigorously defend against this lawsuit. At this time, we are unable to predict the outcome of or estimate the possible loss or range of loss, if any, associated with this lawsuit. Other Legal Matters In addition to the litigation described above, from time to time we are subject to or otherwise involved in various lawsuits, claims, investigations and legal proceedings that arise out of or are incidental to the conduct of our business (collectively, “Legal Matters”), including those relating to employment matters, patent rights, regulatory compliance matters, stockholder claims, and contractual and other commercial disputes. Such Legal Matters, even if not meritorious, could result in the expenditure of significant financial and managerial resources. Additionally, an unfavorable outcome in a legal matter, including in a patent dispute, could require the Company to pay damages, entitle claimants to other relief, such as royalties, or could prevent the Company from selling some of its products in certain jurisdictions. While the Company cannot predict with certainty the results of the Legal Matters in which it is currently involved, the Company does not expect that the ultimate outcome of such Legal Matters will individually or in the aggregate have a material adverse effect on its business, results of operations, financial condition or cash flows. Investment Commitment We have committed to invest up to an aggregate of $7.9 million in two private equity funds, of which $7.7 million has been applied to these commitments as of December 31, 2019. Performance Bonds Certain contracts, customers and/or jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of December 31, 2019, we had commitments related to these bonds totaling $9.3 million which expire at various dates through August 2024. As of December 31, 2018, we had commitments related to these bonds totaling $6.5 million. Although the triggering events vary from contract to contract, in general we would only be liable for the amount of these guarantees in the event of default in our under each contract, the probability of which we believe is remote.

Earnings (Loss) per Share

Earnings (Loss) per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings (Loss) per Share	Note 17 – Earnings (Loss) per Share A summary of the calculation of basic and diluted earnings (loss) per share for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands, except for per share amounts) 2019 2018 2017 Numerator Net Income (Loss) $ (52,982 ) $ (19,342 ) $ 23,840 Denominator Weighted average number of shares – basic 47,836 47,880 48,153 Effect of dilutive securities: Stock options — — 406 Restricted stock and restricted stock units — — 140 Weighted average number of shares – diluted 47,836 47,880 48,699 Earnings (loss) per share – basic $ (1.11 ) $ (0.40 ) $ 0.50 Earnings (loss) per share – diluted $ (1.11 ) $ (0.40 ) $ 0.49 For each of the years ended December 31, 2019 and 2018, 5.7 million and 2.5 million, respectively, shares of unvested stock options, PSUs, RSUs and restricted stock were excluded from the calculation of diluted EPS due to their anti-dilutive effect. For the year ended December 31, 2017, 3.2 million stock options were outstanding but were not included in the computation of diluted earnings (loss) per share 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.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Restructuring	Note 18 – Restructuring During the second half of 2019, the Company implemented a restructuring plan to realign its expense structure with the reduction in revenue experienced in recent years and overall Company objectives. Management assessed the efficiency of our operations and consolidated locations and personnel, among other things, where possible. As part of this restructuring plan, the Company announced plans to reduce its overall operating expenses, both in the U.S and internationally. In February 2019, the Company announced the restructuring of certain of our workforce predominantly in Germany, which included the closure of our office location in Munich, Germany accompanied by relocation or severance benefits for the affected employees. We also offered voluntary early retirement to certain other employees, which was announced in March 2019. In January 2018, the Company announced an early retirement incentive program for employees that met certain defined requirements. The cumulative amount incurred during the year ended December 31, 2018 related to this restructuring program was $7.3 million. We did not incur any additional expenses related to this restructuring program during the year ended December 31, 2019. A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Consolidated Balance Sheets as of December 31, 2019 and 2018, is as follows: (In thousands) 2019 2018 Balance at beginning of period $ 185 $ 205 Plus: Amounts charged to cost and expense 6,014 7,261 Less: Amounts paid (4,631 ) (7,281 ) Balance at end of period $ 1,568 $ 185 The components of restructuring expense in the Consolidated Statements of Income are for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 Selling, general and administrative expenses $ 2,360 $ 2,655 $ 152 Research and development expenses 2,869 1,831 122 Cost of sales 785 2,775 — Total restructuring expenses $ 6,014 $ 7,261 $ 274 The following table represents the components of restructuring expense by geographic area for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 United States $ 3,336 $ 7,120 $ 274 International 2,678 141 — Total restructuring expenses $ 6,014 $ 7,261 $ 274

Summarized Quarterly Financial

Summarized Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Summarized Quarterly Financial Data (Unaudited)	Note 19 – 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 Three Months Ended (In thousands, except for per share amounts) March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 Net sales $ 143,791 $ 156,391 $ 114,092 $ 115,787 Gross profit $ 60,612 $ 65,015 $ 46,331 $ 47,209 Operating income (loss) $ (6,167 ) $ 562 $ (20,288 ) $ (14,070 ) Net income (loss) $ 770 $ 3,995 $ (46,123 ) $ (11,624 ) Earnings (loss) per common share - basic $ 0.02 $ 0.08 $ (0.96 ) $ (0.25 ) Earnings (loss) per common share - diluted $ 0.02 (1) $ 0.08 (1) $ (0.96 ) $ (0.25 ) Three Months Ended (In thousands, except for per share amounts) March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Net sales $ 120,806 $ 128,048 $ 140,335 $ 140,088 Gross profit $ 39,733 $ 49,996 $ 58,448 $ 55,388 Operating income (loss) $ (26,647 ) $ (12,813 ) $ (2,179 ) $ (3,783 ) Net income (loss) $ (10,814 ) $ (7,670 ) $ 7,589 $ (8,447 ) Earnings (loss) per common share - basic $ (0.22 ) $ (0.16 ) $ 0.16 $ (0.18 ) Earnings (loss) per common share - diluted $ (0.22 ) $ (0.16 ) $ 0.16 (1) $ (0.18 ) (1)

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Note 20 – Subsequent Events On January 2, 2020, we paid off the outstanding balance of $24.6 million of the Taxable Revenue Bonds upon their maturity. We used a restricted certificate of deposit which was held as collateral to repay the outstanding balance. On February 5, 2020, 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 20, 2020. The quarterly dividend will be paid on March 5, 2019 payment in the aggregate amount of approximately $4.3 million. In July 2003, our Board of Directors elected to begin declaring quarterly dividends on our common stock considering the tax treatment of dividends and adequate levels of Company liquidity.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
Valuation And Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (In thousands) Balance at Beginning of Period Charged to Costs & Expenses Deductions Balance at End of Period Year ended December 31, 2019 Allowance for Doubtful Accounts $ 128 38 128 $ 38 Inventory Reserve $ 30,009 5,893 1,740 $ 34,162 Warranty Liability $ 8,623 4,569 4,798 $ 8,394 Deferred Tax Asset Valuation Allowance $ 5,816 43,560 760 $ 48,616 Year ended December 31, 2018 Allowance for Doubtful Accounts $ — 128 — $ 128 Inventory Reserve $ 23,355 7,006 352 $ 30,009 Warranty Liability $ 9,724 7,392 8,493 $ 8,623 Deferred Tax Asset Valuation Allowance $ 6,006 — 190 $ 5,816 Year ended December 31, 2017 Allowance for Doubtful Accounts $ — — — $ — Inventory Reserve $ 25,249 6,406 8,300 $ 23,355 Warranty Liability $ 8,548 6,951 5,775 $ 9,724 Deferred Tax Asset Valuation Allowance $ 6,149 18 161 $ 6,006

Nature of Business (Policies)

Nature of Business (Policies)	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the U.S. (“U.S. GAAP”) and include the financial position, results of operations, comprehensive income (loss), changes in equity and cash flows of ADTRAN and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP 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 expenses during the reporting period. Our more significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues and network installations, estimated income tax provision and income tax contingencies, fair value of stock-based compensation, assessment of goodwill and other intangibles for impairment, estimated lives of intangible assets, estimated pension liability, fair value of investments and evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
Correction of Immaterial Misstatements	Correction of Immaterial Misstatement During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserves and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in the Company’s excess and obsolete inventory reserves and cost of goods sold.
Cash and Cash Equivalents	Summary of Significant Accounting Policies 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, 2019, $71.6 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 $24.6 million, which was its fair value as of December 31, 2019. Investments with contractual maturities beyond one year 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 recorded any losses relating to variable rate demand notes. Long-term investments is comprised of deferred compensation plan assets, corporate bonds, municipal fixed-rate bonds, asse t-backed bonds, mortgage/agency- backed bonds, U.S. and foreign government bonds, m arketable 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. Any changes in fair value are recognized in net investment gain (loss). Realized gains and losses on sales of debt securities are computed under the specific identification method and are included in other income (expense) . See Note 5 for additional information.
Accounts Receivable	Accounts Receivable We record accounts receivable at net realizable value. Prior to establishing payment terms for a new customer, we evaluate the credit risk of the customer. Credit limits and payment terms established for new customers are re-evaluated periodically based on customer collection experience and other financial factors. As of December 31, 2019, single customers comprising more than 10% of our total accounts receivable balance included four customers, which accounted for 53.2% of our total accounts receivable. As of December 31, 2018, single customers comprising more than 10% of our total accounts receivable balance included two customers, which accounted for 36.9% of our total accounts receivable. We regularly review the need to maintain an 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 impacting these customers 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 $38 thousand and $0.1 million as of December 31, 2019 and December 31, 2018, respectively.
Inventory	Inventory Inventory is carried at the lower of cost and estimated net realizable value, with cost being determined using the first-in, first-out method. Standard costs for material, labor and manufacturing overhead are used to value inventory and are updated at least quarterly. We establish reserves for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on estimated reserve percentages, which consider historical usage, known trends, inventory age and market conditions. When we dispose of excess and obsolete inventories, the related disposals are charged against the inventory reserve. See Note 7 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. Major improvements that materially prolong the lives of the assets are capitalized. Gains and losses on the disposal of property, plant and equipment are recorded in operating income (loss). See Note 8 for additional information.
Intangible Assets	Intangible Assets 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 two to 14 years .
Impairment of Long-Lived Assets and Intangibles	Impairment of Long-Lived Assets and Intangibles Long-lived assets used in operations and intangible assets are reviewed 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. During the year ended December 31, 2019, we recognized an impairment loss of approximately $3.9 million related to the abandonment of certain information technology implementation projects which we had previously capitalized expenses related to these projects. There were no impairment losses for long-lived assets during the years ended December 31, 2018 or 2017, or for intangible assets recognized during the years ended December 31, 2019, 2018 or 2017.
Goodwill	Goodwill Goodwill represents the excess purchase price over the fair value of net assets acquired. We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. We have elected to by-pass a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount and, in turn, performed a step-1 analysis of goodwill. Based on the results of our step-1 analysis, no impairment charges on goodwill were recognized during the years ended December 31, 2019, 2018 and 2017.
Liability for Warranty	Liability for Warranty Our products generally include warranties of 90 days to five years for product defects. We accrue for warranty returns at the time revenue is recognized based on our historical return rate and 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. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $8.4 million and $8.6 million as of December 31, 2019 and 2018, respectively. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets. During 2017, we recorded a reduction in warranty expense related to a settlement with a third-party supplier for a defective component, the impact of which is reflected in the following table. A summary of warranty expense and write-off activity for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 Year Ended December 31, Balance at beginning of period $ 8,623 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses 4,569 7,392 6,951 Less: Deductions (4,798 ) (8,493 ) (5,775 ) Balance at end of period $ 8,394 $ 8,623 $ 9,724
Pension Benefit Plan Obligations	Pension Benefit Plan Obligations We maintain 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. Our net pension liability totaled $15.9 million and $13.1 million as of December 31, 2019 and 2018, respectively.
Stock-Based Compensation	Stock-Based Compensation We have two stock incentive plans from which stock options, performance stock units (“PSUs”), restricted stock units (“RSUs”) and restricted stock are available for grant to employees and directors. Costs related to these awards are recognized over their vesting periods. 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. All of our outstanding stock option awards are classified as equity awards and therefore are measured at fair value on their grant date. Stock-based compensation expense recognized for the years ended December 31, 2019, 2018 and 2017 was approximately $7.0 million, $7.2 million and $7.4 million, respectively. As of December 31, 2019, total unrecognized compensation cost related to non-vested stock options, PSUs, RSUs and restricted stock was approximately $17.2 million, which is expected to be recognized over an average remaining recognition period of 3.0 years. See Note 4 for additional information.
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, 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 $126.2 million, $124.5 million and $130.7 million for the years ended December 31, 2019, 2018 and 2017, respectively.
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following table presents changes in accumulated other comprehensive income (loss), net of tax, by components of accumulated other comprehensive income (loss) for the years ended December 31, 2019 2018 and 2017: (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (2) Total Balance as of December 31, 2016 $ 404 $ — $ (5,017 ) $ (7,575 ) $ — $ (12,188 ) Other comprehensive income before reclassifications 5,020 (619 ) 451 5,999 — 10,851 Amounts reclassified from accumulated other comprehensive loss (2,857 ) 619 280 — — (1,958 ) Balance as of December 31, 2017 2,567 — (4,286 ) (1,576 ) — (3,295 ) Other comprehensive loss before reclassifications 685 — (3,890 ) (4,236 ) — (7,441 ) Amounts reclassified to retained earnings (1) (3,220 ) — — — — (3,220 ) Amounts reclassified from accumulated other comprehensive loss (595 ) — 135 — — (460 ) Balance as of December 31, 2018 (563 ) — (8,041 ) (5,812 ) — (14,416 ) Other comprehensive loss before reclassifications 573 — (1,717 ) (1,480 ) — (2,624 ) Amounts reclassified to retained earnings (1) — — — — 385 385 Amounts reclassified from accumulated other comprehensive loss (294 ) — 532 — — 238 Balance as of December 31, 2019 $ (284 ) $ — $ (9,226 ) $ (7,292 ) $ 385 $ (16,417 ) (1) With the adoption of ASU 2016-01, the unrealized gains on our equity investments were reclassified to retained earnings. See Recently Issued Accounting Standards below for more information. (2) With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 13 for additional information. The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 397 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (771 ) (1) Total reclassifications for the period, before tax (374 ) Tax benefit 136 Total reclassifications for the period, net of tax $ (238 ) (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2018 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 804 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (196 ) (1) Total reclassifications for the period, before tax 608 Tax expense (148 ) Total reclassifications for the period, net of tax $ 460 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 4,864 Net investment gain (loss) Impairment expense (180 ) Net investment gain (loss) Net losses on derivatives designated as hedging instruments (897 ) Cost of sales Defined benefit plan adjustments – actuarial losses (406 ) (1) Total reclassifications for the period, before tax 3,381 Tax expense (1,423 ) Total reclassifications for the period, net of tax $ 1,958 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. The following tables present the tax effects related to the change in each component of other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 774 $ (201 ) $ 573 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (397 ) 103 (294 ) Defined benefit plan adjustments (2,488 ) 771 (1,717 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 771 (239 ) 532 Foreign currency translation adjustment (1,480 ) — (1,480 ) Total Other Comprehensive Income (Loss) $ (2,820 ) $ 434 $ (2,386 ) 2018 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 926 $ (241 ) $ 685 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (804 ) 209 (595 ) Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01 (4,351 ) 1,131 (3,220 ) Defined benefit plan adjustments (5,638 ) 1,748 (3,890 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 196 (61 ) 135 Foreign currency translation adjustment (4,236 ) — (4,236 ) Total Other Comprehensive Income (Loss) $ (13,907 ) $ 2,786 $ (11,121 ) 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 8,230 $ (3,210 ) $ 5,020 Reclassification adjustment for amounts related to available-for-sale investments included in net income (4,684 ) 1,827 (2,857 ) Unrealized gains (losses) on cash flow hedges (897 ) 278 (619 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 897 (278 ) 619 Defined benefit plan adjustments 654 (203 ) 451 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 406 (126 ) 280 Foreign currency translation adjustment 5,999 — 5,999 Total Other Comprehensive Income (Loss) $ 10,605 $ (1,712 ) $ 8,893
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 using appropriate exchange rates from throughout the year. Assets and liabilities denominated in foreign currencies are remeasured at the balance sheet dates using the closing rates of exchange between those foreign currencies and the functional currency with any transaction gains or losses reported in other income (expense). Our primary exposures to foreign currency exchange rate movements are with our German subsidiary, whose functional currency is the Euro, our Australian subsidiary, whose functional currency is the Australian dollar and our Mexican subsidiary, whose functional currency is the U.S. dollar as most invoices are paid in Mexican Pesos. Adjustments resulting from translating financial statements of international subsidiaries are recorded as a component of accumulated other comprehensive income (loss).
Revenue	Revenue On January 1, 2018, we adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), Revenue Recognition. Accounting Policy under Topic 606 Revenue is measured based on the consideration we expect to receive in exchange for transferring goods or providing services to a customer and as performance obligations under the terms of the contract are satisfied. Generally, this occurs with the transfer of control of a product to the customer. Review of contracts with customers, for both direct customers and distributors, are performed and assessment made regarding principal versus agent considerations to determine primary responsibility for delivery of performance obligation, presumed inventory risk, and discretion in establishing pricing. For transactions where there are multiple performance obligations, we account for individual products and services separately if they are distinct (if a product or service is separately identifiable from other items and if a customer can benefit from it on its own or with other resources that are readily available to the customer). The consideration, including any discounts, is allocated between separate products and services based on their stand-alone selling prices. Stand-alone selling prices are determined based on the prices at which we sell the separate products and services and are allocated based on each item’s relative value to the total value of the products and services in the arrangement. For items that are not sold separately, we estimate stand-alone selling prices primarily using the “expected cost plus a margin” approach. Payment terms are generally 30 days in the U.S. and typically longer in many geographic markets outside the U.S. The following is a description of the principal activities from which we generate our revenue by reportable segment. Network Solutions Segment Network Solutions includes hardware products and software defined next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. The majority of the revenue from this segment is from hardware sales. Hardware and Software Revenue Revenue from hardware sales is recognized when control is transferred to our customers, which is generally when we ship the products. Shipping terms are generally FOB shipping point. This segment also includes revenues from software license sales which is recognized at delivery and transfer of control to the customer. Revenue is recorded net of estimated discounts and rebates using historical trends. Customers are typically invoiced when control is transferred and revenue is recognized. Our products generally include assurance-based warranties of 90 days to five years for product defects, which are accrued at the time revenue is recognized. In certain transactions, we are also the lessor in sales-type lease arrangements for network equipment that have terms of 18 months to five years. These arrangements typically include network equipment, network implementation services and maintenance services. Services & Support Segment To complement our Network Solutions segment, we offer a complete portfolio of maintenance, network implementation and solutions integration and managed services, which include hosted cloud services and subscription services. Maintenance Revenue Our maintenance service periods range from one month to five years. Customers are typically invoiced and pay for maintenance services at the beginning of the maintenance period. We recognize revenue for maintenance services on a straight-line basis over the maintenance period as our customers benefit evenly throughout the contract term and deferred revenues, when applicable, are recorded in current and non-current unearned revenue. Network Implementation Revenue We recognize revenue for network implementation, which primarily consists of engineering, execution and enablement services at a point in time when each performance obligation is complete. If we have recognized revenue but have not billed the customer, the right to consideration is recognized as a contract asset that is included in other receivables on the Consolidated Balance Sheet. The contract asset is transferred to accounts receivable when the completed performance obligation is invoiced to the customer. Accounting Policy under Topic 605 Revenue was generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the product price was fixed or determinable, collection of the resulting receivable was reasonably assured, and product returns were reasonably estimable. For product sales, revenue was generally recognized upon shipment of the product to our customer in accordance with the title transfer terms of the sales agreement, generally Ex Works, per International Commercial Terms. In the case of consigned inventory, revenue was recognized when the end customer assumes ownership of the product. Contracts that contained multiple deliverables were evaluated to determine the units of accounting, and the consideration from the arrangement was allocated to each unit of accounting based on the relative selling price and corresponding terms of the contract. When this was not available, we were 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. In these instances, we used best estimates to allocate consideration to each respective unit of accounting. These estimates included analysis of respective bills of material and review and analysis of similar product and service offerings. We recorded revenue associated with installation services when respective contractual obligations are complete. In instances where customer acceptance was required, revenue was deferred until respective acceptance criteria were met. Contracts that included both installation services and product sales were evaluated for revenue recognition in accordance with contract terms. As a result, installation services may have been considered a separate deliverable or may have been considered a combined single unit of accounting with the delivered product. Generally, either the purchaser, ADTRAN, or a third party would perform the installation of our products. Shipping fees were recorded as revenue and the related costs were included in cost of sales. Sales taxes invoiced to customers were included in revenues and represented less than one percent of total revenues. The corresponding sales taxes paid were included in cost of goods sold. Value-added taxes collected from customers in international jurisdictions were recorded in accrued expenses as a liability. Revenue was recorded net of discounts. Sales returns were recorded as a reduction of revenue and accrued based on historical sales return experience, which we believed provided a reasonable estimate of future returns.
Unearned Revenue	Unearned Revenue Unearned revenue primarily represents customer billings on our maintenance service programs and unearned revenues related to multiple element contracts where we still have contractual obligations to our customers. We currently offer maintenance contracts ranging from one month to five years. 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 customers under contracts with terms up to ten years. When we defer revenue related to multiple performance obligations where we still have contractual obligations, we also defer the related costs. Current deferred costs are included in prepaid expenses and other current assets on the accompanying Consolidated Balance Sheets and totaled $1.6 million and $2.4 million as of December 31, 2019 and 2018, respectively. Non-current deferred costs are included in other assets on the accompanying Consolidated Balance Sheets and totaled $0.1 million and $0.8 million as of December 31, 2019 and 2018, respectively.
Earnings (Loss) per Share	Earnings (Loss) per Share Earnings (loss) per common share and earnings (loss) 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 17 for additional information.
Business Combinations	Business Combinations The Company records assets acquired, liabilities assumed, contractual contingencies, when applicable, and intangible assets recognized as part of business combinations based on their fair values on the date of acquisition. The excess of the purchase price over the estimated fair values of the net tangible and intangible assets and liabilities assumed acquired is recorded as goodwill. If the estimated fair values of net tangible and intangible assets acquired and liabilities assumed exceed the purchase price, a bargain purchase gain is recorded. The Company’s estimates of fair value are based on historical experience, industry knowledge, certain information obtained from the management of the acquired company and, in some cases, valuations performed by independent third-party firms. The results of operations of acquired companies are included in the accompanying Consolidated Statements of Operations since their dates of acquisition. Costs incurred to complete the business combination, such as legal, accounting or other professional fees are charged to selling, general and administrative expenses as incurred.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities Historically, we have participated in foreign exchange forward contracts in connection with the management of exposure to fluctuations in foreign exchange rates as outlined below. Cash Flow Hedges Our cash flow hedging activities utilize foreign exchange forward contracts to reduce the risk that movements in exchange rates will adversely affect the net cash flows resulting from the planned purchase of products from foreign suppliers. Purchases of U.S. denominated inventory by our European subsidiary represent our primary exposure. Changes in the fair value of derivatives designated as cash flow hedges are recorded in accumulated other comprehensive income. Amounts related to cash flow hedges are reclassified from accumulated other comprehensive income to earnings when the underlying hedged item impacts earnings. This reclassification is recorded in the same line item of the consolidated statements of income as where the effects of the hedged item are recorded, which is cost of sales. Undesignated Hedges We have certain customers and suppliers who are invoiced or pay in a non-functional currency. Changes in the monetary exchange rates may adversely affect our results of operations and financial condition, as outstanding non-functional balances are revalued to the functional currency through earnings. When appropriate, we utilize foreign exchange forward contracts to help manage the volatility relating to these valuation exposures. All changes in the fair value of our derivative instruments that do not qualify for, or are not designated for, hedged accounting transactions are recognized in other income (expense), net in the Consolidated Statements of Income. We do not hold or issue derivative instruments for trading or other speculative purposes. Our derivative instruments are recorded on the Consolidated Balance Sheets at their fair values. Our derivative instruments are not subject to master netting arrangements and are not offset on the Consolidated Balance Sheets.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Codification Improvements to Topic 326 Financial Instruments – Credit Losses, Codification Improvements to Topic 326, Financial Instruments–Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief, Codification improvements to Topic 326, Financial Instruments – Credit Losses In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, Fair Value Measurement. Concepts Statement No. 8 — Conceptual Framework for Financial Reporting — Chapter 8 — Notes to Financial Statements In August 2018, the FASB issued ASU 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans, In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementations costs incurred to develop or obtain internal use software. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the effect of ASU 2018-15, but do not expect it will have a material effect on our consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements During 2019, we adopted the following accounting standards, which had the following impacts on our consolidated financial statements: In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), Codification Improvements to Topic 842 Leases Leases (Topic 842), Targeted Improvements Leases (Topic 840) Leases (Topic 842) Codification Improvements The Company adopted the new standard on January 1, 2019, the effective date of our initial application, using the optional transition method. At that time, the Company elected to carry forward the legacy ASC 840 disclosures for comparative periods and, therefore, did not adjust the comparative period financial information prior to January 1, 2019. In addition, the Company elected the package of practical expedients which allows for companies to not reassess whether any expired or existing contracts are or contain leases, not reassess historical lease classifications for expired or existing contracts and not reassess initial direct costs for existing leases. Additionally, the Company elected the practical expedients which allow the use of hindsight when determining the lease term, the short-term lease recognition exemption and the option to not separate lease and nonlease components. The adoption of this standard resulted in the recognition of a right-of-use asset and corresponding right-of-use liability on our Consolidated Balance Sheets of $10.3 million as of January 1, 2019, primarily related to our operating leases for office space, automobiles and other equipment. As a lessee, the adoption of this standard did not have a material impact on our Consolidated Statement of Income or Statement of Cash Flows. See Note 9 for additional information. As a lessor, the adoption of this standard did not have a material impact on our Consolidated Balance Sheet, Consolidated Statement of Income or Consolidated Statement of Cash Flows. Prior to and after adoption, all of our leases in which we are the lessor were classified as sales-type leases. In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities , which shortened the amortization period for the premium on certain purchased callable debt securities to the earliest call date. ASU 2017-08 was effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2018. The amendments were required to be applied through a modified-retrospective transition approach that required a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company adopted ASU 2017-08 on January 1, 2019, and the adoption of this standard did not have a material effect on our consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (“SOFR”) Overnight Index Swap (“OIS”) Rate as a Benchmark Interest Rate for Hedge Accounting, In February 2018, the FASB issued ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Comprehensive Income.

Nature of Business (Tables)

Nature of Business (Tables)	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Warranty Expense and Write-Off Activity	A summary of warranty expense and write-off activity for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 Year Ended December 31, Balance at beginning of period $ 8,623 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses 4,569 7,392 6,951 Less: Deductions (4,798 ) (8,493 ) (5,775 ) Balance at end of period $ 8,394 $ 8,623 $ 9,724
Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Components of Accumulated Other Comprehensive Income (Loss)	The following table presents changes in accumulated other comprehensive income (loss), net of tax, by components of accumulated other comprehensive income (loss) for the years ended December 31, 2019 2018 and 2017: (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (2) Total Balance as of December 31, 2016 $ 404 $ — $ (5,017 ) $ (7,575 ) $ — $ (12,188 ) Other comprehensive income before reclassifications 5,020 (619 ) 451 5,999 — 10,851 Amounts reclassified from accumulated other comprehensive loss (2,857 ) 619 280 — — (1,958 ) Balance as of December 31, 2017 2,567 — (4,286 ) (1,576 ) — (3,295 ) Other comprehensive loss before reclassifications 685 — (3,890 ) (4,236 ) — (7,441 ) Amounts reclassified to retained earnings (1) (3,220 ) — — — — (3,220 ) Amounts reclassified from accumulated other comprehensive loss (595 ) — 135 — — (460 ) Balance as of December 31, 2018 (563 ) — (8,041 ) (5,812 ) — (14,416 ) Other comprehensive loss before reclassifications 573 — (1,717 ) (1,480 ) — (2,624 ) Amounts reclassified to retained earnings (1) — — — — 385 385 Amounts reclassified from accumulated other comprehensive loss (294 ) — 532 — — 238 Balance as of December 31, 2019 $ (284 ) $ — $ (9,226 ) $ (7,292 ) $ 385 $ (16,417 ) (1) With the adoption of ASU 2016-01, the unrealized gains on our equity investments were reclassified to retained earnings. See Recently Issued Accounting Standards below for more information. (2) With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 13 for additional information.
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 397 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (771 ) (1) Total reclassifications for the period, before tax (374 ) Tax benefit 136 Total reclassifications for the period, net of tax $ (238 ) (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2018 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains on available-for-sale securities: Net realized gain on sales of securities $ 804 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (196 ) (1) Total reclassifications for the period, before tax 608 Tax expense (148 ) Total reclassifications for the period, net of tax $ 460 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information. (In thousands) 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain on sales of securities $ 4,864 Net investment gain (loss) Impairment expense (180 ) Net investment gain (loss) Net losses on derivatives designated as hedging instruments (897 ) Cost of sales Defined benefit plan adjustments – actuarial losses (406 ) (1) Total reclassifications for the period, before tax 3,381 Tax expense (1,423 ) Total reclassifications for the period, net of tax $ 1,958 (1) Included in the computation of net periodic pension cost. See Note 14 for additional information.
Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss)	The following tables present the tax effects related to the change in each component of other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 774 $ (201 ) $ 573 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (397 ) 103 (294 ) Defined benefit plan adjustments (2,488 ) 771 (1,717 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 771 (239 ) 532 Foreign currency translation adjustment (1,480 ) — (1,480 ) Total Other Comprehensive Income (Loss) $ (2,820 ) $ 434 $ (2,386 ) 2018 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 926 $ (241 ) $ 685 Reclassification adjustment for amounts related to available-for-sale investments included in net loss (804 ) 209 (595 ) Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01 (4,351 ) 1,131 (3,220 ) Defined benefit plan adjustments (5,638 ) 1,748 (3,890 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net loss 196 (61 ) 135 Foreign currency translation adjustment (4,236 ) — (4,236 ) Total Other Comprehensive Income (Loss) $ (13,907 ) $ 2,786 $ (11,121 ) 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 8,230 $ (3,210 ) $ 5,020 Reclassification adjustment for amounts related to available-for-sale investments included in net income (4,684 ) 1,827 (2,857 ) Unrealized gains (losses) on cash flow hedges (897 ) 278 (619 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 897 (278 ) 619 Defined benefit plan adjustments 654 (203 ) 451 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 406 (126 ) 280 Foreign currency translation adjustment 5,999 — 5,999 Total Other Comprehensive Income (Loss) $ 10,605 $ (1,712 ) $ 8,893

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Final Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed	The final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for SmartRG and the final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for Sumitomo are as follows: (In thousands) Sumitomo SmartRG Assets Tangible assets acquired $ 1,006 $ 8,594 Intangible assets 22,100 9,960 Goodwill — 3,476 Total assets acquired 23,106 22,030 Liabilities Liabilities assumed (3,978 ) (6,001 ) Total liabilities assumed (3,978 ) (6,001 ) Total net assets 19,128 16,029 Gain on bargain purchase of a business, net of tax (11,322 ) — Total purchase price $ 7,806 $ 16,029
Summary of Actual Revenue and Net Loss Included in Consolidated Statements of Income	Our Consolidated Statements of Income include the following revenue and net loss attributable to SmartRG and Sumitomo since the date of acquisition: (In thousands) March 19, 2018 to December 31, 2018 Revenue $ 9,186 Net loss $ (1,297 )
Details of the Acquired Intangible Assets	The details of the acquired intangible assets from the SmartRG and Sumitomo acquisitions are as follows: (In thousands) Value Life (in years) Customer relationships $ 15,190 3 - 12 Developed technology 7,400 7 Licensed technology 5,900 9 Supplier relationship 2,800 2 Licensing agreements 560 5 - 10 Trade name 210 3 Total $ 32,060
Summary of Unaudited Supplemental Pro Forma Information	The following unaudited supplemental pro forma information presents the financial results as if the acquisition of SmartRG and Sumitomo had occurred on January 1, 2017. This unaudited supplemental pro forma information does not purport to be indicative of what would have occurred had the acquisition been completed on January 1, 2017, nor is it indicative of any future results. Aside from revising the 2017 net income for the effect of the bargain purchase gains, there were no material, non-recurring adjustments to this unaudited pro-forma information. (In thousands) 2018 2017 Pro forma revenue $ 559,050 $ 702,573 Pro forma net loss $ (33,862 ) $ 33,206

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Disaggregate of Revenue by Major Source	The following table disaggregates our revenue by major source for the year ended December 31, 2019: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 (1) The following table disaggregates our revenue by major source for the year ended December 31, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 (1) The following tables disaggregates our revenue by major source for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 2018 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 2017 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 361,955 $ 111,989 $ 473,944 Subscriber Solutions & Experience (1) 132,294 6,162 138,456 Traditional & Other Products 46,147 8,353 54,500 Total $ 540,396 $ 126,504 $ 666,900 (1) Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.
Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers	The following table provides information about accounts receivables, contract assets and unearned revenue from contracts with customers: (In thousands) December 31, 2019 December 31, 2018 Accounts receivable $ 90,531 $ 99,385 Contract assets (1) $ 2,812 $ 3,766 Unearned revenue $ 11,963 $ 17,940 Non-current unearned revenue $ 6,012 $ 5,296 (1)

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock	The following table summarizes stock-based compensation expense related to stock options, PSUs, RSUs and restricted stock for the years ended December 31, 2019, 2018 and 2017, which was recognized as follows: (In thousands) 2019 2018 2017 Stock-based compensation expense included in cost of sales $ 369 $ 418 $ 379 Selling, general and administrative expense 3,889 3,989 4,063 Research and development expense 2,704 2,748 2,991 Stock-based compensation expense included in operating expenses 6,593 6,737 7,054 Total stock-based compensation expense 6,962 7,155 7,433 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (1,659 ) (1,432 ) (1,699 ) Total stock-based compensation expense, net of tax $ 5,303 $ 5,723 $ 5,734
Summary of PSUs, RSUs and Restricted Stock Outstanding	The following table is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2018 and 2019 and the changes that occurred during 2019: (In thousands, except per share amounts) Number of shares Weighted Average Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2018 1,570 $ 18.52 PSUs, RSUs and restricted stock granted 897 $ 9.63 PSUs, RSUs and restricted stock vested (368 ) $ 17.23 PSUs, RSUs and restricted stock forfeited (208 ) $ 18.24 Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2019 1,891 $ 14.58
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2019 and 2018 and the changes that occurred during 2019: Number of Options (in thousands) Weighted Average Exercise Price (per share) Weighted Avg. Remaining Contractual Life in Years Aggregate Intrinsic (in thousands) Stock options outstanding, December 31, 2018 4,382 $ 22.91 4.10 $ — Stock options granted — $ — Stock options exercised (34 ) $ 15.53 Stock options forfeited (32 ) $ 15.56 Stock options expired (744 ) $ 23.72 Stock options outstanding, December 31, 2019 3,572 $ 22.88 3.40 $ — Stock options exercisable, December 31, 2019 3,570 $ 22.89 3.40 $ —
Stock Options Outstanding	The following table further describes our stock options outstanding as of December 31, 2019: Options Outstanding Options Exercisable Range of Exercise Prices Options Outstanding at December 31, 2019 (In thousands) Weighted Avg. Remaining Contractual Life in Years Weighted Average Exercise Price Options Exercisable at December 31, 2019 (In thousands) Weighted Average Exercise Price $14.88 – $18.96 1,135 4.90 $ 15.89 1,133 $ 15.89 $18.97 – $23.45 685 4.70 $ 19.10 685 $ 19.10 $23.46 – $30.35 686 3.67 $ 24.17 686 $ 24.17 $30.36 – $41.92 1,066 1.29 $ 31.93 1,066 $ 31.93 3,572 3,570
Market-Based PSUs [Member]
Summary of Weighted-Average Assumptions and Value of Options Granted	The following table details the significant assumptions that impact the fair value estimate of the market-based PSUs: 2019 2018 2017 Estimated fair value per share $9.53 to $18.05 $ 16.59 $ 24.17 Expected volatility 32.7% to 38.9% 27.98% to 31.58% 27.03 % Risk-free interest rate 1.6% to 2.46% 2.11% to 2.99% 1.78 % Expected dividend yield 2.3% to 4.09% 1.83% to 2.49% 1.74 %

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Debt Securities and Other Investments, Recorded at Fair Value	Debt Securities and Other Investments As of December 31, 2019, we held the following debt securities and other investments, recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,304 $ 80 $ — $ 9,384 Municipal fixed-rate bonds 930 — — 930 Asset-backed bonds 6,867 26 (3 ) 6,890 Mortgage/Agency-backed bonds 6,944 26 (8 ) 6,962 U.S. government bonds 12,311 21 (9 ) 12,323 Foreign government bonds 372 — (1 ) 371 Variable rate demand notes 800 — — 800 Available-for-sale debt securities held at fair value $ 37,528 $ 153 $ (21 ) $ 37,660 As of December 31, 2018, we held the following debt securities and other investments, recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 20,777 $ 19 $ (112 ) $ 20,684 Municipal fixed-rate bonds 1,339 — (26 ) 1,313 Asset-backed bonds 5,230 5 (14 ) 5,221 Mortgage/Agency-backed bonds 3,833 2 (44 ) 3,791 U.S. government bonds 9,271 1 (66 ) 9,206 Foreign government bonds 592 — (8 ) 584 Available-for-sale debt securities held at fair value $ 41,042 $ 27 $ (270 ) $ 40,799
Contractual Maturities of Debt Securities	As of December 31, 2019, our debt securities had the following contractual maturities: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset-backed bonds Mortgage / Agency-backed bonds U.S. government bonds Foreign government bonds Less than one year $ 4,005 $ — $ 396 $ — $ — $ — One to two years 4,120 930 760 213 1,347 — Two to three years 967 — 1,632 1,424 9,344 — Three to five years 292 — 2,092 494 1,632 371 Five to ten years — — 1,719 792 — — More than ten years — — 291 4,039 — — Total $ 9,384 $ 930 $ 6,890 $ 6,962 $ 12,323 $ 371
Gross Realized Gains and Losses on Sale of Debt Securities	The following table presents gross realized gains and losses related to our debt securities for the years ended December 31, 2019, 2018 and 2017: (In thousands) Year Ended December 31, 2019 2018 2017 Gross realized gains on debt securities $ 108 $ 57 $ 169 Gross realized losses on debt securities (50 ) (592 ) (226 ) Total gain (loss) recognized, net $ 58 $ (535 ) $ (57 )
Breakdown of Investments with Unrealized Losses	The following table presents the breakdown of debt securities and other investments with unrealized losses as of December 31, 2019: Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 203 — — — 203 — Municipal fixed-rate bonds 930 — — — 930 — Asset-backed bonds 797 (3 ) — — 797 (3 ) Mortgage/Agency-backed bonds 2,594 (6 ) 136 (2 ) 2,730 (8 ) U.S. government bonds 4,070 (9 ) — — 4,070 (9 ) Marketable equity securities 371 (1 ) — — 371 (1 ) Total $ 8,965 $ (19 ) $ 136 $ (2 ) $ 9,101 $ (21 ) The following table presents the breakdown of debt securities and other investments with unrealized losses as of December 31, 2018: Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total (In thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds $ 11,129 $ (60 ) $ 3,608 $ (52 ) $ 14,737 $ (112 ) Municipal fixed-rate bonds — — 1,136 (26 ) 1,136 (26 ) Asset-backed bonds 1,874 (2 ) 1,257 (12 ) 3,131 (14 ) Mortgage/Agency-backed bonds 1,021 (5 ) 1,918 (39 ) 2,939 (44 ) U.S. government bonds 6,527 (48 ) 537 (18 ) 7,064 (66 ) Foreign government bonds 584 (8 ) — — 584 (8 ) Total $ 21,135 $ (123 ) $ 8,456 $ (147 ) $ 29,591 $ (270 )
Realized and Unrealized Gains and Losses for Marketable Equity Securities	Realized and unrealized gains and losses for our marketable equity securities for the twelve months ended December 31, 2019 were as follows: (In thousands) 2019 2018 Realized gains (losses) on equity securities sold $ (96 ) $ 1,306 Unrealized gains (losses) on equity securities held 11,472 (4,821 ) Total gain (loss) recognized, net $ 11,376 $ (3,515 )
Fair Value Measurements of Cash Equivalents and Investments	We have categorized our cash equivalents and our investments held at fair value into this hierarchy as follows: Fair Value Measurements as of December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,309 $ 1,309 $ — $ — Available-for-sale debt securities Corporate bonds 9,384 — 9,384 — Municipal fixed-rate bonds 930 — 930 — Asset-backed bonds 6,890 — 6,890 — Mortgage/Agency-backed bonds 6,962 — 6,962 — U.S. government bonds 12,323 12,323 — — Foreign government bonds 371 — 371 — Variable rate demand notes 800 — 800 — Marketable equity securities Marketable equity securities – various industries 35,501 35,501 — — Equity in escrow 298 298 — — Deferred compensation plan assets 21,698 21,698 — — Other investments 2,442 2,442 — — Total $ 98,908 $ 73,571 $ 25,337 $ — Fair Value Measurements as of December 31, 2018 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,554 $ 1,554 $ — $ — Available-for-sale debt securities Corporate bonds 20,684 — 20,684 — Municipal fixed-rate bonds 1,313 — 1,313 — Asset-backed bonds 5,221 — 5,221 — Mortgage/Agency-backed bonds 3,791 — 3,791 — U.S. government bonds 9,206 9,206 — — Foreign government bonds 584 — 584 — Marketable equity securities Marketable equity securities – various industries 26,763 26,763 — — Equity in escrow 253 253 — — Deferred compensation plan assets 18,256 18,256 — — Total $ 87,625 $ 56,032 $ 31,593 $ —

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Loss)	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income (Loss) during the years ended December 31, 2019, 2018 and 2017 were as follows: (In thousands) Income Statement Location 2019 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ — $ 13 $ (754 )
Schedule of Change in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income and Reclassified to Income, Net of Tax	The change in our derivatives designated as hedging instruments recorded in other comprehensive income and reclassified to income, net of tax, during the twelve months ended December 31, 2019, 2018 and 2017 were as follows: Location of Amount of Losses Reclassified Losses Reclassified from AOCI into Income (In thousands) from AOCI into Income 2019 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts Cost of Sales $ — $ — $ (897 )

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Components of Inventory	As of December 31, 2019 and 2018, inventory was comprised of the following: (In thousands) 2019 2018 Raw materials $ 36,987 $ 45,333 Work in process 1,085 1,638 Finished goods 60,233 52,877 Total Inventory, net $ 98,305 $ 99,848

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	As of December 31, 2019 and 2018, property, plant and equipment was comprised of the following: (In thousands) 2019 2018 Land $ 4,575 $ 4,575 Building and land improvements 34,797 34,379 Building 68,157 68,183 Furniture and fixtures 19,959 19,831 Computer hardware and software 74,399 92,071 Engineering and other equipment 130,430 127,060 Total Property, Plant and Equipment 332,317 346,099 Less accumulated depreciation (258,609 ) (265,464 ) Total Property, Plant and Equipment, net $ 73,708 $ 80,635

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of Supplemental Balance Sheet Information Related to Operating Leases	Supplemental balance sheet information related to operating leases is as follows: December 31, January 1, (In thousands) Classification 2019 2019 (1) Assets Right of use lease assets Other assets $ 8,452 $ 10,322 Total lease asset $ 8,452 $ 10,322 Liabilities Current lease liability Accrued expenses $ 2,676 $ 2,948 Non-current lease liability Other non-current liabilities 5,818 7,374 Total lease liability $ 8,494 $ 10,322 (1)
Components of Lease Expense included in Consolidated Statement of Income	The components of lease expense included in the Consolidated Statements of Income for the twelve months ended December 31, 2019 were as follows: For the Year Ended December 31, (In thousands) 2019 Research and development expenses $ 2,417 Selling, general and administrative expenses 1,400 Cost of sales 64 Total operating lease expense $ 3,881
Schedule of Maturity of Operating Lease Liabilities	As of December 31, 2019, operating lease liabilities included on the Consolidated Balance Sheet by future maturity were as follows: (In thousands) Amount 2020 $ 2,856 2021 2,412 2022 1,705 2023 1,160 2024 482 Thereafter 264 Total lease payments 8,879 Less: Interest (385 ) Present value of lease liabilities $ 8,494
Future Minimum Rental Payments under Non-Cancelable Operating Leases, Including Renewals Determined to be Reasonably Assured, with Original Maturities of Greater than 12 Months	A s of December 31, 2018, future minimum rental payments under non-cancelable operating leases, including renewals determined to be reasonably assured as of December 31, 2018, with original maturities of greater than 12 months, were as follows: (In thousands) Amount (1) 2019 $ 3,873 2020 3,580 2021 2,771 2022 2,053 2023 1,317 Thereafter 762 Total $ 14,356 (1) Certain renewal options were subsequently determined to not be reasonably assured of renewal upon the Company’s adoption of the new lease accounting standard on January 1, 2019.
Schedule of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates	The following table provides information about our weighted average lease terms and weighted average discount rates as of December 31, 2019 As of December 31, 2019 Weighted average remaining lease term (years) Operating leases with USD functional currency 2.6 Operating leases with Euro functional currency 4.4 Weighted average discount rate Operating leases with USD functional currency 4.02 % Operating leases with Euro functional currency 1.84 %
Schedule of Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases is as follows: As of December 31, (In thousands) 2019 Cash paid for amounts included in the measurement of operating lease assets / liabilities Cash used in operating activities related to operating leases $ 3,439 Right-of-use assets obtained in exchange for lease obligations $ 11,615
Components of Net Investment in Sales-Type Leases	As of December 31, 2019 and 2018, the components of the net investment in sales-type leases were as follows: December 31, December 31, (In thousands) 2019 2018 Current minimum lease payments receivable (1) $ 1,201 $ 11,339 Non-current minimum lease payments receivable (2) 889 1,670 Total minimum lease payments receivable 2,090 13,009 Less: Current unearned revenue (1) 365 631 Less: Non-current unearned revenue (2) 163 473 Net investment in sales-type leases $ 1,562 $ 11,905 (1) Included in other receivables on the Consolidated Balance Sheet. (2) Included in other assets on the Consolidated Balance Sheet.
Schedule of Components of Sales-type Lease Gross Profit and Interest and Dividend Income Included in Consolidated Statements of Income	The components of sales-type lease gross profit recognized at the lease commencement date and interest and dividend income, included in the Consolidated Statements of Income for the twelve months ended December 31, 2019 were as follows: (In thousands) For the Year Ended December 31, 2019 Sales - Network Solutions $ 1,723 Cost of sales - Network Solutions 675 Gross profit $ 1,048 Interest and dividend income $ 357
Schedule of Future Minimum Lease Payments to be Received from Sales-Type Leases	As of December 31, 2019 future minimum lease payments to be received from sales-type leases were as follows: (In thousands) Amount 2020 $ 1,201 2021 565 2022 232 2023 86 2024 6 Total $ 2,090

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Intangible Assets Net Excluding Goodwill [Abstract]
Summary of Intangible Assets	As of December 31, 2019 and 2018, our intangible assets were comprised of the following: 2019 2018 (In thousands) Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 22,356 $ (7,233 ) $ 15,123 $ 22,455 $ (5,380 ) $ 17,075 Developed technology 10,170 (3,379 ) 6,791 12,801 (4,867 ) 7,934 Licensed technology 5,900 (1,174 ) 4,726 5,900 (520 ) 5,380 Supplier relationships 2,800 (2,508 ) 292 2,800 (1,108 ) 1,692 Intellectual property — — — 930 (930 ) — Licensing agreements 560 (79 ) 481 560 (5 ) 555 Patents 500 (226 ) 274 500 (157 ) 343 Trade names 310 (176 ) 134 310 (106 ) 204 Non-compete — — — 200 (200 ) — Total $ 42,596 $ (14,775 ) $ 27,821 $ 46,456 $ (13,273 ) $ 33,183
Estimated Future Amortization Expense Related to Intangible Assets	As of December 31, 2019, the estimated future amortization expense of intangible assets is as follows: (In thousands) Amount 2020 $ 4,444 2021 4,095 2022 3,471 2023 3,320 2024 3,226 Thereafter 9,265 Total $ 27,821

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Summary of Components of Expense (Benefit) for Income Taxes	A summary of the components of the expense (benefit) for income taxes for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 Current Federal $ (518 ) $ (8,001 ) $ 466 State (1,065 ) (476 ) (150 ) International (282 ) 11,705 6,458 Total Current (1,865 ) 3,228 6,774 Deferred Federal 24,801 (14,448 ) 8,024 State 5,815 (3,390 ) 1,882 International (546 ) 581 4,167 Total Deferred 30,070 (17,257 ) 14,073 Total Income Tax Expense (Benefit) $ 28,205 $ (14,029 ) $ 20,847
Effective Income Tax Rate Differs from Federal Statutory Rate	Our effective income tax rate differs from the federal statutory rate due to the following: 2019 2018 2017 Tax provision computed at the federal statutory rate 21.00 % 21.00 % 35.00 % State income tax provision, net of federal benefit 6.97 14.53 2.17 Federal research credits 15.53 14.23 (11.88 ) Foreign taxes 2.83 (11.45 ) (2.27 ) Tax-exempt income 0.49 0.45 (0.75 ) State tax incentives 3.85 3.15 (2.71 ) Change in valuation allowance (172.82 ) — — Foreign tax credits 16.69 — — Stock-based compensation (6.01 ) (2.87 ) 1.43 Domestic production activity deduction — — (1.13 ) Bargain purchase — 8.82 — Impact of U.S. tax reform — 12.00 26.70 Global intangible low-taxed income ("GILTI") (1.87 ) (17.48 ) — Other, net (0.49 ) (0.34 ) 0.09 Effective Tax Rate (113.83 )% 42.04 % 46.65 %
Income (Loss) Before Expense (Benefit) for Income Taxes	Income (loss) before expense (benefit) for income taxes for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands) 2019 2018 2017 U.S. entities $ (29,829 ) $ (74,131 ) $ 26,552 International entities 5,052 40,760 18,135 Total $ (24,777 ) $ (33,371 ) $ 44,687
Components of Deferred Income Taxes Assets and Liabilities	Deferred income taxes on the Consolidated Balance Sheets 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 were as follows: (In thousands) 2019 2018 Deferred tax assets Inventory $ 7,144 $ 6,609 Accrued expenses 2,330 2,850 Investments — 1,122 Deferred compensation 5,660 4,779 Stock-based compensation 2,451 3,069 Uncertain tax positions related to state taxes and related interest 241 326 Pensions 7,074 5,538 Foreign losses 2,925 3,097 State losses and credit carry-forwards 3,995 8,164 Federal loss and research carry-forwards 12,171 17,495 Lease liabilities 2,496 — Capitalized research and development expenditures 22,230 — Valuation allowance (48,616 ) (5,816 ) Total Deferred Tax Assets 20,101 47,233 Deferred tax liabilities Property, plant and equipment (2,815 ) (3,515 ) Intellectual property (5,337 ) (6,531 ) Right of use lease assets (2,496 ) — Investments (1,892 ) — Total Deferred Tax Liabilities (12,540 ) (10,046 ) Net Deferred Tax Assets $ 7,561 $ 37,187 Supplemental balance sheet information related to deferred tax assets is as follows: December 31, 2019 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 46,266 $ (46,266 ) $ — International 9,911 (2,350 ) 7,561 Total $ 56,177 $ (48,616 ) $ 7,561
Change in Unrecognized Income Tax Benefits	The change in the unrecognized income tax benefits for the years ended December 31, 2019, 2018 and 2017 is reconciled below: (In thousands) 2019 2018 2017 Balance at beginning of period $ 1,868 $ 2,366 $ 2,226 Increases for tax position related to: Prior years — 3 465 Current year 161 254 285 Decreases for tax positions related to: Prior years (71 ) — (14 ) Expiration of applicable statute of limitations (471 ) (755 ) (596 ) Balance at end of period $ 1,487 $ 1,868 $ 2,366

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Schedule of Pension Benefit Plan Obligations and Funded Status	The pension benefit plan obligations and funded status as of December 31, 2019 and 2018, were as follows: (In thousands) 2019 2018 Change in projected benefit obligation: Projected benefit obligation at beginning of period $ 37,245 $ 34,893 Service cost 1,471 1,193 Interest cost 634 727 Actuarial loss - experience 453 38 Actuarial loss - assumptions 5,091 2,139 Benefit payments (166 ) (138 ) Effects of foreign currency exchange rate changes (826 ) (1,607 ) Projected benefit obligation at end of period 43,902 37,245 Change in plan assets: Fair value of plan assets at beginning of period 24,159 26,624 Actual gain (loss) on plan assets 4,392 (2,024 ) Contributions — 688 Effects of foreign currency exchange rate changes (535 ) (1,129 ) Fair value of plan assets at end of period 28,016 24,159 Unfunded status at end of period $ (15,886 ) $ (13,086 )
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, 2019 and 2018 were as follows: (In thousands) 2019 2018 Current liability $ — $ — Pension liability 15,886 13,086 Total $ 15,886 $ 13,086
Components of Net Periodic Pension Cost and Amounts Recognized Other Comprehensive Income (Loss)	The components of net periodic pension cost, other than the service cost component, are included in other income (expense), net in the Consolidated Statements of Income (Loss). The components of net periodic pension cost and amounts recognized in other comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017 were as follows: (In thousands) 2019 2018 2017 Net periodic benefit cost: Service cost $ 1,471 $ 1,193 $ 1,260 Interest cost 634 727 607 Expected return on plan assets (1,392 ) (1,548 ) (1,267 ) Amortization of actuarial losses 795 247 309 Net periodic benefit cost 1,508 619 909 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Net actuarial (gain) loss 2,488 5,638 (654 ) Amortization of actuarial losses (771 ) (196 ) (406 ) Amount recognized in other comprehensive income (loss) 1,717 5,442 (1,060 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 3,225 $ 6,061 $ (151 )
Accumulated Other Comprehensive Income (Loss)	The amounts recognized in accumulated other comprehensive income (loss) as of December 31, 2019 and 2018 were as follows: (In thousands) 2019 2018 Net actuarial loss $ (12,973 ) $ (11,256 )
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 years ended December 31, 2019, 2018 and 2017 were as follows: 2019 2018 2017 Discount rate 1.75 % 2.13 % 1.90 % Rate of compensation increase 2.00 % 2.00 % 2.00 % Expected long-term rates of return 5.90 % 5.90 % 5.90 %
Weighted-Average Assumptions Used to Determine Benefit Obligation	The weighted-average assumptions that were used to determine the benefit obligation as of December 31, 2019 and 2018: 2019 2018 Discount rate 1.00 % 1.75 % Rate of compensation increase 2.00 % 2.00 %
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) 2020 $ 515 2021 582 2022 619 2023 706 2024 789 Thereafter 4,872 Total $ 8,083
Schedule of Cash Equivalents and Investments Held at Fair Value	We have categorized our cash equivalents and our investments held at fair value into this hierarchy as follows: Fair Value Measurements at December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and cash equivalents $ 691 $ 691 $ — $ — Available-for-sale securities Bond funds: Government bonds 6,645 6,645 — — Corporate bonds 5,514 5,514 — — Emerging markets bonds 531 531 — — Equity funds: Global equity 11,071 11,071 — — Emerging markets 956 956 — — Balanced fund 863 863 — — Large cap value 312 312 — — Global real estate fund 902 902 — — Managed futures fund 531 531 — — Available-for-sale securities 27,325 27,325 — — Total $ 28,016 $ 28,016 $ — $ — Fair Value Measurements at December 31, 2018 Using (In thousands) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and cash equivalents $ 1,010 $ 1,010 $ — $ — Available-for-sale securities Bond funds: Government bonds 6,268 6,268 — — Corporate bonds 4,840 4,840 — — Emerging markets bonds 443 443 — — Equity funds: Global equity 7,743 7,743 — — Emerging markets 1,188 1,188 — — Balanced fund 815 815 — — Large cap value 262 262 — — Global real estate fund 926 926 — — Managed futures fund 664 664 — — Available-for-sale securities 23,149 23,149 — — Total $ 24,159 $ 24,159 $ — $ —
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 a s of December 31, 2019 and 2018 wer e as follows: (In thousands) 2019 2018 Fair Value of Plan Assets Long-term investments $ 21,698 $ 18,256 Total Fair Value of Plan Assets $ 21,698 $ 18,256 Amounts Payable to Plan Participants Deferred compensation liability $ 21,698 $ 18,256 Total Amounts Payable to Plan Participants $ 21,698 $ 18,256

Segment Information and Major_2

Segment Information and Major Customers (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019, 2018 and 2017. Asset information by reportable segment is not reported, since we do not produce such information internally. (In thousands) 2019 2018 2017 Sales Gross Profit Sales Gross Profit Sales Gross Profit Network Solutions $ 455,226 $ 191,549 $ 458,232 $ 179,303 $ 540,396 $ 260,833 Services & Support 74,835 27,618 71,045 24,262 126,504 42,802 Total $ 530,061 $ 219,167 $ 529,277 $ 203,565 $ 666,900 $ 303,635
Disaggregate of Revenue by Major Source	The following table disaggregates our revenue by major source for the year ended December 31, 2019: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 (1) The following table disaggregates our revenue by major source for the year ended December 31, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 (1) The following tables disaggregates our revenue by major source for the years ended December 31, 2019, 2018 and 2017: 2019 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 289,980 $ 58,894 $ 348,874 Subscriber Solutions & Experience (1) 144,651 8,269 152,920 Traditional & Other Products 20,595 7,672 28,267 Total $ 455,226 $ 74,835 $ 530,061 2018 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 301,801 $ 57,069 $ 358,870 Subscriber Solutions & Experience (1) 129,067 5,393 134,460 Traditional & Other Products 27,364 8,583 35,947 Total $ 458,232 $ 71,045 $ 529,277 2017 (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 361,955 $ 111,989 $ 473,944 Subscriber Solutions & Experience (1) 132,294 6,162 138,456 Traditional & Other Products 46,147 8,353 54,500 Total $ 540,396 $ 126,504 $ 666,900 (1) Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.
Sales Information by Geographic Area	The following table presents sales information by geographic area for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 United States $ 300,853 $ 288,843 $ 508,178 Mexico 90,795 12,186 2,246 Germany 78,062 167,251 119,502 Other international 60,351 60,997 36,974 Total $ 530,061 $ 529,277 $ 666,900

Earnings (Loss) per Share (Tabl

Earnings (Loss) per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share	A summary of the calculation of basic and diluted earnings (loss) per share for the years ended December 31, 2019, 2018 and 2017 is as follows: (In thousands, except for per share amounts) 2019 2018 2017 Numerator Net Income (Loss) $ (52,982 ) $ (19,342 ) $ 23,840 Denominator Weighted average number of shares – basic 47,836 47,880 48,153 Effect of dilutive securities: Stock options — — 406 Restricted stock and restricted stock units — — 140 Weighted average number of shares – diluted 47,836 47,880 48,699 Earnings (loss) per share – basic $ (1.11 ) $ (0.40 ) $ 0.50 Earnings (loss) per share – diluted $ (1.11 ) $ (0.40 ) $ 0.49

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Schedule of Reconciliation of Restructuring Liability	A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Consolidated Balance Sheets as of December 31, 2019 and 2018, is as follows: (In thousands) 2019 2018 Balance at beginning of period $ 185 $ 205 Plus: Amounts charged to cost and expense 6,014 7,261 Less: Amounts paid (4,631 ) (7,281 ) Balance at end of period $ 1,568 $ 185
Schedule of Components of Restructuring Expense	The components of restructuring expense in the Consolidated Statements of Income are for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 Selling, general and administrative expenses $ 2,360 $ 2,655 $ 152 Research and development expenses 2,869 1,831 122 Cost of sales 785 2,775 — Total restructuring expenses $ 6,014 $ 7,261 $ 274 The following table represents the components of restructuring expense by geographic area for the years ended December 31, 2019, 2018 and 2017: (In thousands) 2019 2018 2017 United States $ 3,336 $ 7,120 $ 274 International 2,678 141 — Total restructuring expenses $ 6,014 $ 7,261 $ 274

Summarized Quarterly Financia_2

Summarized Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Operating Results	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 Three Months Ended (In thousands, except for per share amounts) March 31, 2019 June 30, 2019 September 30, 2019 December 31, 2019 Net sales $ 143,791 $ 156,391 $ 114,092 $ 115,787 Gross profit $ 60,612 $ 65,015 $ 46,331 $ 47,209 Operating income (loss) $ (6,167 ) $ 562 $ (20,288 ) $ (14,070 ) Net income (loss) $ 770 $ 3,995 $ (46,123 ) $ (11,624 ) Earnings (loss) per common share - basic $ 0.02 $ 0.08 $ (0.96 ) $ (0.25 ) Earnings (loss) per common share - diluted $ 0.02 (1) $ 0.08 (1) $ (0.96 ) $ (0.25 ) Three Months Ended (In thousands, except for per share amounts) March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Net sales $ 120,806 $ 128,048 $ 140,335 $ 140,088 Gross profit $ 39,733 $ 49,996 $ 58,448 $ 55,388 Operating income (loss) $ (26,647 ) $ (12,813 ) $ (2,179 ) $ (3,783 ) Net income (loss) $ (10,814 ) $ (7,670 ) $ 7,589 $ (8,447 ) Earnings (loss) per common share - basic $ (0.22 ) $ (0.16 ) $ 0.16 $ (0.18 ) Earnings (loss) per common share - diluted $ (0.22 ) $ (0.16 ) $ 0.16 (1) $ (0.18 ) (1)

Nature of Business - Additional

Nature of Business - Additional Information (Detail)	Jan. 01, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)CustomerIncentivePlan	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Summary Of Significant Accounting Policy [Line Items]
Cash, uninsured amount				$ 71,600,000
Bonds payable, carrying amount				24,600,000
Bonds payable, fair value				$ 24,600,000
Number of single customer comprising more than 10% of account receivable | Customer				4	2
Allowance for doubtful accounts				$ 38,000	$ 128,000
Asset impairments				3,872,000	0	$ 0
Impairment charges recognized on goodwill				$ 0	0	0
Period of assurance-based warranty for product defects				90 days to five years
Liability for warranty obligations				$ 8,394,000	8,623,000	9,724,000	$ 8,548,000
Pension liability				$ 15,886,000	13,086,000
Number of stock incentive plans | IncentivePlan				2
Stock-based compensation expense				$ 6,962,000	7,155,000	7,433,000
Total unrecognized compensation cost related to non-vested stock options, PSUs, RSUs and restricted stock				$ 17,200,000
Recognition period of unvested compensation expense				3 years
Research and development costs				$ 126,200,000	124,547,000	$ 130,666,000
Operating lease, right-of-use asset	$ 10,322,000			8,452,000
Operating lease, right-of-use liability	10,322,000			8,494,000
Prepaid Expenses and Other Current Assets [Member]
Summary Of Significant Accounting Policy [Line Items]
Current deferred costs related to prepaid and other assets				1,600,000	2,400,000
Other Assets [Member]
Summary Of Significant Accounting Policy [Line Items]
Non-current deferred costs related to other assets				$ 100,000	$ 800,000
ASU 2018-02 [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassification of tax effects related to adoption ASU	$ 400,000
Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives				2 years
Lessor sales type lease arrangement terms for network equipments				18 months
Maintenance service periods				1 month
Maintenance contract period				1 month
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives				14 years
Lessor sales type lease arrangement terms for network equipments				5 years
Maintenance service periods				5 years
Maintenance contract period				5 years
Maximum [Member] | Accounting Policy under Topic 605 [Member]
Summary Of Significant Accounting Policy [Line Items]
Invoiced sales tax as percentage on total revenues.				1.00%
Building and Land Improvements [Member] | Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				5 years
Building and Land Improvements [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				39 years
Office Machinery and Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				3 years
Office Machinery and Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				7 years
Engineering Machinery and Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				3 years
Engineering Machinery and Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				7 years
Computer Software [Member] | Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				3 years
Computer Software [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives				5 years
Credit Concentration Risk [Member] | Accounts Receivable [Member]
Summary Of Significant Accounting Policy [Line Items]
Percentage of accounts receivable accounted by each customers				53.20%	36.90%
Out-of-Period Adjustment [Member]
Summary Of Significant Accounting Policy [Line Items]
Increase (decrease) in cost of goods sold		$ 800,000	$ (200,000)
Increase (decrease) in excess and obsolete inventory reserve		$ 800,000	$ (200,000)

Nature of Business - Summary of

Nature of Business - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 8,623	$ 9,724	$ 8,548
Plus: Amounts charged to cost and expenses	4,569	7,392	6,951
Less: Deductions	(4,798)	(8,493)	(5,775)
Balance at end of period	$ 8,394	$ 8,623	$ 9,724

Nature of Business - Changes in

Nature of Business - Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Components Of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 446,279	$ 497,911	$ 479,517
Other comprehensive income (loss) before reclassifications	(2,624)	(7,441)	10,851
Amounts reclassified to retained earnings	385	(3,220)
Amounts reclassified from accumulated other comprehensive loss	238	(460)	(1,958)
Ending Balance	380,426	446,279	497,911
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified to retained earnings	385
Ending Balance	385
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(563)	2,567	404
Other comprehensive income (loss) before reclassifications	573	685	5,020
Amounts reclassified to retained earnings		(3,220)
Amounts reclassified from accumulated other comprehensive loss	(294)	(595)	(2,857)
Ending Balance	(284)	(563)	2,567
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications			(619)
Amounts reclassified from accumulated other comprehensive loss			619
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(8,041)	(4,286)	(5,017)
Other comprehensive income (loss) before reclassifications	(1,717)	(3,890)	451
Amounts reclassified from accumulated other comprehensive loss	532	135	280
Ending Balance	(9,226)	(8,041)	(4,286)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,812)	(1,576)	(7,575)
Other comprehensive income (loss) before reclassifications	(1,480)	(4,236)	5,999
Ending Balance	(7,292)	(5,812)	(1,576)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(14,416)	(3,295)	(12,188)
Ending Balance	$ (16,417)	$ (14,416)	$ (3,295)

Nature of Business - Reclassifi

Nature of Business - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales									$ (310,894)	$ (325,712)	$ (363,265)
Defined benefit plan adjustments – actuarial losses									5,091	2,139
Income (Loss) Before Income Taxes									(24,777)	(33,371)	44,687
Tax benefit (expense)									(28,205)	14,029	(20,847)
Total reclassifications for the period, net of tax	$ (11,624)	$ (46,123)	$ 3,995	$ 770	$ (8,447)	$ 7,589	$ (7,670)	$ (10,814)	(52,982)	(19,342)	23,840
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments – actuarial losses									(771)	(196)	(406)
Income (Loss) Before Income Taxes									(374)	608	3,381
Tax benefit (expense)									136	(148)	(1,423)
Total reclassifications for the period, net of tax									(238)	460	1,958
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain (loss)									$ 397	$ 804	4,864
Impairment Expense [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain (loss)											(180)
Net Losses on Derivatives Designated as Hedging Instruments [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales											$ (897)

Nature of Business - Tax Effect

Nature of Business - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Unrealized gain (loss) on available-for-sale securities, Before-Tax Amount	$ 774	$ 926	$ 8,230
Unrealized gain (loss) on available-for-sale securities, Tax (Expense) Benefit	(201)	(241)	(3,210)
Unrealized gain (loss) on available-for-sale securities, Net-of-Tax Amount	573	685	5,020
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Before-Tax Amount	(397)	(804)	(4,684)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Tax (Expense) Benefit	103	209	1,827
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Net-of-Tax Amount	(294)	(595)	(2,857)
Reclassification adjustment for amounts reclassed to retained earnings related of the adoption of ASU 2018-02/2016-01, Before-Tax Amount		(4,351)
Reclassification adjustment for amounts reclassed to retained earnings related of the adoption of ASU 2018-02/2016-01, Tax (Expense) Benefit		1,131
Reclassification adjustment for amounts reclassed to retained earnings related of the adoption of ASU 2018-02/2016-01, Net-of-Tax Amount		(3,220)
Unrealized gains (losses) on cash flow hedges, Before-Tax Amount			(897)
Unrealized gains (losses) on cash flow hedges, Tax (Expense) Benefit			278
Unrealized gains (losses) on cash flow hedges, Net-of-Tax Amount			(619)
Reclassification adjustment for amounts related to cash flow hedges included in net income, Before-Tax Amount			897
Reclassification adjustment for amounts related to cash flow hedges included in net income, Tax (Expense) Benefit			(278)
Reclassification adjustment for amounts related to cash flow hedges included in net income, Net-of-Tax Amount			619
Defined benefit plan adjustments, Before-Tax Amount	(2,488)	(5,638)	654
Defined benefit plan adjustments, Tax (Expense) Benefit	771	1,748	(203)
Defined benefit plan adjustments, Net-of-Tax Amount	(1,717)	(3,890)	451
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Before-Tax Amount	771	196	406
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Tax (Expense) Benefit	(239)	(61)	(126)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Net-of-Tax Amount	532	135	280
Foreign currency translation adjustment, Before-Tax Amount	(1,480)	(4,236)	5,999
Foreign currency translation adjustment, Net-of-Tax Amount	(1,480)	(4,236)	5,999
Total Other Comprehensive Income (Loss), Before-Tax Amount	(2,820)	(13,907)	10,605
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	434	2,786	(1,712)
Other Comprehensive Income (Loss), net of tax	$ (2,386)	$ (11,121)	$ 8,893

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - USD ($)	Nov. 30, 2018	Mar. 19, 2018	Jun. 30, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Gain on contingency					$ 1,230,000
Goodwill					$ 7,000,000	$ 7,100,000
Bargain purchase gain net of income taxes						11,322,000
SmartRG Inc [Member]
Business Acquisition [Line Items]
Business acquisition, agreement month and year					2018-11
Business acquisition, description					In November 2018, we acquired SmartRG, Inc., a provider of carrier-class, open-source connected home platforms and cloud services for broadband service providers for cash consideration. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. These revenues are included in the Subscriber Solutions & Experience category within the Network Solutions and Services & Support reportable segments.
Business combination, contingent consideration, liability	$ 1,200,000
Gain on contingency			$ 1,200,000
Business combination escrow amount	2,800,000
Business combination escrow fund released					$ 1,300,000
Goodwill	3,500,000
SmartRG Inc [Member] | Minimum [Member]
Business Acquisition [Line Items]
Business combination potential release of funds	0
SmartRG Inc [Member] | Maximum [Member]
Business Acquisition [Line Items]
Business combination potential release of funds	$ 1,500,000
Sumitomo [Member]
Business Acquisition [Line Items]
Business acquisition, description					On March 19, 2018, we acquired Sumitomo Electric Lightwave Corp.’s (SEL) North American EPON business and entered into a technology license and OEM supply agreement with Sumitomo Electric Industries, Ltd. (SEI).
Date of acquisition					Mar. 19, 2018
Bargain purchase gain net of income taxes		$ 11,322,000		$ 11,300,000
Smart RG and Sumitomo [Member]
Business Acquisition [Line Items]
Acquisition and integration related expenses and amortization of acquired intangibles					$ 5,000,000	$ 2,900,000	$ 0

Business Combinations - Final A

Business Combinations - Final Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Nov. 30, 2018	Mar. 19, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2019
Assets
Goodwill				$ 7,106	$ 6,968
Liabilities
Gain on bargain purchase of a business, net of tax				$ (11,322)
Sumitomo [Member]
Assets
Tangible assets acquired		$ 1,006
Intangible assets		22,100
Total assets acquired		23,106
Liabilities
Liabilities assumed		(3,978)
Total liabilities assumed		(3,978)
Total net assets		19,128
Gain on bargain purchase of a business, net of tax		(11,322)	$ (11,300)
Total purchase price		$ 7,806
SmartRG Inc [Member]
Assets
Tangible assets acquired	$ 8,594
Intangible assets	9,960
Goodwill	3,476
Total assets acquired	22,030
Liabilities
Liabilities assumed	(6,001)
Total liabilities assumed	(6,001)
Total net assets	16,029
Total purchase price	$ 16,029

Business Combinations - Summary

Business Combinations - Summary of Actual Revenue and Net Loss Included in Consolidated Statements of Income (Detail) - Smart RG and Sumitomo [Member] $ in Thousands	9 Months Ended
	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Revenue	$ 9,186
Net loss	$ (1,297)

Business Combinations - Details

Business Combinations - Details of the Acquired Intangible Assets (Detail) - Smart RG and Sumitomo [Member] $ in Thousands	Nov. 30, 2018USD ($)
Business Acquisition [Line Items]
Total, Value	$ 32,060
Developed Technology [Member]
Business Acquisition [Line Items]
Total, Value	$ 7,400
Life (in years)	7 years
Customer Relationships [Member]
Business Acquisition [Line Items]
Total, Value	$ 15,190
Customer Relationships [Member] | Minimum [Member]
Business Acquisition [Line Items]
Life (in years)	3 years
Customer Relationships [Member] | Maximum [Member]
Business Acquisition [Line Items]
Life (in years)	12 years
Licensed Technology [Member]
Business Acquisition [Line Items]
Total, Value	$ 5,900
Life (in years)	9 years
Supplier Relationship [Member]
Business Acquisition [Line Items]
Total, Value	$ 2,800
Life (in years)	2 years
Licensing Agreements [Member]
Business Acquisition [Line Items]
Total, Value	$ 560
Licensing Agreements [Member] | Minimum [Member]
Business Acquisition [Line Items]
Life (in years)	5 years
Licensing Agreements [Member] | Maximum [Member]
Business Acquisition [Line Items]
Life (in years)	10 years
Trade Name [Member]
Business Acquisition [Line Items]
Total, Value	$ 210
Life (in years)	3 years

Business Combinations - Summa_2

Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail) - Smart RG and Sumitomo [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Pro forma revenue	$ 559,050	$ 702,573
Pro forma net loss	$ (33,862)	$ 33,206

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Revenue	$ 115,787	$ 114,092	$ 156,391	$ 143,791	$ 140,088	$ 140,335	$ 128,048	$ 120,806	$ 530,061	$ 529,277	$ 666,900
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue									348,874	358,870
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue									152,920	134,460	138,456
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue									28,267	35,947	54,500
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue									455,226	458,232	540,396
Network Solutions [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue									289,980	301,801
Network Solutions [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue									144,651	129,067	132,294
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue									20,595	27,364	46,147
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue									74,835	71,045	126,504
Services & Support [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue									58,894	57,069
Services & Support [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue									8,269	5,393	6,162
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue									$ 7,672	$ 8,583	$ 8,353

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue [Line Items]
Remaining performance obligations	$ 0
Recognized revenue	12,700,000
Other Than Maintenance Services
Revenue [Line Items]
Remaining performance obligations	$ 13,600,000	$ 13,300,000

Revenue - Additional Informat_2

Revenue - Additional Information (Detail1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01	Dec. 31, 2019
Revenue [Line Items]
Remaining performance obligations, percentage	64.00%
Remaining performance obligations, period	12 months

Revenue - Information about Rec

Revenue - Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Accounts receivable	$ 90,531	$ 99,385
Contract assets	2,812	3,766
Unearned revenue	11,963	17,940
Non-current unearned revenue	$ 6,012	$ 5,296

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Incentive Program Descriptions) - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2015
2006 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock authorized	13,000,000
Vesting period	4 years
Contractual term	10 years
2015 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock authorized		7,700,000
Vesting period	4 years
Contractual term	10 years
Multiplier used when issuing PSUs, restricted stock and RSUs		2.5
2010 Directors Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock authorized	500,000
Contractual term	10 years
Expiration date of options	2019
Minimum [Member] | 2006 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration date of options	2020
Minimum [Member] | 2015 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration date of options	2025
Maximum [Member] | 2006 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration date of options	2024
Maximum [Member] | 2015 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration date of options	2026

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,962	$ 7,155	$ 7,433
Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock	(1,659)	(1,432)	(1,699)
Total stock-based compensation expense, net of tax	5,303	5,723	5,734
Stock-based Compensation Expense Included in Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	369	418	379
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	3,889	3,989	4,063
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,704	2,748	2,991
Stock-based Compensation Expense Included in Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,593	$ 6,737	$ 7,054

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
One-time PSU shares grant approved by board of directors		897
Recognition period of unvested compensation expense		3 years
Performance Stock Units (PSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
One-time PSU shares grant approved by board of directors	500
Performance Stock Units (PSUs) [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of performance stock units granted		0.00%
Performance Stock Units (PSUs) [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of performance stock units granted		150.00%
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		1 year
Market-Based PSUs, RSUs and Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to other than options		$ 17.2
Recognition period of unvested compensation expense		2 years 10 months 24 days
Stock Options, PSUs, RSUs or Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for issuance under shareholders-approved equity plan		1,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	1,570
Number of Shares, PSUs, RSUs and restricted stock granted | shares	897
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(368)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(208)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,891
Weighted Average Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance | $ / shares	$ 18.52
Weighted Average Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	9.63
Weighted Average Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	17.23
Weighted Average Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	18.24
Weighted Average Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 14.58

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) - Market-Based PSUs [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value per share		$ 16.59	$ 24.17
Expected volatility			27.03%
Risk-free interest rate			1.78%
Expected dividend yield			1.74%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value per share	$ 9.53
Expected volatility	32.70%	27.98%
Risk-free interest rate	1.60%	2.11%
Expected dividend yield	2.30%	1.83%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value per share	$ 18.05
Expected volatility	38.90%	31.58%
Risk-free interest rate	2.46%	2.99%
Expected dividend yield	4.09%	2.49%

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Stock options outstanding, Beginning Balance	4,382,000
Number of Options, Stock options granted	0	0	0
Number of Options, Stock options exercised	(34,000)
Number of Options, Stock options forfeited	(32,000)
Number of Options, Stock options expired	(744,000)
Number of Options, Stock options outstanding, Ending Balance	3,572,000	4,382,000
Number of Options, Stock options exercisable	3,570,000
Weighted Average Exercise Price, Stock options outstanding, Beginning Balance	$ 22.91
Weighted Average Exercise Price, Stock options exercised	15.53
Weighted Average Exercise Price, Stock options forfeited	15.56
Weighted Average Exercise Price, Stock options expired	23.72
Weighted Average Exercise Price, Stock options outstanding, Ending Balance	22.88	$ 22.91
Weighted Average Exercise Price, Stock options exercisable	$ 22.89
Weighted Avg. Remaining Contractual Life in Years, Stock options outstanding	3 years 4 months 24 days	4 years 1 month 6 days
Weighted Avg. Remaining Contractual Life in Years, Stock options exercisable	3 years 4 months 24 days
Aggregate Intrinsic Value, Stock options outstanding	$ 0

Stock-Based Compensation (Sto_2

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Recognition period of unvested compensation expense	3 years
Aggregate intrinsic value based on fair market value	$ 0
Total pre-tax intrinsic value of options exercised	100	$ 200	$ 3,400
Fair value of options fully vested	$ 900	$ 2,500	$ 4,300
Number of Stock options, granted	0	0	0
Unvested Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to non-vested stock options	$ 11
Recognition period of unvested compensation expense	1 year

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock Options Outstanding (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at 12/31/19	3,572	4,382
Options Exercisable at 12/31/19	3,570
Weighted Average Exercise Price, Options exercisable	$ 22.89
$14.88 - 18.96 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Range Limit	14.88
Upper Range Limit	$ 18.96
Options Outstanding at 12/31/19	1,135
Weighted Avg. Remaining Contractual Life In Years, Options Outstanding	4 years 10 months 24 days
Weighted Average Exercise Price, Options Outstanding	$ 15.89
Options Exercisable at 12/31/19	1,133
Weighted Average Exercise Price, Options exercisable	$ 15.89
$18.97 - 23.45 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Range Limit	18.97
Upper Range Limit	$ 23.45
Options Outstanding at 12/31/19	685
Weighted Avg. Remaining Contractual Life In Years, Options Outstanding	4 years 8 months 12 days
Weighted Average Exercise Price, Options Outstanding	$ 19.10
Options Exercisable at 12/31/19	685
Weighted Average Exercise Price, Options exercisable	$ 19.10
$23.46 - 30.35 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Range Limit	23.46
Upper Range Limit	$ 30.35
Options Outstanding at 12/31/19	686
Weighted Avg. Remaining Contractual Life In Years, Options Outstanding	3 years 8 months 1 day
Weighted Average Exercise Price, Options Outstanding	$ 24.17
Options Exercisable at 12/31/19	686
Weighted Average Exercise Price, Options exercisable	$ 24.17
$30.36 - 41.92 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Range Limit	30.36
Upper Range Limit	$ 41.92
Options Outstanding at 12/31/19	1,066
Weighted Avg. Remaining Contractual Life In Years, Options Outstanding	1 year 3 months 14 days
Weighted Average Exercise Price, Options Outstanding	$ 31.93
Options Exercisable at 12/31/19	1,066
Weighted Average Exercise Price, Options exercisable	$ 31.93

Investments - Debt Securities a

Investments - Debt Securities and Other Investments, Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 37,528	$ 41,042
Gross Unrealized Gains	153	27
Gross Unrealized Losses	(21)	(270)
Fair Value	37,660	40,799
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,304	20,777
Gross Unrealized Gains	80	19
Gross Unrealized Losses		(112)
Fair Value	9,384	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	930	1,339
Gross Unrealized Losses		(26)
Fair Value	930	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,867	5,230
Gross Unrealized Gains	26	5
Gross Unrealized Losses	(3)	(14)
Fair Value	6,890	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,944	3,833
Gross Unrealized Gains	26	2
Gross Unrealized Losses	(8)	(44)
Fair Value	6,962	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,311	9,271
Gross Unrealized Gains	21	1
Gross Unrealized Losses	(9)	(66)
Fair Value	12,323	9,206
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800
Fair Value	800
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	372	592
Gross Unrealized Losses	(1)	(8)
Fair Value	$ 371	$ 584

Investments - Contractual Matur

Investments - Contractual Maturities of Debt Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 37,660	$ 40,799
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	4,005
One to two years	4,120
Two to three years	967
Three to five years	292
Available-for-sale debt securities, Fair Value/Carrying Value	9,384	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	930
Available-for-sale debt securities, Fair Value/Carrying Value	930	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	396
One to two years	760
Two to three years	1,632
Three to five years	2,092
Five to ten years	1,719
More than ten years	291
Available-for-sale debt securities, Fair Value/Carrying Value	6,890	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	213
Two to three years	1,424
Three to five years	494
Five to ten years	792
More than ten years	4,039
Available-for-sale debt securities, Fair Value/Carrying Value	6,962	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	1,347
Two to three years	9,344
Three to five years	1,632
Available-for-sale debt securities, Fair Value/Carrying Value	12,323	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Three to five years	371
Available-for-sale debt securities, Fair Value/Carrying Value	$ 371	$ 584

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Gross realized gains on debt securities	$ 108	$ 57	$ 169
Gross realized losses on debt securities	(50)	(592)	(226)
Total gain (loss) recognized, net	$ 58	$ (535)	$ (57)

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Schedule of Investments [Line Items]
Transfer to investments	$ 3.4
Carrying value		$ 3.4
Other Receivables [Member]
Schedule of Investments [Line Items]
Note receivable		$ 0.9	$ 4.3
ASU 2016-01 [Member]
Schedule of Investments [Line Items]
Reclassification of net unrealized gains of marketable equity securities from AOCI to retained earnings				$ 3.2
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member]
Schedule of Investments [Line Items]
Investment concentration risk percentage		5.00%

Investments - Breakdown of Inve

Investments - Breakdown of Investments with Unrealized Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	$ 8,965	$ 21,135
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(19)	(123)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	136	8,456
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	(2)	(147)
Total Fair Value	9,101	29,591
Total Unrealized Losses	(21)	(270)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	203	11,129
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(60)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		3,608
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(52)
Total Fair Value	203	14,737
Total Unrealized Losses		(112)
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	930
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		1,136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(26)
Total Fair Value	930	1,136
Total Unrealized Losses		(26)
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	797	1,874
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(3)	(2)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		1,257
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(12)
Total Fair Value	797	3,131
Total Unrealized Losses	(3)	(14)
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	2,594	1,021
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(6)	(5)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value	136	1,918
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses	(2)	(39)
Total Fair Value	2,730	2,939
Total Unrealized Losses	(8)	(44)
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	4,070	6,527
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(9)	(48)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		537
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(18)
Total Fair Value	4,070	7,064
Total Unrealized Losses	(9)	(66)
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	371
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(1)
Total Fair Value	371
Total Unrealized Losses	$ (1)
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value		584
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(8)
Total Fair Value		584
Total Unrealized Losses		$ (8)

Investments - Realized and Unre

Investments - Realized and Unrealized Gains and Losses for Marketable Equity Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on equity securities sold	$ (96)	$ 1,306
Unrealized gains (losses) on equity securities held	11,472	(4,821)
Total gain (loss) recognized, net	$ 11,376	$ (3,515)

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 37,660	$ 40,799
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	98,908	87,625
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	73,571	56,032
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	25,337	31,593
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,309	1,554
Money Market Funds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,309	1,554
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,384	20,684
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,384	20,684
Corporate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,384	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	930	1,313
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	930	1,313
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	930	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,890	5,221
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,890	5,221
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,890	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,962	3,791
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,962	3,791
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,962	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	12,323	9,206
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	12,323	9,206
U.S. Government Bonds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	12,323	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Foreign Government Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	35,501	26,763
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	35,501	26,763
Equity in Escrow [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	298	253
Equity in Escrow [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	298	253
Other Investments [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	2,442
Other Investments [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	2,442
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	21,698	18,256
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	$ 21,698	$ 18,256

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Derivative instruments, amount	$ 0	$ 0

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ 13	$ (754)

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Schedule of Change in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income and Reclassified to Income, Net of Tax (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Foreign Exchange Contracts [Member] | Derivatives Designated as Hedging Instruments [Member] | Cost of Sales [Member]
Derivative [Line Items]
Amount of Losses Reclassified from AOCI into Income	$ (897)

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 36,987	$ 45,333
Work in process	1,085	1,638
Finished goods	60,233	52,877
Total Inventory, net	$ 98,305	$ 99,848

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventory valuation reserves	$ 34.1	$ 30

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Land	$ 4,575	$ 4,575
Building and land improvements	34,797	34,379
Building	68,157	68,183
Furniture and fixtures	19,959	19,831
Computer hardware and software	74,399	92,071
Engineering and other equipment	130,430	127,060
Total Property, Plant and Equipment	332,317	346,099
Less accumulated depreciation	(258,609)	(265,464)
Total Property, Plant and Equipment, net	$ 73,708	$ 80,635

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation	$ 12,500,000	$ 12,700,000	$ 12,800,000
Asset impairments	$ 3,872,000	$ 0	$ 0

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Lessor and Lessee Lease Description [Line Items]
Operating lease, option to extend, existence	true
Operating lease, option to terminate, existence	true
Short-term lease cost	$ 400,000
Variable lease cost	900,000
Future operating lease payments	8,879,000	$ 700,000
Allowance for credit losses for our investment in sales type leases	$ 0	$ 0
Minimum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms	1 month
Operating lease, options to terminate term	3 months
Lessor sales type lease arrangement terms for network equipments	18 months
Maximum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms	6 years
Operating lease, renewal term	9 years
Lessor sales type lease arrangement terms for network equipments	5 years

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Balance Sheet Information Related to Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
ASSETS
Right of use lease assets	$ 8,452	$ 10,322
Operating lease, right-of-use asset, statement of financial position [extensible list]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Liabilities
Current lease liability	$ 2,676	$ 2,948
Non-current lease liability	$ 5,818	$ 7,374
Operating lease, liability, current, statement of financial position [extensible list]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating lease, liability, noncurrent, statement of financial position [extensible list]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total lease liability	$ 8,494	$ 10,322

Leases - Components of Lease Ex

Leases - Components of Lease Expense included in Consolidated Statement of Income (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Lessor Lease Description [Line Items]
Total operating lease expense	$ 3,881
Research and Development Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	2,417
Selling, General and Administrative Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	1,400
Cost of Sales [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	$ 64

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Lease Liabilities Payments Due [Abstract]
2020	$ 2,856
2021	2,412
2022	1,705
2023	1,160
2024	482
Thereafter	264
Total lease payments	8,879		$ 700
Less: Interest	(385)
Present value of lease liabilities	$ 8,494	$ 10,322

Leases - Future Minimum Rental

Leases - Future Minimum Rental Payments under Non-Cancelable Operating Leases, Including Renewals Determined to be Reasonably Assured, with Original Maturities of Greater than 12 Months (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2019	$ 3,873
2020	3,580
2021	2,771
2022	2,053
2023	1,317
Thereafter	762
Total	$ 14,356

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates (Detail)	Dec. 31, 2019
USD
Weighted average remaining lease term (years)
Operating leases with functional currency	2 years 7 months 6 days
Weighted average discount rate
Operating leases with functional currency	4.02%
Euro
Weighted average remaining lease term (years)
Operating leases with functional currency	4 years 4 months 24 days
Weighted average discount rate
Operating leases with functional currency	1.84%

Leases - Schedule of Suppleme_2

Leases - Schedule of Supplemental Cash Flow Information Related to Operating Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Cash paid for amounts included in the measurement of operating lease assets / liabilities
Cash used in operating activities related to operating leases	$ 3,439
Right-of-use assets obtained in exchange for lease obligations	$ 11,615

Leases - Components of Net Inve

Leases - Components of Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Sales Type Leases Net Investment In Leases [Abstract]
Current minimum lease payments receivable	$ 1,201	$ 11,339
Non-current minimum lease payments receivable	889	1,670
Total minimum lease payments receivable	2,090	13,009
Less: Current unearned revenue	365	631
Less: Non-current unearned revenue	163	473
Net investment in sales-type leases	$ 1,562	$ 11,905

Leases - Schedule of Components

Leases - Schedule of Components of Sales-type Lease Gross Profit and Interest and Dividend Income Included in Consolidated Statements of Income (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 1,723
Stock-based Compensation Expense Included in Cost of Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	675
Gross Profit [Member]
Lessor Lease Description [Line Items]
Sales type leases	1,048
Interest and Dividend Income [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 357

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments to be Received from Sales-Type Leases (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Sales Type And Direct Financing Leases Lease Receivable Fiscal Year Maturity [Abstract]
2020	$ 1,201
2021	565
2022	232
2023	86
2024	6
Total	$ 2,090

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($) $ in Millions	Nov. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill		$ 7	$ 7.1
Network Solutions [Member]
Goodwill [Line Items]
Goodwill		6.6	6.7
Services & Support [Member]
Goodwill [Line Items]
Goodwill		0.4	$ 0.4
SmartRG Inc [Member]
Goodwill [Line Items]
Goodwill	$ 3.5
Goodwill, reduced amount relates to acquisition		$ 0.1

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Value	$ 42,596	$ 46,456
Accumulated Amortization	(14,775)	(13,273)
Net Value	27,821	33,183
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	22,356	22,455
Accumulated Amortization	(7,233)	(5,380)
Net Value	15,123	17,075
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	10,170	12,801
Accumulated Amortization	(3,379)	(4,867)
Net Value	6,791	7,934
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	5,900	5,900
Accumulated Amortization	(1,174)	(520)
Net Value	4,726	5,380
Supplier Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	2,800	2,800
Accumulated Amortization	(2,508)	(1,108)
Net Value	292	1,692
Intellectual Property [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value		930
Accumulated Amortization		(930)
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	560	560
Accumulated Amortization	(79)	(5)
Net Value	481	555
Patent [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	500	500
Accumulated Amortization	(226)	(157)
Net Value	274	343
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	310	310
Accumulated Amortization	(176)	(106)
Net Value	$ 134	204
Non-compete [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value		200
Accumulated Amortization		$ (200)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets Net Excluding Goodwill [Abstract]
Amortization expense	$ 5.3	$ 2.3	$ 2.9

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
2020	$ 4,444
2021	4,095
2022	3,471
2023	3,320
2024	3,226
Thereafter	9,265
Net Value	$ 27,821	$ 33,183

Alabama State Industrial Deve_2

Alabama State Industrial Development Authority Financing and Economic Incentives - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 02, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2008	Jan. 13, 1995
Debt Instrument [Line Items]
Proceeds from state industrial development authority issued taxable bonds loaned to ADTRAN		$ 24,600
Estimated fair value of bond		24,600
Total realized economic incentives		1,200	$ 1,400	$ 1,500
Payments on long-term debt		1,000	$ 1,100	$ 1,100
Taxable Revenue Bonds [Member]
Debt Instrument [Line Items]
Proceeds from state industrial development authority issued taxable bonds loaned to ADTRAN		$ 24,600			$ 50,000	$ 20,000
Repayment of bond	$ 24,600
Percentage of interest on bond		2.00%
Maturity date of bond			Jan. 1, 2020
Estimated fair value of bond		$ 24,600
Certificate of deposit		$ 25,600

Income Taxes - Summary of Compo

Income Taxes - Summary of Components of Expense (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current
Federal	$ (518)	$ (8,001)	$ 466
State	(1,065)	(476)	(150)
International	(282)	11,705	6,458
Total Current	(1,865)	3,228	6,774
Deferred
Federal	24,801	(14,448)	8,024
State	5,815	(3,390)	1,882
International	(546)	581	4,167
Total Deferred	30,070	(17,257)	14,073
Total Income Tax Expense (Benefit)	$ 28,205	$ (14,029)	$ 20,847

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Differs from Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax provision computed at the federal statutory rate	21.00%	21.00%	35.00%
State income tax provision, net of federal benefit	6.97%	14.53%	2.17%
Federal research credits	15.53%	14.23%	(11.88%)
Foreign taxes	2.83%	(11.45%)	(2.27%)
Tax-exempt income	0.49%	0.45%	(0.75%)
State tax incentives	3.85%	3.15%	(2.71%)
Change in valuation allowance	(172.82%)
Foreign tax credits	16.69%
Stock-based compensation	(6.01%)	(2.87%)	1.43%
Domestic production activity deduction			(1.13%)
Bargain purchase		8.82%
Impact of U.S. tax reform		12.00%	26.70%
Global intangible low-taxed income ("GILTI")	(1.87%)	(17.48%)
Other, net	(0.49%)	(0.34%)	0.09%
Effective Tax Rate	(113.83%)	42.04%	46.65%

Income Taxes - Income (Loss) Be

Income Taxes - Income (Loss) Before Expense (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. entities	$ (29,829)	$ (74,131)	$ 26,552
International entities	5,052	40,760	18,135
Income (Loss) Before Income Taxes	$ (24,777)	$ (33,371)	$ 44,687

Income Taxes - Principal Compon

Income Taxes - Principal Components of Current and Non-current Deferred Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Inventory	$ 7,144	$ 6,609
Accrued expenses	2,330	2,850
Investments		1,122
Deferred compensation	5,660	4,779
Stock-based compensation	2,451	3,069
Uncertain tax positions related to state taxes and related interest	241	326
Pensions	7,074	5,538
Foreign losses	2,925	3,097
State losses and credit carry-forwards	3,995	8,164
Federal loss and research carry-forwards	12,171	17,495
Lease liabilities	2,496
Capitalized research and development expenditures	22,230
Valuation allowance	(48,616)	(5,816)
Total Deferred Tax Assets	20,101	47,233
Property, plant and equipment	(2,815)	(3,515)
Intellectual property	(5,337)	(6,531)
Right of use lease assets	(2,496)
Investments	(1,892)
Total Deferred Tax Liabilities	(12,540)	(10,046)
Net Deferred Tax Assets	$ 7,561	$ 37,187

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Tax cuts and jobs act, incomplete accounting, estimated income tax expense	$ 11,900,000
Tax cuts and jobs act, incomplete accounting, estimated write-down of deferred tax assets	9,200,000
Tax cuts and jobs act, incomplete accounting, change in tax rate estimate income tax expense related to unrepatriated foreign earnings	2,700,000
Tax cuts and jobs act, complete accounting, income tax expense (benefit)			$ (4,000,000)
Deferred tax benefit recorded as an adjustment to other comprehensive income		$ 400,000	2,800,000
Deferred tax assets, gross		56,177,000
Valuation allowance established against deferred tax assets		48,616,000
Deferred tax assets, state research and development credits		12,171,000	17,495,000
Net of deferred tax liabilities		7,561,000	37,187,000
Foreign and domestic loss carry-forwards, research and development tax credits, unamortized research and development cost and state credit carry-forwards		$ 41,300,000	28,800,000
Operating loss carry forwards expiration year		2029
Deferred tax assets		$ 20,101,000	47,233,000
Cash and cash equivalents		73,773,000	105,504,000
Short-term investments		33,243,000	3,246,000
Short-term liquidity amount		107,000,000	108,700,000
Income tax benefit (expense) from stock options exercised adjustment to equity		0	0	$ 0
Unrecognized tax benefits	2,366,000	1,487,000	1,868,000	2,366,000	$ 2,226,000
Unrecognized tax benefits, effective tax rate	2,200,000	1,400,000	1,700,000	2,200,000
Accrued interest and penalties	$ 800,000	500,000	700,000	$ 800,000
Foreign Subsidiaries [Member]
Income Tax Disclosure [Line Items]
Short-term liquidity amount		$ 52,300,000	$ 87,100,000
Short-term liquidity, in percentage		48.90%	80.10%
Operating Losses Expiration Between 2020 and 2039 [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets		$ 19,100,000
Minimum [Member]
Income Tax Disclosure [Line Items]
Operating loss carry forwards expiration year		2020
Maximum [Member]
Income Tax Disclosure [Line Items]
Operating loss carry forwards expiration year		2039
Domestic [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, gross		$ 46,266,000
Valuation allowance established against deferred tax assets		46,266,000
Valuation allowance established against deferred tax assets		42,800,000
State And Foreign Country [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, state research and development credits		$ 5,800,000

Income Taxes - Summary of Suppl

Income Taxes - Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	$ 56,177
Valuation Allowance	(48,616)
Net Deferred Tax Assets	7,561	$ 37,187
Domestic [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	46,266
Valuation Allowance	(46,266)
International [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	9,911
Valuation Allowance	(2,350)
Net Deferred Tax Assets	$ 7,561

Income Taxes - Change in Unreco

Income Taxes - Change in Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 1,868	$ 2,366	$ 2,226
Increases for tax position related to, Prior years		3	465
Increases for tax position related to, Current year	161	254	285
Decreases for tax positions related to, Prior years	(71)		(14)
Expiration of applicable statute of limitations	(471)	(755)	(596)
Balance at end of period	$ 1,487	$ 1,868	$ 2,366

Employee Benefit Plans (Pension

Employee Benefit Plans (Pension Benefit Plan) - Schedule of Pension Benefit Plan Obligations and Funded Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in projected benefit obligation:
Projected benefit obligation at beginning of period	$ 37,245	$ 34,893
Service cost	1,471	1,193	$ 1,260
Interest cost	634	727	607
Actuarial loss - experience	453	38
Actuarial loss - assumptions	5,091	2,139
Benefit payments	(166)	(138)
Effects of foreign currency exchange rate changes	(826)	(1,607)
Projected benefit obligation at end of period	43,902	37,245	34,893
Change in plan assets:
Fair value of plan assets at beginning of period	24,159	26,624
Actual gain (loss) on plan assets	4,392	(2,024)
Contributions		688
Effects of foreign currency exchange rate changes	(535)	(1,129)
Fair value of plan assets at end of period	28,016	24,159	$ 26,624
Unfunded status at end of period	$ (15,886)	$ (13,086)

Employee Benefit Plans (Pensi_2

Employee Benefit Plans (Pension Benefit Plan) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 43.9	$ 37.2
Estimated amortization from accumulated other comprehensive income (loss) into net periodic pension cost in 2020	$ 0.8
Bond Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation ranges by asset class	50.00%
Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation ranges by asset class	40.00%
Cash, Real Estate, and Managed Futures [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of target allocation ranges by asset class	10.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Threshold for unamortized gain losses	10.00%

Employee Benefit Plans (Pensi_3

Employee Benefit Plans (Pension Benefit Plan) - Summary of Net Amounts Recognized Balance Sheet for the Unfunded Pension Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Current liability	$ 0	$ 0
Pension liability	15,886	13,086
Total	$ 15,886	$ 13,086

Employee Benefit Plans (Pensi_4

Employee Benefit Plans (Pension Benefit Plan) - Components of Net Periodic Pension Cost and Amounts Recognized Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net periodic benefit cost:
Service cost	$ 1,471	$ 1,193	$ 1,260
Interest cost	634	727	607
Expected return on plan assets	(1,392)	(1,548)	(1,267)
Amortization of actuarial losses	795	247	309
Net periodic benefit cost	1,508	619	909
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net actuarial (gain) loss	2,488	5,638	(654)
Amortization of actuarial losses	(771)	(196)	(406)
Amount recognized in other comprehensive income (loss)	1,717	5,442	(1,060)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 3,225	$ 6,061	$ (151)

Employee Benefit Plans (Pensi_5

Employee Benefit Plans (Pension Benefit Plan) - Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Net actuarial loss	$ (12,973)	$ (11,256)

Employee Benefit Plans (Pensi_6

Employee Benefit Plans (Pension Benefit Plan) - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Discount rate	1.75%	2.13%	1.90%
Rate of compensation increase	2.00%	2.00%	2.00%
Expected long-term rates of return	5.90%	5.90%	5.90%

Employee Benefit Plans (Pensi_7

Employee Benefit Plans (Pension Benefit Plan) - Weighted-Average Assumptions Used to Determine Benefit Obligation (Detail)	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Discount rate	1.00%	1.75%
Rate of compensation increase	2.00%	2.00%

Employee Benefit Plans (Pensi_8

Employee Benefit Plans (Pension Benefit Plan) - Schedule of Pension Benefit Payments Expected Future Service (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Compensation And Retirement Disclosure [Abstract]
2020	$ 515
2021	582
2022	619
2023	706
2024	789
Thereafter	4,872
Total	$ 8,083

Employee Benefit Plans (Pensi_9

Employee Benefit Plans (Pension Benefit Plan) - Schedule of Cash Equivalents and Investments Held at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 28,016	$ 24,159	$ 26,624
Pension Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28,016	24,159
Pension Benefit Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	691	1,010
Pension Benefit Plan [Member] | Available-For-Sale Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,325	23,149
Pension Benefit Plan [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,645	6,268
Pension Benefit Plan [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,514	4,840
Pension Benefit Plan [Member] | Emerging Markets Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	531	443
Pension Benefit Plan [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,071	7,743
Pension Benefit Plan [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	956	1,188
Pension Benefit Plan [Member] | Balanced Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	863	815
Pension Benefit Plan [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312	262
Pension Benefit Plan [Member] | Global Real Estate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	902	926
Pension Benefit Plan [Member] | Managed Futures Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	531	664
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28,016	24,159
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	691	1,010
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Available-For-Sale Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,325	23,149
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,645	6,268
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,514	4,840
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Emerging Markets Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	531	443
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,071	7,743
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	956	1,188
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Balanced Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	863	815
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312	262
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Global Real Estate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	902	926
Pension Benefit Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Managed Futures Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 531	$ 664

Employee Benefit Plans (401(k)

Employee Benefit Plans (401(k) Savings Plan) - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
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
Percentage of employer match to employee's contribution	100.00%
Percentage of employer match to employee's contribution	50.00%
Upper limit of employer match	4.00%
Maximum statutory compensation under code	$ 280,000
Contribution expense and plan administration costs for savings plan	$ 4,400,000	$ 4,400,000	$ 4,600,000

Employee Benefit Plans (Deferre

Employee Benefit Plans (Deferred Compensation Plans) - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Compensation_Program	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Compensation And Retirement Disclosure [Abstract]
Number of deferred compensation programs | Compensation_Program	4
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 based on the participant’s election
Deferred compensation income (expense) adjustments due to fair value of the trust assets | $	$ 3.6	$ (2.1)	$ (2.6)

Employee Benefit Plans (Defer_2

Employee Benefit Plans (Deferred Compensation Plans) - Fair Value of Assets Held by Trust and Amounts Payable to Plan Participants (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Long-term Investments	$ 21,698	$ 18,256
Amounts Payable to Plan Participants Deferred Compensation Liability	21,698	18,256
Deferred Compensation Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term investments	21,698	18,256
Deferred Compensation Liability [Member]
Defined Benefit Plan Disclosure [Line Items]
Amounts Payable to Plan Participants Deferred Compensation Liability	$ 21,698	$ 18,256

Employee Benefit Plans (Retiree

Employee Benefit Plans (Retiree Medical Coverage) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Maximum number of years medical, dental and prescription drug coverage to spouses of retired former officers	30 years
Total liability recorded to provide medical, dental and prescription drug coverage	$ 0.1	$ 0.1

Segment Information and Major_3

Segment Information and Major Customers - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)CustomerSegmentCategory	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017Customer
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	2
Number of categories | Category	3
Number of single customer comprising more than 10% of revenue | Customer	3	2	2
Long-lived assets	$ 73.7	$ 80.6
U.S. [Member]
Segment Reporting Information [Line Items]
Long-lived assets	69.9	77.3
Outside U.S. [Member]
Segment Reporting Information [Line Items]
Long-lived assets	$ 3.9	$ 3.3
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Customer 1 [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	19.00%	27.00%	40.00%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Customer 2 [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	17.00%	17.00%	16.00%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Customer 3 [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	13.00%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | The Five Largest Customers Other Than Those With More Than 10% Of Revenues and Excluding Distributors [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	15.00%	18.00%	15.00%

Segment Information and Major_4

Segment Information and Major Customers - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Sales	$ 115,787	$ 114,092	$ 156,391	$ 143,791	$ 140,088	$ 140,335	$ 128,048	$ 120,806	$ 530,061	$ 529,277	$ 666,900
Gross Profit	$ 47,209	$ 46,331	$ 65,015	$ 60,612	$ 55,388	$ 58,448	$ 49,996	$ 39,733	219,167	203,565	303,635
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales									455,226	458,232	540,396
Gross Profit									191,549	179,303	260,833
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales									74,835	71,045	126,504
Gross Profit									$ 27,618	$ 24,262	$ 42,802

Segment Information and Major_5

Segment Information and Major Customers - Disaggregation of Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Revenue	$ 115,787	$ 114,092	$ 156,391	$ 143,791	$ 140,088	$ 140,335	$ 128,048	$ 120,806	$ 530,061	$ 529,277	$ 666,900
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue									455,226	458,232	540,396
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue									74,835	71,045	126,504
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue									348,874	358,870	473,944
Access & Aggregation [Member] | Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue									289,980	301,801	361,955
Access & Aggregation [Member] | Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue									58,894	57,069	111,989
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue									152,920	134,460	138,456
Subscriber Solutions & Experience [Member] | Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue									144,651	129,067	132,294
Subscriber Solutions & Experience [Member] | Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue									8,269	5,393	6,162
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue									28,267	35,947	54,500
Traditional & Other Products [Member] | Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue									20,595	27,364	46,147
Traditional & Other Products [Member] | Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue									$ 7,672	$ 8,583	$ 8,353

Segment Information and Major_6

Segment Information and Major Customers - Sales Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Sales	$ 115,787	$ 114,092	$ 156,391	$ 143,791	$ 140,088	$ 140,335	$ 128,048	$ 120,806	$ 530,061	$ 529,277	$ 666,900
United States [Member]
Revenue from External Customer [Line Items]
Sales									300,853	288,843	508,178
Mexico [Member]
Revenue from External Customer [Line Items]
Sales									90,795	12,186	2,246
Germany [Member]
Revenue from External Customer [Line Items]
Sales									78,062	167,251	119,502
Other International [Member]
Revenue from External Customer [Line Items]
Sales									$ 60,351	$ 60,997	$ 36,974

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Oct. 17, 2019Officer	Dec. 31, 2019USD ($)EquityFund	Dec. 31, 2018USD ($)
Contingencies And Commitments [Line Items]
Number of private equity funds | EquityFund		2
Commitments towards private equity funds		$ 7.7
Commitments related to performance bonds		$ 9.3	$ 6.5
Commitments related to performance bonds expiration month and year		2024-08
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds		$ 7.9
Current Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	2
Former Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	1

Earnings (Loss) Per Share - Sum

Earnings (Loss) Per Share - Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net Income (Loss)	$ (11,624)	$ (46,123)	$ 3,995	$ 770	$ (8,447)	$ 7,589	$ (7,670)	$ (10,814)	$ (52,982)	$ (19,342)	$ 23,840
Denominator
Weighted average number of shares – basic									47,836	47,880	48,153
Effect of dilutive securities:
Stock options											406
Restricted stock and restricted stock units											140
Weighted average number of shares – diluted									47,836	47,880	48,699
Earnings (loss) per share – basic	$ (0.25)	$ (0.96)	$ 0.08	$ 0.02	$ (0.18)	$ 0.16	$ (0.16)	$ (0.22)	$ (1.11)	$ (0.40)	$ 0.50
Earnings (loss) per share – diluted	$ (0.25)	$ (0.96)	$ 0.08	$ 0.02	$ (0.18)	$ 0.16	$ (0.16)	$ (0.22)	$ (1.11)	$ (0.40)	$ 0.49

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings (loss) per share			3.2
Unvested Stock Options, PSUs, RSUs and Restricted Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings (loss) per share	5.7	2.5

Restructuring - Additional Info

Restructuring - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Restructuring And Related Activities [Abstract]
Cumulative amount incurred for restructuring program	$ 7.3

Restructuring - Schedule of Rec

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring And Related Activities [Abstract]
Balance at beginning of period	$ 185	$ 205
Plus: Amounts charged to cost and expense	6,014	7,261	$ 274
Less: Amounts paid	(4,631)	(7,281)
Balance at end of period	$ 1,568	$ 185	$ 205

Restructuring - Schedule of Com

Restructuring - Schedule of Components of Restructuring Expense in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 6,014	$ 7,261	$ 274
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	2,360	2,655	152
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	2,869	1,831	$ 122
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 785	$ 2,775

Restructuring - Schedule of C_2

Restructuring - Schedule of Components of Restructuring Expense by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 6,014	$ 7,261	$ 274
United States [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	3,336	7,120	$ 274
International [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 2,678	$ 141

Summarized Quarterly Financia_3

Summarized Quarterly Financial Data (Unaudited) - Quarterly Operating Results (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 115,787	$ 114,092	$ 156,391	$ 143,791	$ 140,088	$ 140,335	$ 128,048	$ 120,806	$ 530,061	$ 529,277	$ 666,900
Gross profit	47,209	46,331	65,015	60,612	55,388	58,448	49,996	39,733	219,167	203,565	303,635
Operating income (loss)	(14,070)	(20,288)	562	(6,167)	(3,783)	(2,179)	(12,813)	(26,647)	(39,963)	(45,422)	37,386
Net income (loss)	$ (11,624)	$ (46,123)	$ 3,995	$ 770	$ (8,447)	$ 7,589	$ (7,670)	$ (10,814)	$ (52,982)	$ (19,342)	$ 23,840
Earnings (loss) per common share - basic	$ (0.25)	$ (0.96)	$ 0.08	$ 0.02	$ (0.18)	$ 0.16	$ (0.16)	$ (0.22)	$ (1.11)	$ (0.40)	$ 0.50
Earnings (loss) per common share - diluted	$ (0.25)	$ (0.96)	$ 0.08	$ 0.02	$ (0.18)	$ 0.16	$ (0.16)	$ (0.22)	$ (1.11)	$ (0.40)	$ 0.49

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 05, 2020	Jan. 02, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 05, 2019
Subsequent Event [Line Items]
Payments on long-term debt			$ 1,000	$ 1,100	$ 1,100
Dividend payments			$ 0.09	$ 0.09	$ 0.09
Quarterly dividend payable, aggregate amount						$ 4,300
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declaration date	Feb. 5, 2020
Dividend payments	$ 0.09
Dividend record date	Feb. 20, 2020
Dividend payment date	Mar. 5, 2019
Subsequent Event [Member] | Taxable Revenue Bonds [Member]
Subsequent Event [Line Items]
Payments on long-term debt		$ 24,600

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 128
Charged to costs & expenses	38	$ 128
Deductions	128
Balance at end of period	38	128
Inventory Reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	30,009	23,355	$ 25,249
Charged to costs & expenses	5,893	7,006	6,406
Deductions	1,740	352	8,300
Balance at end of period	34,162	30,009	23,355
Warranty Liability [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	8,623	9,724	8,548
Charged to costs & expenses	4,569	7,392	6,951
Deductions	4,798	8,493	5,775
Balance at end of period	8,394	8,623	9,724
Deferred Tax Asset Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	5,816	6,006	6,149
Charged to costs & expenses	43,560		18
Deductions	760	190	161
Balance at end of period	$ 48,616	$ 5,816	$ 6,006