ADTRAN (ADTN) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	ADTN
Entity Registrant Name	ADTRAN INC
Entity Central Index Key	926,282
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		47,650,245

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 94,173	$ 86,433
Short-term investments	5,912	16,129
Accounts receivable, less allowance for doubtful accounts of $— at September 30, 2018 and December 31, 2017	101,865	144,150
Other receivables	30,084	26,578
Inventory, net	106,060	122,542
Prepaid expenses and other current assets	10,428	17,282
Total Current Assets	348,522	413,114
Property, plant and equipment, net	81,457	85,079
Deferred tax assets, net	39,595	23,428
Goodwill	3,492	3,492
Other assets	31,523	13,725
Long-term investments	144,241	130,256
Total Assets	648,830	669,094
Current Liabilities
Accounts payable	65,032	60,632
Unearned revenue	17,004	13,070
Accrued expenses	14,548	13,232
Accrued wages and benefits	12,604	15,948
Income tax payable	14,340	3,936
Total Current Liabilities	123,528	106,818
Non-current unearned revenue	3,846	4,556
Other non-current liabilities	32,255	34,209
Bonds payable	25,600	25,600
Total Liabilities	185,229	171,183
Commitments and contingencies (see Note 15)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 47,711 shares outstanding at September 30, 2018 and 79,652 shares issued and 48,485 shares outstanding at December 31, 2017	797	797
Additional paid-in capital	265,757	260,515
Accumulated other comprehensive loss	(9,564)	(3,295)
Retained earnings	900,324	922,178
Less treasury stock at cost: 31,941 and 31,167 shares at September 30, 2018 and December 31, 2017, respectively	(693,713)	(682,284)
Total Stockholders’ Equity	463,601	497,911
Total Liabilities and Stockholders’ Equity	$ 648,830	$ 669,094

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
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	47,711,000	48,485,000
Treasury stock, shares	31,941,000	31,167,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sales
Total Sales	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Cost of Sales
Total Cost of Sales	81,887	98,621	241,012	295,238
Gross Profit	58,448	86,491	148,177	244,826
Selling, general and administrative expenses	30,750	34,676	96,361	104,171
Research and development expenses	29,877	33,588	93,455	99,116
Operating Income (Loss)	(2,179)	18,227	(41,639)	41,539
Interest and dividend income	825	952	2,604	2,857
Interest expense	(134)	(139)	(398)	(417)
Net investment gain	4,507	1,009	5,400	2,869
Other income (expense), net	201	(842)	(73)	(1,427)
Gain on bargain purchase of a business			11,322
Income (Loss) Before Provision for Income Taxes	3,220	19,207	(22,784)	45,421
(Provision) benefit for income taxes	4,369	(3,309)	11,889	(10,471)
Net Income (Loss)	$ 7,589	$ 15,898	$ (10,895)	$ 34,950
Weighted average shares outstanding – basic	47,710	47,870	47,927	48,110
Weighted average shares outstanding – diluted	47,834	48,531	47,927	48,618
Earnings (loss) per common share – basic	$ 0.16	$ 0.33	$ (0.23)	$ 0.73
Earnings (loss) per common share – diluted	0.16	0.33	(0.23)	0.72
Dividend per share	$ 0.09	$ 0.09	$ 0.27	$ 0.27
Product [Member]
Sales
Total Sales	$ 121,043	$ 145,467	$ 341,359	$ 444,607
Cost of Sales
Total Cost of Sales	69,943	73,534	208,184	229,861
Service [Member]
Sales
Total Sales	19,292	39,645	47,830	95,457
Cost of Sales
Total Cost of Sales	$ 11,944	$ 25,087	$ 32,828	$ 65,377

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 7,589	$ 15,898	$ (10,895)	$ 34,950
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	(32)	804	(3,340)	2,512
Net unrealized gains (losses) on cash flow hedges		142		(196)
Defined benefit plan adjustments	37	73	104	214
Foreign currency translation	(451)	1,541	(3,033)	5,402
Other Comprehensive Income (Loss), net of tax	(446)	2,560	(6,269)	7,932
Comprehensive Income (Loss), net of tax	$ 7,143	$ 18,458	$ (17,164)	$ 42,882

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ (10,895)	$ 34,950
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	11,952	12,034
Amortization of net premium on available-for-sale investments	(14)	352
Net gain on long-term investments	(5,400)	(2,869)
Net (gain) loss on disposal of property, plant and equipment	68	(10)
Gain on bargain purchase of a business	(11,322)
Stock-based compensation expense	5,243	5,573
Deferred income taxes	(20,368)
Changes in operating assets and liabilities:
Accounts receivable, net	41,166	(6,975)
Other receivables	(1,842)	(2,924)
Inventory	16,543	(9,483)
Prepaid expenses and other assets	8,722	(9,647)
Accounts payable	5,223	(4,727)
Accrued expenses and other liabilities	156	(2,820)
Income tax payable	9,461	8,571
Net cash provided by operating activities	48,693	22,025
Cash flows from investing activities:
Purchases of property, plant and equipment	(5,695)	(12,304)
Proceeds from disposals of property, plant and equipment		16
Proceeds from sales and maturities of available-for-sale investments	116,757	137,272
Purchases of available-for-sale investments	(115,271)	(79,713)
Acquisition of business	(7,806)
Net cash provided by (used in) investing activities	(12,015)	45,271
Cash flows from financing activities:
Proceeds from stock option exercises	1,321	6,606
Purchases of treasury stock	(14,185)	(17,348)
Dividend payments	(12,976)	(13,031)
Net cash used in financing activities	(25,840)	(23,773)
Net increase in cash and cash equivalents	10,838	43,523
Effect of exchange rate changes	(3,098)	4,835
Cash and cash equivalents, beginning of period	86,433	79,895
Cash and cash equivalents, end of period	94,173	128,253
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 355	$ 272

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2017, filed on February 23, 2018 with the SEC. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842) Codification Improvements to Topic 842, Leases, Leases (Topic 842), Targeted Improvements, Topic 842 In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment . ASU 2017-04 simplifies the measurement of goodwill by eliminating step 2 of the goodwill impairment test. Under ASU 2017-04, entities will be required to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for annual or interim impairment tests performed in fiscal years beginning after December 15, 2019, with early adoption permitted for annual or interim impairment tests performed on testing dates after January 1, 2017. The amendments should be applied prospectively. We are currently evaluating whether to early adopt ASU 2017-04, but we do not expect it will have a material effect on our consolidated financial statements. 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 In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities 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. 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 whether to early adopt , but we do not expect it will have a material effect on our consolidated financial statements. During 2018, we adopted the following accounting standards, which had the following effects on our consolidated financial statements: In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, These ASUs primarily affected our network implementation service revenue performance obligations and contract costs. We are using the “output method” to measure network implementation services progress, which 1) accelerates revenue recognition for certain performance obligations related to service revenue arrangements that were previously deferred until customer acceptance and 2) requires capitalization and amortization of the incremental costs of obtaining a contract as described below. In connection with the adoption of the new revenue standard, effective January 1, 2018, we adopted ASC 340-40, Other Assets and Deferred Costs – Contracts with Customers The cumulative effect of the changes made to our Consolidated Balance Sheet on January 1, 2018 for the adoption of ASU 2014-09 and the related ASUs was as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASU 2014-09 Balance at January 1, 2018 Other receivables $ 26,578 $ 374 $ 26,952 Deferred tax assets, net $ 23,428 $ (96 ) $ 23,332 Retained earnings $ 922,178 $ 278 $ 922,456 The effect of the adoption of ASU 2014-09 and the related ASUs on our financial statements was as follows: For the three months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 121,043 $ 120,588 $ 455 Services $ 19,292 $ 17,932 $ 1,360 Cost of Sales Products $ 69,943 $ 69,754 $ 189 Services $ 11,944 $ 11,046 $ 898 Income before benefit for income taxes $ 3,220 $ 2,492 $ 728 Benefit for income taxes $ 4,369 $ 3,382 $ 987 Net income $ 7,589 $ 5,874 $ 1,715 For the nine months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 341,359 $ 341,464 $ (105 ) Services $ 47,830 $ 46,062 $ 1,768 Cost of Sales Products $ 208,184 $ 208,480 $ (296 ) Services $ 32,828 $ 31,743 $ 1,085 Loss before benefit for income taxes $ (22,784 ) $ (23,658 ) $ 874 Benefit for income taxes $ 11,889 $ 10,938 $ 951 Net loss $ (10,895 ) $ (12,720 ) $ 1,825 As of September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 30,084 $ 27,917 $ 2,167 Inventory $ 106,060 $ 106,402 $ (342 ) Equity Retained earnings $ 900,324 $ 898,499 $ 1,825 In January 2016, the FASB issued ASU 2016-01, Financial Instruments — Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, Technical Corrections and Improvements to Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, See Note 7 of Notes to Consolidated Financial Statements for additional information. In March 2017, the FASB issued ASU 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost Compensation — Retirement Benefits

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Business Combinations	2. BUSINESS COMBINATIONS 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 Customer Devices 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 preliminary allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date is as follows: (In thousands) Assets Other receivables $ 104 Inventory 510 Property, plant and equipment 392 Intangible assets 22,100 Total assets acquired 23,106 Liabilities Deferred income taxes (3,978 ) Total liabilities assumed (3,978 ) Total net assets 19,128 Gain on bargain purchase of a business, net of tax (11,322 ) Total purchase price $ 7,806 The actual revenue and net loss included in our Consolidated Statements of Income for the three months ended September 30, 2018 and the period March 19, 2018 to September 30, 2018 are as follows: Three Months Ended March 19, 2018 to (In thousands) September 30, 2018 September 30, 2018 Revenue $ 1,021 $ 2,218 Net income (loss) $ 564 $ (322 ) The details of the acquired intangible assets are as follows: (In thousands) Value Life (years) Customer relationships $ 13,400 12.0 Licensed technology 5,900 9.0 Supplier relationship 2,800 2.0 Total $ 22,100 The following unaudited supplemental pro forma information presents the financial results as if the acquisition 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 and 2018 net income for the effect of the bargain purchase gain, there were no material, non-recurring adjustments to this unaudited pro forma information. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2017 2018 2017 Pro forma revenue $ 187,027 $ 390,449 $ 545,706 Pro forma net income (loss) $ 14,997 $ (23,431 ) $ 43,826 Pro forma earnings per share - basic $ 0.31 $ (0.49 ) $ 0.91 Pro forma earnings per share - diluted $ 0.31 $ (0.49 ) $ 0.90 For the three and nine months ended September 30, 2018, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $0.7 million and $1.6 million, respectively, related to this acquisition.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Revenue	3. REVENUE 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 or service to the customer. 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. The 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 typically 30 days. Shipping fees are recorded as revenue and the related cost is included in cost of sales. Sales, value-added, and other taxes collected concurrently with revenue-producing activities are excluded from revenue. Costs of obtaining a contract are capitalized and amortized over the period that the related revenue is recognized if greater than one year. We have elected to apply the practical expedient related to the incremental costs of obtaining contracts and recognize those costs as an expense when incurred if the amortization period of the assets is one year or less. These costs are included in selling, general and administrative expenses. Capitalized costs with an amortization period greater than one year were immaterial. 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 next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. Hardware The majority of the revenue from this segment is from hardware sales and is recognized when control is transferred to our customers, which is generally when we ship the products. Shipping terms are generally FOB shipping point. 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. Product revenue for these leases is generally recorded when we transfer control of the product to our customers. Revenue for network implementation and maintenance services is recognized as described below. Customers are typically invoiced and pay in equal installments over the lease term. In relation to these lease agreements, during the three months ended September 30, 2018 and 2017, we recognized revenue of $4.2 million and $8.4 million, respectively, and during the nine months ended September 30, 2018 and 2017 we recognized revenue of $10.5 million and $15.4 million, respectively. 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 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 in services revenue as our customers benefit evenly throughout the contract term and deferred revenues are recorded in current and non-current unearned revenue. Network Implementation 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 in the Consolidated Balance Sheet. The contract asset is transferred to accounts receivable when the completed performance obligation is invoiced to the customer. As of September 30, 2018, 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. The following table provides information about receivables, contract assets, and unearned revenue from contracts with customers: (In thousands) September 30, 2018 January 1, 2018 Accounts receivable $ 101,865 $ 144,150 Contract assets $ 4,564 $ 374 Unearned revenue $ 17,004 $ 13,070 Non-current unearned revenue $ 3,846 $ 4,556 The decrease in accounts receivable is due to the collection of customer specific payment terms that became due in the first quarter of 2018. The increase in the contract asset balance for the nine months ended September 30, 2018 is primarily attributable to revenue recognized that has not yet been billed to the customer during the period. The increase in the unearned revenue balance as of nine months ended September 30, 2018 is primarily attributable to cash payments received or due in advance of satisfying our performance obligations, offset by $8.9 million of revenues recognized that were included in the unearned revenue balance as of December 31, 2017. The following table disaggregates our revenue by major source for the three months ended September 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 76,046 $ 15,855 $ 91,901 Customer Devices 37,313 1,239 38,552 Traditional & Other Products 7,684 2,198 9,882 Total $ 121,043 $ 19,292 $ 140,335 The following table disaggregates our revenue by major source for the nine months ended September 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 220,653 $ 37,670 $ 258,323 Customer Devices 99,396 3,817 103,213 Traditional & Other Products 21,310 6,343 27,653 Total $ 341,359 $ 47,830 $ 389,189

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	4. INCOME TAXES Our effective tax rate decreased from an expense of 23.1% in the nine months ended September 30, 2017, to a benefit of 34.9%, excluding the tax effect of the bargain purchase gain, in the nine months ended September 30, 2018. The decrease in the effective tax rate between the two periods is primarily driven by the completion of other tax projects, current year net losses in our domestic business and the effect of the U.S. Tax Cuts and Jobs Act, which was signed into law on December 22, 2017.

Pension Benefit Plan

Pension Benefit Plan	9 Months Ended
	Sep. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Pension Benefit Plan	5. PENSION BENEFIT PLAN We maintain a defined benefit pension plan covering employees in certain foreign countries. The following table summarizes the components of net periodic pension cost for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Service cost $ 294 $ 327 $ 905 $ 930 Interest cost 179 158 551 448 Expected return on plan assets (381 ) (329 ) (1,174 ) (935 ) Amortization of actuarial losses 61 80 188 228 Net periodic pension cost $ 153 $ 236 $ 470 $ 671 The components of net periodic pension cost other than the service cost component are included in the line item “Other income (expense), net” in the Consolidated Statements of Income.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	6. STOCK-BASED COMPENSATION The following table summarizes the stock-based compensation expense related to stock options, performance stock units (PSUs), restricted stock units (RSUs) and restricted stock for the three and nine months ended September 30, 2018 and 2017, which was recognized as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Stock-based compensation expense included in cost of sales $ 101 $ 97 $ 298 $ 281 Selling, general and administrative expense 894 994 2,924 3,018 Research and development expense 645 743 2,021 2,274 Stock-based compensation expense included in operating expenses 1,539 1,737 4,945 5,292 Total stock-based compensation expense 1,640 1,834 5,243 5,573 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (292 ) (402 ) (1,016 ) (1,215 ) Total stock-based compensation expense, net of tax $ 1,348 $ 1,432 $ 4,227 $ 4,358 Stock Options The following table is a summary of our stock options outstanding as of December 31, 2017 and September 30, 2018 and the changes that occurred during the nine months ended September 30, 2018: (In thousands, except per share amounts) Number of Stock Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Stock options outstanding, December 31, 2017 5,148 $ 22.65 4.87 $ 6,109 Stock options granted — $ — Stock options exercised (85 ) $ 15.48 Stock options forfeited (71 ) $ 16.50 Stock options expired (331 ) $ 25.87 Stock options outstanding, September 30, 2018 4,661 $ 22.64 4.12 $ 2,730 Stock options vested and expected to vest, September 30, 2018 4,661 $ 22.64 4.12 $ 2,730 Stock options exercisable, September 30, 2018 3,952 $ 23.75 3.63 $ 1,600 The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between the closing price of our stock on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money stock options) that would have been received by the option holders had all option holders exercised their options on September 30, 2018. The aggregate intrinsic value will change based on the fair market value of our stock. The total pre-tax intrinsic value of options exercised during the three and nine months ended September 30, 2018 was $0.1 million and $0.2 million, respectively. As of September 30, 2018, there was $1.2 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over an average remaining recognition period of 1.0 years. The fair value of our stock options is estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price, as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate. There were no stock options granted during the three and nine months ended September 30, 2018 or 2017. PSUs, RSUs and restricted stock The following table is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2017 and the changes that occurred during the nine months ended September 30, 2018: (In thousands, except per share amounts) Number of Shares Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2017 1,292 $ 21.33 PSUs, RSUs and restricted stock granted 22 $ 17.84 PSUs, RSUs and restricted stock vested (14 ) $ 20.19 PSUs, RSUs and restricted stock forfeited (165 ) $ 21.66 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2018 1,135 $ 21.23 The fair value of our PSUs with market conditions is calculated using a Monte Carlo simulation valuation method. The fair value of RSUs and restricted stock is equal to the closing price of our stock on the date of grant. During the first quarter of 2017, the Compensation Committee of the Board of Directors approved a PSU grant of 0.5 million shares that contain performance conditions. The fair value of these performance-based PSU awards was equal to the closing price of our stock on the date of grant. As of September 30, 2018, there was $9.8 million of unrecognized compensation expense related to unvested market-based PSUs, RSUs and restricted stock, which is expected to be recognized over an average remaining recognition period of 2.6 years. In addition, there was $9.4 million of unrecognized compensation expense related to unvested performance-based PSUs, which will be recognized over the requisite service period of three years as the achievement of the performance objective becomes probable. For the three and nine months ended September 30, 2018, no compensation expense was recognized related to these performance-based PSU awards.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Investments	7. INVESTMENTS Debt Securities and Other Investments At September 30, 2018, we held the following debt securities and other investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Corporate bonds $ 25,758 $ 13 $ (209 ) $ 25,562 Municipal fixed-rate bonds 1,451 — (36 ) 1,415 Asset-backed bonds 8,384 — (29 ) 8,355 Mortgage/Agency-backed bonds 5,450 — (87 ) 5,363 U.S. government bonds 19,957 — (184 ) 19,773 Foreign government bonds 593 2 — 595 Available-for-sale debt securities held at fair value $ 61,593 $ 15 $ (545 ) $ 61,063 Restricted investment held at cost 26,700 Other investments held at cost 520 Total carrying value of available-for-sale investments $ 88,283 At December 31, 2017, we held the following debt securities and other investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Corporate bonds $ 32,654 $ 44 $ (155 ) $ 32,543 Municipal fixed-rate bonds 2,902 2 (22 ) 2,882 Asset-backed bonds 6,545 1 (20 ) 6,526 Mortgage/Agency-backed bonds 5,554 1 (46 ) 5,509 U.S. government bonds 14,477 — (174 ) 14,303 Foreign government bonds 725 5 — 730 Available-for-sale debt securities held at fair value $ 62,857 $ 53 $ (417 ) $ 62,493 Restricted investment held at cost 27,800 Other investments held at cost 547 Total carrying value of available-for-sale investments $ 90,840 As of September 30, 2018 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 $ 2,800 $ — $ 3,112 $ — $ — $ — One to two years 10,122 287 657 — 11,716 285 Two to three years 9,898 1,128 714 425 5,565 310 Three to five years 2,742 — 2,244 1,561 2,492 — Five to ten years — — 445 525 — — More than ten years — — 1,183 2,852 — — Total $ 25,562 $ 1,415 $ 8,355 $ 5,363 $ 19,773 $ 595 Actual maturities may differ from contractual maturities because some borrowers have the right to call or prepay obligations with or without call or prepayment penalties. Realized gains and losses on sales of debt securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our debt securities: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Gross realized gains on debt securities $ 24 $ 91 $ 49 $ 148 Gross realized losses on debt securities (50 ) (28 ) (365 ) (179 ) Total gain (loss) recognized, net $ (26 ) $ 63 $ (316 ) $ (31 ) Our investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5% of the market value of our total investment portfolio. At September 30, 2018, we held a $26.7 million restricted certificate of deposit that is carried at cost. This investment serves as a collateral deposit against the principal amount outstanding under loans made to ADTRAN pursuant to an Alabama State Industrial Development Authority revenue bond (the Bond), which totaled $26.7 million at September 30, 2018 and December 31, 2017. At September 30, 2018 and December 31, 2017, the estimated fair value of the Bond using a level 2 valuation technique was approximately $26.5 million and $26.7 million, respectively, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of AAA. We have the right to set-off the balance of the Bond with the collateral deposit in order to reduce the balance of the indebtedness. The Bond matures on January 1, 2020, and bears interest at the rate of 2% per annum. In conjunction with this program, we are eligible to receive certain economic incentives from the state of Alabama that reduce the amount of payroll withholdings we are required to remit to the state for those employment positions that qualify under this program. We are required to make payments in the amounts necessary to pay the interest on the amounts currently outstanding. It is our intent to make annual principal payments in addition to the interest amounts that are due. 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, 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. Realized and unrealized gains and losses for our marketable equity securities for the three and nine months ended September 30, 2018 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2018 Realized gains (losses) on equity securities sold $ 1,240 $ 1,587 Unrealized gains (losses) on equity securities held 3,293 4,129 Total gain (loss) recognized, net $ 4,533 $ 5,716 As of September 30, 2018 and 2017, gross unrealized losses related to individual investments in a continuous loss position for twelve months or longer were not significant. We have categorized our cash equivalents and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 - Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at September 30, 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 $ 1,423 $ 1,423 $ — $ — Foreign government securities 600 — 600 — Cash equivalents 2,023 1,423 600 — Available-for-sale debt securities Corporate bonds 25,562 — 25,562 — Municipal fixed-rate bonds 1,415 — 1,415 — Asset-backed bonds 8,355 — 8,355 — Mortgage/Agency-backed bonds 5,363 — 5,363 — U.S. government bonds 19,773 19,773 — — Foreign government bonds 595 — 595 — Marketable equity securities — Marketable equity securities – various industries 40,645 40,645 — — Equity in escrow 277 277 — — Deferred compensation plan assets 20,948 20,948 — — Available-for-sale securities 122,933 81,643 41,290 — Total $ 124,956 $ 83,066 $ 41,890 $ — Fair Value Measurements at December 31, 2017 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 $ 5,851 $ 5,851 $ — $ — Commercial paper 3,999 — 3,999 — Cash equivalents 9,850 5,851 3,999 — Available-for-sale debt securities Corporate bonds 32,543 — 32,543 — Municipal fixed-rate bonds 2,882 — 2,882 — Asset-backed bonds 6,526 — 6,526 — Mortgage/Agency-backed bonds 5,509 — 5,509 — U.S. government bonds 14,303 14,303 — — Foreign government bonds 730 — 730 — Marketable equity securities Marketable equity securities – various industries 35,662 35,662 — — Deferred compensation plan assets 19,883 19,883 — — Available-for-sale securities 118,038 69,848 48,190 — Total $ 127,888 $ 75,699 $ 52,189 $ — 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.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	8. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES We participate in foreign exchange forward contracts in connection with the management of exposure to fluctuations in foreign exchange rates. 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 not recognized in current operating results, but are recorded in accumulated other comprehensive income. Amounts related to cash flow hedges are reclassified from accumulated other comprehensive income when the underlying hedged item impacts earnings. This reclassification is recorded in cost of sales, the same line item of the Consolidated Statements of Income at which the effects of the hedged item are recorded. 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 profit and loss. 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 as 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 in the Consolidated Balance Sheets at their fair values. Our derivative instruments are not subject to master netting arrangements and are not offset in the Consolidated Balance Sheets. As of September 30, 2018, we had no foreign exchange forward contracts. The changes in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and nine months ended September 30, 2018 and 2017 were as follows: Three Months Ended Nine Months Ended Income Statement September 30, September 30, (In thousands) Location 2018 2017 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense), net $ — $ (334 ) $ 13 $ (819 ) The changes in our derivatives designated as hedging instruments recorded in other comprehensive income (OCI) and reclassified to income, net of tax, during the three and nine months ended September 30, 2018 and 2017, were as follows: Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Location of Gains Three Months Ended September 30, (Losses) Reclassified Three Months Ended September 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (127 ) Cost of Sales $ — $ (269 ) Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Location of Gains Nine Months Ended September 30, (Losses) Reclassified Nine Months Ended September 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (619 ) Cost of Sales $ — $ (423 )

Inventory

Inventory	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Inventory	9. INVENTORY At September 30, 2018 and December 31, 2017, inventory consisted of the following: September 30, December 31, (In thousands) 2018 2017 Raw materials $ 47,664 $ 44,185 Work in process 1,289 1,939 Finished goods 57,107 76,418 Total $ 106,060 $ 122,542 We establish reserves for estimated excess, obsolete, or unmarketable inventory equal to the difference between the cost of the inventory and the estimated fair value of the inventory based upon assumptions about future demand and market conditions. At September 30, 2018 and December 31, 2017, raw materials reserves totaled $17.2 million and $15.0 million, respectively, and finished goods inventory reserves totaled $10.6 million and $8.3 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	10. GOODWILL AND INTANGIBLE ASSETS Goodwill, all of which relates to our acquisition of Bluesocket, Inc., was $3.5 million at September 30, 2018 and December 31, 2017, of which $3.1 million and $0.4 million is allocated to our Network Solutions and Services & Support reportable segments, respectively. 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 in 2017, we concluded that it was not necessary to perform the two-step impairment test. There have been no impairment losses recognized since the acquisition in 2011. Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangibles acquired in conjunction with our acquisitions of Bluesocket, Inc. on August 4, 2011, the NSN BBA business on May 4, 2012, CommScope’s active fiber access business on September 13, 2016 and Sumitomo Electric Lightwave Corp.’s North American EPON business and technology license and OEM supply agreement with Sumitomo Electric Industries, Ltd. on March 19, 2018. The following table presents our intangible assets as of September 30, 2018 and December 31, 2017. Fully amortized intangible assets have been removed from prior year balances for comparability. (In thousands) September 30, 2018 December 31, 2017 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 20,724 $ (5,072 ) $ 15,652 $ 7,474 $ (4,283 ) $ 3,191 Licensed technology 5,900 (355 ) 5,545 — — — Developed technology 5,435 (4,799 ) 636 5,524 (4,663 ) 861 Supplier relationship 2,800 (758 ) 2,042 — — — Intellectual property 930 (930 ) — 930 (852 ) 78 Patent 500 (140 ) 360 500 (89 ) 411 Non-compete 200 (181 ) 19 200 (115 ) 85 Trade names 100 (100 ) — 100 (65 ) 35 Total $ 36,589 $ (12,335 ) $ 24,254 $ 14,728 $ (10,067 ) $ 4,661 Amortization expense, all of which relates to business acquisitions, was $0.9 million and $0.5 million for the three months ended September 30, 2018 and 2017, respectively, and $2.4 million for the nine months ended September 30, 2018 and 2017. As of September 30, 2018, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2018 $ 859 2019 3,540 2020 2,657 2021 2,364 2022 2,350 Thereafter 12,484 Total $ 24,254

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	11. STOCKHOLDERS’ EQUITY A summary of the changes in stockholders’ equity for the nine months ended September 30, 2018 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2017 $ 497,911 Net income (loss) (10,895 ) Dividend payments (12,976 ) Dividends accrued for unvested restricted stock units (15 ) Net unrealized gains (losses) on available-for-sale securities (net of tax) (3,340 ) Defined benefit plan adjustments (net of tax) 104 Foreign currency translation adjustment (3,033 ) Proceeds from stock option exercises 1,321 Purchase of treasury stock (14,185 ) Adoption of new accounting standards (see Note 1) 3,499 Stock-based compensation expense 5,243 RSU's and restricted stock vested (33 ) Balance, September 30, 2018 $ 463,601 Stock Repurchase Program Since 1997, our Board of Directors has approved multiple share repurchase programs that have authorized open market repurchase transactions of up to 50.0 million shares of our common stock that are implemented through open market or private purchases from time to time as conditions warrant. During the nine months ended September 30, 2018, we repurchased 0.9 million shares of our common stock at an average price of $15.75 per share. As of September 30, 2018, we have the authority to purchase an additional 2.7 million shares of our common stock under the current plans approved by the Board of Directors. Stock Option Exercises We issued 0.1 million shares of treasury stock during the nine months ended September 30, 2018 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $18.97. We received proceeds totaling $1.3 million from the exercise of these stock options during the nine months ended September 30, 2018. Dividend Payments During the nine months ended September 30, 2018, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid January 31, 2018 February 14, 2018 $ 0.09 $ 4,367 May 2, 2018 May 16, 2018 $ 0.09 $ 4,312 August 1, 2018 August 15, 2018 $ 0.09 $ 4,297 Other Comprehensive Income Other comprehensive income consists of unrealized gains (losses) on available-for-sale debt securities; unrealized gains (losses) on cash flow hedges; reclassification adjustments for amounts included in net income related to impairments of available-for-sale debt securities, realized gains (losses) on available-for-sale debt securities, realized gains (losses) on cash flow hedges, and amortization of actuarial gains (losses) related to our defined benefit plan; defined benefit plan adjustments; and foreign currency translation adjustments. The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the three months ended September 30, 2018 and 2017: Three Months Ended September 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) Other comprehensive income (loss) before reclassifications 1,208 — (451 ) 757 Amounts reclassified from accumulated other comprehensive income (loss) (1,240 ) 37 — (1,203 ) Net current period other comprehensive income (loss) (32 ) 37 (451 ) (446 ) Ending balance $ (773 ) $ (4,182 ) $ (4,609 ) $ (9,564 ) Three Months Ended September 30, 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 Total Beginning balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Other comprehensive income (loss) before reclassifications 1,420 (127 ) — 1,541 2,834 Amounts reclassified from accumulated other comprehensive income (loss) (616 ) 269 73 — (274 ) Net current period other comprehensive income (loss) 804 142 73 1,541 2,560 Ending balance $ 2,916 $ (196 ) $ (4,803 ) $ (2,173 ) $ (4,256 ) The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the nine months ended September 30, 2018 and 2017 : Nine Months Ended September 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 2,567 $ (4,286 ) $ (1,576 ) $ (3,295 ) Other comprehensive income (loss) before reclassifications 869 — (3,033 ) (2,164 ) Amounts reclassified from accumulated other comprehensive income (loss) (989 ) 104 — (885 ) Amounts reclassified to retained earnings (1) (3,220 ) — — (3,220 ) Net current period other comprehensive income (loss) (3,340 ) 104 (3,033 ) (6,269 ) Ending balance $ (773 ) $ (4,182 ) $ (4,609 ) $ (9,564 ) (1) Nine Months Ended September 30, 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 Total Beginning balance $ 404 $ — $ (5,017 ) $ (7,575 ) $ (12,188 ) Other comprehensive income (loss) before reclassifications 4,262 (619 ) — 5,402 9,045 Amounts reclassified from accumulated other comprehensive income (loss) (1,750 ) 423 214 — (1,113 ) Net current period other comprehensive income (loss) 2,512 (196 ) 214 5,402 7,932 Ending balance $ 2,916 $ (196 ) $ (4,803 ) $ (2,173 ) $ (4,256 ) The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the three months ended September 30, 2018 and 2017: (In thousands) Three Months Ended September 30, 2018 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,676 Net investment gain Defined benefit plan adjustments – actuarial losses (54 ) (1) Total reclassifications for the period, before tax 1,622 Tax (expense) benefit (419 ) Total reclassifications for the period, net of tax $ 1,203 (1) (In thousands) Three Months Ended September 30, 2017 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,066 Net investment gain Impairment expense (57 ) Net investment gain Net losses on derivatives designated as hedging instruments (385 ) Cost of sales Defined benefit plan adjustments – actuarial losses (106 ) (1) Total reclassifications for the period, before tax 518 Tax (expense) benefit (244 ) Total reclassifications for the period, net of tax $ 274 (1) The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the nine months ended September 30, 2018 and 2017 : (In thousands) Nine Months Ended September 30, 2018 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,352 Net investment gain Defined benefit plan adjustments – actuarial losses (151 ) (1) Total reclassifications for the period, before tax 1,201 Tax (expense) benefit (316 ) Total reclassifications for the period, net of tax $ 885 (1) (In thousands) Nine Months Ended September 30, 2017 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain (loss) on sales of securities $ 3,031 Net investment gain Impairment expense (162 ) Net investment gain Net losses on derivatives designated as hedging instruments (539 ) Cost of sales Defined benefit plan adjustments – actuarial losses (310 ) (1) Total reclassifications for the period, before tax 2,020 Tax (expense) benefit (907 ) Total reclassifications for the period, net of tax $ 1,113 (1) The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the three months ended September 30, 2018 and 2017: Three Months Ended Three Months Ended September 30, 2018 September 30, 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 1,632 $ (424 ) $ 1,208 $ 2,328 $ (908 ) $ 1,420 Unrealized gains (losses) on cash flow hedges — — — (184 ) 57 (127 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,676 ) 436 (1,240 ) (1,009 ) 393 (616 ) Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 385 (116 ) 269 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 54 (17 ) 37 106 (33 ) 73 Foreign currency translation adjustment (451 ) — (451 ) 1,541 — 1,541 Total Other Comprehensive Income (Loss) $ (441 ) $ (5 ) $ (446 ) $ 3,167 $ (607 ) $ 2,560 The following table presents the tax effects related to the change in each component of other comprehensive income for the nine months ended September 30, 2018 and 2017: Nine Months Ended Nine Months Ended September 30, 2018 September 30, 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 1,174 $ (305 ) $ 869 $ 6,987 $ (2,725 ) $ 4,262 Unrealized gains (losses) on cash flow hedges — — — (897 ) 278 (619 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,352 ) 363 (989 ) (2,869 ) 1,119 (1,750 ) Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01 (3,220 ) — (3,220 ) — — — Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 539 (116 ) 423 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 151 (47 ) 104 310 (96 ) 214 Foreign currency translation adjustment (3,033 ) — (3,033 ) 5,402 — 5,402 Total Other Comprehensive Income (Loss) $ (6,280 ) $ 11 $ (6,269 ) $ 9,472 $ (1,540 ) $ 7,932

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	12. EARNINGS PER SHARE A summary of the calculation of basic and diluted earnings per share for the three and nine months ended September 30, 2018 and 2017 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2018 2017 2018 2017 Numerator Net income (loss) $ 7,589 $ 15,898 $ (10,895 ) $ 34,950 Denominator Weighted average number of shares – basic 47,710 47,870 47,927 48,110 Effect of dilutive securities Stock options 27 487 — 385 PSUs, RSUs and restricted stock 97 174 — 123 Weighted average number of shares – diluted 47,834 48,531 47,927 48,618 Net income (loss) per share – basic $ 0.16 $ 0.33 $ (0.23 ) $ 0.73 Net income (loss) per share – diluted $ 0.16 $ 0.33 $ (0.23 ) $ 0.72 Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 3.9 million and 3.2 million for the three months ended September 30, 2018 and 2017, respectively, and 4.8 million and 3.9 million for the nine months ended September 30, 2018 and 2017. As a result of the net loss for the nine months ended September 30, 2018, we excluded 0.1 million of unvested stock options, PSUs, RSUs and restricted stock from the calculation of diluted EPS due to their anti-dilutive effect.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	13. SEGMENT INFORMATION We operate in two reportable segments: (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes our suite of ProCloud ® We evaluate the performance of our segments based on gross profit; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment gain, other income (expense) and provision for taxes 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 the three and nine months ended September 30, 2018 and 2017. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended September 30, 2018 September 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 121,043 $ 51,100 $ 145,467 $ 71,933 Services & Support 19,292 7,348 39,645 14,558 Total $ 140,335 $ 58,448 $ 185,112 $ 86,491 Nine Months Ended September 30, 2018 September 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 341,359 $ 133,175 $ 444,607 $ 214,746 Services & Support 47,830 15,002 95,457 30,080 Total $ 389,189 $ 148,177 $ 540,064 $ 244,826 Sales by Category In addition to our reporting segments, we also report revenue for the following three categories – Access & Aggregation, Customer Devices, Traditional & Other Products. The table below presents sales information by category for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Access & Aggregation $ 91,901 $ 135,959 $ 258,323 $ 394,741 Customer Devices 38,552 35,582 103,213 105,683 Traditional & Other Products 9,882 13,571 27,653 39,640 Total $ 140,335 $ 185,112 $ 389,189 $ 540,064

Liability for Warranty Returns

Liability for Warranty Returns	9 Months Ended
	Sep. 30, 2018
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	14. LIABILITY FOR WARRANTY RETURNS 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 estimate of the cost to repair or replace the defective products. We engage in extensive product quality programs and processes, including actively monitoring and evaluating the quality of our component suppliers. Our products continue to become more complex in both size and functionality as many of our product offerings migrate from line card applications to total systems. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage, and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $9.0 million and $9.7 million at September 30, 2018 and December 31, 2017. During the three months ended March 31, 2017, we recorded a receivable and 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 table below. During the three months ended September 30, 2018, we had a reversal of prior provisions, the impact of which is reflected in the table below. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets. A summary of warranty expense and write-off activity for the three and nine months ended September 30, 2018 and 2017 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Balance at beginning of period $ 10,111 $ 9,180 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses (34 ) 4,087 6,649 6,401 Less: Deductions (1,053 ) (2,328 ) (7,349 ) (4,010 ) Balance at end of period $ 9,024 $ 10,939 $ 9,024 $ 10,939

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. COMMITMENTS AND CONTINGENCIES In the ordinary course of business, we may be subject to various legal proceedings and claims, including employment disputes, patent claims, disputes over contract agreements and other commercial disputes. In some cases, claimants seek damages or other relief, such as royalty payments related to patents, which, if granted, could require significant expenditures. Although the outcome of any claim or litigation can never be certain, it is our opinion that the outcome of all contingencies of which we are currently aware will not materially affect our business, operations, financial condition or cash flows. We have committed to invest up to an aggregate of $7.9 million in two private equity funds, and we have contributed $8.4 million as of September 30, 2018, of which $7.7 million has been applied to these commitments.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	16. SUBSEQUENT EVENTS On October 16, 2018, we announced that our Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to stockholders of record at the close of business on October 31, 2018. The payment date will be November 14, 2018. The quarterly dividend payment will be 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. During the 4 th

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2017, filed on February 23, 2018 with the SEC.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842) Codification Improvements to Topic 842, Leases, Leases (Topic 842), Targeted Improvements, Topic 842 In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment . ASU 2017-04 simplifies the measurement of goodwill by eliminating step 2 of the goodwill impairment test. Under ASU 2017-04, entities will be required to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for annual or interim impairment tests performed in fiscal years beginning after December 15, 2019, with early adoption permitted for annual or interim impairment tests performed on testing dates after January 1, 2017. The amendments should be applied prospectively. We are currently evaluating whether to early adopt ASU 2017-04, but we do not expect it will have a material effect on our consolidated financial statements. 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 In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities 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. 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 whether to early adopt , but we do not expect it will have a material effect on our consolidated financial statements. During 2018, we adopted the following accounting standards, which had the following effects on our consolidated financial statements: In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, These ASUs primarily affected our network implementation service revenue performance obligations and contract costs. We are using the “output method” to measure network implementation services progress, which 1) accelerates revenue recognition for certain performance obligations related to service revenue arrangements that were previously deferred until customer acceptance and 2) requires capitalization and amortization of the incremental costs of obtaining a contract as described below. In connection with the adoption of the new revenue standard, effective January 1, 2018, we adopted ASC 340-40, Other Assets and Deferred Costs – Contracts with Customers The cumulative effect of the changes made to our Consolidated Balance Sheet on January 1, 2018 for the adoption of ASU 2014-09 and the related ASUs was as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASU 2014-09 Balance at January 1, 2018 Other receivables $ 26,578 $ 374 $ 26,952 Deferred tax assets, net $ 23,428 $ (96 ) $ 23,332 Retained earnings $ 922,178 $ 278 $ 922,456 The effect of the adoption of ASU 2014-09 and the related ASUs on our financial statements was as follows: For the three months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 121,043 $ 120,588 $ 455 Services $ 19,292 $ 17,932 $ 1,360 Cost of Sales Products $ 69,943 $ 69,754 $ 189 Services $ 11,944 $ 11,046 $ 898 Income before benefit for income taxes $ 3,220 $ 2,492 $ 728 Benefit for income taxes $ 4,369 $ 3,382 $ 987 Net income $ 7,589 $ 5,874 $ 1,715 For the nine months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 341,359 $ 341,464 $ (105 ) Services $ 47,830 $ 46,062 $ 1,768 Cost of Sales Products $ 208,184 $ 208,480 $ (296 ) Services $ 32,828 $ 31,743 $ 1,085 Loss before benefit for income taxes $ (22,784 ) $ (23,658 ) $ 874 Benefit for income taxes $ 11,889 $ 10,938 $ 951 Net loss $ (10,895 ) $ (12,720 ) $ 1,825 As of September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 30,084 $ 27,917 $ 2,167 Inventory $ 106,060 $ 106,402 $ (342 ) Equity Retained earnings $ 900,324 $ 898,499 $ 1,825 In January 2016, the FASB issued ASU 2016-01, Financial Instruments — Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, Technical Corrections and Improvements to Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, See Note 7 of Notes to Consolidated Financial Statements for additional information. In March 2017, the FASB issued ASU 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost Compensation — Retirement Benefits

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Schedule of Cumulative Effect of Changes made to Consolidated Balance Sheet	The cumulative effect of the changes made to our Consolidated Balance Sheet on January 1, 2018 for the adoption of ASU 2014-09 and the related ASUs was as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASU 2014-09 Balance at January 1, 2018 Other receivables $ 26,578 $ 374 $ 26,952 Deferred tax assets, net $ 23,428 $ (96 ) $ 23,332 Retained earnings $ 922,178 $ 278 $ 922,456
Summary of Effect of Adoption of ASU 2014-09 and Related ASUs	The effect of the adoption of ASU 2014-09 and the related ASUs on our financial statements was as follows: For the three months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 121,043 $ 120,588 $ 455 Services $ 19,292 $ 17,932 $ 1,360 Cost of Sales Products $ 69,943 $ 69,754 $ 189 Services $ 11,944 $ 11,046 $ 898 Income before benefit for income taxes $ 3,220 $ 2,492 $ 728 Benefit for income taxes $ 4,369 $ 3,382 $ 987 Net income $ 7,589 $ 5,874 $ 1,715 For the nine months ended September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 341,359 $ 341,464 $ (105 ) Services $ 47,830 $ 46,062 $ 1,768 Cost of Sales Products $ 208,184 $ 208,480 $ (296 ) Services $ 32,828 $ 31,743 $ 1,085 Loss before benefit for income taxes $ (22,784 ) $ (23,658 ) $ 874 Benefit for income taxes $ 11,889 $ 10,938 $ 951 Net loss $ (10,895 ) $ (12,720 ) $ 1,825 As of September 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 30,084 $ 27,917 $ 2,167 Inventory $ 106,060 $ 106,402 $ (342 ) Equity Retained earnings $ 900,324 $ 898,499 $ 1,825

Business Combinations (Tables)

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Preliminary Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed	The preliminary allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date is as follows: (In thousands) Assets Other receivables $ 104 Inventory 510 Property, plant and equipment 392 Intangible assets 22,100 Total assets acquired 23,106 Liabilities Deferred income taxes (3,978 ) Total liabilities assumed (3,978 ) Total net assets 19,128 Gain on bargain purchase of a business, net of tax (11,322 ) Total purchase price $ 7,806
Summary of Actual Revenue and Net Loss Included in Consolidated Statements of Income	The actual revenue and net loss included in our Consolidated Statements of Income for the three months ended September 30, 2018 and the period March 19, 2018 to September 30, 2018 are as follows: Three Months Ended March 19, 2018 to (In thousands) September 30, 2018 September 30, 2018 Revenue $ 1,021 $ 2,218 Net income (loss) $ 564 $ (322 )
Details of the Acquired Intangible Assets	The details of the acquired intangible assets are as follows: (In thousands) Value Life (years) Customer relationships $ 13,400 12.0 Licensed technology 5,900 9.0 Supplier relationship 2,800 2.0 Total $ 22,100
Summary of Unaudited Supplemental Pro Forma Information	The following unaudited supplemental pro forma information presents the financial results as if the acquisition 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 and 2018 net income for the effect of the bargain purchase gain, there were no material, non-recurring adjustments to this unaudited pro forma information. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2017 2018 2017 Pro forma revenue $ 187,027 $ 390,449 $ 545,706 Pro forma net income (loss) $ 14,997 $ (23,431 ) $ 43,826 Pro forma earnings per share - basic $ 0.31 $ (0.49 ) $ 0.91 Pro forma earnings per share - diluted $ 0.31 $ (0.49 ) $ 0.90

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers	The following table provides information about receivables, contract assets, and unearned revenue from contracts with customers: (In thousands) September 30, 2018 January 1, 2018 Accounts receivable $ 101,865 $ 144,150 Contract assets $ 4,564 $ 374 Unearned revenue $ 17,004 $ 13,070 Non-current unearned revenue $ 3,846 $ 4,556
Disaggregate of Revenue by Major Source	The following table disaggregates our revenue by major source for the three months ended September 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 76,046 $ 15,855 $ 91,901 Customer Devices 37,313 1,239 38,552 Traditional & Other Products 7,684 2,198 9,882 Total $ 121,043 $ 19,292 $ 140,335 The following table disaggregates our revenue by major source for the nine months ended September 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 220,653 $ 37,670 $ 258,323 Customer Devices 99,396 3,817 103,213 Traditional & Other Products 21,310 6,343 27,653 Total $ 341,359 $ 47,830 $ 389,189

Pension Benefit Plan (Tables)

Pension Benefit Plan (Tables)	9 Months Ended
	Sep. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Summarization of Components of Net Periodic Pension Cost	The following table summarizes the components of net periodic pension cost for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Service cost $ 294 $ 327 $ 905 $ 930 Interest cost 179 158 551 448 Expected return on plan assets (381 ) (329 ) (1,174 ) (935 ) Amortization of actuarial losses 61 80 188 228 Net periodic pension cost $ 153 $ 236 $ 470 $ 671 The components of net periodic pension cost other than the service cost component are included in the line item “Other income (expense), net” in the Consolidated Statements of Income.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense Related to Stock Options, Performance Stock Units (PSUs), Restricted Stock Units (RSUs) and Restricted Stock	The following table summarizes the stock-based compensation expense related to stock options, performance stock units (PSUs), restricted stock units (RSUs) and restricted stock for the three and nine months ended September 30, 2018 and 2017, which was recognized as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Stock-based compensation expense included in cost of sales $ 101 $ 97 $ 298 $ 281 Selling, general and administrative expense 894 994 2,924 3,018 Research and development expense 645 743 2,021 2,274 Stock-based compensation expense included in operating expenses 1,539 1,737 4,945 5,292 Total stock-based compensation expense 1,640 1,834 5,243 5,573 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (292 ) (402 ) (1,016 ) (1,215 ) Total stock-based compensation expense, net of tax $ 1,348 $ 1,432 $ 4,227 $ 4,358
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2017 and September 30, 2018 and the changes that occurred during the nine months ended September 30, 2018: (In thousands, except per share amounts) Number of Stock Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Stock options outstanding, December 31, 2017 5,148 $ 22.65 4.87 $ 6,109 Stock options granted — $ — Stock options exercised (85 ) $ 15.48 Stock options forfeited (71 ) $ 16.50 Stock options expired (331 ) $ 25.87 Stock options outstanding, September 30, 2018 4,661 $ 22.64 4.12 $ 2,730 Stock options vested and expected to vest, September 30, 2018 4,661 $ 22.64 4.12 $ 2,730 Stock options exercisable, September 30, 2018 3,952 $ 23.75 3.63 $ 1,600
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, 2017 and the changes that occurred during the nine months ended September 30, 2018: (In thousands, except per share amounts) Number of Shares Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2017 1,292 $ 21.33 PSUs, RSUs and restricted stock granted 22 $ 17.84 PSUs, RSUs and restricted stock vested (14 ) $ 20.19 PSUs, RSUs and restricted stock forfeited (165 ) $ 21.66 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2018 1,135 $ 21.23

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Debt Securities and Other Investments, Recorded at Either Fair Value or Cost	Debt Securities and Other Investments At September 30, 2018, we held the following debt securities and other investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Corporate bonds $ 25,758 $ 13 $ (209 ) $ 25,562 Municipal fixed-rate bonds 1,451 — (36 ) 1,415 Asset-backed bonds 8,384 — (29 ) 8,355 Mortgage/Agency-backed bonds 5,450 — (87 ) 5,363 U.S. government bonds 19,957 — (184 ) 19,773 Foreign government bonds 593 2 — 595 Available-for-sale debt securities held at fair value $ 61,593 $ 15 $ (545 ) $ 61,063 Restricted investment held at cost 26,700 Other investments held at cost 520 Total carrying value of available-for-sale investments $ 88,283 At December 31, 2017, we held the following debt securities and other investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Corporate bonds $ 32,654 $ 44 $ (155 ) $ 32,543 Municipal fixed-rate bonds 2,902 2 (22 ) 2,882 Asset-backed bonds 6,545 1 (20 ) 6,526 Mortgage/Agency-backed bonds 5,554 1 (46 ) 5,509 U.S. government bonds 14,477 — (174 ) 14,303 Foreign government bonds 725 5 — 730 Available-for-sale debt securities held at fair value $ 62,857 $ 53 $ (417 ) $ 62,493 Restricted investment held at cost 27,800 Other investments held at cost 547 Total carrying value of available-for-sale investments $ 90,840
Contractual Maturities of Debt Securities	As of September 30, 2018 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 $ 2,800 $ — $ 3,112 $ — $ — $ — One to two years 10,122 287 657 — 11,716 285 Two to three years 9,898 1,128 714 425 5,565 310 Three to five years 2,742 — 2,244 1,561 2,492 — Five to ten years — — 445 525 — — More than ten years — — 1,183 2,852 — — Total $ 25,562 $ 1,415 $ 8,355 $ 5,363 $ 19,773 $ 595
Gross Realized Gains and Losses on Sale of Debt Securities	The following table presents gross realized gains and losses related to our debt securities: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Gross realized gains on debt securities $ 24 $ 91 $ 49 $ 148 Gross realized losses on debt securities (50 ) (28 ) (365 ) (179 ) Total gain (loss) recognized, net $ (26 ) $ 63 $ (316 ) $ (31 )
Realized and Unrealized Gains and Losses for Marketable Equity Securities	Realized and unrealized gains and losses for our marketable equity securities for the three and nine months ended September 30, 2018 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2018 Realized gains (losses) on equity securities sold $ 1,240 $ 1,587 Unrealized gains (losses) on equity securities held 3,293 4,129 Total gain (loss) recognized, net $ 4,533 $ 5,716
Fair Value Measurements of Cash Equivalents and Investments	We have categorized our cash equivalents and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 - Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at September 30, 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 $ 1,423 $ 1,423 $ — $ — Foreign government securities 600 — 600 — Cash equivalents 2,023 1,423 600 — Available-for-sale debt securities Corporate bonds 25,562 — 25,562 — Municipal fixed-rate bonds 1,415 — 1,415 — Asset-backed bonds 8,355 — 8,355 — Mortgage/Agency-backed bonds 5,363 — 5,363 — U.S. government bonds 19,773 19,773 — — Foreign government bonds 595 — 595 — Marketable equity securities — Marketable equity securities – various industries 40,645 40,645 — — Equity in escrow 277 277 — — Deferred compensation plan assets 20,948 20,948 — — Available-for-sale securities 122,933 81,643 41,290 — Total $ 124,956 $ 83,066 $ 41,890 $ — Fair Value Measurements at December 31, 2017 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 $ 5,851 $ 5,851 $ — $ — Commercial paper 3,999 — 3,999 — Cash equivalents 9,850 5,851 3,999 — Available-for-sale debt securities Corporate bonds 32,543 — 32,543 — Municipal fixed-rate bonds 2,882 — 2,882 — Asset-backed bonds 6,526 — 6,526 — Mortgage/Agency-backed bonds 5,509 — 5,509 — U.S. government bonds 14,303 14,303 — — Foreign government bonds 730 — 730 — Marketable equity securities Marketable equity securities – various industries 35,662 35,662 — — Deferred compensation plan assets 19,883 19,883 — — Available-for-sale securities 118,038 69,848 48,190 — Total $ 127,888 $ 75,699 $ 52,189 $ —

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Changes in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income	The changes in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and nine months ended September 30, 2018 and 2017 were as follows: Three Months Ended Nine Months Ended Income Statement September 30, September 30, (In thousands) Location 2018 2017 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense), net $ — $ (334 ) $ 13 $ (819 )
Schedule of Changes in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income (OCI) and Reclassified to Income, Net of Tax	The changes in our derivatives designated as hedging instruments recorded in other comprehensive income (OCI) and reclassified to income, net of tax, during the three and nine months ended September 30, 2018 and 2017, were as follows: Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Location of Gains Three Months Ended September 30, (Losses) Reclassified Three Months Ended September 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (127 ) Cost of Sales $ — $ (269 ) Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Location of Gains Nine Months Ended September 30, (Losses) Reclassified Nine Months Ended September 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (619 ) Cost of Sales $ — $ (423 )

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Components of Inventory	At September 30, 2018 and December 31, 2017, inventory consisted of the following: September 30, December 31, (In thousands) 2018 2017 Raw materials $ 47,664 $ 44,185 Work in process 1,289 1,939 Finished goods 57,107 76,418 Total $ 106,060 $ 122,542

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of September 30, 2018 and December 31, 2017. Fully amortized intangible assets have been removed from prior year balances for comparability. (In thousands) September 30, 2018 December 31, 2017 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 20,724 $ (5,072 ) $ 15,652 $ 7,474 $ (4,283 ) $ 3,191 Licensed technology 5,900 (355 ) 5,545 — — — Developed technology 5,435 (4,799 ) 636 5,524 (4,663 ) 861 Supplier relationship 2,800 (758 ) 2,042 — — — Intellectual property 930 (930 ) — 930 (852 ) 78 Patent 500 (140 ) 360 500 (89 ) 411 Non-compete 200 (181 ) 19 200 (115 ) 85 Trade names 100 (100 ) — 100 (65 ) 35 Total $ 36,589 $ (12,335 ) $ 24,254 $ 14,728 $ (10,067 ) $ 4,661
Estimated Future Amortization Expense Related to Intangible Assets	As of September 30, 2018, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2018 $ 859 2019 3,540 2020 2,657 2021 2,364 2022 2,350 Thereafter 12,484 Total $ 24,254

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the nine months ended September 30, 2018 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2017 $ 497,911 Net income (loss) (10,895 ) Dividend payments (12,976 ) Dividends accrued for unvested restricted stock units (15 ) Net unrealized gains (losses) on available-for-sale securities (net of tax) (3,340 ) Defined benefit plan adjustments (net of tax) 104 Foreign currency translation adjustment (3,033 ) Proceeds from stock option exercises 1,321 Purchase of treasury stock (14,185 ) Adoption of new accounting standards (see Note 1) 3,499 Stock-based compensation expense 5,243 RSU's and restricted stock vested (33 ) Balance, September 30, 2018 $ 463,601
Cash Dividends	During the nine months ended September 30, 2018, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid January 31, 2018 February 14, 2018 $ 0.09 $ 4,367 May 2, 2018 May 16, 2018 $ 0.09 $ 4,312 August 1, 2018 August 15, 2018 $ 0.09 $ 4,297
Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Component	The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the three months ended September 30, 2018 and 2017: Three Months Ended September 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) Other comprehensive income (loss) before reclassifications 1,208 — (451 ) 757 Amounts reclassified from accumulated other comprehensive income (loss) (1,240 ) 37 — (1,203 ) Net current period other comprehensive income (loss) (32 ) 37 (451 ) (446 ) Ending balance $ (773 ) $ (4,182 ) $ (4,609 ) $ (9,564 ) Three Months Ended September 30, 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 Total Beginning balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Other comprehensive income (loss) before reclassifications 1,420 (127 ) — 1,541 2,834 Amounts reclassified from accumulated other comprehensive income (loss) (616 ) 269 73 — (274 ) Net current period other comprehensive income (loss) 804 142 73 1,541 2,560 Ending balance $ 2,916 $ (196 ) $ (4,803 ) $ (2,173 ) $ (4,256 ) The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the nine months ended September 30, 2018 and 2017 : Nine Months Ended September 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 2,567 $ (4,286 ) $ (1,576 ) $ (3,295 ) Other comprehensive income (loss) before reclassifications 869 — (3,033 ) (2,164 ) Amounts reclassified from accumulated other comprehensive income (loss) (989 ) 104 — (885 ) Amounts reclassified to retained earnings (1) (3,220 ) — — (3,220 ) Net current period other comprehensive income (loss) (3,340 ) 104 (3,033 ) (6,269 ) Ending balance $ (773 ) $ (4,182 ) $ (4,609 ) $ (9,564 ) (1) Nine Months Ended September 30, 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 Total Beginning balance $ 404 $ — $ (5,017 ) $ (7,575 ) $ (12,188 ) Other comprehensive income (loss) before reclassifications 4,262 (619 ) — 5,402 9,045 Amounts reclassified from accumulated other comprehensive income (loss) (1,750 ) 423 214 — (1,113 ) Net current period other comprehensive income (loss) 2,512 (196 ) 214 5,402 7,932 Ending balance $ 2,916 $ (196 ) $ (4,803 ) $ (2,173 ) $ (4,256 )
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 three months ended September 30, 2018 and 2017: (In thousands) Three Months Ended September 30, 2018 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,676 Net investment gain Defined benefit plan adjustments – actuarial losses (54 ) (1) Total reclassifications for the period, before tax 1,622 Tax (expense) benefit (419 ) Total reclassifications for the period, net of tax $ 1,203 (1) (In thousands) Three Months Ended September 30, 2017 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,066 Net investment gain Impairment expense (57 ) Net investment gain Net losses on derivatives designated as hedging instruments (385 ) Cost of sales Defined benefit plan adjustments – actuarial losses (106 ) (1) Total reclassifications for the period, before tax 518 Tax (expense) benefit (244 ) Total reclassifications for the period, net of tax $ 274 (1) The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the nine months ended September 30, 2018 and 2017 : (In thousands) Nine Months Ended September 30, 2018 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gain (loss) on sales of securities $ 1,352 Net investment gain Defined benefit plan adjustments – actuarial losses (151 ) (1) Total reclassifications for the period, before tax 1,201 Tax (expense) benefit (316 ) Total reclassifications for the period, net of tax $ 885 (1) (In thousands) Nine Months Ended September 30, 2017 Details about Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain (loss) on sales of securities $ 3,031 Net investment gain Impairment expense (162 ) Net investment gain Net losses on derivatives designated as hedging instruments (539 ) Cost of sales Defined benefit plan adjustments – actuarial losses (310 ) (1) Total reclassifications for the period, before tax 2,020 Tax (expense) benefit (907 ) Total reclassifications for the period, net of tax $ 1,113 (1)
Other Comprehensive Income (Loss)	The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the three months ended September 30, 2018 and 2017: Three Months Ended Three Months Ended September 30, 2018 September 30, 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 1,632 $ (424 ) $ 1,208 $ 2,328 $ (908 ) $ 1,420 Unrealized gains (losses) on cash flow hedges — — — (184 ) 57 (127 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,676 ) 436 (1,240 ) (1,009 ) 393 (616 ) Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 385 (116 ) 269 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 54 (17 ) 37 106 (33 ) 73 Foreign currency translation adjustment (451 ) — (451 ) 1,541 — 1,541 Total Other Comprehensive Income (Loss) $ (441 ) $ (5 ) $ (446 ) $ 3,167 $ (607 ) $ 2,560 The following table presents the tax effects related to the change in each component of other comprehensive income for the nine months ended September 30, 2018 and 2017: Nine Months Ended Nine Months Ended September 30, 2018 September 30, 2017 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gains (losses) on available-for-sale securities $ 1,174 $ (305 ) $ 869 $ 6,987 $ (2,725 ) $ 4,262 Unrealized gains (losses) on cash flow hedges — — — (897 ) 278 (619 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,352 ) 363 (989 ) (2,869 ) 1,119 (1,750 ) Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01 (3,220 ) — (3,220 ) — — — Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 539 (116 ) 423 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 151 (47 ) 104 310 (96 ) 214 Foreign currency translation adjustment (3,033 ) — (3,033 ) 5,402 — 5,402 Total Other Comprehensive Income (Loss) $ (6,280 ) $ 11 $ (6,269 ) $ 9,472 $ (1,540 ) $ 7,932

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings Per Share	A summary of the calculation of basic and diluted earnings per share for the three and nine months ended September 30, 2018 and 2017 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2018 2017 2018 2017 Numerator Net income (loss) $ 7,589 $ 15,898 $ (10,895 ) $ 34,950 Denominator Weighted average number of shares – basic 47,710 47,870 47,927 48,110 Effect of dilutive securities Stock options 27 487 — 385 PSUs, RSUs and restricted stock 97 174 — 123 Weighted average number of shares – diluted 47,834 48,531 47,927 48,618 Net income (loss) per share – basic $ 0.16 $ 0.33 $ (0.23 ) $ 0.73 Net income (loss) per share – diluted $ 0.16 $ 0.33 $ (0.23 ) $ 0.72

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Sales and Gross Profit of Reportable Segments	The following table presents information about the reported sales and gross profit of our reportable segments for the three and nine months ended September 30, 2018 and 2017. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended September 30, 2018 September 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 121,043 $ 51,100 $ 145,467 $ 71,933 Services & Support 19,292 7,348 39,645 14,558 Total $ 140,335 $ 58,448 $ 185,112 $ 86,491 Nine Months Ended September 30, 2018 September 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 341,359 $ 133,175 $ 444,607 $ 214,746 Services & Support 47,830 15,002 95,457 30,080 Total $ 389,189 $ 148,177 $ 540,064 $ 244,826
Sales Information by Category	The table below presents sales information by category for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Access & Aggregation $ 91,901 $ 135,959 $ 258,323 $ 394,741 Customer Devices 38,552 35,582 103,213 105,683 Traditional & Other Products 9,882 13,571 27,653 39,640 Total $ 140,335 $ 185,112 $ 389,189 $ 540,064

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	9 Months Ended
	Sep. 30, 2018
Product Warranties Disclosures [Abstract]
Summary of Warranty Expense and Write-Off Activity	A summary of warranty expense and write-off activity for the three and nine months ended September 30, 2018 and 2017 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2018 2017 2018 2017 Balance at beginning of period $ 10,111 $ 9,180 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses (34 ) 4,087 6,649 6,401 Less: Deductions (1,053 ) (2,328 ) (7,349 ) (4,010 ) Balance at end of period $ 9,024 $ 10,939 $ 9,024 $ 10,939

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Cumulative Effect of Changes made to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other receivables	$ 30,084		$ 26,578
Deferred tax assets, net	39,595		23,428
Retained earnings	900,324		$ 922,178
ASU 2014-09 [member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other receivables		$ 26,952
Deferred tax assets, net		23,332
Retained earnings		922,456
ASU 2014-09 [member] | Adjustments Due to ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other receivables	2,167	374
Deferred tax assets, net		(96)
Retained earnings	$ 1,825	$ 278

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Effect of Adoption of ASU 2014-09 and Related ASUs (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Sales
Sales	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Cost of Sales
Cost of Sales	81,887	98,621	241,012	295,238
Income before benefit for income taxes	3,220	19,207	(22,784)	45,421
(Provision) benefit for income taxes	4,369	(3,309)	11,889	(10,471)
Net income	7,589	15,898	(10,895)	34,950
Net Income (Loss)	7,589	15,898	(10,895)	34,950
ASSETS
Other receivables	30,084		30,084			$ 26,578
Inventory	106,060		106,060			122,542
Equity
Retained earnings	900,324		900,324			$ 922,178
Product [Member]
Sales
Sales	121,043	145,467	341,359	444,607
Cost of Sales
Cost of Sales	69,943	73,534	208,184	229,861
Service [Member]
Sales
Sales	19,292	39,645	47,830	95,457
Cost of Sales
Cost of Sales	11,944	$ 25,087	32,828	$ 65,377
ASU 2014-09 [member]
ASSETS
Other receivables					$ 26,952
Equity
Retained earnings					922,456
ASU 2014-09 [member] | Balances Without Adoption of ASC 606 [Member]
Cost of Sales
Income before benefit for income taxes	2,492		(23,658)
(Provision) benefit for income taxes	3,382		10,938
Net income	5,874		(12,720)
Net Income (Loss)	5,874		(12,720)
ASSETS
Other receivables	27,917		27,917
Inventory	106,402		106,402
Equity
Retained earnings	898,499		898,499
ASU 2014-09 [member] | Adjustments Due to ASU 2014-09 [Member]
Cost of Sales
Income before benefit for income taxes	728		874
(Provision) benefit for income taxes	987		951
Net income	1,715		1,825
Net Income (Loss)	1,715		1,825
ASSETS
Other receivables	2,167		2,167		374
Inventory	(342)		(342)
Equity
Retained earnings	1,825		1,825		$ 278
ASU 2014-09 [member] | Product [Member] | Balances Without Adoption of ASC 606 [Member]
Sales
Sales	120,588		341,464
Cost of Sales
Cost of Sales	69,754		208,480
ASU 2014-09 [member] | Product [Member] | Adjustments Due to ASU 2014-09 [Member]
Sales
Sales	455		(105)
Cost of Sales
Cost of Sales	189		(296)
ASU 2014-09 [member] | Service [Member] | Balances Without Adoption of ASC 606 [Member]
Sales
Sales	17,932		46,062
Cost of Sales
Cost of Sales	11,046		31,743
ASU 2014-09 [member] | Service [Member] | Adjustments Due to ASU 2014-09 [Member]
Sales
Sales	1,360		1,768
Cost of Sales
Cost of Sales	$ 898		$ 1,085

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Jan. 01, 2018
ASU 2016-01 [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassification of net unrealized gains from accumulated other comprehensive income to opening retained earnings			$ 3.2
ASU 2017-07 [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassified from cost of sales, selling, general and administrative expenses, and research and development expense to other income (expense), net	$ 0.1	$ 0.3

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 19, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Bargain purchase gain net of income taxes				$ 11,322
Sumitomo Electric Lightwave Corp.'s North American EPON Business [Member]
Business Acquisition [Line Items]
Date of acquisition				Mar. 19, 2018
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). 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.
Bargain purchase gain net of income taxes	$ 11,322		$ 11,300
Acquisition and integration related expenses and amortization of acquired intangibles		$ 700		$ 1,600

Business Combinations - Prelimi

Business Combinations - Preliminary Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Mar. 19, 2018	Mar. 31, 2018	Sep. 30, 2018
Liabilities
Gain on bargain purchase of a business, net of tax			$ (11,322)
Total purchase price			$ 7,806
Sumitomo Electric Lightwave Corp.'s North American EPON Business [Member]
Assets
Other receivables	$ 104
Inventory	510
Property, plant and equipment	392
Intangible assets	22,100
Total assets acquired	23,106
Liabilities
Deferred income taxes	(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

Business Combinations - Summary

Business Combinations - Summary of Actual Revenue and Net Loss Included in Consolidated Statements of Income (Detail) - Sumitomo Electric Lightwave Corp.'s North American EPON Business [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Revenue	$ 1,021	$ 2,218
Net income (loss)	$ 564	$ (322)

Business Combinations - Details

Business Combinations - Details of the Acquired Intangible Assets (Detail) - Sumitomo Electric Lightwave Corp.'s North American EPON Business [Member] $ in Thousands	Mar. 19, 2018USD ($)
Business Acquisition [Line Items]
Total, Value	$ 22,100
Customer Relationships [Member]
Business Acquisition [Line Items]
Total, Value	$ 13,400
Life (years)	12 years
Licensed Technology [Member]
Business Acquisition [Line Items]
Total, Value	$ 5,900
Life (years)	9 years
Supplier Relationship [Member]
Business Acquisition [Line Items]
Total, Value	$ 2,800
Life (years)	2 years

Business Combinations - Summa_2

Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Combinations [Abstract]
Pro forma revenue	$ 187,027	$ 390,449	$ 545,706
Pro forma net income (loss)	$ 14,997	$ (23,431)	$ 43,826
Pro forma earnings per share - basic	$ 0.31	$ (0.49)	$ 0.91
Pro forma earnings per share - diluted	$ 0.31	$ (0.49)	$ 0.90

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue [Line Items]
Period of assurance-based warranty for product defects			90 days to five years
Remaining performance obligations	$ 0		$ 0
Revenue recognized that was included in unearned revenue					$ 8,900,000
Lease Agreements [Member]
Revenue [Line Items]
Recognized revenue	$ 4,200,000	$ 8,400,000	$ 10,500,000	$ 15,400,000
Minimum [Member]
Revenue [Line Items]
Lessor sales type lease arrangement terms for network equipments			18 months
Maintenance service periods			1 month
Maximum [Member]
Revenue [Line Items]
Lessor sales type lease arrangement terms for network equipments			5 years
Maintenance service periods			5 years

Revenue - Information about Rec

Revenue - Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue From Contract With Customer [Abstract]
Accounts receivable	$ 101,865	$ 144,150	$ 144,150
Contract assets	4,564	374
Unearned revenue	17,004	13,070	13,070
Non-current unearned revenue	$ 3,846	$ 4,556	$ 4,556

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenue	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	91,901		258,323
Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	38,552	35,582	103,213	105,683
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	9,882	13,571	27,653	39,640
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	121,043	145,467	341,359	444,607
Network Solutions [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	76,046		220,653
Network Solutions [Member] | Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	37,313		99,396
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	7,684		21,310
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	19,292	$ 39,645	47,830	$ 95,457
Services & Support [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	15,855		37,670
Services & Support [Member] | Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,239		3,817
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,198		$ 6,343

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective tax rate expense (benefit)	(34.90%)	23.10%

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 294	$ 327	$ 905	$ 930
Interest cost	179	158	551	448
Expected return on plan assets	(381)	(329)	(1,174)	(935)
Amortization of actuarial losses	61	80	188	228
Net periodic pension cost	$ 153	$ 236	$ 470	$ 671

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, Performance Stock Units (PSUs), Restricted Stock Units (RSUs) and Restricted Stock (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,640	$ 1,834	$ 5,243	$ 5,573
Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock	(292)	(402)	(1,016)	(1,215)
Total stock-based compensation expense, net of tax	1,348	1,432	4,227	4,358
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	101	97	298	281
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	894	994	2,924	3,018
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	645	743	2,021	2,274
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	$ 1,539	$ 1,737	$ 4,945	$ 5,292

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance			5,148,000
Number of Stock Options, Stock options granted	0	0	0	0
Number of Stock Options, Stock options exercised			(85,000)
Number of Stock Options, Stock options forfeited			(71,000)
Number of Stock Options, Stock options expired			(331,000)
Number of Stock Options, Stock options outstanding, Ending Balance	4,661,000		4,661,000		5,148,000
Number of Stock Options, Stock options vested and expected to vest	4,661,000		4,661,000
Number of Stock Options, Stock options exercisable	3,952,000		3,952,000
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance			$ 22.65
Weighted Avg. Exercise Price, Stock options exercised			15.48
Weighted Avg. Exercise Price, Stock options forfeited			16.50
Weighted Avg. Exercise Price, Stock options expired			25.87
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	$ 22.64		22.64		$ 22.65
Weighted Avg. Exercise Price, Stock options vested and expected to vest	22.64		22.64
Weighted Avg. Exercise Price, Stock options exercisable	$ 23.75		$ 23.75
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding			4 years 1 month 13 days		4 years 10 months 13 days
Weighted Avg. Remaining Contractual Life In Years, Stock options vested and expected to vest			4 years 1 month 13 days
Weighted Avg. Remaining Contractual Life In Years, Stock options exercisable			3 years 7 months 17 days
Aggregate Intrinsic Value, Stock options outstanding	$ 2,730		$ 2,730		$ 6,109
Aggregate Intrinsic Value, Stock options vested and expected to vest	2,730		2,730
Aggregate Intrinsic Value, Stock options exercisable	$ 1,600		$ 1,600

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pre-tax intrinsic value of options exercised	$ 0.1		$ 0.2
Number of Stock options, granted	0	0	0	0
Unvested Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 1.2		$ 1.2
Recognition period of unvested compensation expense			1 year

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	1,292
Number of Shares, PSUs, RSUs and restricted stock granted | shares	22
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(14)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(165)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,135
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance | $ / shares	$ 21.33
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	17.84
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	20.19
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	21.66
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 21.23

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU shares grant approved by board of directors				22
Stock-based compensation expense	$ 1,640,000	$ 1,834,000		$ 5,243,000	$ 5,573,000
Performance Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU shares grant approved by board of directors			500
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	9,800,000			$ 9,800,000
Recognition period of unvested compensation expense				2 years 7 months 6 days
Performance-Based PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	9,400,000			$ 9,400,000
Recognition period of unvested compensation expense				3 years
Performance-Based PSU Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0			$ 0

Investments - Debt Securities a

Investments - Debt Securities and Other Investments, Recorded at Either Fair Value or Cost (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 61,593	$ 62,857
Gross Unrealized Gains	15	53
Gross Unrealized Losses	(545)	(417)
Available-for-sale debt securities, Carrying Value	61,063	62,493
Restricted investment held at cost	26,700	27,800
Other investments held at cost	520	547
Total carrying value of available-for-sale investments	88,283	90,840
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,758	32,654
Gross Unrealized Gains	13	44
Gross Unrealized Losses	(209)	(155)
Available-for-sale debt securities, Carrying Value	25,562	32,543
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,451	2,902
Gross Unrealized Gains		2
Gross Unrealized Losses	(36)	(22)
Available-for-sale debt securities, Carrying Value	1,415	2,882
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,384	6,545
Gross Unrealized Gains		1
Gross Unrealized Losses	(29)	(20)
Available-for-sale debt securities, Carrying Value	8,355	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,450	5,554
Gross Unrealized Gains		1
Gross Unrealized Losses	(87)	(46)
Available-for-sale debt securities, Carrying Value	5,363	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,957	14,477
Gross Unrealized Losses	(184)	(174)
Available-for-sale debt securities, Carrying Value	19,773	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	593	725
Gross Unrealized Gains	2	5
Available-for-sale debt securities, Carrying Value	$ 595	$ 730

Investments - Contractual Matur

Investments - Contractual Maturities of Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 61,063	$ 62,493
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,800
One to two years	10,122
Two to three years	9,898
Three to five years	2,742
Available-for-sale debt securities, Fair Value/Carrying Value	25,562	32,543
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	287
Two to three years	1,128
Available-for-sale debt securities, Fair Value/Carrying Value	1,415	2,882
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	3,112
One to two years	657
Two to three years	714
Three to five years	2,244
Five to ten years	445
More than ten years	1,183
Available-for-sale debt securities, Fair Value/Carrying Value	8,355	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Two to three years	425
Three to five years	1,561
Five to ten years	525
More than ten years	2,852
Available-for-sale debt securities, Fair Value/Carrying Value	5,363	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	11,716
Two to three years	5,565
Three to five years	2,492
Available-for-sale debt securities, Fair Value/Carrying Value	19,773	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	285
Two to three years	310
Available-for-sale debt securities, Fair Value/Carrying Value	$ 595	$ 730

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments Debt And Equity Securities [Abstract]
Gross realized gains on debt securities	$ 24	$ 91	$ 49	$ 148
Gross realized losses on debt securities	(50)	(28)	(365)	(179)
Total gain (loss) recognized, net	$ (26)	$ 63	$ (316)	$ (31)

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Restricted certificate of deposit held	$ 26,700		$ 27,800
ASU 2016-01 [Member]
Schedule of Investments [Line Items]
Reclassification of net unrealized gains of marketable equity securities from AOCI to retained earnings		$ 3,200
Alabama State Industrial Development Authority [Member]
Schedule of Investments [Line Items]
Maturity date of bond	Jan. 1, 2020
Percentage of interest on bond	2.00%
Alabama State Industrial Development Authority [Member] | Taxable Revenue Bond [Member]
Schedule of Investments [Line Items]
Collateral deposit against outstanding principal amount	$ 26,700		26,700
Alabama State Industrial Development Authority [Member] | Taxable Revenue Bond [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Investments [Line Items]
Estimated fair value of bond	$ 26,500		$ 26,700
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member]
Schedule of Investments [Line Items]
Investment concentration risk percentage	5.00%

Investments - Realized and Unre

Investments - Realized and Unrealized Gains and Losses for Marketable Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on equity securities sold	$ 1,240	$ 1,587
Unrealized gains (losses) on equity securities held	3,293	4,129
Total gain (loss) recognized, net	$ 4,533	$ 5,716

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 61,063	$ 62,493
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,023	9,850
Available-for-sale securities	122,933	118,038
Total	124,956	127,888
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	1,423	5,851
Available-for-sale securities	81,643	69,848
Total	83,066	75,699
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	600	3,999
Available-for-sale securities	41,290	48,190
Total	41,890	52,189
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,423	5,851
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	1,423	5,851
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	25,562	32,543
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	25,562	32,543
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	25,562	32,543
Foreign Government Securities [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	600
Foreign Government Securities [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	600
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,415	2,882
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,415	2,882
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	1,415	2,882
Commercial Paper [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		3,999
Commercial Paper [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		3,999
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	8,355	6,526
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	8,355	6,526
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	8,355	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,363	5,509
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,363	5,509
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	5,363	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	19,773	14,303
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	19,773	14,303
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	19,773	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	595	730
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	595	730
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	595	730
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	40,645	35,662
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	40,645	35,662
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	20,948	19,883
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	20,948	$ 19,883
Equity in Escrow [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	277
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	$ 277

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Additional Information (Detail)	Sep. 30, 2018USD ($)
Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Derivative instruments, amount	$ 0

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Schedule of Changes in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Foreign Exchange Contracts [Member] | Other Income (Expense), Net [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ (334)	$ 13	$ (819)

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Schedule of Changes in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income (OCI) and Reclassified to Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Derivative [Line Items]
Amount of Gains (Losses) Recognized in OCI on Derivatives	$ (127)	$ (619)
Foreign Exchange Contracts [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Amount of Gains (Losses) Recognized in OCI on Derivatives	(127)	(619)
Foreign Exchange Contracts [Member] | Derivatives Designated as Hedging Instruments [Member] | Cost of Sales [Member]
Derivative [Line Items]
Amount of Gains (Losses) Reclassified from AOCI into Income	$ (269)	$ (423)

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 47,664	$ 44,185
Work in process	1,289	1,939
Finished goods	57,107	76,418
Total	$ 106,060	$ 122,542

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 17.2	$ 15
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 10.6	$ 8.3

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, relates to acquisition			$ 3,500,000		$ 3,500,000
Impairment losses			0
Amortization expense	$ 900,000	$ 500,000	2,400,000	$ 2,400,000
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition			3,100,000
Services & Support [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition			$ 400,000

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Gross Value	$ 36,589	$ 14,728
Accumulated Amortization	(12,335)	(10,067)
Net Value	24,254	4,661
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	20,724	7,474
Accumulated Amortization	(5,072)	(4,283)
Net Value	15,652	3,191
Licensed Technology [Member]
Goodwill [Line Items]
Gross Value	5,900
Accumulated Amortization	(355)
Net Value	5,545
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	5,435	5,524
Accumulated Amortization	(4,799)	(4,663)
Net Value	636	861
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	930	930
Accumulated Amortization	(930)	(852)
Net Value		78
Supplier Relationship [Member]
Goodwill [Line Items]
Gross Value	2,800
Accumulated Amortization	(758)
Net Value	2,042
Trade Names [Member]
Goodwill [Line Items]
Gross Value	100	100
Accumulated Amortization	(100)	(65)
Net Value		35
Patent [Member]
Goodwill [Line Items]
Gross Value	500	500
Accumulated Amortization	(140)	(89)
Net Value	360	411
Non-compete [Member]
Goodwill [Line Items]
Gross Value	200	200
Accumulated Amortization	(181)	(115)
Net Value	$ 19	$ 85

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Remainder of 2018	$ 859
2,019	3,540
2,020	2,657
2,021	2,364
2,022	2,350
Thereafter	12,484
Net Value	$ 24,254	$ 4,661

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Beginning Balance			$ 497,911
Net Income (Loss)	$ 7,589	$ 15,898	(10,895)	$ 34,950
Dividend payments			(12,976)
Dividends accrued for unvested restricted stock units			(15)
Net unrealized gains (losses) on available-for-sale securities	(32)	804	(3,340)	2,512
Defined benefit plan adjustments (net of tax)	37	73	104	214
Foreign currency translation adjustment	(451)	$ 1,541	(3,033)	5,402
Proceeds from stock option exercises			1,321	$ 6,606
Purchase of treasury stock			(14,185)
Adoption of new accounting standards (see Note 1)			3,499
Stock-based compensation expense			5,243
RSU's and restricted stock vested			(33)
Ending Balance	$ 463,601		$ 463,601

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	50,000,000
Stock repurchased, shares	900,000
Shares repurchased, average price per share	$ 15.75
Additional shares authorized for purchase	2,700,000
Treasury stock shares issued to accommodate employee stock option exercises	100,000
Exercise price of stock options, lower range limit	$ 15.29
Exercise price of stock options, upper range limit	$ 18.97
Proceeds from stock option exercises	$ 1,321	$ 6,606

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Dividends Payable [Line Items]
Per Share Amount	$ 0.09	$ 0.09	$ 0.27	$ 0.27
Total Dividend Paid			$ 12,976	$ 13,031
Cash Dividends Paid in February [Member]
Dividends Payable [Line Items]
Record Date			Jan. 31, 2018
Payment Date			Feb. 14, 2018
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,367
Cash Dividends Paid in May [Member]
Dividends Payable [Line Items]
Record Date			May 2, 2018
Payment Date			May 16, 2018
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,312
Cash Dividends Paid in August [Member]
Dividends Payable [Line Items]
Record Date			Aug. 1, 2018
Payment Date			Aug. 15, 2018
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,297

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 497,911
Other comprehensive income (loss) before reclassifications	$ 757	$ 2,834	(2,164)	$ 9,045
Amounts reclassified from accumulated other comprehensive income (loss)	(1,203)	(274)	(885)	(1,113)
Amounts reclassified to retained earnings			(3,220)
Other Comprehensive Income (Loss), net of tax	(446)	2,560	(6,269)	7,932
Ending Balance	463,601		463,601
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(741)	2,112	2,567	404
Other comprehensive income (loss) before reclassifications	1,208	1,420	869	4,262
Amounts reclassified from accumulated other comprehensive income (loss)	(1,240)	(616)	(989)	(1,750)
Amounts reclassified to retained earnings			(3,220)
Other Comprehensive Income (Loss), net of tax	(32)	804	(3,340)	2,512
Ending Balance	(773)	2,916	(773)	2,916
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(338)
Other comprehensive income (loss) before reclassifications		(127)		(619)
Amounts reclassified from accumulated other comprehensive income (loss)		269		423
Other Comprehensive Income (Loss), net of tax		142		(196)
Ending Balance		(196)		(196)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,219)	(4,876)	(4,286)	(5,017)
Amounts reclassified from accumulated other comprehensive income (loss)	37	73	104	214
Other Comprehensive Income (Loss), net of tax	37	73	104	214
Ending Balance	(4,182)	(4,803)	(4,182)	(4,803)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,158)	(3,714)	(1,576)	(7,575)
Other comprehensive income (loss) before reclassifications	(451)	1,541	(3,033)	5,402
Other Comprehensive Income (Loss), net of tax	(451)	1,541	(3,033)	5,402
Ending Balance	(4,609)	(2,173)	(4,609)	(2,173)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,118)	(6,816)	(3,295)	(12,188)
Ending Balance	$ (9,564)	$ (4,256)	$ (9,564)	$ (4,256)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	$ (81,887)	$ (98,621)	$ (241,012)	$ (295,238)
Income (Loss) Before Provision for Income Taxes	3,220	19,207	(22,784)	45,421
Tax (expense) benefit	4,369	(3,309)	11,889	(10,471)
Total reclassifications for the period, net of tax	7,589	15,898	(10,895)	34,950
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	(54)	(106)	(151)	(310)
Income (Loss) Before Provision for Income Taxes	1,622	518	1,201	2,020
Tax (expense) benefit	(419)	(244)	(316)	(907)
Total reclassifications for the period, net of tax	1,203	274	885	1,113
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	$ 1,676	1,066	$ 1,352	3,031
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		(57)		(162)
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		$ (385)		$ (539)

Stockholders' Equity - Tax Effe

Stockholders' Equity - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 1,632	$ 2,328	$ 1,174	$ 6,987
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(424)	(908)	(305)	(2,725)
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	1,208	1,420	869	4,262
Unrealized gains (losses) on cash flow hedges, Before-Tax Amount		(184)		(897)
Unrealized gains (losses) on cash flow hedges, Tax (Expense) Benefit		57		278
Unrealized gains (losses) on cash flow hedges, Net-of-Tax Amount		(127)		(619)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	(1,676)	(1,009)	(1,352)	(2,869)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	436	393	363	1,119
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	(1,240)	(616)	(989)	(1,750)
Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01, Before-Tax Amount			(3,220)
Reclassification adjustment for amounts reclassed to retained earnings related to the adoption of ASU 2016-01, Net-of-Tax Amount			(3,220)
Reclassification adjustment for amounts related to cash flow hedges included in net income, Before-Tax Amount		385		539
Reclassification adjustment for amounts related to cash flow hedges included in net income, Tax (Expense) Benefit		(116)		(116)
Reclassification adjustment for amounts related to cash flow hedges included in net income, Net-of-Tax Amount		269		423
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	54	106	151	310
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(17)	(33)	(47)	(96)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	37	73	104	214
Foreign currency translation adjustment, Before-Tax Amount	(451)	1,541	(3,033)	5,402
Foreign currency translation adjustment, Net-of-Tax Amount	(451)	1,541	(3,033)	5,402
Total Other Comprehensive Income (Loss), Before-Tax Amount	(441)	3,167	(6,280)	9,472
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(5)	(607)	11	(1,540)
Other Comprehensive Income (Loss), net of tax	$ (446)	$ 2,560	$ (6,269)	$ 7,932

Earnings Per Share - Summary of

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator
Net Income (Loss)	$ 7,589	$ 15,898	$ (10,895)	$ 34,950
Denominator
Weighted average number of shares – basic	47,710	47,870	47,927	48,110
Effect of dilutive securities
Stock options	27	487		385
PSUs, RSUs and restricted stock	97	174		123
Weighted average number of shares – diluted	47,834	48,531	47,927	48,618
Net income (loss) per share – basic	$ 0.16	$ 0.33	$ (0.23)	$ 0.73
Net income (loss) per share – diluted	$ 0.16	$ 0.33	$ (0.23)	$ 0.72

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted EPS	3.9	3.2	4.8	3.9
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 EPS			0.1

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018SegmentCategory
Segment Reporting [Abstract]
Number of reportable segments | Segment	2
Number of categories | Category	3

Segment Information - Sales and

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Gross Profit	58,448	86,491	148,177	244,826
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	121,043	145,467	341,359	444,607
Gross Profit	51,100	71,933	133,175	214,746
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	19,292	39,645	47,830	95,457
Gross Profit	$ 7,348	$ 14,558	$ 15,002	$ 30,080

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from External Customer [Line Items]
Sales	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Access & Aggregation [Member]
Revenue from External Customer [Line Items]
Sales	91,901	135,959	258,323	394,741
Customer Devices [Member]
Revenue from External Customer [Line Items]
Sales	38,552	35,582	103,213	105,683
Traditional & Other Products [Member]
Revenue from External Customer [Line Items]
Sales	$ 9,882	$ 13,571	$ 27,653	$ 39,640

Liability for Warranty Return_2

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Product Warranties Disclosures [Abstract]
Period of assurance-based warranty for product defects	90 days to five years
Liability for warranty obligations	$ 9,024	$ 10,111	$ 9,724	$ 10,939	$ 9,180	$ 8,548

Liability for Warranty Return_3

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 10,111	$ 9,180	$ 9,724	$ 8,548
Plus: Amounts charged to cost and expenses	(34)	4,087	6,649	6,401
Less: Deductions	(1,053)	(2,328)	(7,349)	(4,010)
Balance at end of period	$ 9,024	$ 10,939	$ 9,024	$ 10,939

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Sep. 30, 2018USD ($)EquityUnit
Contingencies And Commitments [Line Items]
Number of private equity funds | EquityUnit	2
Commitments towards private equity funds	$ 7.7
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds	7.9
Private Equity Funds [Member]
Contingencies And Commitments [Line Items]
Contribution to private equity funds	$ 8.4

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Nov. 06, 2018	Oct. 16, 2018	Sep. 30, 2018	Nov. 14, 2018
Subsequent Event [Line Items]
Stock repurchased, shares			900,000
Shares repurchased, average price per share			$ 15.75
Additional shares authorized for purchase			2,700,000
Scenario Forecast [Member]
Subsequent Event [Line Items]
Quarterly dividend payable subsequent to balance sheet date				$ 4.3
Subsequent Events [Member]
Subsequent Event [Line Items]
Dividend declaration date		Oct. 16, 2018
Common stock dividends per share declared		$ 0.09
Dividend record date		Oct. 31, 2018
Dividend payment date		Nov. 14, 2018
Stock repurchased, shares	100,000
Shares repurchased, average price per share	$ 13.60
Additional shares authorized for purchase	2,600,000