ADTRAN (ADTN) 10-Q 3 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 20, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
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 Common Stock, Shares Outstanding		47,739,170

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 100,319	$ 86,433
Short-term investments	6,069	16,129
Accounts receivable, less allowance for doubtful accounts of $— at June 30, 2018 and December 31, 2017	76,135	144,150
Other receivables	28,163	26,578
Inventory, net	120,537	122,542
Prepaid expenses and other current assets	9,464	17,282
Total Current Assets	340,687	413,114
Property, plant and equipment, net	82,910	85,079
Deferred tax assets, net	35,615	23,428
Goodwill	3,492	3,492
Other assets	32,429	13,725
Long-term investments	144,437	130,256
Total Assets	639,570	669,094
Current Liabilities
Accounts payable	60,150	60,632
Unearned revenue	14,307	13,070
Accrued expenses	14,785	13,232
Accrued wages and benefits	14,913	15,948
Income tax payable	11,948	3,936
Total Current Liabilities	116,103	106,818
Non-current unearned revenue	3,639	4,556
Other non-current liabilities	34,601	34,209
Bonds payable	25,600	25,600
Total Liabilities	179,943	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 47,733 shares outstanding at June 30, 2018 and 79,652 shares issued and 48,485 shares outstanding at December 31, 2017	797	797
Additional paid-in capital	264,118	260,515
Accumulated other comprehensive loss	(9,118)	(3,295)
Retained earnings	897,586	922,178
Less treasury stock at cost: 31,919 and 31,167 shares at June 30, 2018 and December 31, 2017, respectively	(693,756)	(682,284)
Total Stockholders’ Equity	459,627	497,911
Total Liabilities and Stockholders’ Equity	$ 639,570	$ 669,094

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 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	47,733,000	48,485,000
Treasury stock, shares	31,919,000	31,167,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Sales
Total Sales	$ 128,048	$ 184,673	$ 248,854	$ 354,952
Cost of Sales
Total Cost of Sales	78,052	100,047	159,125	196,617
Gross Profit	49,996	84,626	89,729	158,335
Selling, general and administrative expenses	32,080	34,706	65,611	69,495
Research and development expenses	30,729	33,557	63,578	65,528
Operating Income (Loss)	(12,813)	16,363	(39,460)	23,312
Interest and dividend income	913	972	1,779	1,905
Interest expense	(132)	(137)	(264)	(278)
Net realized investment gain	990	1,390	893	1,860
Other expense, net	(217)	(719)	(274)	(585)
Gain on bargain purchase of a business			11,322
Income (Loss) Before Provision for Income Taxes	(11,259)	17,869	(26,004)	26,214
(Provision) benefit for income taxes	3,589	(5,468)	7,520	(7,162)
Net Income (Loss)	$ (7,670)	$ 12,401	$ (18,484)	$ 19,052
Weighted average shares outstanding – basic	47,856	48,036	48,043	48,232
Weighted average shares outstanding – diluted	47,902	48,413	48,091	48,675
Earnings (loss) per common share – basic	$ (0.16)	$ 0.26	$ (0.38)	$ 0.40
Earnings (loss) per common share – diluted	(0.16)	0.26	(0.38)	0.39
Dividend per share	$ 0.09	$ 0.09	$ 0.18	$ 0.18
Product [Member]
Sales
Total Sales	$ 115,063	$ 155,543	$ 220,316	$ 299,140
Cost of Sales
Total Cost of Sales	69,629	79,663	138,241	156,327
Service [Member]
Sales
Total Sales	12,985	29,130	28,538	55,812
Cost of Sales
Total Cost of Sales	$ 8,423	$ 20,384	$ 20,884	$ 40,290

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ (7,670)	$ 12,401	$ (18,484)	$ 19,052
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	104	373	(3,308)	1,708
Net unrealized losses on cash flow hedges		(417)		(338)
Defined benefit plan adjustments	5	86	67	141
Foreign currency translation	(3,424)	2,619	(2,582)	3,861
Other Comprehensive Income (Loss), net of tax	(3,315)	2,661	(5,823)	5,372
Comprehensive Income (Loss), net of tax	$ (10,985)	$ 15,062	$ (24,307)	$ 24,424

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net Income (Loss)	$ (18,484)	$ 19,052
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	7,526	8,377
Amortization of net premium on available-for-sale investments	20	238
Net realized gain on long-term investments	(893)	(1,860)
Net (gain) loss on disposal of property, plant and equipment	68	(11)
Gain on bargain purchase of a business	(11,322)
Stock-based compensation expense	3,603	3,739
Deferred income taxes	(16,384)	(2,772)
Changes in operating assets and liabilities:
Accounts receivable, net	66,931	13,911
Other receivables	9	571
Inventory	2,063	(7,547)
Prepaid expenses and other assets	10,157	(9,853)
Accounts payable	683	(10,910)
Accrued expenses and other liabilities	2,008	(2,629)
Income tax payable	6,945	10,273
Net cash provided by operating activities	52,930	20,579
Cash flows from investing activities:
Purchases of property, plant and equipment	(4,183)	(7,509)
Proceeds from disposals of property, plant and equipment		16
Proceeds from sales and maturities of available-for-sale investments	86,436	81,891
Purchases of available-for-sale investments	(89,801)	(65,140)
Acquisition of business	(7,806)
Net cash provided by (used in) investing activities	(15,354)	9,258
Cash flows from financing activities:
Proceeds from stock option exercises	369	1,722
Purchases of treasury stock	(12,774)	(17,311)
Dividend payments	(8,679)	(8,719)
Net cash used in financing activities	(21,084)	(24,308)
Net increase in cash and cash equivalents	16,492	5,529
Effect of exchange rate changes	(2,606)	3,374
Cash and cash equivalents, beginning of period	86,433	79,895
Cash and cash equivalents, end of period	100,319	88,798
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 209	$ 454

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 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, 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 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. 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 June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 115,063 115,437 $ (374 ) Services $ 12,985 13,430 $ (445 ) Cost of Sales Products $ 69,629 70,003 $ (374 ) Services $ 8,423 8,772 $ (349 ) Loss before benefit for income taxes $ (11,259 ) (11,163 ) $ (96 ) Benefit for income taxes $ 3,589 3,558 $ 31 Net loss $ (7,670 ) (7,605 ) $ (65 ) For the six months ended June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 220,316 220,876 $ (560 ) Services $ 28,538 28,130 $ 408 Cost of Sales Products $ 138,241 138,726 $ (485 ) Services $ 20,884 20,697 $ 187 Loss before benefit for income taxes $ (26,004 ) (26,150 ) $ 146 Benefit for income taxes $ 7,520 7,556 $ (36 ) Net loss $ (18,484 ) (18,594 ) $ 110 As of June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 28,163 28,164 $ (1 ) Inventory $ 120,537 120,426 $ 111 Equity Retained earnings $ 897,586 897,476 $ 110 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, We are currently evaluating the effect ASU 2018-03 will have on our consolidated financial statements. 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	6 Months Ended
	Jun. 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 June 30, 2018 and the period March 19, 2018 to June 30, 2018 are as follows: Three Months Ended March 19, 2018 to (In thousands) June 30, 2018 June 30, 2018 Revenue $ 1,197 $ 1,197 Net loss $ (809 ) $ (886 ) 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 Six Months Ended June 30, June 30, (In thousands) 2017 2018 2017 Pro forma revenue $ 187,987 $ 250,114 $ 358,679 Pro forma net income (loss) $ 11,628 $ (31,020 ) $ 28,829 Pro forma earnings per share - basic $ 0.24 $ (0.65 ) $ 0.60 Pro forma earnings per share - diluted $ 0.24 $ (0.65 ) $ 0.59 For the three and six months ended June 30, 2018, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $0.8 million and $1.0 million, respectively, related to this acquisition.

Revenue

Revenue	6 Months Ended
	Jun. 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 the most likely amount. 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 June 30, 2018 and 2017, we recognized revenue of $4.0 million and $5.2 million, respectively, and during the six months ended June 30, 2018 and 2017 we recognized revenue of $6.3 million and $7.0 million, respectively. Services & Support Segment To complement our Network Solutions segment, we offer a complete portfolio of maintenance, network implementation, 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. Payments received are recorded in current or non-current unearned revenue depending on the length of the service 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. 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 June 30, 2018, we did not have any remaining 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) June 30, 2018 January 1, 2018 Accounts receivable $ 76,135 $ 144,150 Contract assets 1,672 374 Unearned revenue 14,307 13,070 Non-current unearned revenue 3,639 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 six months ended June 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 June 30, 2018 is primarily attributable to cash payments received or due in advance of satisfying our performance obligations, offset by $7.1 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 June 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 75,222 $ 9,520 $ 84,742 Customer Devices 33,306 1,254 34,560 Traditional & Other Products 6,535 2,211 8,746 Total $ 115,063 $ 12,985 $ 128,048 The following table disaggregates our revenue by major source for the six months ended June 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 144,607 $ 21,815 $ 166,422 Customer Devices 62,083 2,578 64,661 Traditional & Other Products 13,626 4,145 17,771 Total $ 220,316 $ 28,538 $ 248,854

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	4. INCOME TAXES Our effective tax rate decreased from an expense of 27.3% in the six months ended June 30, 2017, to a benefit of 20.1%, excluding the tax effect of the bargain purchase gain, in the six months ended June 30, 2018. The decrease in the effective tax rate between the two periods is primarily attributable to the change in income 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	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Service cost $ 303 $ 306 $ 611 $ 603 Interest cost 185 147 372 290 Expected return on plan assets (394 ) (307 ) (793 ) (606 ) Amortization of actuarial losses 63 75 127 148 Net periodic pension cost $ 157 $ 221 $ 317 $ 435 The components of net periodic pension cost other than the service cost component are included in the line item “Other expense, net” in the Consolidated Statements of Income.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017, which was recognized as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Stock-based compensation expense included in cost of sales $ 102 $ 93 $ 197 $ 184 Selling, general and administrative expense 995 1,008 2,030 2,024 Research and development expense 687 755 1,376 1,531 Stock-based compensation expense included in operating expenses 1,682 1,763 3,406 3,555 Total stock-based compensation expense 1,784 1,856 3,603 3,739 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (340 ) (433 ) (724 ) (813 ) Total stock-based compensation expense, net of tax $ 1,444 $ 1,423 $ 2,879 $ 2,926 Stock Options The following table is a summary of our stock options outstanding as of December 31, 2017 and June 30, 2018 and the changes that occurred during the six months ended June 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 (24 ) $ 15.48 Stock options forfeited (42 ) $ 16.54 Stock options expired (282 ) $ 25.63 Stock options outstanding, June 30, 2018 4,800 $ 22.56 4.39 $ — Stock options vested and expected to vest, June 30, 2018 4,800 $ 22.56 4.39 $ — Stock options exercisable, June 30, 2018 4,063 $ 23.67 3.90 $ — 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 June 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 six months ended June 30, 2018 was $33 thousand. There were no options exercised during the three months ended June 30, 2018. As of June 30, 2018, there was $1.9 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over an average remaining recognition period of 1.1 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 six months ended June 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 six months ended June 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 8 $ 20.68 PSUs, RSUs and restricted stock vested (7 ) $ 19.99 PSUs, RSUs and restricted stock forfeited (105 ) $ 21.59 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2018 1,188 $ 21.31 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 June 30, 2018, there was $11.4 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 2.7 years. In addition, there was $10.1 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 six months ended June 30, 2018, no compensation expense was recognized related to these performance-based PSU awards.

Investments

Investments	6 Months Ended
	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Investments	7. INVESTMENTS Debt Securities and Other Investments At June 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 $ 35,896 $ 27 $ (250 ) $ 35,673 Municipal fixed-rate bonds 2,259 — (38 ) 2,221 Asset-backed bonds 10,355 1 (37 ) 10,319 Mortgage/Agency-backed bonds 7,292 — (85 ) 7,207 U.S. government bonds 8,953 — (104 ) 8,849 Foreign government bonds 1,036 2 — 1,038 Available-for-sale debt securities held at fair value $ 65,791 $ 30 $ (514 ) $ 65,307 Restricted investment held at cost 26,700 Other investments held at cost 520 Total carrying value of available-for-sale investments $ 92,527 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 June 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 $ 1,500 $ 490 $ 4,079 $ — $ — $ — One to two years 16,694 603 2,270 — 1,519 729 Two to three years 12,264 1,128 556 — 3,845 309 Three to five years 5,215 — 1,939 1,970 3,485 — Five to ten years — — — 588 — — More than ten years — — 1,475 4,649 — — Total $ 35,673 $ 2,221 $ 10,319 $ 7,207 $ 8,849 $ 1,038 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 Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Gross realized gains $ 25 $ 33 $ 25 $ 57 Gross realized losses $ (241 ) $ (113 ) $ (315 ) $ (152 ) Our investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5% of the market value of our total investment portfolio. At June 30, 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 June 30, 2018 and December 31, 2017. At June 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 realized 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 realized 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 six months ended June 30, 2018 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2018 Realized gains (losses) on equity securities sold $ (52 ) $ 347 Unrealized gains (losses) on equity securities held 1,258 836 Total gain (loss) recognized, net $ 1,206 $ 1,183 As of June 30, 2018 and 2017, gross unrealized losses related to individual investments in a continuous loss position for 12 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 June 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 $ 2,008 $ 2,008 $ — $ — Foreign government securities 350 — 350 — Cash equivalents 2,358 2,008 350 — Available-for-sale debt securities Corporate bonds 35,673 — 35,673 — Municipal fixed-rate bonds 2,221 — 2,221 — Asset-backed bonds 10,319 — 10,319 — Mortgage/Agency-backed bonds 7,207 — 7,207 — U.S. government bonds 8,849 8,849 — — Foreign government bonds 1,038 — 1,038 — Marketable equity securities Marketable equity securities – various industries 37,600 37,600 — — Deferred compensation plan assets 20,379 20,379 — — Available-for-sale securities 123,286 66,828 56,458 — Total $ 125,644 $ 68,836 $ 56,808 $ — 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	6 Months Ended
	Jun. 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 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 June 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 six months ended June 30, 2018 and 2017 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2018 2017 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other expense, net $ — $ (451 ) $ 13 $ (485 ) 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 six months ended June 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 Three Months Ended Location of Gains Three Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (571 ) Cost of Sales $ — $ (154 ) Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Six Months Ended Location of Gains Six Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (492 ) Cost of Sales $ — $ (154 )

Inventory

Inventory	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Inventory	9. INVENTORY At June 30, 2018 and December 31, 2017, inventory consisted of the following: June 30, December 31, (In thousands) 2018 2017 Raw materials $ 50,844 $ 44,185 Work in process 1,985 1,939 Finished goods 67,708 76,418 Total $ 120,537 $ 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 June 30, 2018 and December 31, 2017, raw materials reserves totaled $17.5 million and $15.0 million, respectively, and finished goods inventory reserves totaled $9.7 million and $8.3 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 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 June 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 June 30, 2018 and December 31, 2017. Fully amortized intangible assets have been removed from prior year balances for comparability. (In thousands) June 30, 2018 December 31, 2017 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 20,752 $ (4,781 ) $ 15,971 $ 7,474 $ (4,283 ) $ 3,191 Licensed technology 5,900 (191 ) 5,709 — — — Developed technology 5,452 (4,772 ) 680 5,524 (4,663 ) 861 Supplier relationship 2,800 (408 ) 2,392 — — — Intellectual property 930 (919 ) 11 930 (852 ) 78 Patent 500 (123 ) 377 500 (89 ) 411 Non-compete 200 (159 ) 41 200 (115 ) 85 Trade names 100 (90 ) 10 100 (65 ) 35 Total $ 36,634 $ (11,443 ) $ 25,191 $ 14,728 $ (10,067 ) $ 4,661 Amortization expense, all of which relates to business acquisitions, was $1.0 million and $1.1 million for the three months ended June 30, 2018 and 2017, respectively, and $1.5 million and $1.9 million for the six months ended June 30, 2018 and 2017, respectively. As of June 30, 2018, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2018 $ 1,785 2019 3,542 2020 2,659 2021 2,365 2022 2,352 Thereafter 12,488 Total $ 25,191

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Stockholders' Equity	11. STOCKHOLDERS’ EQUITY A summary of the changes in stockholders’ equity for the six months ended June 30, 2018 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2017 $ 497,911 Net income (loss) (18,484 ) Dividend payments (8,679 ) Dividends accrued for unvested restricted stock units 5 Net unrealized gains (losses) on available-for-sale securities (net of tax) (3,308 ) Defined benefit plan adjustments (net of tax) 67 Foreign currency translation adjustment (2,582 ) Proceeds from stock option exercises 369 Purchase of treasury stock (12,774 ) Adoption of new accounting standards (see Note 1) 3,499 Stock-based compensation expense 3,603 Balance, June 30, 2018 $ 459,627 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 six months ended June 30, 2018, we repurchased 0.8 million shares of our common stock at an average price of $15.72 per share. As of June 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 24 thousand shares of treasury stock during the six months ended June 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 $0.4 million from the exercise of these stock options during the six months ended June 30, 2018. Dividend Payments During the six months ended June 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 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 June 30, 2018 and 2017: Three Months Ended June 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ (845 ) $ (4,224 ) $ (734 ) $ (5,803 ) Other comprehensive income (loss) before reclassifications (82 ) — (3,424 ) (3,506 ) Amounts reclassified from accumulated other comprehensive income (loss) 186 5 — 191 Net current period other comprehensive income (loss) 104 5 (3,424 ) (3,315 ) Ending balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) Three Months Ended June 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 $ 1,739 $ 79 $ (4,962 ) $ (6,333 ) $ (9,477 ) Other comprehensive income (loss) before reclassifications 1,222 (571 ) — 2,619 3,270 Amounts reclassified from accumulated other comprehensive income (loss) (849 ) 154 86 — (609 ) Net current period other comprehensive income (loss) 373 (417 ) 86 2,619 2,661 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the six months ended June 30, 2018 and 2017: Six Months Ended June 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 (339 ) — (2,582 ) (2,921 ) Amounts reclassified from accumulated other comprehensive income (loss) 251 67 — 318 Amounts reclassified to retained earnings (1) (3,220 ) — — (3,220 ) Net current period other comprehensive income (loss) (3,308 ) 67 (2,582 ) (5,823 ) Ending balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) (1) With the adoption of ASU 2016-01, the unrealized gains on our equity investments were reclassified to retained earnings. See Note 1 for more information. Six Months Ended June 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 2,842 (492 ) — 3,861 6,211 Amounts reclassified from accumulated other comprehensive income (loss) (1,134 ) 154 141 — (839 ) Net current period other comprehensive income (loss) 1,708 (338 ) 141 3,861 5,372 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the three months ended June 30, 2018 and 2017: (In thousands) Three Months Ended June 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 $ (251 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (7 ) (1) Total reclassifications for the period, before tax (258 ) Tax (expense) benefit 67 Total reclassifications for the period, net of tax $ (191 ) (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 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 $ 1,393 Net realized investment gain Impairment expense (2 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (124 ) (1) Total reclassifications for the period, before tax 1,113 Tax (expense) benefit (504 ) Total reclassifications for the period, net of tax $ 609 (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the six months ended June 30, 2018 and 2017: (In thousands) Six Months Ended June 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 $ (324 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (97 ) (1) Total reclassifications for the period, before tax (421 ) Tax (expense) benefit 103 Total reclassifications for the period, net of tax $ (318 ) (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 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 $ 1,965 Net realized investment gain Impairment expense (105 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (204 ) (1) Total reclassifications for the period, before tax 1,502 Tax (expense) benefit (663 ) Total reclassifications for the period, net of tax $ 839 (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the three months ended June 30, 2018 and 2017: Three Months Ended Three Months Ended June 30, 2018 June 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 $ (111 ) $ 29 $ (82 ) $ 2,003 $ (781 ) $ 1,222 Unrealized gains (losses) on cash flow hedges — — — (571 ) — (571 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income 251 (65 ) 186 (1,391 ) 542 (849 ) Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 154 — 154 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 7 (2 ) 5 124 (38 ) 86 Foreign currency translation adjustment (3,424 ) — (3,424 ) 2,619 — 2,619 Total Other Comprehensive Income (Loss) $ (3,277 ) $ (38 ) $ (3,315 ) $ 2,938 $ (277 ) $ 2,661 The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2018 and 2017: Six Months Ended Six Months Ended June 30, 2018 June 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 $ (458 ) $ 119 $ (339 ) $ 4,659 $ (1,817 ) $ 2,842 Unrealized gains (losses) on cash flow hedges — — — (492 ) — (492 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income 324 (73 ) 251 (1,860 ) 726 (1,134 ) 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 — — — 154 — 154 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 97 (30 ) 67 204 (63 ) 141 Foreign currency translation adjustment (2,582 ) — (2,582 ) 3,861 — 3,861 Total Other Comprehensive Income (Loss) $ (5,839 ) $ 16 $ (5,823 ) $ 6,526 $ (1,154 ) $ 5,372

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2018 2017 2018 2017 Numerator Net income (loss) $ (7,670 ) $ 12,401 $ (18,484 ) $ 19,052 Denominator Weighted average number of shares – basic 47,856 48,036 48,043 48,232 Effect of dilutive securities Stock options — 279 8 348 PSUs, RSUs and restricted stock 46 98 40 95 Weighted average number of shares – diluted 47,902 48,413 48,091 48,675 Net income (loss) per share – basic $ (0.16 ) $ 0.26 $ (0.38 ) $ 0.40 Net income (loss) per share – diluted $ (0.16 ) $ 0.26 $ (0.38 ) $ 0.39 Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 5.0 million and 4.1 million for the three months ended June 30, 2018 and 2017, respectively, and 4.8 million and 4.1 million for the six months ended June 30, 2018 and 2017.

Segment Information

Segment Information	6 Months Ended
	Jun. 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 realized investment gain/loss, 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 six months ended June 30, 2018 and 2017. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2018 June 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 115,063 $ 45,434 $ 155,543 $ 75,880 Services & Support 12,985 4,562 29,130 8,746 Total $ 128,048 $ 49,996 $ 184,673 $ 84,626 Six Months Ended June 30, 2018 June 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 220,316 $ 82,075 $ 299,140 $ 142,813 Services & Support 28,538 7,654 55,812 15,522 Total $ 248,854 $ 89,729 $ 354,952 $ 158,335 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 six months ended June 30, 2018 and 2017: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Access & Aggregation $ 84,742 $ 138,639 $ 166,422 $ 258,782 Customer Devices 34,560 33,833 64,661 70,101 Traditional & Other Products 8,746 12,201 17,771 26,069 Total $ 128,048 $ 184,673 $ 248,854 $ 354,952

Liability for Warranty Returns

Liability for Warranty Returns	6 Months Ended
	Jun. 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 $10.1 million and $9.7 million at June 30, 2018 and December 31, 2017, respectively. 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. 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 six months ended June 30, 2018 and 2017 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Balance at beginning of period $ 9,687 $ 8,988 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses 4,860 3,055 6,683 2,314 Less: Deductions (4,436 ) (2,863 ) (6,296 ) (1,682 ) Balance at end of period $ 10,111 $ 9,180 $ 10,111 $ 9,180

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 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 June 30, 2018, of which $7.7 million has been applied to these commitments.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	16. SUBSEQUENT EVENTS On July 17, 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 August 1, 2018. The payment date will be August 15, 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.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 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, 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 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. 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 June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 115,063 115,437 $ (374 ) Services $ 12,985 13,430 $ (445 ) Cost of Sales Products $ 69,629 70,003 $ (374 ) Services $ 8,423 8,772 $ (349 ) Loss before benefit for income taxes $ (11,259 ) (11,163 ) $ (96 ) Benefit for income taxes $ 3,589 3,558 $ 31 Net loss $ (7,670 ) (7,605 ) $ (65 ) For the six months ended June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 220,316 220,876 $ (560 ) Services $ 28,538 28,130 $ 408 Cost of Sales Products $ 138,241 138,726 $ (485 ) Services $ 20,884 20,697 $ 187 Loss before benefit for income taxes $ (26,004 ) (26,150 ) $ 146 Benefit for income taxes $ 7,520 7,556 $ (36 ) Net loss $ (18,484 ) (18,594 ) $ 110 As of June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 28,163 28,164 $ (1 ) Inventory $ 120,537 120,426 $ 111 Equity Retained earnings $ 897,586 897,476 $ 110 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, We are currently evaluating the effect ASU 2018-03 will have on our consolidated financial statements. 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 Accoun24

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 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 June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 115,063 115,437 $ (374 ) Services $ 12,985 13,430 $ (445 ) Cost of Sales Products $ 69,629 70,003 $ (374 ) Services $ 8,423 8,772 $ (349 ) Loss before benefit for income taxes $ (11,259 ) (11,163 ) $ (96 ) Benefit for income taxes $ 3,589 3,558 $ 31 Net loss $ (7,670 ) (7,605 ) $ (65 ) For the six months ended June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Sales Products $ 220,316 220,876 $ (560 ) Services $ 28,538 28,130 $ 408 Cost of Sales Products $ 138,241 138,726 $ (485 ) Services $ 20,884 20,697 $ 187 Loss before benefit for income taxes $ (26,004 ) (26,150 ) $ 146 Benefit for income taxes $ 7,520 7,556 $ (36 ) Net loss $ (18,484 ) (18,594 ) $ 110 As of June 30, 2018 (In thousands) As Reported Balances Without Adoption of ASC 606 Effect of Adoption of ASC 606 Assets Other receivables $ 28,163 28,164 $ (1 ) Inventory $ 120,537 120,426 $ 111 Equity Retained earnings $ 897,586 897,476 $ 110

Business Combinations (Tables)

Business Combinations (Tables)	6 Months Ended
	Jun. 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 June 30, 2018 and the period March 19, 2018 to June 30, 2018 are as follows: Three Months Ended March 19, 2018 to (In thousands) June 30, 2018 June 30, 2018 Revenue $ 1,197 $ 1,197 Net loss $ (809 ) $ (886 )
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 Six Months Ended June 30, June 30, (In thousands) 2017 2018 2017 Pro forma revenue $ 187,987 $ 250,114 $ 358,679 Pro forma net income (loss) $ 11,628 $ (31,020 ) $ 28,829 Pro forma earnings per share - basic $ 0.24 $ (0.65 ) $ 0.60 Pro forma earnings per share - diluted $ 0.24 $ (0.65 ) $ 0.59

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 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) June 30, 2018 January 1, 2018 Accounts receivable $ 76,135 $ 144,150 Contract assets 1,672 374 Unearned revenue 14,307 13,070 Non-current unearned revenue 3,639 4,556
Disaggregate of Revenue by Major Source	The following table disaggregates our revenue by major source for the three months ended June 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 75,222 $ 9,520 $ 84,742 Customer Devices 33,306 1,254 34,560 Traditional & Other Products 6,535 2,211 8,746 Total $ 115,063 $ 12,985 $ 128,048 The following table disaggregates our revenue by major source for the six months ended June 30, 2018: (In thousands) Network Solutions Services & Support Total Access & Aggregation $ 144,607 $ 21,815 $ 166,422 Customer Devices 62,083 2,578 64,661 Traditional & Other Products 13,626 4,145 17,771 Total $ 220,316 $ 28,538 $ 248,854

Pension Benefit Plan (Tables)

Pension Benefit Plan (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Service cost $ 303 $ 306 $ 611 $ 603 Interest cost 185 147 372 290 Expected return on plan assets (394 ) (307 ) (793 ) (606 ) Amortization of actuarial losses 63 75 127 148 Net periodic pension cost $ 157 $ 221 $ 317 $ 435 The components of net periodic pension cost other than the service cost component are included in the line item “Other expense, net” in the Consolidated Statements of Income.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017, which was recognized as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Stock-based compensation expense included in cost of sales $ 102 $ 93 $ 197 $ 184 Selling, general and administrative expense 995 1,008 2,030 2,024 Research and development expense 687 755 1,376 1,531 Stock-based compensation expense included in operating expenses 1,682 1,763 3,406 3,555 Total stock-based compensation expense 1,784 1,856 3,603 3,739 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (340 ) (433 ) (724 ) (813 ) Total stock-based compensation expense, net of tax $ 1,444 $ 1,423 $ 2,879 $ 2,926
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2017 and June 30, 2018 and the changes that occurred during the six months ended June 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 (24 ) $ 15.48 Stock options forfeited (42 ) $ 16.54 Stock options expired (282 ) $ 25.63 Stock options outstanding, June 30, 2018 4,800 $ 22.56 4.39 $ — Stock options vested and expected to vest, June 30, 2018 4,800 $ 22.56 4.39 $ — Stock options exercisable, June 30, 2018 4,063 $ 23.67 3.90 $ —
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 six months ended June 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 8 $ 20.68 PSUs, RSUs and restricted stock vested (7 ) $ 19.99 PSUs, RSUs and restricted stock forfeited (105 ) $ 21.59 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2018 1,188 $ 21.31

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 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 June 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 $ 35,896 $ 27 $ (250 ) $ 35,673 Municipal fixed-rate bonds 2,259 — (38 ) 2,221 Asset-backed bonds 10,355 1 (37 ) 10,319 Mortgage/Agency-backed bonds 7,292 — (85 ) 7,207 U.S. government bonds 8,953 — (104 ) 8,849 Foreign government bonds 1,036 2 — 1,038 Available-for-sale debt securities held at fair value $ 65,791 $ 30 $ (514 ) $ 65,307 Restricted investment held at cost 26,700 Other investments held at cost 520 Total carrying value of available-for-sale investments $ 92,527 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 June 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 $ 1,500 $ 490 $ 4,079 $ — $ — $ — One to two years 16,694 603 2,270 — 1,519 729 Two to three years 12,264 1,128 556 — 3,845 309 Three to five years 5,215 — 1,939 1,970 3,485 — Five to ten years — — — 588 — — More than ten years — — 1,475 4,649 — — Total $ 35,673 $ 2,221 $ 10,319 $ 7,207 $ 8,849 $ 1,038
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 Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Gross realized gains $ 25 $ 33 $ 25 $ 57 Gross realized losses $ (241 ) $ (113 ) $ (315 ) $ (152 )
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 six months ended June 30, 2018 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2018 Realized gains (losses) on equity securities sold $ (52 ) $ 347 Unrealized gains (losses) on equity securities held 1,258 836 Total gain (loss) recognized, net $ 1,206 $ 1,183
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 June 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 $ 2,008 $ 2,008 $ — $ — Foreign government securities 350 — 350 — Cash equivalents 2,358 2,008 350 — Available-for-sale debt securities Corporate bonds 35,673 — 35,673 — Municipal fixed-rate bonds 2,221 — 2,221 — Asset-backed bonds 10,319 — 10,319 — Mortgage/Agency-backed bonds 7,207 — 7,207 — U.S. government bonds 8,849 8,849 — — Foreign government bonds 1,038 — 1,038 — Marketable equity securities Marketable equity securities – various industries 37,600 37,600 — — Deferred compensation plan assets 20,379 20,379 — — Available-for-sale securities 123,286 66,828 56,458 — Total $ 125,644 $ 68,836 $ 56,808 $ — 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 He30

Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2018 2017 2018 2017 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other expense, net $ — $ (451 ) $ 13 $ (485 )
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 six months ended June 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 Three Months Ended Location of Gains Three Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (571 ) Cost of Sales $ — $ (154 ) Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Six Months Ended Location of Gains Six Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2018 2017 from AOCI into Income 2018 2017 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ — $ (492 ) Cost of Sales $ — $ (154 )

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Components of Inventory	At June 30, 2018 and December 31, 2017, inventory consisted of the following: June 30, December 31, (In thousands) 2018 2017 Raw materials $ 50,844 $ 44,185 Work in process 1,985 1,939 Finished goods 67,708 76,418 Total $ 120,537 $ 122,542

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of June 30, 2018 and December 31, 2017. Fully amortized intangible assets have been removed from prior year balances for comparability. (In thousands) June 30, 2018 December 31, 2017 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 20,752 $ (4,781 ) $ 15,971 $ 7,474 $ (4,283 ) $ 3,191 Licensed technology 5,900 (191 ) 5,709 — — — Developed technology 5,452 (4,772 ) 680 5,524 (4,663 ) 861 Supplier relationship 2,800 (408 ) 2,392 — — — Intellectual property 930 (919 ) 11 930 (852 ) 78 Patent 500 (123 ) 377 500 (89 ) 411 Non-compete 200 (159 ) 41 200 (115 ) 85 Trade names 100 (90 ) 10 100 (65 ) 35 Total $ 36,634 $ (11,443 ) $ 25,191 $ 14,728 $ (10,067 ) $ 4,661
Estimated Future Amortization Expense Related to Intangible Assets	As of June 30, 2018, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2018 $ 1,785 2019 3,542 2020 2,659 2021 2,365 2022 2,352 Thereafter 12,488 Total $ 25,191

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the six months ended June 30, 2018 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2017 $ 497,911 Net income (loss) (18,484 ) Dividend payments (8,679 ) Dividends accrued for unvested restricted stock units 5 Net unrealized gains (losses) on available-for-sale securities (net of tax) (3,308 ) Defined benefit plan adjustments (net of tax) 67 Foreign currency translation adjustment (2,582 ) Proceeds from stock option exercises 369 Purchase of treasury stock (12,774 ) Adoption of new accounting standards (see Note 1) 3,499 Stock-based compensation expense 3,603 Balance, June 30, 2018 $ 459,627
Cash Dividends	During the six months ended June 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
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 June 30, 2018 and 2017: Three Months Ended June 30, 2018 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ (845 ) $ (4,224 ) $ (734 ) $ (5,803 ) Other comprehensive income (loss) before reclassifications (82 ) — (3,424 ) (3,506 ) Amounts reclassified from accumulated other comprehensive income (loss) 186 5 — 191 Net current period other comprehensive income (loss) 104 5 (3,424 ) (3,315 ) Ending balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) Three Months Ended June 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 $ 1,739 $ 79 $ (4,962 ) $ (6,333 ) $ (9,477 ) Other comprehensive income (loss) before reclassifications 1,222 (571 ) — 2,619 3,270 Amounts reclassified from accumulated other comprehensive income (loss) (849 ) 154 86 — (609 ) Net current period other comprehensive income (loss) 373 (417 ) 86 2,619 2,661 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the six months ended June 30, 2018 and 2017: Six Months Ended June 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 (339 ) — (2,582 ) (2,921 ) Amounts reclassified from accumulated other comprehensive income (loss) 251 67 — 318 Amounts reclassified to retained earnings (1) (3,220 ) — — (3,220 ) Net current period other comprehensive income (loss) (3,308 ) 67 (2,582 ) (5,823 ) Ending balance $ (741 ) $ (4,219 ) $ (4,158 ) $ (9,118 ) (1) With the adoption of ASU 2016-01, the unrealized gains on our equity investments were reclassified to retained earnings. See Note 1 for more information. Six Months Ended June 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 2,842 (492 ) — 3,861 6,211 Amounts reclassified from accumulated other comprehensive income (loss) (1,134 ) 154 141 — (839 ) Net current period other comprehensive income (loss) 1,708 (338 ) 141 3,861 5,372 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 )
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 June 30, 2018 and 2017: (In thousands) Three Months Ended June 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 $ (251 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (7 ) (1) Total reclassifications for the period, before tax (258 ) Tax (expense) benefit 67 Total reclassifications for the period, net of tax $ (191 ) (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 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 $ 1,393 Net realized investment gain Impairment expense (2 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (124 ) (1) Total reclassifications for the period, before tax 1,113 Tax (expense) benefit (504 ) Total reclassifications for the period, net of tax $ 609 (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the six months ended June 30, 2018 and 2017: (In thousands) Six Months Ended June 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 $ (324 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (97 ) (1) Total reclassifications for the period, before tax (421 ) Tax (expense) benefit 103 Total reclassifications for the period, net of tax $ (318 ) (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 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 $ 1,965 Net realized investment gain Impairment expense (105 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (204 ) (1) Total reclassifications for the period, before tax 1,502 Tax (expense) benefit (663 ) Total reclassifications for the period, net of tax $ 839 (1) Included in the computation of net periodic pension cost. See Note 5 of Notes to Consolidated Financial Statements.
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 June 30, 2018 and 2017: Three Months Ended Three Months Ended June 30, 2018 June 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 $ (111 ) $ 29 $ (82 ) $ 2,003 $ (781 ) $ 1,222 Unrealized gains (losses) on cash flow hedges — — — (571 ) — (571 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income 251 (65 ) 186 (1,391 ) 542 (849 ) Reclassification adjustment for amounts related to cash flow hedges included in net income — — — 154 — 154 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 7 (2 ) 5 124 (38 ) 86 Foreign currency translation adjustment (3,424 ) — (3,424 ) 2,619 — 2,619 Total Other Comprehensive Income (Loss) $ (3,277 ) $ (38 ) $ (3,315 ) $ 2,938 $ (277 ) $ 2,661 The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2018 and 2017: Six Months Ended Six Months Ended June 30, 2018 June 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 $ (458 ) $ 119 $ (339 ) $ 4,659 $ (1,817 ) $ 2,842 Unrealized gains (losses) on cash flow hedges — — — (492 ) — (492 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income 324 (73 ) 251 (1,860 ) 726 (1,134 ) 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 — — — 154 — 154 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 97 (30 ) 67 204 (63 ) 141 Foreign currency translation adjustment (2,582 ) — (2,582 ) 3,861 — 3,861 Total Other Comprehensive Income (Loss) $ (5,839 ) $ 16 $ (5,823 ) $ 6,526 $ (1,154 ) $ 5,372

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2018 2017 2018 2017 Numerator Net income (loss) $ (7,670 ) $ 12,401 $ (18,484 ) $ 19,052 Denominator Weighted average number of shares – basic 47,856 48,036 48,043 48,232 Effect of dilutive securities Stock options — 279 8 348 PSUs, RSUs and restricted stock 46 98 40 95 Weighted average number of shares – diluted 47,902 48,413 48,091 48,675 Net income (loss) per share – basic $ (0.16 ) $ 0.26 $ (0.38 ) $ 0.40 Net income (loss) per share – diluted $ (0.16 ) $ 0.26 $ (0.38 ) $ 0.39

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2018 June 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 115,063 $ 45,434 $ 155,543 $ 75,880 Services & Support 12,985 4,562 29,130 8,746 Total $ 128,048 $ 49,996 $ 184,673 $ 84,626 Six Months Ended June 30, 2018 June 30, 2017 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 220,316 $ 82,075 $ 299,140 $ 142,813 Services & Support 28,538 7,654 55,812 15,522 Total $ 248,854 $ 89,729 $ 354,952 $ 158,335
Sales Information by Category	The table below presents sales information by category for the three and six months ended June 30, 2018 and 2017: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Access & Aggregation $ 84,742 $ 138,639 $ 166,422 $ 258,782 Customer Devices 34,560 33,833 64,661 70,101 Traditional & Other Products 8,746 12,201 17,771 26,069 Total $ 128,048 $ 184,673 $ 248,854 $ 354,952

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2018 and 2017 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2018 2017 2018 2017 Balance at beginning of period $ 9,687 $ 8,988 $ 9,724 $ 8,548 Plus: Amounts charged to cost and expenses 4,860 3,055 6,683 2,314 Less: Deductions (4,436 ) (2,863 ) (6,296 ) (1,682 ) Balance at end of period $ 10,111 $ 9,180 $ 10,111 $ 9,180

Summary of Significant Accoun37

Summary of Significant Accounting Policies - Schedule of Cumulative Effect of Changes made to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other receivables	$ 28,163		$ 26,578
Deferred tax assets, net	35,615		23,428
Retained earnings	897,586		$ 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	(1)	374
Deferred tax assets, net		(96)
Retained earnings	$ 110	$ 278

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Summary of Effect of Adoption of ASU 2014-09 and Related ASUs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Sales
Sales	$ 128,048	$ 184,673	$ 248,854	$ 354,952
Cost of Sales
Cost of Sales	78,052	100,047	159,125	196,617
Loss before benefit for income taxes	(11,259)	17,869	(26,004)	26,214
(Provision) benefit for income taxes	3,589	(5,468)	7,520	(7,162)
Net Income (Loss)	(7,670)	12,401	(18,484)	19,052
ASSETS
Other receivables	28,163		28,163			$ 26,578
Inventory	120,537		120,537			122,542
Equity
Retained earnings	897,586		897,586			$ 922,178
Product [Member]
Sales
Sales	115,063	155,543	220,316	299,140
Cost of Sales
Cost of Sales	69,629	79,663	138,241	156,327
Service [Member]
Sales
Sales	12,985	29,130	28,538	55,812
Cost of Sales
Cost of Sales	8,423	$ 20,384	20,884	$ 40,290
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
Loss before benefit for income taxes	(11,163)		(26,150)
(Provision) benefit for income taxes	3,558		7,556
Net Income (Loss)	(7,605)		(18,594)
ASSETS
Other receivables	28,164		28,164
Inventory	120,426		120,426
Equity
Retained earnings	897,476		897,476
ASU 2014-09 [member] | Effect of Adoption of ASC 606
Cost of Sales
Loss before benefit for income taxes	(96)		146
(Provision) benefit for income taxes	31		(36)
Net Income (Loss)	(65)		110
ASSETS
Other receivables	(1)		(1)		374
Inventory	111		111
Equity
Retained earnings	110		110		$ 278
ASU 2014-09 [member] | Product [Member] | Balances Without Adoption of ASC 606 [Member]
Sales
Sales	115,437		220,876
Cost of Sales
Cost of Sales	70,003		138,726
ASU 2014-09 [member] | Product [Member] | Effect of Adoption of ASC 606
Sales
Sales	(374)		(560)
Cost of Sales
Cost of Sales	(374)		(485)
ASU 2014-09 [member] | Service [Member] | Balances Without Adoption of ASC 606 [Member]
Sales
Sales	13,430		28,130
Cost of Sales
Cost of Sales	8,772		20,697
ASU 2014-09 [member] | Service [Member] | Effect of Adoption of ASC 606
Sales
Sales	(445)		408
Cost of Sales
Cost of Sales	$ (349)		$ 187

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 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 expense, net	$ 0.1	$ 0.2

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 19, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 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		$ 800		$ 1,000

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	Jun. 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
	Jun. 30, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Revenue	$ 1,197	$ 1,197
Net loss	$ (886)	$ (809)

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 - Summa44

Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Combinations [Abstract]
Pro forma revenue	$ 187,987	$ 250,114	$ 358,679
Pro forma net income (loss)	$ 11,628	$ (31,020)	$ 28,829
Pro forma earnings per share - basic	$ 0.24	$ (0.65)	$ 0.60
Pro forma earnings per share - diluted	$ 0.24	$ (0.65)	$ 0.59

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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					$ 7,100,000
Lease Agreements [Member]
Revenue [Line Items]
Recognized revenue	$ 4,000,000	$ 5,200,000	$ 6,300,000	$ 7,000,000
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	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue From Contract With Customer [Abstract]
Accounts receivable	$ 76,135	$ 144,150	$ 144,150
Contract assets	1,672	374
Unearned revenue	14,307	13,070
Non-current unearned revenue	$ 3,639	$ 4,556

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenue	$ 128,048	$ 184,673	$ 248,854	$ 354,952
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	84,742		166,422
Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	34,560	33,833	64,661	70,101
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	8,746	12,201	17,771	26,069
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	115,063	155,543	220,316	299,140
Network Solutions [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	75,222		144,607
Network Solutions [Member] | Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	33,306		62,083
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	6,535		13,626
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,985	$ 29,130	28,538	$ 55,812
Services & Support [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	9,520		21,815
Services & Support [Member] | Customer Devices [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,254		2,578
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,211		$ 4,145

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Effective tax rate expense (benefit)	(20.10%)	27.30%

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 303	$ 306	$ 611	$ 603
Interest cost	185	147	372	290
Expected return on plan assets	(394)	(307)	(793)	(606)
Amortization of actuarial losses	63	75	127	148
Net periodic pension cost	$ 157	$ 221	$ 317	$ 435

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,784	$ 1,856	$ 3,603	$ 3,739
Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock	(340)	(433)	(724)	(813)
Total stock-based compensation expense, net of tax	1,444	1,423	2,879	2,926
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	102	93	197	184
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	995	1,008	2,030	2,024
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	687	755	1,376	1,531
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	$ 1,682	$ 1,763	$ 3,406	$ 3,555

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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	0		(24,000)
Number of Stock Options, Stock options forfeited			(42,000)
Number of Stock Options, Stock options expired			(282,000)
Number of Stock Options, Stock options outstanding, Ending Balance	4,800,000		4,800,000		5,148,000
Number of Stock Options, Stock options vested and expected to vest	4,800,000		4,800,000
Number of Stock Options, Stock options exercisable	4,063,000		4,063,000
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			16.54
Weighted Avg. Exercise Price, Stock options expired			25.63
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	$ 22.56		22.56		$ 22.65
Weighted Avg. Exercise Price, Stock options vested and expected to vest	22.56		22.56
Weighted Avg. Exercise Price, Stock options exercisable	$ 23.67		$ 23.67
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding			4 years 4 months 20 days		4 years 10 months 13 days
Weighted Avg. Remaining Contractual Life In Years, Stock options vested and expected to vest			4 years 4 months 20 days
Weighted Avg. Remaining Contractual Life In Years, Stock options exercisable			3 years 10 months 24 days
Aggregate Intrinsic Value, Stock options outstanding					$ 6,109

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pre-tax intrinsic value of options exercised			$ 33
Number of Options, exercised	0		24,000
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	$ 1,900		$ 1,900
Recognition period of unvested compensation expense			1 year 1 month 6 days

Stock-Based Compensation - Su53

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	6 Months Ended
	Jun. 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	8
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(7)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(105)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,188
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	20.68
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	19.99
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	21.59
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 21.31

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU shares grant approved by board of directors				8
Stock-based compensation expense	$ 1,784,000	$ 1,856,000		$ 3,603,000	$ 3,739,000
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	11,400,000			$ 11,400,000
Recognition period of unvested compensation expense				2 years 8 months 12 days
Performance-Based PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	10,100,000			$ 10,100,000
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	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 65,791	$ 62,857
Gross Unrealized Gains	30	53
Gross Unrealized Losses	(514)	(417)
Available-for-sale debt securities, Carrying Value	65,307	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	92,527	90,840
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,896	32,654
Gross Unrealized Gains	27	44
Gross Unrealized Losses	(250)	(155)
Available-for-sale debt securities, Carrying Value	35,673	32,543
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,259	2,902
Gross Unrealized Gains		2
Gross Unrealized Losses	(38)	(22)
Available-for-sale debt securities, Carrying Value	2,221	2,882
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,355	6,545
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(37)	(20)
Available-for-sale debt securities, Carrying Value	10,319	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,292	5,554
Gross Unrealized Gains		1
Gross Unrealized Losses	(85)	(46)
Available-for-sale debt securities, Carrying Value	7,207	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,953	14,477
Gross Unrealized Losses	(104)	(174)
Available-for-sale debt securities, Carrying Value	8,849	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,036	725
Gross Unrealized Gains	2	5
Available-for-sale debt securities, Carrying Value	$ 1,038	$ 730

Investments - Contractual Matur

Investments - Contractual Maturities of Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 65,307	$ 62,493
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,500
One to two years	16,694
Two to three years	12,264
Three to five years	5,215
Available-for-sale debt securities, Fair Value/Carrying Value	35,673	32,543
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	490
One to two years	603
Two to three years	1,128
Available-for-sale debt securities, Fair Value/Carrying Value	2,221	2,882
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	4,079
One to two years	2,270
Two to three years	556
Three to five years	1,939
More than ten years	1,475
Available-for-sale debt securities, Fair Value/Carrying Value	10,319	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Three to five years	1,970
Five to ten years	588
More than ten years	4,649
Available-for-sale debt securities, Fair Value/Carrying Value	7,207	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	1,519
Two to three years	3,845
Three to five years	3,485
Available-for-sale debt securities, Fair Value/Carrying Value	8,849	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	729
Two to three years	309
Available-for-sale debt securities, Fair Value/Carrying Value	$ 1,038	$ 730

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - Debt Securities [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	$ 25	$ 33	$ 25	$ 57
Gross realized losses	$ (241)	$ (113)	$ (315)	$ (152)

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Net realized investment gain	$ 990	$ 1,390	$ 893	$ 1,860
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Net realized investment gain	(52)		347
Unrealized gains (losses) on equity securities held	1,258		836
Total gain (loss) recognized, net	$ 1,206		$ 1,183

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 65,307	$ 62,493
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,358	9,850
Available-for-sale securities	123,286	118,038
Total	125,644	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	2,008	5,851
Available-for-sale securities	66,828	69,848
Total	68,836	75,699
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	350	3,999
Available-for-sale securities	56,458	48,190
Total	56,808	52,189
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,008	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	2,008	5,851
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	35,673	32,543
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	35,673	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	35,673	32,543
Foreign Government Securities [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	350
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	350
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,221	2,882
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,221	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	2,221	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	10,319	6,526
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	10,319	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	10,319	6,526
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	7,207	5,509
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	7,207	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	7,207	5,509
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	8,849	14,303
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	8,849	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	8,849	14,303
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,038	730
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,038	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	1,038	730
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	37,600	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]
Available-for-sale securities	37,600	35,662
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	20,379	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]
Available-for-sale securities	$ 20,379	$ 19,883

Derivative Instruments and He61

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

Derivative Instruments and He62

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	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Foreign Exchange Contracts [Member] | Other Expense, Net [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ (451)	$ 13	$ (485)

Derivative Instruments and He63

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	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Derivative [Line Items]
Amount of Gains (Losses) Recognized in OCI on Derivatives	$ (571)	$ (492)
Foreign Exchange Contracts [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Amount of Gains (Losses) Recognized in OCI on Derivatives	(571)	(492)
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	$ (154)	$ (154)

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 50,844	$ 44,185
Work in process	1,985	1,939
Finished goods	67,708	76,418
Total	$ 120,537	$ 122,542

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 17.5	$ 15
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 9.7	$ 8.3

Goodwill and Intangible Asset66

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, relates to acquisition			$ 3,500,000		$ 3,500,000
Impairment losses			0
Amortization expense	$ 1,000,000	$ 1,100,000	1,500,000	$ 1,900,000
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 Asset67

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Gross Value	$ 36,634	$ 14,728
Accumulated Amortization	(11,443)	(10,067)
Net Value	25,191	4,661
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	20,752	7,474
Accumulated Amortization	(4,781)	(4,283)
Net Value	15,971	3,191
Licensed Technology [Member]
Goodwill [Line Items]
Gross Value	5,900
Accumulated Amortization	(191)
Net Value	5,709
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	5,452	5,524
Accumulated Amortization	(4,772)	(4,663)
Net Value	680	861
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	930	930
Accumulated Amortization	(919)	(852)
Net Value	11	78
Supplier Relationship [Member]
Goodwill [Line Items]
Gross Value	2,800
Accumulated Amortization	(408)
Net Value	2,392
Trade Names [Member]
Goodwill [Line Items]
Gross Value	100	100
Accumulated Amortization	(90)	(65)
Net Value	10	35
Patent [Member]
Goodwill [Line Items]
Gross Value	500	500
Accumulated Amortization	(123)	(89)
Net Value	377	411
Non-compete [Member]
Goodwill [Line Items]
Gross Value	200	200
Accumulated Amortization	(159)	(115)
Net Value	$ 41	$ 85

Goodwill and Intangible Asset68

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Remainder of 2018	$ 1,785
2,019	3,542
2,020	2,659
2,021	2,365
2,022	2,352
Thereafter	12,488
Net Value	$ 25,191	$ 4,661

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Beginning Balance			$ 497,911
Net Income (Loss)	$ (7,670)	$ 12,401	(18,484)	$ 19,052
Dividend payments			(8,679)
Dividends accrued for unvested restricted stock units			5
Net unrealized gains (losses) on available-for-sale securities	104	373	(3,308)	1,708
Defined benefit plan adjustments (net of tax)	5	86	67	141
Foreign currency translation adjustment	(3,424)	$ 2,619	(2,582)	3,861
Proceeds from stock option exercises			369	$ 1,722
Purchase of treasury stock			(12,774)
Adoption of new accounting standards (see Note 1)			3,499
Stock-based compensation expense			3,603
Ending Balance	$ 459,627		$ 459,627

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	50,000,000	50,000,000
Stock repurchased, shares		800,000
Shares repurchased, average price per share		$ 15.72
Additional shares authorized for purchase	2,700,000	2,700,000
Number of Options, exercised	0	24,000
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		$ 369	$ 1,722

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Dividends Payable [Line Items]
Per Share Amount	$ 0.09	$ 0.09	$ 0.18	$ 0.18
Total Dividend Paid			$ 8,679	$ 8,719
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

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 497,911
Other comprehensive income (loss) before reclassifications	$ (3,506)	$ 3,270	(2,921)	$ 6,211
Amounts reclassified from accumulated other comprehensive income (loss)	191	(609)	318	(839)
Amounts reclassified to retained earnings			(3,220)
Other Comprehensive Income (Loss), net of tax	(3,315)	2,661	(5,823)	5,372
Ending Balance	459,627		459,627
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(845)	1,739	2,567	404
Other comprehensive income (loss) before reclassifications	(82)	1,222	(339)	2,842
Amounts reclassified from accumulated other comprehensive income (loss)	186	(849)	251	(1,134)
Amounts reclassified to retained earnings			(3,220)
Other Comprehensive Income (Loss), net of tax	104	373	(3,308)	1,708
Ending Balance	(741)	2,112	(741)	2,112
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		79
Other comprehensive income (loss) before reclassifications		(571)		(492)
Amounts reclassified from accumulated other comprehensive income (loss)		154		154
Other Comprehensive Income (Loss), net of tax		(417)		(338)
Ending Balance		(338)		(338)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,224)	(4,962)	(4,286)	(5,017)
Amounts reclassified from accumulated other comprehensive income (loss)	5	86	67	141
Other Comprehensive Income (Loss), net of tax	5	86	67	141
Ending Balance	(4,219)	(4,876)	(4,219)	(4,876)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(734)	(6,333)	(1,576)	(7,575)
Other comprehensive income (loss) before reclassifications	(3,424)	2,619	(2,582)	3,861
Other Comprehensive Income (Loss), net of tax	(3,424)	2,619	(2,582)	3,861
Ending Balance	(4,158)	(3,714)	(4,158)	(3,714)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,803)	(9,477)	(3,295)	(12,188)
Ending Balance	$ (9,118)	$ (6,816)	$ (9,118)	$ (6,816)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	$ (78,052)	$ (100,047)	$ (159,125)	$ (196,617)
Income (Loss) Before Provision for Income Taxes	(11,259)	17,869	(26,004)	26,214
Tax (expense) benefit	3,589	(5,468)	7,520	(7,162)
Total reclassifications for the period, net of tax	(7,670)	12,401	(18,484)	19,052
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	(7)	(124)	(97)	(204)
Income (Loss) Before Provision for Income Taxes	(258)	1,113	(421)	1,502
Tax (expense) benefit	67	(504)	103	(663)
Total reclassifications for the period, net of tax	(191)	609	(318)	839
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 realized investment gain	$ (251)	1,393	$ (324)	1,965
Impairment Expense [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized investment gain		(2)		(105)
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		$ (154)		$ (154)

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ (111)	$ 2,003	$ (458)	$ 4,659
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	29	(781)	119	(1,817)
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	(82)	1,222	(339)	2,842
Unrealized gains (losses) on cash flow hedges, Before-Tax Amount		(571)		(492)
Unrealized gains (losses) on cash flow hedges, Net-of-Tax Amount		(571)		(492)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	251	(1,391)	324	(1,860)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	(65)	542	(73)	726
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	186	(849)	251	(1,134)
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		154		154
Reclassification adjustment for amounts related to cash flow hedges included in net income, Net-of-Tax Amount		154		154
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	7	124	97	204
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(2)	(38)	(30)	(63)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	5	86	67	141
Foreign currency translation adjustment, Before-Tax Amount	(3,424)	2,619	(2,582)	3,861
Foreign currency translation adjustment, Net-of-Tax Amount	(3,424)	2,619	(2,582)	3,861
Total Other Comprehensive Income (Loss), Before-Tax Amount	(3,277)	2,938	(5,839)	6,526
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(38)	(277)	16	(1,154)
Other Comprehensive Income (Loss), net of tax	$ (3,315)	$ 2,661	$ (5,823)	$ 5,372

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator
Net Income (Loss)	$ (7,670)	$ 12,401	$ (18,484)	$ 19,052
Denominator
Weighted average number of shares – basic	47,856	48,036	48,043	48,232
Effect of dilutive securities
Stock options		279	8	348
PSUs, RSUs and restricted stock	46	98	40	95
Weighted average number of shares – diluted	47,902	48,413	48,091	48,675
Net income (loss) per share – basic	$ (0.16)	$ 0.26	$ (0.38)	$ 0.40
Net income (loss) per share – diluted	$ (0.16)	$ 0.26	$ (0.38)	$ 0.39

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Anti-dilutive options, Total	5	4.1	4.8	4.1

Segment Information - Additiona

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 128,048	$ 184,673	$ 248,854	$ 354,952
Gross Profit	49,996	84,626	89,729	158,335
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	115,063	155,543	220,316	299,140
Gross Profit	45,434	75,880	82,075	142,813
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	12,985	29,130	28,538	55,812
Gross Profit	$ 4,562	$ 8,746	$ 7,654	$ 15,522

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue from External Customer [Line Items]
Sales	$ 128,048	$ 184,673	$ 248,854	$ 354,952
Access & Aggregation [Member]
Revenue from External Customer [Line Items]
Sales	84,742	138,639	166,422	258,782
Customer Devices [Member]
Revenue from External Customer [Line Items]
Sales	34,560	33,833	64,661	70,101
Traditional & Other Products [Member]
Revenue from External Customer [Line Items]
Sales	$ 8,746	$ 12,201	$ 17,771	$ 26,069

Liability for Warranty Return80

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 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	$ 10,111	$ 9,687	$ 9,724	$ 9,180	$ 8,988	$ 8,548

Liability for Warranty Return81

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 9,687	$ 8,988	$ 9,724	$ 8,548
Plus: Amounts charged to cost and expenses	4,860	3,055	6,683	2,314
Less: Deductions	(4,436)	(2,863)	(6,296)	(1,682)
Balance at end of period	$ 10,111	$ 9,180	$ 10,111	$ 9,180

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Jun. 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	Jul. 17, 2018	Aug. 15, 2018
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	Jul. 17, 2018
Common stock dividends per share declared	$ 0.09
Dividend record date	Aug. 1, 2018
Dividend payment date	Aug. 15, 2018