Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 01, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Registrant Name	ADTRAN INC
Trading Symbol	ADTN
Entity Central Index Key	0000926282
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		47,826,323
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	000-24612
Entity Tax Identification Number	630918200
Entity Address, Address Line One	901 Explorer Boulevard
Entity Address, City or Town	Huntsville
Entity Address, State or Province	Alabama
Entity Address, Postal Zip Code	35806-2807
City Area Code	(256)
Local Phone Number	963-8000

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 106,817	$ 105,504
Short-term investments	30,888	3,246
Accounts receivable, less allowance for doubtful accounts of $81 and $128 at June 30, 2019 and December 31, 2018, respectively	116,661	99,385
Other receivables	24,984	36,699
Inventory, net	95,110	99,848
Prepaid expenses and other current assets	8,909	10,744
Total Current Assets	383,369	355,426
Property, plant and equipment, net	78,813	80,635
Deferred tax assets, net	39,033	37,187
Goodwill	6,968	7,106
Intangibles, net	30,503	33,183
Other assets	13,820	5,668
Long-term investments	87,280	108,822
Total Assets	639,786	628,027
Current Liabilities
Accounts payable	63,827	60,054
Bonds payable	25,600	1,000
Unearned revenue	12,910	17,940
Accrued expenses	14,331	11,746
Accrued wages and benefits	19,126	14,752
Income tax payable, net	9,571	12,518
Total Current Liabilities	145,365	118,010
Non-current unearned revenue	4,265	5,296
Other non-current liabilities	44,181	33,842
Bonds payable		24,600
Total Liabilities	193,811	181,748
Commitments and contingencies (see Note 16)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 47,811 shares outstanding at June 30, 2019 and 79,652 shares issued and 47,751 shares outstanding at December 31, 2018	797	797
Additional paid-in capital	270,983	267,670
Accumulated other comprehensive loss	(14,095)	(14,416)
Retained earnings	878,630	883,975
Less treasury stock at cost: 31,841 and 31,901 shares at June 30, 2019 and December 31, 2018, respectively	(690,340)	(691,747)
Total Stockholders’ Equity	445,975	446,279
Total Liabilities and Stockholders’ Equity	$ 639,786	$ 628,027

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 81	$ 128
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,652,000	79,652,000
Common stock, shares outstanding	47,811,000	47,751,000
Treasury stock, shares	31,841,000	31,901,000

Condensed Consolidated Statements of Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Sales
Total Sales	$ 156,391	$ 128,048	$ 300,182	$ 248,854
Cost of Sales
Total Cost of Sales	91,376	78,052	174,555	159,125
Gross Profit	65,015	49,996	125,627	89,729
Selling, general and administrative expenses	33,619	32,080	68,751	65,611
Research and development expenses	32,064	30,729	63,711	63,578
Gain on contingency	(1,230)		(1,230)
Operating Income (Loss)	562	(12,813)	(5,605)	(39,460)
Interest and dividend income	692	913	1,283	1,779
Interest expense	(127)	(132)	(254)	(264)
Net investment gain	2,485	990	8,411	893
Other income (expense), net	(205)	(217)	650	(274)
Gain on bargain purchase of a business, net				11,322
Income (Loss) Before Benefit for Income Taxes	3,407	(11,259)	4,485	(26,004)
Benefit for income taxes	588	3,589	280	7,520
Net Income (Loss)	$ 3,995	$ (7,670)	$ 4,765	$ (18,484)
Weighted average shares outstanding – basic	47,802	47,856	47,792	48,043
Weighted average shares outstanding – diluted	48,036	47,856	47,939	48,043
Earnings (loss) per common share – basic	$ 0.08	$ (0.16)	$ 0.10	$ (0.38)
Earnings (loss) per common share – diluted	$ 0.08	$ (0.16)	$ 0.10	$ (0.38)
Network Solutions [Member]
Sales
Total Sales	$ 139,167	$ 115,063	$ 264,989	$ 220,316
Cost of Sales
Total Cost of Sales	80,175	69,629	150,909	138,241
Gross Profit	58,992	45,434	114,080	82,075
Services & Support [Member]
Sales
Total Sales	17,224	12,985	35,193	28,538
Cost of Sales
Total Cost of Sales	11,201	8,423	23,646	20,884
Gross Profit	$ 6,023	$ 4,562	$ 11,547	$ 7,654

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 3,995	$ (7,670)	$ 4,765	$ (18,484)
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	107	104	292	(3,308)
Defined benefit plan adjustments	150	5	271	67
Foreign currency translation	533	(3,424)	(627)	(2,582)
Other Comprehensive Income (Loss), net of tax	790	(3,315)	(64)	(5,823)
Comprehensive Income (Loss), net of tax	$ 4,785	$ (10,985)	$ 4,701	$ (24,307)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2017	$ 497,911	$ 797	$ 260,515	$ 922,178	$ (682,284)	$ (3,295)
Beginning Balance, Shares at Dec. 31, 2017		79,652
Net income (loss)	(10,814)			(10,814)
Adoption of new accounting standards (See Note 1)	3,499			3,499
Other comprehensive income (loss), net of tax	(2,508)					(2,508)
Dividend payments ($0.09 per share)	(4,367)			(4,367)
Dividends accrued on unvested RSUs	(2)			(2)
Stock options exercised	369			(150)	519
PSUs, RSUs and restricted stock vested				(733)	733
Purchase of treasury stock	(10,171)				(10,171)
Stock-based compensation expense	1,819		1,819
Ending Balance at Mar. 31, 2018	475,736	$ 797	262,334	909,611	(691,203)	(5,803)
Ending Balance, Shares at Mar. 31, 2018		79,652
Beginning Balance at Dec. 31, 2017	497,911	$ 797	260,515	922,178	(682,284)	(3,295)
Beginning Balance, Shares at Dec. 31, 2017		79,652
Net income (loss)	(18,484)
Other comprehensive income (loss), net of tax	(5,823)
Ending Balance at Jun. 30, 2018	459,627	$ 797	264,118	897,587	(693,757)	(9,118)
Ending Balance, Shares at Jun. 30, 2018		79,652
Beginning Balance at Mar. 31, 2018	475,736	$ 797	262,334	909,611	(691,203)	(5,803)
Beginning Balance, Shares at Mar. 31, 2018		79,652
Net income (loss)	(7,670)			(7,670)
Other comprehensive income (loss), net of tax	(3,315)					(3,315)
Dividend payments ($0.09 per share)	(4,312)			(4,312)
Dividends accrued on unvested RSUs	7			7
PSUs, RSUs and restricted stock vested				(49)	49
Purchase of treasury stock	(2,603)				(2,603)
Stock-based compensation expense	1,784		1,784
Ending Balance at Jun. 30, 2018	459,627	$ 797	264,118	897,587	(693,757)	(9,118)
Ending Balance, Shares at Jun. 30, 2018		79,652
Beginning Balance at Dec. 31, 2018	$ 446,279	$ 797	267,670	883,975	(691,747)	(14,416)
Beginning Balance, Shares at Dec. 31, 2018	79,652	79,652
Net income (loss)	$ 770			770
Adoption of new accounting standards (See Note 1)	4			(381)		385
Other comprehensive income (loss), net of tax	(854)					(854)
Dividend payments ($0.09 per share)	(4,301)			(4,301)
Dividends accrued on unvested RSUs	(18)			(18)
PSUs, RSUs and restricted stock vested	(8)			(865)	857
Purchase of treasury stock	(184)				(184)
Stock-based compensation expense	1,859		1,859
Ending Balance at Mar. 31, 2019	443,547	$ 797	269,529	879,180	(691,074)	(14,885)
Ending Balance, Shares at Mar. 31, 2019		79,652
Beginning Balance at Dec. 31, 2018	$ 446,279	$ 797	267,670	883,975	(691,747)	(14,416)
Beginning Balance, Shares at Dec. 31, 2018	79,652	79,652
Net income (loss)	$ 4,765
Other comprehensive income (loss), net of tax	(64)
Ending Balance at Jun. 30, 2019	$ 445,975	$ 797	270,983	878,630	(690,340)	(14,095)
Ending Balance, Shares at Jun. 30, 2019	79,652	79,652
Beginning Balance at Mar. 31, 2019	$ 443,547	$ 797	269,529	879,180	(691,074)	(14,885)
Beginning Balance, Shares at Mar. 31, 2019		79,652
Net income (loss)	3,995			3,995
Other comprehensive income (loss), net of tax	790					790
Dividend payments ($0.09 per share)	(4,303)			(4,303)
Dividends accrued on unvested RSUs	(34)			(34)
Stock options exercised	526			(208)	734
Stock-based compensation expense	1,454		1,454
Ending Balance at Jun. 30, 2019	$ 445,975	$ 797	$ 270,983	$ 878,630	$ (690,340)	$ (14,095)
Ending Balance, Shares at Jun. 30, 2019	79,652	79,652

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018
Statement Of Stockholders Equity [Abstract]
Dividend payments	$ 0.09	$ 0.09	$ 0.09	$ 0.09

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income (loss)	$ 4,765	$ (18,484)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	8,913	7,526
Amortization of net premium on available-for-sale investments	(57)	20
Net gain on long-term investments	(8,411)	(893)
Net loss on disposal of property, plant and equipment	58	68
Gain on contingency	(1,230)
Gain on bargain purchase of a business		(11,322)
Gain on life insurance proceeds	(1,000)
Stock-based compensation expense	3,313	3,603
Deferred income taxes	(1,880)	(16,384)
Changes in operating assets and liabilities:
Accounts receivable, net	(17,288)	66,931
Other receivables	11,678	9
Inventory, net	4,612	2,063
Prepaid expenses and other assets	4,715	10,157
Accounts payable, net	5,009	683
Accrued expenses and other liabilities	640	2,008
Income tax payable	(2,830)	6,945
Net cash provided by operating activities	11,007	52,930
Cash flows from investing activities:
Purchases of property, plant and equipment	(4,307)	(4,183)
Proceeds from sales and maturities of debt and equity investments	24,306	86,436
Purchases of debt and equity investments	(21,544)	(89,801)
Life insurance proceeds received	1,000
Acquisition of business	13	(7,806)
Net cash used in investing activities	(532)	(15,354)
Cash flows from financing activities:
Proceeds from stock option exercises	526	369
Purchases of treasury stock	(184)	(12,774)
Dividend payments	(8,604)	(8,679)
Net cash used in financing activities	(8,262)	(21,084)
Net increase in cash and cash equivalents	2,213	16,492
Effect of exchange rate changes	(900)	(2,606)
Cash and cash equivalents, beginning of period	105,504	86,433
Cash and cash equivalents, end of period	106,817	100,319
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 205	$ 209

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements of ADTRAN^®, Inc. and its subsidiaries (“ADTRAN”, the “Company”, “we”, “our” or “us”) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles in the United States of America (“GAAP”) for complete financial statements are not included herein. The December 31, 2018 Condensed Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by GAAP.

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 financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K/A for the year ended December 31, 2018, filed on September 20, 2019, with the SEC.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the excess, obsolete and slow moving inventory reserves, warranty reserves, customer rebates, determination of the deferred and accrued revenue components of multiple performance obligations sales agreements, estimated costs to complete obligations associated with deferred and accrued revenue, 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.

During the three months ended June 30, 2019, the Company revised the methodology in how it estimates its excess and obsolete inventory reserves. Under the revised methodology, we establish reserves for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on historical usage, known trends, inventory age, and market conditions. When we dispose of excess and obsolete inventories, the related disposals are charged against the inventory reserve. See Note 8 of Notes to Condensed Consolidated Financial Statements for additional information.

Correction of Immaterial Misstatements.

During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserve and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in its excess and obsolete inventory reserve and cost of goods sold. In addition, the Company determined that a $1.0 million cash inflow related to an insurance recovery was incorrectly classified as a cash flow from operations instead of a cash flow from investing activities within the unaudited Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2019. The accompanying Unaudited Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2019 correctly reflects the $1.0 million insurance recovery as a cash inflow from investing activities. Management has determined that these misstatements were not material to any of its previously issued financial statements and that correction of the misstatements is also not material to the current or estimated annual 2019 financial results on both a quantitative and qualitative basis.

Recent Accounting Pronouncements Not Yet Adopted

In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 requires the measurement and recognition of expected credit losses for financial instruments held at amortized cost. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326 Financial Instruments – Credit Losses, that clarifies receivables arising from operating leases are not within the scope of the credit losses standard, but rather should be accounted for in accordance with the leases standard. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments–Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, which clarifies the accounting for transfers between classifications of debt securities and clarifies that entities should include expected recoveries on financial assets in the calculation of the current expected credit loss allowance. In addition, renewal options that are not unconditionally cancelable should be considered in the determination of expected credit losses. In May 2019, the FASB issued ASU 2019-05, Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief, which amends ASU 2016-13 to allow companies, upon adoption, to elect the fair value option on financial instruments that were previously recorded at amortized cost if they meet certain criteria. All of these ASUs are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the effect these ASUs will have on our consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the measurement of goodwill by eliminating step 2 of the goodwill impairment test. Under ASU 2017-04, entities will be required to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for annual or interim impairment tests performed in fiscal years beginning after December 15, 2019, with early adoption permitted for annual or interim impairment tests performed on testing dates after January 1, 2017. The amendments should be applied prospectively. We are currently evaluating whether to early adopt ASU 2017-04, but do not expect it will have a material effect on our consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, which changes the fair value measurement disclosure requirements of Accounting Standards Codification (“ASC”) 820, Fair Value Measurement. The amendments in this ASU are the result of a broader disclosure project, Concepts Statement No. 8 — Conceptual Framework for Financial Reporting — Chapter 8 — Notes to Financial Statements, which the FASB finalized on August 28, 2018. The FASB used the guidance in the Concepts Statement to improve the effectiveness of ASC 820’s disclosure requirements. ASU 2018-13 provides users of financial statements with information about assets and liabilities measured at fair value in the statement of financial position or disclosed in the notes to the financial statements. More specifically, ASU 2018-13 requires disclosures about the valuation techniques and inputs that are used to arrive at measures of fair value, including judgments and assumptions that are made in determining fair value. In addition, ASU 2018-13 requires disclosures regarding the uncertainty in the fair value measurements as of the reporting date and how changes in fair value measurements affect performance and cash flows. ASU 2018-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. We are currently evaluating the effect of ASU 2018-13, but do not expect it will have a material effect on our financial statement disclosures.

In August 2018, the FASB issued ASU 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans, which makes changes to and clarifies the disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 requires additional disclosures related to the reasons for significant gains and losses affecting the benefit obligation and an explanation of any other significant changes in the benefit obligation or plan assets that are not otherwise apparent in other disclosures required by ASC 715. ASU 2018-14 also clarifies the guidance in ASC 715 to require disclosure of the projected benefit obligation (PBO) and fair value of plan assets for pension plans with PBOs in excess of plan assets and the accumulated benefit obligation (ABO) and fair value of plan assets for pension plans with ABOs in excess of plan assets. ASU 2018-14 is effective for public business entities for fiscal years ending after December 15, 2020. We are currently evaluating the effect of ASU 2018-14, but do not expect it will have a material effect on our financial statement disclosures.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementations costs incurred to develop or obtain internal use software. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the effect of ASU 2018-15, but do not expect it will have a material effect on our consolidated financial statements.

Recently Adopted Accounting Pronouncements

During 2019, we adopted the following accounting standards, which had the following impacts on our consolidated financial statements:

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires an entity to recognize right-of-use assets and lease liabilities on the balance sheet and to disclose key information about the entity’s leasing arrangements. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases, which clarified certain aspects of ASU 2016-02, as well as ASU 2018-11, Leases (Topic 842), Targeted Improvements, which provided for an optional transition method allowing for the application of the legacy lease guidance, Leases (Topic 840), including its disclosure requirements, for the comparative periods presented in the year of adoption, with the cumulative effect of initially applying the new lease standard recognized as an adjustment to retained earnings as of the date of adoption. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842) Codification Improvements, which removed the requirement for an entity to disclose in the interim periods after adoption, the effect of the change on income from continuing operations, net income, any other affected financial statement line item, and any affected per share amount. For lessors, the new leasing standard requires leases to be classified as sales-type, direct financing or operating leases. These criteria focus on the transfer of control of the underlying lease asset. This standard and related updates were effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years.

The Company adopted the new standard on January 1, 2019, the effective date of our initial application, using the optional transition method. The Company has elected to carry forward the legacy ASC 840 disclosures for comparative periods and, therefore, did not adjust the comparative period financial information prior to January 1, 2019. In addition, the Company elected the package of practical expedients which allows for companies to not reassess whether any expired or existing contracts are or contain leases, not reassess historical lease classifications for expired or existing contracts and not reassess initial direct costs for existing leases. Additionally, the Company elected the practical expedients which allow the use of hindsight when determining the lease term, the short-term lease recognition exemption and the option to not separate lease and non-lease components. The adoption of this standard resulted in the recognition of a right-of-use asset and corresponding right-of-use liability on our Condensed Consolidated Balance Sheet of $10.3 million, primarily related to our operating leases for office space, automobiles and other equipment.

As a lessee, the adoption of this standard did not have a material impact on our Condensed Consolidated Statement of Income or Statement of Cash Flow. See Note 11 for additional information.

As a lessor, the adoption of this standard did not have a material impact on the Company’s Condensed Consolidated Balance Sheet, Condensed Consolidated Statement of Income or Condensed Statement of Cash Flow. Prior to and after adoption, all of our leases in which we are the lessor were classified as sales-types leases.

In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities, which shortened the amortization period for the premium on certain purchased callable debt securities to the earliest call date. ASU 2017-08 was effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2018. The amendments were required to be applied through a modified-retrospective transition approach that required a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company adopted ASU 2017-08 on January 1, 2019, and the adoption of this standard did not have a material effect on our consolidated financial statements.

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 expanded and refined hedge accounting for both financial and non-financial risk components, aligned the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and included certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting, which permits the OIS rate based on SOFR as a U.S. benchmark interest rate. Both ASU 2017-12 and ASU 2018-16 were effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted ASU 2017-12 on January 1, 2019, and the adoption of this standard did not have a material effect on our consolidated financial statements as we currently do not have any hedging instruments.

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. ASU 2018-02 allowed for an optional reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. ASU 2018-02 was effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted ASU 2018-02 on January 1, 2019, and upon adoption reclassified $0.4 million of stranded tax effects created by rate changes related to the Tax Cuts and Jobs Act of 2017 to retained earnings. See Note 12 for additional information.

Business Combinations

6 Months Ended

Jun. 30, 2019

Business Combinations [Abstract]

Business Combinations

2. BUSINESS COMBINATIONS

On November 30, 2018, we acquired SmartRG, Inc., a provider of carrier-class, open connected home platforms and cloud services for broadband service providers in exchange for cash consideration. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. The revenue from the SmartRG portfolio is included in the Subscriber Solutions & Experience category within the Network Solutions and Services & Support reportable segments.

Contingent liabilities with a fair value totaling $1.2 million were recognized at the acquisition date, the payments of which were dependent upon SmartRG achieving future revenue, EBIT or customer purchase order milestones during the first half of 2019. The required milestones were not achieved and, therefore, we recognized a gain of $1.2 million upon the reversal of these liabilities during the second quarter of 2019.

An escrow in the amount of $2.8 million was set up at the acquisition date to fund post-closing working capital settlements and to satisfy indemnity obligations to the Company arising from any inaccuracy or breach of representations, warranties, covenants, agreements or obligations of the sellers. The escrow is subject to arbitration with final settlement expected during the fourth quarter of 2020. The minimum and maximum potential release of funds to the sellers ranges from zero to $2.8 million.

We recorded goodwill of $3.5 million as a result of this acquisition, which represents the excess of the purchase price over the fair value of net assets acquired. We assessed the recognition and measurement of the assets acquired and liabilities assumed based on historical and forecasted data for future periods and concluded that our valuation procedures and resulting measures were appropriate.

The final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for SmartRG are as follows:

(In thousands)
Assets
Tangible assets acquired	$	8,594
Intangible assets		9,960
Goodwill		3,476
Total assets acquired		22,030
Liabilities
Liabilities assumed		(6,001	)
Total liabilities assumed		(6,001	)
Total purchase price	$	16,029

The details of the acquired intangible assets from the SmartRG acquisition are as follows:

(In thousands)	Value		Life (in years)
Developed technology	$	7,400	7
Customer relationships		1,790	3
Licensing agreements		560	5 – 10
Trade name		210	3
Total	$	9,960

For the three and six months ended June 30, 2019, we incurred amortization of acquired intangibles of $0.6 million and $1.2 million, respectively, related to the SmartRG acquisition. No acquisition-related expenses were incurred during the three and six months ended June 30, 2018 related to the SmartRG acquisition.

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 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. This revenue is included in the Access & Aggregation and Subscriber Solutions & Experience categories within the Network Solutions reportable segment.

We recorded a bargain purchase gain, net of income taxes, of $11.3 million during the first quarter of 2018, which represents the difference between the fair-value of the net assets acquired over the cash paid. We assessed the recognition and measurement of the assets acquired and liabilities assumed based on historical and forecasted data for future periods and concluded that our valuation procedures and resulting measures were appropriate.

The following unaudited supplemental pro forma information presents the financial results of the Company, for the six months ended June 30, 2018, as if the acquisition of the Sumitomo EPON business 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. There were no material, non-recurring adjustments to this unaudited pro forma information.

	Six Months Ended
(In thousands)	June 30, 2018
Pro forma revenue	$	250,114
Pro forma net loss	$	(31,020	)

Revenue

6 Months Ended

Jun. 30, 2019

Revenue From Contract With Customer [Abstract]

Revenue

3. REVENUE

The following is a description of the principal activities from which we generate our revenue by reportable segment.

Network Solutions Segment

Network Solutions includes hardware products and software-defined next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. The majority of the revenue from this segment is from hardware sales. In certain transactions, we are also the lessor in sales-type lease arrangements for network equipment. These arrangements typically include network equipment, network implementation services and maintenance services. Network implementation services and maintenance services are included in the Services & Support segment discussed below. See Note 11 for additional information.

Services & Support Segment

To complement our Network Solutions segment, we offer a complete portfolio of maintenance, network implementation and solutions integration and managed services, which include hosted cloud services and subscription services.

In addition to our reporting segments, we also report revenue in the following three categories – Access & Aggregation, Subscriber Solutions & Experience, and Traditional & Other Products.

The following table disaggregates our revenue by reportable segment and revenue category for the three months ended June 30, 2019 and 2018:

	For the Three Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	96,262	$	13,159	$	109,421	$	75,222	$	9,520	$	84,742
Subscriber Solutions & Experience⁽¹⁾		38,444		2,058		40,502		33,306		1,254		34,560
Traditional & Other Products		4,461		2,007		6,468		6,535		2,211		8,746
Total	$	139,167	$	17,224	$	156,391	$	115,063	$	12,985	$	128,048

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

The following table disaggregates our revenue by reportable segment and revenue category for the six months ended June 30, 2019 and 2018:

	For the Six Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	181,935	$	27,264	$	209,199	$	144,607	$	21,815	$	166,422
Subscriber Solutions & Experience⁽¹⁾		73,163		4,092		77,255		62,083		2,578		64,661
Traditional & Other Products		9,891		3,837		13,728		13,626		4,145		17,771
Total	$	264,989	$	35,193	$	300,182	$	220,316	$	28,538	$	248,854

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

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. 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). As of June 30, 2019, we did not have any significant performance obligations related to customer contracts that had an original expected duration of one year or more, other than maintenance services, which are satisfied over time.

The following table provides information about receivables, contract assets and unearned revenue from contracts with customers:

(In thousands)	June 30, 2019		December 31, 2018
Accounts receivable, net	$	116,661	$	99,385
Contract assets⁽¹⁾	$	2,251	$	3,766
Unearned revenue	$	12,910	$	17,940
Non-current unearned revenue	$	4,265	$	5,296

⁽¹⁾

^{Included in other receivables on the Condensed Consolidated Balance Sheet.}

Of the outstanding unearned revenue balance at December 31, 2018, $3.6 million and $10.5 million was recognized as revenue during the three and six months ended June 30, 2019, respectively.

Income Taxes

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Income Taxes

4. INCOME TAXES

Our effective tax rate decreased from a benefit of 20.1%, excluding the tax effect of the bargain purchase gain, in the six months ended June 30, 2018, to a benefit of 6.2% in the six months ended June 30, 2019. The decrease in the effective tax rate between the two periods was primarily driven by the shift to profitability in the six months ended June 30, 2019, with tax expense being offset by a 29.1% rate reduction related to a transfer pricing study completed during the second quarter of 2019 that resulted in the assignment of operating expenditures to specific company locations, and the effective income tax rates among the respective jurisdictions.

The Company continually reviews the adequacy of the valuation allowance and recognizes the benefits of deferred tax assets only as the reassessment indicates that it is more likely than not that the deferred tax assets will be recognized in accordance with ASC 740, Income Taxes. As of June 30, 2019, we had net deferred tax assets of $39.0 million. Since management continues to assess the realization of these deferred tax assets and related valuation allowance(s), as such, we may release a portion of the valuation allowance or establish a new valuation allowance based on operations in the jurisdictions in which these assets arose. Our assessment includes the evaluation of evidence, some of which requires significant judgment, including historical operating results, the evaluation of our three-year cumulative income position, future taxable income projections and tax planning strategies. Due to operating losses incurred in prior quarters in the United States, the Company is currently near breakeven on its three-year cumulative income position for this tax jurisdiction. Should the Company determine that a valuation allowance is needed in the future due to management’s conclusion that it is no longer more likely than not that the Company will be able to utilize its deferred tax assets in a particular jurisdiction, it could have a material effect on our consolidated financial statements.

Pension Benefit Plan

6 Months Ended

Jun. 30, 2019

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, 2019 and 2018:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Service cost	$	368		$	303		$	743		$	611
Interest cost		159			185			321			372
Expected return on plan assets		(348	)		(394	)		(703	)		(793	)
Amortization of actuarial losses		199			63			402			127
Net periodic pension cost	$	378		$	157		$	763		$	317

The components of net periodic pension cost, other than the service cost component, are included in other income (expense), net in the Condensed Consolidated Statements of Income. Service cost are included in cost of sales, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Income.

Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

6. STOCK-BASED COMPENSATION

The following table summarizes 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, 2019 and 2018:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Stock-based compensation expense included in cost of sales	$	85		$	102		$	189		$	197
Selling, general and administrative expense		662			995			1,725			2,030
Research and development expense		707			687			1,399			1,376
Stock-based compensation expense included in operating expenses		1,369			1,682			3,124			3,406
Total stock-based compensation expense		1,454			1,784			3,313			3,603
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock		(332	)		(340	)		(775	)		(724	)
Total stock-based compensation expense, net of tax	$	1,122		$	1,444		$	2,538		$	2,879

Stock Options

The following table is a summary of our stock options outstanding as of December 31, 2018 and June 30, 2019, and the changes that occurred during the six months ended June 30, 2019:

	Number of Stock Options (in thousands)			Weighted Avg. Exercise Price (per share)		Weighted Avg. Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Stock options outstanding, December 31, 2018		4,382		$	22.91		4.10	$	—
Stock options exercised		(34	)	$	15.53
Stock options forfeited		(10	)	$	15.67
Stock options expired		(156	)	$	24.50
Stock options outstanding, June 30, 2019		4,182		$	22.93		3.64	$	—
Stock options exercisable, June 30, 2019		3,942		$	23.39		3.47	$	—

At June 30, 2019, total unrecognized compensation expense related to non-vested stock options was approximately $0.3 million, which is expected to be recognized over an average remaining recognition period of 0.4 years.

All of the options above were issued at exercise prices that approximated fair market value at the date of grant.

The aggregate intrinsic value of stock options represents the total pre-tax intrinsic value (the difference between ADTRAN’s closing stock price on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on June 30, 2019. The amount of aggregate intrinsic value will change based on the fair market value of ADTRAN’s stock and was zero as of June 30, 2019. The total pre-tax intrinsic value of options exercised during the six months ended June 30, 2019 was $0.1 million.

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. The stock option pricing model requires the use of several assumptions that impact the fair value estimate. These variables include, but are not limited to, the volatility of our stock price and employee exercise behaviors.

There were no stock options granted during the three and six months ended June 30, 2019 or 2018.

PSUs, RSUs and Restricted Stock

The following table is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2018 and June 30, 2019 and the changes that occurred during the six months ended June 30, 2019:

	Number of Shares (in thousands)			Weighted Avg. Grant Date Fair Value (per share)
Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2018		1,570		$	18.52
PSUs, RSUs and restricted stock granted		59		$	12.54
PSUs, RSUs and restricted stock vested		(1	)	$	18.86
PSUs, RSUs and restricted stock forfeited		(63	)	$	16.66
Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2019		1,565		$	18.37

The fair value of our PSUs with market and performance 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 business day immediately preceding the grant date.

At June 30, 2019, total unrecognized compensation expense related to the non-vested portion of market-based PSUs, RSUs and restricted stock was approximately $14.2 million, which is expected to be recognized over an average remaining recognition period of 2.6 years. In addition, there was $8.3 million of unrecognized compensation expense related to unvested 2017 performance-based PSUs, which will be recognized over the remaining requisite service period of 0.5 years if achievement of the performance obligation becomes probable. For the three and six months ending June 30, 2019 and 2018, no compensation expense was recognized related to these 2017 performance-based PSUs.

At June 30, 2019, 2.6 million stock options, PSUs, RSUs or restricted stock were available for grant under shareholder-approved equity plans.

Investments

6 Months Ended

Jun. 30, 2019

Investments Debt And Equity Securities [Abstract]

Investments

7. INVESTMENTS

Debt Securities and Other Investments

At June 30, 2019, 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	$	14,132	$	111	$	(4	)	$	14,239
Municipal fixed-rate bonds		930		—		(3	)		927
Asset-backed bonds		6,580		32		(3	)		6,609
Mortgage/Agency-backed bonds		5,362		23		(6	)		5,379
U.S. government bonds		5,027		6		(6	)		5,027
Foreign government bonds		1,852		1		(1	)		1,852
Available-for-sale debt securities held at fair value	$	33,883	$	173	$	(23	)	$	34,033
Restricted investment held at cost									25,600
Other investments held at cost									1,199
Total carrying value of available-for-sale investments								$	60,832

At December 31, 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	$	20,777	$	19	$	(112	)	$	20,684
Municipal fixed-rate bonds		1,339		—		(26	)		1,313
Asset-backed bonds		5,230		5		(14	)		5,221
Mortgage/Agency-backed bonds		3,833		2		(44	)		3,791
U.S. government bonds		9,271		1		(66	)		9,206
Foreign government bonds		592		—		(8	)		584
Available-for-sale debt securities held at fair value	$	41,042	$	27	$	(270	)	$	40,799
Restricted investment held at cost									25,600
Other investments held at cost									397
Total carrying value of available-for-sale investments								$	66,796

As of June 30, 2019, our debt securities had the following contractual maturities:

(In thousands)	Corporate bonds		Municipal fixed-rate bonds		Asset- backed bonds		Mortgage / Agency- backed bonds		U.S. government bonds		Foreign government bonds
Less than one year	$	2,749	$	—	$	96	$	—	$	2,443	$	—
One to two years		8,460		927		430		264		—		891
Two to three years		3,030		—		1,667		588		1,346		961
Three to five years		—		—		2,018		510		1,238		—
Five to ten years		—		—		1,772		425		—		—
More than ten years		—		—		626		3,592		—		—
Total	$	14,239	$	927	$	6,609	$	5,379	$	5,027	$	1,852

Actual maturities may differ from contractual maturities as some borrowers have the right to call or prepay obligations with or without call or prepayment penalties.

Realized gains and losses on sales of 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)	2019			2018			2019			2018
Gross realized gains on debt securities	$	8		$	25		$	49		$	25
Gross realized losses on debt securities		(14	)		(241	)		(33	)		(315	)
Total gain (loss) recognized, net	$	(6	)	$	(216	)	$	16		$	(290	)

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, 2019, we held a $25.6 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 $25.6 million at June 30, 2019 and December 31, 2018. At June 30, 2019 and December 31, 2018, the estimated fair value of the Bond using a level 2 valuation technique was approximately $25.6 million and $25.4 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 offset 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. We have made annual principal payments in addition to the interest amounts that are due. The restricted funds held as collateral against the outstanding principal amount of the Bond will be used to pay the outstanding principal and interest upon the Bond’s maturity on January 1, 2020.

Marketable Equity Securities

Our marketable equity securities consist of publicly traded stock, funds and certain other investments measured at fair value or cost (where appropriate).

On January 1, 2018, we adopted ASU 2016-01, which requires us to measure all equity investments that do not result in consolidation and are not accounted for under the equity method at fair value, with any changes in fair value recognized in net investment gain (loss). Upon adoption, we reclassified $3.2 million of net unrealized gains related to marketable equity securities from accumulated other comprehensive income (loss) to retained earnings.

ASU 2016-01 also provides a measurement alternative for equity investments that do not have a readily determinable fair value in which investments can be recorded at cost less impairment, if any, adjusted for observable price changes for an identical or similar investment. We elected to record our equity investment that does not have a readily determinable fair value using the measurement alternative method. As of December 31, 2018, the Company had a note receivable of approximately $4.3 million, which was included in other receivables on the Condensed Consolidated Balance Sheet. During the three months ended March 31, 2019, this amount was repaid as follows. Approximately $3.4 million was issued as an equity investment, which represented a non-cash investing activity. The carrying value of this investment under the measurement alternative was $3.4 million as of June 30, 2019. The remaining amount was converted into a new note receivable, which is included in other receivables on the Condensed Consolidated Balance Sheet and represents a non-cash operating activity.

Realized and unrealized gains and losses for our marketable equity securities for the three and six months ended June 30, 2019 and 2018 were as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Realized gains (losses) on equity securities sold	$	(49	)	$	(52	)	$	(63	)	$	347
Unrealized gains on equity securities held		2,540			1,258			8,458			836
Total gain recognized, net	$	2,491		$	1,206		$	8,395		$	1,183

As of June 30, 2019 and 2018, gross unrealized losses related to individual investments in a continuous loss position for twelve months or longer were not material.

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, 2019 Using
(In thousands)	Cost or Fair Value		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	1,337	$	1,337	$	—	$	—
Commercial paper		2,973		—		2,973		—
Cash equivalents		4,310		1,337		2,973		—
Available-for-sale debt securities
Corporate bonds		14,239		—		14,239		—
Municipal fixed-rate bonds		927		—		927		—
Asset-backed bonds		6,609		—		6,609		—
Mortgage/Agency-backed bonds		5,379		—		5,379		—
U.S. government bonds		5,027		5,027		—		—
Foreign government bonds		1,852		—		1,852		—
Marketable equity securities
Marketable equity securities – various industries		32,548		32,548		—		—
Equity in escrow		185		185		—		—
Deferred compensation plan assets		21,228		21,228		—		—
Total debt and equity securities at fair value		87,994		58,988		29,006		—
Other investments held at cost
Other investments		3,375		—		—		—
Total other investments held at cost		3,375		—		—		—
Total	$	95,679	$	60,325	$	31,979	$	—

			Fair Value Measurements at December 31, 2018 Using
(In thousands)	Cost or Fair Value		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	1,554	$	1,554	$	—	$	—
Cash equivalents		1,554		1,554		—		—
Available-for-sale debt securities
Corporate bonds		20,684		—		20,684		—
Municipal fixed-rate bonds		1,313		—		1,313		—
Asset-backed bonds		5,221		—		5,221		—
Mortgage/Agency-backed bonds		3,791		—		3,791		—
U.S. government bonds		9,206		9,206		—		—
Foreign government bonds		584		—		584		—
Marketable equity securities
Marketable equity securities – various industries		26,763		26,763		—		—
Equity in escrow		253		253		—		—
Deferred compensation plan assets		18,256		18,256		—		—
Total debt and equity securities at fair value		86,071		54,478		31,593		—
Total	$	87,625	$	56,032	$	31,593	$	—

The fair value of our Level 2 securities is calculated using a weighted average market price for each security. Market prices are obtained from a variety of industry standard data providers, security master files from large financial institutions, and other third-party sources. These multiple market prices are used as inputs into a distribution-curve-based algorithm to determine the daily market value of each security.

Inventory

6 Months Ended

Jun. 30, 2019

Inventory Disclosure [Abstract]

Inventory

8. INVENTORY

At June 30, 2019 and December 31, 2018, inventory consisted of the following:

	June 30,		December 31,
(In thousands)	2019		2018
Raw materials	$	38,844	$	45,333
Work in process		1,383		1,638
Finished goods		54,883		52,877
Total	$	95,110	$	99,848

Inventory reserves are established for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on historical usage, known trends, inventory age, and market conditions. At June 30, 2019 and December 31, 2018, our inventory reserve was $31.0 million and $30.0 million, respectively.

Goodwill

6 Months Ended

Jun. 30, 2019

Goodwill Disclosure [Abstract]

Goodwill

9. GOODWILL

Goodwill, all of which relates to our acquisitions of Bluesocket, Inc. in 2011 and SmartRG in 2018, was $7.0 million and $7.1 million at June 30, 2019 and December 31, 2018, respectively, of which $6.6 million and $0.4 million is allocated to our Network Solutions and Services & Support reportable segments, respectively, as of June 30, 2019, and of which $6.7 million and $0.4 million was allocated to our Network Solutions and Services & Support reportable segments, respectively, as of December 31, 2018. Goodwill related to our SmartRG acquisition was reduced by $0.1 million during the six months ended June 30, 2019, as a result of a measurement period adjustment.

We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. We have elected to first assess the qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step impairment test. If we determine that it is more likely than not that its fair value is less than its carrying amount, then the two-step impairment test will be performed. Based on the results of our qualitative assessment in 2018, we concluded that it was not necessary to perform the two-step impairment test.

Intangible Assets

6 Months Ended

Jun. 30, 2019

Intangible Assets Net Excluding Goodwill [Abstract]

Intangible Assets

10. INTANGIBLE ASSETS

Intangible assets include intangibles acquired in conjunction with several acquisitions since 2011, with the most recent being SmartRG, Inc. in November 2018.

The following table presents our intangible assets as of June 30, 2019 and December 31, 2018:

	June 30, 2019							December 31, 2018
(In thousands)	Gross Value		Accumulated Amortization			Net Value		Gross Value		Accumulated Amortization			Net Value
Customer relationships	$	22,414	$	(6,311	)	$	16,103	$	22,455	$	(5,380	)	$	17,075
Developed technology		10,170		(2,810	)		7,360		12,801		(4,867	)		7,934
Licensed technology		5,900		(847	)		5,053		5,900		(520	)		5,380
Supplier relationships		2,800		(1,808	)		992		2,800		(1,108	)		1,692
Licensing agreements		560		(43	)		517		560		(5	)		555
Patents		500		(191	)		309		500		(157	)		343
Trade names		310		(141	)		169		310		(106	)		204
Total	$	42,654	$	(12,151	)	$	30,503	$	45,326	$	(12,143	)	$	33,183

Amortization expense was $1.3 million and $1.0 million for the three months ended June 30, 2019 and 2018 respectively, and $2.7 million and $1.5 million for the six months ended June 30, 2019 and 2018.

As of June 30, 2019, the estimated future amortization expense of our intangible assets was as follows:

(In thousands)	Amount
Remainder of 2019	$	2,665
2020		4,448
2021		4,099
2022		3,475
2023		3,322
Thereafter		12,494
Total	$	30,503

Leases

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Leases

11. LEASES

Operating Lease Arrangements

We have operating leases for office space, automobiles, and various other equipment in the United States and in certain international locations in which we do business. We also have other contracts, such as manufacturing agreements and service agreements, which we reviewed to determine if they contain any embedded leases. We specifically reviewed these other contracts to determine whether we have the right to substantially all of the economic benefit from the use of any specified assets or the right to direct the use of any specified assets, either of which would indicate the existence of a lease.

As of June 30, 2019, our operating leases have remaining lease terms of one month to six years, some of which include options to extend the leases for up to three years, and some of which include options to terminate the leases within three months. For those leases that are reasonably assured to be renewed, we have included the option to extend as part of our right of use asset and right of use liability. Leases with an initial term of 12 months or less are not recorded on the balance sheet and lease expense for these leases is recognized on a straight-line basis over the lease term. Lease expense related to these short-term leases was $0.1 million and $0.3 million for the three and six months ended June 30, 2019, respectively, and is included in selling, general and administrative expenses on the Condensed Consolidated Statements of Income. For lease agreements entered into or reassessed after the adoption of Topic 842, we elected the practical expedient which allows us to not separate lease and non-lease components. None of our lease agreements contain any material residual value guarantees or material restrictive covenants.

Supplemental balance sheet information related to operating leases is as follows:

		June 30,		January 1,
(In thousands)	Classification	2019		2019 ⁽¹⁾
Assets
Operating lease asset	Other assets	$	8,838	$	10,322
Total lease assets		$	8,838	$	10,322

Liabilities
Current operating lease liability	Accrued expenses	$	2,514	$	2,948
Non-current operating lease liability	Other non-current liabilities		6,349		7,374
Total lease liability		$	8,863	$	10,322

⁽¹⁾

^{Reflects the adoption of the new lease accounting standard on January 1, 2019.}

The components of lease expense included in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2019 are as follows:

(In thousands)	Three Months Ended June 30, 2019		Six Months Ended June 30, 2019
Selling, general and administrative expenses	$	349	$	698
Research and development expenses		430		884
Cost of sales		17		33
Total operating lease expense	$	796	$	1,615

As of June 30, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheet by future maturity are as follows:

(In thousands)	Amount
Remainder of 2019	$	1,583
2020		2,203
2021		2,047
2022		1,560
2023		1,173
Thereafter		756
Total lease payments		9,322
Less: Interest		(459	)
Present value of lease liabilities	$	8,863

Operating lease payments include $1.2 million related to options to extend lease terms that are reasonably certain of being exercised. There are no legally binding leases that have not yet commenced.

As of December 31, 2018, future minimum rental payments under non-cancelable operating leases, including renewals determined to be reasonably assured as of December 31, 2018, with original maturities of greater than 12 months, are as follows:

(In thousands)	Amount ⁽¹⁾
2019	$	3,873
2020		3,580
2021		2,771
2022		2,053
2023		1,317
Thereafter		762
Total	$	14,356

⁽¹⁾

^{Certain renewal options were subsequently determined to not be reasonably assured of renewal upon the Company’s adoption of the new lease accounting standard on January 1, 2019.}

Our leases do not provide an implicit borrowing rate and therefore we use an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We used the incremental borrowing rate on January 1, 2019, for operating leases that commenced on or prior to that date. The incremental borrowing rate was determined on a portfolio basis by grouping leases with similar terms as well as grouping leases based on a U.S. dollar or Euro functional currency. The actual rate is then determined based on a credit spread over LIBOR as well as the Bloomberg Curve Matrix for the U.S. Communications section.

	As of June 30, 2019
Weighted average remaining lease term (years)
Operating leases with USD functional currency		2.9
Operating leases with Euro functional currency		4.8
Weighted average discount rate
Operating leases with USD functional currency		4.61	%
Operating leases with Euro functional currency		1.85	%

Supplemental cash flow information related to operating leases was as follows:

(In thousands)	As of June 30, 2019
Cash paid for amounts included in the measurement of operating lease liabilities / assets
Cash used in operating activities related to operating leases	$	(797	)

Right-of-use assets obtained in exchange for lease obligations	$	10,396

Sales-Type Lease Arrangements

We are the lessor in sales-type lease arrangements for network equipment, which have initial terms of up to five years. Our sales-type lease arrangements contain either a provision whereby the network equipment reverts back to us upon the expiration of the lease or a provision that allows the lessee to purchase the network equipment at a bargain purchase amount. In addition, our sales-type lease arrangements do not contain any residual value guarantees or material restrictive covenants. The allocation of the consideration between lease and non-lease components is determined by standalone sales price by component. The net investment in sales-type leases consists of lease receivables less unearned income. Collectability of sales-type leases is evaluated periodically at an individual customer level. At June 30, 2019 and December 31, 2018, we had no allowance for credit losses for our net investment in sales-type leases. As of June 30, 2019 and December 31, 2018, the components of the net investment in sales-type leases were as follows:

	June 30,		December 31,
(In thousands)	2019		2018
Current minimum lease payments receivable (included in other receivables)	$	6,360	$	11,339
Non-current minimum lease payments receivable (included in other assets)		1,286		1,670
Total minimum lease payments receivable		7,646		13,009
Less: Current unearned revenue		495		631
Less: Non-current unearned revenue		269		473
Net investment in sales-type leases	$	6,882	$	11,905

The components of sales-type lease gross profit recognized at the lease commencement date and interest and dividend income, included in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2019, are as follows:

(In thousands)	Classification	Three Months Ended June 30, 2019		Six Months Ended June 30, 2019
Sales type leases	Sales - Network Solutions	$	109	$	1,621
Sales type leases	Cost of sales - Network Solutions		44		635
Sales type leases	Gross profit	$	65	$	986

Sales type leases	Interest and dividend income	$	99	$	186

As of June 30, 2019, future minimum lease payments to be received from sales-type leases are as follows:

(In thousands)	Amount
Remainder of 2019	$	5,705
2020		1,112
2021		525
2022		220
2023		81
Thereafter		3
Total	$	7,646

Stockholders' Equity

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Stockholders' Equity

12. STOCKHOLDERS’ EQUITY

Stock Repurchase Program

Since 1997, our Board of Directors has approved multiple share repurchase programs that have authorized repurchases of our common stock, which are implemented through open market or private purchases from time to time as conditions warrant. During the six months ended June 30, 2019, we repurchased 13,000 shares of our common stock at an average price of $14.06 per share. As of June 30, 2019, we had the authority to purchase an additional 2.5 million shares of our common stock under the current authorization of up to 5.0 million shares.

Other Comprehensive Income

The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the three months ended June 30, 2019 and 2018:

	Three Months Ended June 30, 2019
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			ASU 2018-02 Adoption ⁽¹⁾		Total
As of March 31, 2019	$	(378	)	$	(7,920	)	$	(6,972	)	$	385	$	(14,885	)
Other comprehensive income before reclassifications		180			—			533			—		713
Amounts reclassified from accumulated other comprehensive income (loss)		(73	)		150			—			—		77
Net current period other comprehensive income		107			150			533			—		790
As of June 30, 2019	$	(271	)	$	(7,770	)	$	(6,439	)	$	385	$	(14,095	)

⁽¹⁾

^{With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 1.}

	Three Months Ended June 30, 2018
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			Total
As of March 31, 2018	$	(845	)	$	(4,224	)	$	(734	)	$	(5,803	)
Other comprehensive loss before reclassifications		(82	)		—			(3,424	)		(3,506	)
Amounts reclassified from accumulated other comprehensive income		186			5			—			191
Net current period other comprehensive income (loss)		104			5			(3,424	)		(3,315	)
As of June 30, 2018	$	(741	)	$	(4,219	)	$	(4,158	)	$	(9,118	)

The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the six months ended June 30, 2019 and 2018:

	Six Months Ended June 30, 2019
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			ASU 2018-02 Adoption		Total
As of December 31, 2018	$	(563	)	$	(8,041	)	$	(5,812	)	$	—	$	(14,416	)
Other comprehensive income (loss) before reclassifications		411			—			(627	)		—		(216	)
Amounts reclassified from accumulated other comprehensive income (loss)		(119	)		271			—			—		152
Amounts reclassified to retained earnings ⁽¹⁾		—			—			—			385		385
Net current period other comprehensive income (loss)		292			271			(627	)		385		321
As of June 30, 2019	$	(271	)	$	(7,770	)	$	(6,439	)	$	385	$	(14,095	)

⁽¹⁾

^{With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 1.}

	Six Months Ended June 30, 2018
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			Total
As of December 31, 2017	$	2,567		$	(4,286	)	$	(1,576	)	$	(3,295	)
Other comprehensive (loss) before reclassifications		(339	)		—			(2,582	)		(2,921	)
Amounts reclassified from accumulated other comprehensive income		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	)
As of June 30, 2018	$	(741	)	$	(4,219	)	$	(4,158	)	$	(9,118	)

⁽¹⁾

^{With the Company’s adoption of ASU 2016-01 on January 1, 2018, unrealized gains on our equity investments were reclassified to retained earnings. See Note 7.}

The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the three months ended June 30, 2019 and 2018:

	Three Months Ended June 30, 2019
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 gains on sales of securities	$	99		Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(217	)	⁽¹⁾
Total reclassifications for the period, before tax		(118	)
Tax benefit		41
Total reclassifications for the period, net of tax	$	(77	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

	Three Months Ended June 30, 2018
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	Amount Reclassified from Accumulated Other Comprehensive Income (Loss)			Affected Line Item in the Statement Where Net Income Is Presented
Unrealized gain (losses) on available-for-sale securities:
Net realized losses on sales of securities	$	(251	)	Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(7	)	⁽¹⁾
Total reclassifications for the period, before tax		(258	)
Tax benefit		67
Total reclassifications for the period, net of tax	$	(191	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the six months ended June 30, 2019 and 2018:

	Six Months Ended June 30, 2019
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 gains on sales of securities	$	161		Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(393	)	⁽¹⁾
Total reclassifications for the period, before tax		(232	)
Tax benefit		80
Total reclassifications for the period, net of tax	$	(152	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

	Six Months Ended June 30, 2018
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 losses on sales of securities	$	(324	)	Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(97	)	⁽¹⁾
Total reclassifications for the period, before tax		(421	)
Tax benefit		103
Total reclassifications for the period, net of tax	$	(318	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

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, 2019 and 2018:

	Three Months Ended									Three Months Ended
	June 30, 2019									June 30, 2018
(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	$	243		$	(63	)	$	180		$	(111	)	$	29		$	(82	)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss)		(99	)		26			(73	)		251			(65	)		186
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss)		217			(67	)		150			7			(2	)		5
Foreign currency translation adjustment		533			—			533			(3,424	)		—			(3,424	)
Total Other Comprehensive Income (Loss)	$	894		$	(104	)	$	790		$	(3,277	)	$	(38	)	$	(3,315	)

The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the six months ended June 30, 2019 and 2018:

	Six Months Ended									Six Months Ended
	June 30, 2019									June 30, 2018
(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	$	555		$	(144	)	$	411		$	(458	)	$	119		$	(339	)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss)		(161	)		42			(119	)		324			(73	)		251
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 defined benefit plan adjustments included in net income (loss)		393			(122	)		271			97			(30	)		67
Foreign currency translation adjustment		(627	)		—			(627	)		(2,582	)		—			(2,582	)
Total Other Comprehensive Income (Loss)	$	160		$	(224	)	$	(64	)	$	(5,839	)	$	16		$	(5,823	)

Earnings (Loss) Per Share

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Earnings (Loss) Per Share

13. EARNINGS (LOSS) PER SHARE

A summary of the calculation of basic and diluted earnings (loss) per share for the three and six months ended June 30, 2019 and 2018 is as follows:

	Three Months Ended					Six Months Ended
	June 30,					June 30,
(In thousands, except per share amounts)	2019		2018			2019		2018
Numerator
Net income (loss)	$	3,995	$	(7,670	)	$	4,765	$	(18,484	)
Denominator
Weighted average number of shares – basic		47,802		47,856			47,792		48,043
Effect of dilutive securities
Stock options		7		—			—		—
PSUs, RSUs and restricted stock		227		—			147		—
Weighted average number of shares – diluted		48,036		47,856			47,939		48,043
Earnings (loss) per share – basic	$	0.08	$	(0.16	)	$	0.10	$	(0.38	)
Earnings (loss) per share – diluted	$	0.08	$	(0.16	)	$	0.10	$	(0.38	)

For the three months ended June 30, 2019 and 2018, 1.9 million and 5.0 million, respectively, and for the six months ended June 30, 2019 and 2018, 2.3 million and 4.8 million, respectively, stock options were outstanding but were not included in the computation of diluted earnings (loss) per share because the stock options’ exercise prices were greater than the average market price of the common shares, during the applicable periods, therefore making them anti-dilutive under the treasury stock method. For the three months ended June 30, 2019 and 2018, 15,000 and 0.1 million, respectively, and for both the six months ended June 30, 2019 and 2018, 0.1 million PSUs, RSUs and restricted stock awards were not included in the computation of diluted earnings (loss) per share because the weighted average assumed proceeds per share were greater than the average market price of the common shares, during the applicable periods, therefore making them anti-dilutive under the treasury stock method.

Segment Information

6 Months Ended

Jun. 30, 2019

Segment Reporting [Abstract]

Segment Information

14. SEGMENT INFORMATION

We operate in two reportable segments: (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware products and software defined next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes our suite of ProCloud managed services, network installation, engineering and maintenance services and fee-based technical support and equipment repair/replacement plans.

We evaluate the performance of our segments based on gross profit; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment gain, other income (expense) and (provision) benefit for income taxes are reported on a company-wide, functional basis only. There is no inter-segment revenue.

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, 2019 and 2018. We do not produce asset information by reportable segment; therefore, it is not reported.

	Three Months Ended
	June 30, 2019				June 30, 2018
(In thousands)	Sales		Gross Profit		Sales		Gross Profit
Network Solutions	$	139,167	$	58,992	$	115,063	$	45,434
Services & Support		17,224		6,023		12,985		4,562
Total	$	156,391	$	65,015	$	128,048	$	49,996

	Six Months Ended
	June 30, 2019				June 30, 2018
(In thousands)	Sales		Gross Profit		Sales		Gross Profit
Network Solutions	$	264,989	$	114,080	$	220,316	$	82,075
Services & Support		35,193		11,547		28,538		7,654
Total	$	300,182	$	125,627	$	248,854	$	89,729

Sales by Category

In addition to our reporting segments, we also report revenue for the following three categories – Access & Aggregation, Subscriber Solutions & Experience (formerly Customer Devices) and Traditional & Other Products.

The table below presents sales information by category for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Access & Aggregation	$	109,421	$	84,742	$	209,199	$	166,422
Subscriber Solutions & Experience		40,502		34,560		77,255		64,661
Traditional & Other Products		6,468		8,746		13,728		17,771
Total	$	156,391	$	128,048	$	300,182	$	248,854

The following table represents sales information by geographic area for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
United States	$	75,288	$	68,222	$	147,816	$	130,308
International		81,103		59,826		152,366		118,546
Total	$	156,391	$	128,048	$	300,182	$	248,854

Liability for Warranty Returns

6 Months Ended

Jun. 30, 2019

Product Warranties Disclosures [Abstract]

Liability for Warranty Returns

15. LIABILITY FOR WARRANTY RETURNS

Our products generally include warranties of 90 days to five years for product defects. We accrue for warranty returns at the time revenue is recognized based on our estimate of the cost to repair or replace the defective products. We engage in extensive product quality programs and processes, including actively monitoring and evaluating the quality of our component suppliers. Our products continue to become more complex in both size and functionality as many of our product offerings migrate from line card applications to total systems. The increasing complexity of our products will cause warranty incidences, when they arise, to be more costly. Our estimates regarding future warranty obligations may change due to product failure rates, material usage and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. Alternatively, if we provide for more reserves than we require, we will reverse a portion of such provisions in future periods. The liability for warranty obligations totaled $9.0 million and $8.6 million at June 30, 2019 and December 31, 2018, respectively, which amounts are included in accrued expenses in the accompanying Condensed Consolidated Balance Sheets.

A reconciliation of the beginning and ending warranty accrual for the three and six months ended June 30, 2019 and 2018 is as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Warranty accrual at beginning of period	$	8,802		$	9,687		$	8,623		$	9,724
Plus: Amounts charged to expense		1,849			4,860			2,980			6,683
Less: Deductions		(1,679	)		(4,436	)		(2,631	)		(6,296	)
Warranty accrual at end of period	$	8,972		$	10,111		$	8,972		$	10,111

Commitments and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

16. 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 may 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, of which $7.7 million has been applied to these commitments as of June 30, 2019.

Restructuring

6 Months Ended

Jun. 30, 2019

Restructuring And Related Activities [Abstract]

Restructuring

17. RESTRUCTURING

In February 2019, we announced the restructuring of certain of our workforce predominantly in Germany, which included the closure of the office location in Munich, Germany accompanied by relocation or severance benefits for the affected employees. We also offered voluntary early retirement to certain other employees, which was announced to employees in March 2019. The restructuring is expected to be completed in the fourth quarter of 2019.

In January 2018, we announced an early retirement incentive program for employees that met certain requirements. The cumulative amount incurred during the year ended December 31, 2018 related to this restructuring program was $7.3 million, of which $1.0 million and $7.0 million was incurred during the three and six months ended June 30, 2018, respectively. We do not expect to incur any additional expenses related to this restructuring program.

A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits on the Condensed Consolidated Balance Sheet, is as follows:

	Three Months Ended			Six Months Ended
	June 30,			June 30,
(In thousands)	2019			2019
Balance at beginning of period	$	1,971		$	185
Plus: Amounts charged to cost and expense		1,400			3,463
Less: Amounts paid		(716	)		(993	)
Balance at end of period	$	2,655		$	2,655

The components of restructuring expense in the Condensed Consolidated Statements of Income are as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Selling, general and administrative expenses	$	703	$	634	$	1,547	$	2,400
Research and development expenses		647		—		1,231		1,814
Cost of sales		50		391		685		2,761
Total restructuring expenses	$	1,400	$	1,025	$	3,463	$	6,975

Subsequent Events

6 Months Ended

Jun. 30, 2019

Subsequent Events [Abstract]

Subsequent Events

18. SUBSEQUENT EVENTS

On July 17, 2019, 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, 2019. The dividend was paid on August 15, 2019 and totaled $4.3 million.

In September 2019, we entered into an operating lease for office space in India. This lease has an initial term of five years and includes an option to renew for an additional five-year period. As a result of this agreement, we will record a right-of-use asset and corresponding lease liability of approximately $10.2 million in our Condensed Consolidated Balance Sheet during the third quarter of 2019.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of ADTRAN^®, Inc. and its subsidiaries (“ADTRAN”, the “Company”, “we”, “our” or “us”) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles in the United States of America (“GAAP”) for complete financial statements are not included herein. The December 31, 2018 Condensed Consolidated Balance Sheet is derived from audited financial statements, but does not include all disclosures required by GAAP. 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 financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K/A for the year ended December 31, 2018, filed on September 20, 2019, with the SEC.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the excess, obsolete and slow moving inventory reserves, warranty reserves, customer rebates, determination of the deferred and accrued revenue components of multiple performance obligations sales agreements, estimated costs to complete obligations associated with deferred and accrued revenue, 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. During the three months ended June 30, 2019, the Company revised the methodology in how it estimates its excess and obsolete inventory reserves. Under the revised methodology, we establish reserves for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on historical usage, known trends, inventory age, and market conditions. When we dispose of excess and obsolete inventories, the related disposals are charged against the inventory reserve. See Note 8 of Notes to Condensed Consolidated Financial Statements for additional information.
Correction of Immaterial Misstatements	Correction of Immaterial Misstatements. During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserve and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in its excess and obsolete inventory reserve and cost of goods sold. In addition, the Company determined that a $1.0 million cash inflow related to an insurance recovery was incorrectly classified as a cash flow from operations instead of a cash flow from investing activities within the unaudited Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2019. The accompanying Unaudited Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2019 correctly reflects the $1.0 million insurance recovery as a cash inflow from investing activities. Management has determined that these misstatements were not material to any of its previously issued financial statements and that correction of the misstatements is also not material to the current or estimated annual 2019 financial results on both a quantitative and qualitative basis.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 requires the measurement and recognition of expected credit losses for financial instruments held at amortized cost. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326 Financial Instruments – Credit Losses, that clarifies receivables arising from operating leases are not within the scope of the credit losses standard, but rather should be accounted for in accordance with the leases standard. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments–Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, which clarifies the accounting for transfers between classifications of debt securities and clarifies that entities should include expected recoveries on financial assets in the calculation of the current expected credit loss allowance. In addition, renewal options that are not unconditionally cancelable should be considered in the determination of expected credit losses. In May 2019, the FASB issued ASU 2019-05, Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief, which amends ASU 2016-13 to allow companies, upon adoption, to elect the fair value option on financial instruments that were previously recorded at amortized cost if they meet certain criteria. All of these ASUs are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the effect these ASUs will have on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the measurement of goodwill by eliminating step 2 of the goodwill impairment test. Under ASU 2017-04, entities will be required to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. ASU 2017-04 is effective for annual or interim impairment tests performed in fiscal years beginning after December 15, 2019, with early adoption permitted for annual or interim impairment tests performed on testing dates after January 1, 2017. The amendments should be applied prospectively. We are currently evaluating whether to early adopt ASU 2017-04, but do not expect it will have a material effect on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, which changes the fair value measurement disclosure requirements of Accounting Standards Codification (“ASC”) 820, Fair Value Measurement. The amendments in this ASU are the result of a broader disclosure project, Concepts Statement No. 8 — Conceptual Framework for Financial Reporting — Chapter 8 — Notes to Financial Statements, which the FASB finalized on August 28, 2018. The FASB used the guidance in the Concepts Statement to improve the effectiveness of ASC 820’s disclosure requirements. ASU 2018-13 provides users of financial statements with information about assets and liabilities measured at fair value in the statement of financial position or disclosed in the notes to the financial statements. More specifically, ASU 2018-13 requires disclosures about the valuation techniques and inputs that are used to arrive at measures of fair value, including judgments and assumptions that are made in determining fair value. In addition, ASU 2018-13 requires disclosures regarding the uncertainty in the fair value measurements as of the reporting date and how changes in fair value measurements affect performance and cash flows. ASU 2018-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. We are currently evaluating the effect of ASU 2018-13, but do not expect it will have a material effect on our financial statement disclosures. In August 2018, the FASB issued ASU 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans, which makes changes to and clarifies the disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 requires additional disclosures related to the reasons for significant gains and losses affecting the benefit obligation and an explanation of any other significant changes in the benefit obligation or plan assets that are not otherwise apparent in other disclosures required by ASC 715. ASU 2018-14 also clarifies the guidance in ASC 715 to require disclosure of the projected benefit obligation (PBO) and fair value of plan assets for pension plans with PBOs in excess of plan assets and the accumulated benefit obligation (ABO) and fair value of plan assets for pension plans with ABOs in excess of plan assets. ASU 2018-14 is effective for public business entities for fiscal years ending after December 15, 2020. We are currently evaluating the effect of ASU 2018-14, but do not expect it will have a material effect on our financial statement disclosures. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementations costs incurred to develop or obtain internal use software. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We are currently evaluating the effect of ASU 2018-15, but do not expect it will have a material effect on our consolidated financial statements.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements During 2019, we adopted the following accounting standards, which had the following impacts on our consolidated financial statements: In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires an entity to recognize right-of-use assets and lease liabilities on the balance sheet and to disclose key information about the entity’s leasing arrangements. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases, which clarified certain aspects of ASU 2016-02, as well as ASU 2018-11, Leases (Topic 842), Targeted Improvements, which provided for an optional transition method allowing for the application of the legacy lease guidance, Leases (Topic 840), including its disclosure requirements, for the comparative periods presented in the year of adoption, with the cumulative effect of initially applying the new lease standard recognized as an adjustment to retained earnings as of the date of adoption. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842) Codification Improvements, which removed the requirement for an entity to disclose in the interim periods after adoption, the effect of the change on income from continuing operations, net income, any other affected financial statement line item, and any affected per share amount. For lessors, the new leasing standard requires leases to be classified as sales-type, direct financing or operating leases. These criteria focus on the transfer of control of the underlying lease asset. This standard and related updates were effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The Company adopted the new standard on January 1, 2019, the effective date of our initial application, using the optional transition method. The Company has elected to carry forward the legacy ASC 840 disclosures for comparative periods and, therefore, did not adjust the comparative period financial information prior to January 1, 2019. In addition, the Company elected the package of practical expedients which allows for companies to not reassess whether any expired or existing contracts are or contain leases, not reassess historical lease classifications for expired or existing contracts and not reassess initial direct costs for existing leases. Additionally, the Company elected the practical expedients which allow the use of hindsight when determining the lease term, the short-term lease recognition exemption and the option to not separate lease and non-lease components. The adoption of this standard resulted in the recognition of a right-of-use asset and corresponding right-of-use liability on our Condensed Consolidated Balance Sheet of $10.3 million, primarily related to our operating leases for office space, automobiles and other equipment. As a lessee, the adoption of this standard did not have a material impact on our Condensed Consolidated Statement of Income or Statement of Cash Flow. See Note 11 for additional information. As a lessor, the adoption of this standard did not have a material impact on the Company’s Condensed Consolidated Balance Sheet, Condensed Consolidated Statement of Income or Condensed Statement of Cash Flow. Prior to and after adoption, all of our leases in which we are the lessor were classified as sales-types leases. In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities, which shortened the amortization period for the premium on certain purchased callable debt securities to the earliest call date. ASU 2017-08 was effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2018. The amendments were required to be applied through a modified-retrospective transition approach that required a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company adopted ASU 2017-08 on January 1, 2019, and the adoption of this standard did not have a material effect on our consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 expanded and refined hedge accounting for both financial and non-financial risk components, aligned the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and included certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting, which permits the OIS rate based on SOFR as a U.S. benchmark interest rate. Both ASU 2017-12 and ASU 2018-16 were effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted ASU 2017-12 on January 1, 2019, and the adoption of this standard did not have a material effect on our consolidated financial statements as we currently do not have any hedging instruments. 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. ASU 2018-02 allowed for an optional reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. ASU 2018-02 was effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted ASU 2018-02 on January 1, 2019, and upon adoption reclassified $0.4 million of stranded tax effects created by rate changes related to the Tax Cuts and Jobs Act of 2017 to retained earnings. See Note 12 for additional information.

Business Combinations (Tables)

6 Months Ended

Jun. 30, 2019

Business Combinations [Abstract]

Final Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed

The final allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date for SmartRG are as follows:

(In thousands)
Assets
Tangible assets acquired	$	8,594
Intangible assets		9,960
Goodwill		3,476
Total assets acquired		22,030
Liabilities
Liabilities assumed		(6,001	)
Total liabilities assumed		(6,001	)
Total purchase price	$	16,029

Details of the Acquired Intangible Assets

The details of the acquired intangible assets from the SmartRG acquisition are as follows:

(In thousands)	Value		Life (in years)
Developed technology	$	7,400	7
Customer relationships		1,790	3
Licensing agreements		560	5 – 10
Trade name		210	3
Total	$	9,960

Summary of Unaudited Supplemental Pro Forma Information

The following unaudited supplemental pro forma information presents the financial results of the Company, for the six months ended June 30, 2018, as if the acquisition of the Sumitomo EPON business 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. There were no material, non-recurring adjustments to this unaudited pro forma information.

	Six Months Ended
(In thousands)	June 30, 2018
Pro forma revenue	$	250,114
Pro forma net loss	$	(31,020	)

Revenue (Tables)

6 Months Ended

Jun. 30, 2019

Revenue From Contract With Customer [Abstract]

Disaggregate of Revenue by Reportable Segment and Revenue Category

The following table disaggregates our revenue by reportable segment and revenue category for the three months ended June 30, 2019 and 2018:

	For the Three Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	96,262	$	13,159	$	109,421	$	75,222	$	9,520	$	84,742
Subscriber Solutions & Experience⁽¹⁾		38,444		2,058		40,502		33,306		1,254		34,560
Traditional & Other Products		4,461		2,007		6,468		6,535		2,211		8,746
Total	$	139,167	$	17,224	$	156,391	$	115,063	$	12,985	$	128,048

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

The following table disaggregates our revenue by reportable segment and revenue category for the six months ended June 30, 2019 and 2018:

	For the Six Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	181,935	$	27,264	$	209,199	$	144,607	$	21,815	$	166,422
Subscriber Solutions & Experience⁽¹⁾		73,163		4,092		77,255		62,083		2,578		64,661
Traditional & Other Products		9,891		3,837		13,728		13,626		4,145		17,771
Total	$	264,989	$	35,193	$	300,182	$	220,316	$	28,538	$	248,854

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

The table below presents sales information by category for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Access & Aggregation	$	109,421	$	84,742	$	209,199	$	166,422
Subscriber Solutions & Experience		40,502		34,560		77,255		64,661
Traditional & Other Products		6,468		8,746		13,728		17,771
Total	$	156,391	$	128,048	$	300,182	$	248,854

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, 2019		December 31, 2018
Accounts receivable, net	$	116,661	$	99,385
Contract assets⁽¹⁾	$	2,251	$	3,766
Unearned revenue	$	12,910	$	17,940
Non-current unearned revenue	$	4,265	$	5,296

⁽¹⁾

^{Included in other receivables on the Condensed Consolidated Balance Sheet.}

Pension Benefit Plan (Tables)

6 Months Ended

Jun. 30, 2019

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, 2019 and 2018:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Service cost	$	368		$	303		$	743		$	611
Interest cost		159			185			321			372
Expected return on plan assets		(348	)		(394	)		(703	)		(793	)
Amortization of actuarial losses		199			63			402			127
Net periodic pension cost	$	378		$	157		$	763		$	317

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

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 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, 2019 and 2018:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Stock-based compensation expense included in cost of sales	$	85		$	102		$	189		$	197
Selling, general and administrative expense		662			995			1,725			2,030
Research and development expense		707			687			1,399			1,376
Stock-based compensation expense included in operating expenses		1,369			1,682			3,124			3,406
Total stock-based compensation expense		1,454			1,784			3,313			3,603
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock		(332	)		(340	)		(775	)		(724	)
Total stock-based compensation expense, net of tax	$	1,122		$	1,444		$	2,538		$	2,879

Summary of Stock Options Outstanding

The following table is a summary of our stock options outstanding as of December 31, 2018 and June 30, 2019, and the changes that occurred during the six months ended June 30, 2019:

	Number of Stock Options (in thousands)			Weighted Avg. Exercise Price (per share)		Weighted Avg. Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Stock options outstanding, December 31, 2018		4,382		$	22.91		4.10	$	—
Stock options exercised		(34	)	$	15.53
Stock options forfeited		(10	)	$	15.67
Stock options expired		(156	)	$	24.50
Stock options outstanding, June 30, 2019		4,182		$	22.93		3.64	$	—
Stock options exercisable, June 30, 2019		3,942		$	23.39		3.47	$	—

Summary of PSUs, RSUs and Restricted Stock Outstanding

The following table is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2018 and June 30, 2019 and the changes that occurred during the six months ended June 30, 2019:

	Number of Shares (in thousands)			Weighted Avg. Grant Date Fair Value (per share)
Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2018		1,570		$	18.52
PSUs, RSUs and restricted stock granted		59		$	12.54
PSUs, RSUs and restricted stock vested		(1	)	$	18.86
PSUs, RSUs and restricted stock forfeited		(63	)	$	16.66
Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2019		1,565		$	18.37

Investments (Tables)

6 Months Ended

Jun. 30, 2019

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, 2019, 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	$	14,132	$	111	$	(4	)	$	14,239
Municipal fixed-rate bonds		930		—		(3	)		927
Asset-backed bonds		6,580		32		(3	)		6,609
Mortgage/Agency-backed bonds		5,362		23		(6	)		5,379
U.S. government bonds		5,027		6		(6	)		5,027
Foreign government bonds		1,852		1		(1	)		1,852
Available-for-sale debt securities held at fair value	$	33,883	$	173	$	(23	)	$	34,033
Restricted investment held at cost									25,600
Other investments held at cost									1,199
Total carrying value of available-for-sale investments								$	60,832

At December 31, 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	$	20,777	$	19	$	(112	)	$	20,684
Municipal fixed-rate bonds		1,339		—		(26	)		1,313
Asset-backed bonds		5,230		5		(14	)		5,221
Mortgage/Agency-backed bonds		3,833		2		(44	)		3,791
U.S. government bonds		9,271		1		(66	)		9,206
Foreign government bonds		592		—		(8	)		584
Available-for-sale debt securities held at fair value	$	41,042	$	27	$	(270	)	$	40,799
Restricted investment held at cost									25,600
Other investments held at cost									397
Total carrying value of available-for-sale investments								$	66,796

Contractual Maturities of Debt Securities

As of June 30, 2019, our debt securities had the following contractual maturities:

(In thousands)	Corporate bonds		Municipal fixed-rate bonds		Asset- backed bonds		Mortgage / Agency- backed bonds		U.S. government bonds		Foreign government bonds
Less than one year	$	2,749	$	—	$	96	$	—	$	2,443	$	—
One to two years		8,460		927		430		264		—		891
Two to three years		3,030		—		1,667		588		1,346		961
Three to five years		—		—		2,018		510		1,238		—
Five to ten years		—		—		1,772		425		—		—
More than ten years		—		—		626		3,592		—		—
Total	$	14,239	$	927	$	6,609	$	5,379	$	5,027	$	1,852

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)	2019			2018			2019			2018
Gross realized gains on debt securities	$	8		$	25		$	49		$	25
Gross realized losses on debt securities		(14	)		(241	)		(33	)		(315	)
Total gain (loss) recognized, net	$	(6	)	$	(216	)	$	16		$	(290	)

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, 2019 and 2018 were as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Realized gains (losses) on equity securities sold	$	(49	)	$	(52	)	$	(63	)	$	347
Unrealized gains on equity securities held		2,540			1,258			8,458			836
Total gain recognized, net	$	2,491		$	1,206		$	8,395		$	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, 2019 Using
(In thousands)	Cost or Fair Value		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	1,337	$	1,337	$	—	$	—
Commercial paper		2,973		—		2,973		—
Cash equivalents		4,310		1,337		2,973		—
Available-for-sale debt securities
Corporate bonds		14,239		—		14,239		—
Municipal fixed-rate bonds		927		—		927		—
Asset-backed bonds		6,609		—		6,609		—
Mortgage/Agency-backed bonds		5,379		—		5,379		—
U.S. government bonds		5,027		5,027		—		—
Foreign government bonds		1,852		—		1,852		—
Marketable equity securities
Marketable equity securities – various industries		32,548		32,548		—		—
Equity in escrow		185		185		—		—
Deferred compensation plan assets		21,228		21,228		—		—
Total debt and equity securities at fair value		87,994		58,988		29,006		—
Other investments held at cost
Other investments		3,375		—		—		—
Total other investments held at cost		3,375		—		—		—
Total	$	95,679	$	60,325	$	31,979	$	—

			Fair Value Measurements at December 31, 2018 Using
(In thousands)	Cost or Fair Value		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents
Money market funds	$	1,554	$	1,554	$	—	$	—
Cash equivalents		1,554		1,554		—		—
Available-for-sale debt securities
Corporate bonds		20,684		—		20,684		—
Municipal fixed-rate bonds		1,313		—		1,313		—
Asset-backed bonds		5,221		—		5,221		—
Mortgage/Agency-backed bonds		3,791		—		3,791		—
U.S. government bonds		9,206		9,206		—		—
Foreign government bonds		584		—		584		—
Marketable equity securities
Marketable equity securities – various industries		26,763		26,763		—		—
Equity in escrow		253		253		—		—
Deferred compensation plan assets		18,256		18,256		—		—
Total debt and equity securities at fair value		86,071		54,478		31,593		—
Total	$	87,625	$	56,032	$	31,593	$	—

Inventory (Tables)

6 Months Ended

Jun. 30, 2019

Inventory Disclosure [Abstract]

Components of Inventory

At June 30, 2019 and December 31, 2018, inventory consisted of the following:

	June 30,		December 31,
(In thousands)	2019		2018
Raw materials	$	38,844	$	45,333
Work in process		1,383		1,638
Finished goods		54,883		52,877
Total	$	95,110	$	99,848

Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2019

Intangible Assets Net Excluding Goodwill [Abstract]

Summary of Intangible Assets

The following table presents our intangible assets as of June 30, 2019 and December 31, 2018:

	June 30, 2019							December 31, 2018
(In thousands)	Gross Value		Accumulated Amortization			Net Value		Gross Value		Accumulated Amortization			Net Value
Customer relationships	$	22,414	$	(6,311	)	$	16,103	$	22,455	$	(5,380	)	$	17,075
Developed technology		10,170		(2,810	)		7,360		12,801		(4,867	)		7,934
Licensed technology		5,900		(847	)		5,053		5,900		(520	)		5,380
Supplier relationships		2,800		(1,808	)		992		2,800		(1,108	)		1,692
Licensing agreements		560		(43	)		517		560		(5	)		555
Patents		500		(191	)		309		500		(157	)		343
Trade names		310		(141	)		169		310		(106	)		204
Total	$	42,654	$	(12,151	)	$	30,503	$	45,326	$	(12,143	)	$	33,183

Estimated Future Amortization Expense Related to Intangible Assets

As of June 30, 2019, the estimated future amortization expense of our intangible assets was as follows:

(In thousands)	Amount
Remainder of 2019	$	2,665
2020		4,448
2021		4,099
2022		3,475
2023		3,322
Thereafter		12,494
Total	$	30,503

Leases (Tables)

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Schedule of Supplemental Balance Sheet Information Related to Operating Leases

Supplemental balance sheet information related to operating leases is as follows:

		June 30,		January 1,
(In thousands)	Classification	2019		2019 ⁽¹⁾
Assets
Operating lease asset	Other assets	$	8,838	$	10,322
Total lease assets		$	8,838	$	10,322

Liabilities
Current operating lease liability	Accrued expenses	$	2,514	$	2,948
Non-current operating lease liability	Other non-current liabilities		6,349		7,374
Total lease liability		$	8,863	$	10,322

⁽¹⁾

^{Reflects the adoption of the new lease accounting standard on January 1, 2019.}

Components of Lease Expense included in Condensed Consolidated Statement of Income

The components of lease expense included in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2019 are as follows:

(In thousands)	Three Months Ended June 30, 2019		Six Months Ended June 30, 2019
Selling, general and administrative expenses	$	349	$	698
Research and development expenses		430		884
Cost of sales		17		33
Total operating lease expense	$	796	$	1,615

Schedule of Maturity of Operating Lease Liabilities

As of June 30, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheet by future maturity are as follows:

(In thousands)	Amount
Remainder of 2019	$	1,583
2020		2,203
2021		2,047
2022		1,560
2023		1,173
Thereafter		756
Total lease payments		9,322
Less: Interest		(459	)
Present value of lease liabilities	$	8,863

Future Minimum Rental Payments under Non-Cancelable Operating Leases, Including Renewals Determined to be Reasonably Assured, with Original Maturities of Greater than 12 Months

As of December 31, 2018, future minimum rental payments under non-cancelable operating leases, including renewals determined to be reasonably assured as of December 31, 2018, with original maturities of greater than 12 months, are as follows:

(In thousands)	Amount ⁽¹⁾
2019	$	3,873
2020		3,580
2021		2,771
2022		2,053
2023		1,317
Thereafter		762
Total	$	14,356

⁽¹⁾

^{Certain renewal options were subsequently determined to not be reasonably assured of renewal upon the Company’s adoption of the new lease accounting standard on January 1, 2019.}

Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate

Our leases do not provide an implicit borrowing rate and therefore we use an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We used the incremental borrowing rate on January 1, 2019, for operating leases that commenced on or prior to that date. The incremental borrowing rate was determined on a portfolio basis by grouping leases with similar terms as well as grouping leases based on a U.S. dollar or Euro functional currency. The actual rate is then determined based on a credit spread over LIBOR as well as the Bloomberg Curve Matrix for the U.S. Communications section.

	As of June 30, 2019
Weighted average remaining lease term (years)
Operating leases with USD functional currency		2.9
Operating leases with Euro functional currency		4.8
Weighted average discount rate
Operating leases with USD functional currency		4.61	%
Operating leases with Euro functional currency		1.85	%

Schedule of Supplemental Cash Flow Information Related to Operating Leases

Supplemental cash flow information related to operating leases was as follows:

(In thousands)	As of June 30, 2019
Cash paid for amounts included in the measurement of operating lease liabilities / assets
Cash used in operating activities related to operating leases	$	(797	)

Right-of-use assets obtained in exchange for lease obligations	$	10,396

Components of Net Investment in Sales-Type Leases

As of June 30, 2019 and December 31, 2018, the components of the net investment in sales-type leases were as follows:

	June 30,		December 31,
(In thousands)	2019		2018
Current minimum lease payments receivable (included in other receivables)	$	6,360	$	11,339
Non-current minimum lease payments receivable (included in other assets)		1,286		1,670
Total minimum lease payments receivable		7,646		13,009
Less: Current unearned revenue		495		631
Less: Non-current unearned revenue		269		473
Net investment in sales-type leases	$	6,882	$	11,905

Schedule of Components of Sales-type Lease Gross Profit and Interest and Dividend Income Included in Condensed Consolidated Statements of Income

The components of sales-type lease gross profit recognized at the lease commencement date and interest and dividend income, included in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2019, are as follows:

(In thousands)	Classification	Three Months Ended June 30, 2019		Six Months Ended June 30, 2019
Sales type leases	Sales - Network Solutions	$	109	$	1,621
Sales type leases	Cost of sales - Network Solutions		44		635
Sales type leases	Gross profit	$	65	$	986

Sales type leases	Interest and dividend income	$	99	$	186

Schedule of Future Minimum Lease Payments to be Received from Sales-Type Leases

As of June 30, 2019, future minimum lease payments to be received from sales-type leases are as follows:

(In thousands)	Amount
Remainder of 2019	$	5,705
2020		1,112
2021		525
2022		220
2023		81
Thereafter		3
Total	$	7,646

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

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, 2019 and 2018:

	Three Months Ended June 30, 2019
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			ASU 2018-02 Adoption ⁽¹⁾		Total
As of March 31, 2019	$	(378	)	$	(7,920	)	$	(6,972	)	$	385	$	(14,885	)
Other comprehensive income before reclassifications		180			—			533			—		713
Amounts reclassified from accumulated other comprehensive income (loss)		(73	)		150			—			—		77
Net current period other comprehensive income		107			150			533			—		790
As of June 30, 2019	$	(271	)	$	(7,770	)	$	(6,439	)	$	385	$	(14,095	)

⁽¹⁾

^{With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 1.}

	Three Months Ended June 30, 2018
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			Total
As of March 31, 2018	$	(845	)	$	(4,224	)	$	(734	)	$	(5,803	)
Other comprehensive loss before reclassifications		(82	)		—			(3,424	)		(3,506	)
Amounts reclassified from accumulated other comprehensive income		186			5			—			191
Net current period other comprehensive income (loss)		104			5			(3,424	)		(3,315	)
As of June 30, 2018	$	(741	)	$	(4,219	)	$	(4,158	)	$	(9,118	)

The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the six months ended June 30, 2019 and 2018:

	Six Months Ended June 30, 2019
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			ASU 2018-02 Adoption		Total
As of December 31, 2018	$	(563	)	$	(8,041	)	$	(5,812	)	$	—	$	(14,416	)
Other comprehensive income (loss) before reclassifications		411			—			(627	)		—		(216	)
Amounts reclassified from accumulated other comprehensive income (loss)		(119	)		271			—			—		152
Amounts reclassified to retained earnings ⁽¹⁾		—			—			—			385		385
Net current period other comprehensive income (loss)		292			271			(627	)		385		321
As of June 30, 2019	$	(271	)	$	(7,770	)	$	(6,439	)	$	385	$	(14,095	)

⁽¹⁾

^{With the adoption of ASU 2018-02 on January 1, 2019, stranded tax effects related to the Tax Cuts and Jobs Act of 2017 were reclassified to retained earnings. See Note 1.}

	Six Months Ended June 30, 2018
(In thousands)	Unrealized Gains (Losses) on Available- for-Sale Securities			Defined Benefit Plan Adjustments			Foreign Currency Adjustments			Total
As of December 31, 2017	$	2,567		$	(4,286	)	$	(1,576	)	$	(3,295	)
Other comprehensive (loss) before reclassifications		(339	)		—			(2,582	)		(2,921	)
Amounts reclassified from accumulated other comprehensive income		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	)
As of June 30, 2018	$	(741	)	$	(4,219	)	$	(4,158	)	$	(9,118	)

⁽¹⁾

^{With the Company’s adoption of ASU 2016-01 on January 1, 2018, unrealized gains on our equity investments were reclassified to retained earnings. See Note 7.}

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, 2019 and 2018:

	Three Months Ended June 30, 2019
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 gains on sales of securities	$	99		Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(217	)	⁽¹⁾
Total reclassifications for the period, before tax		(118	)
Tax benefit		41
Total reclassifications for the period, net of tax	$	(77	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

	Three Months Ended June 30, 2018
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	Amount Reclassified from Accumulated Other Comprehensive Income (Loss)			Affected Line Item in the Statement Where Net Income Is Presented
Unrealized gain (losses) on available-for-sale securities:
Net realized losses on sales of securities	$	(251	)	Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(7	)	⁽¹⁾
Total reclassifications for the period, before tax		(258	)
Tax benefit		67
Total reclassifications for the period, net of tax	$	(191	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the six months ended June 30, 2019 and 2018:

	Six Months Ended June 30, 2019
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 gains on sales of securities	$	161		Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(393	)	⁽¹⁾
Total reclassifications for the period, before tax		(232	)
Tax benefit		80
Total reclassifications for the period, net of tax	$	(152	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

	Six Months Ended June 30, 2018
Details about Accumulated Other Comprehensive Income (Loss) Components (In thousands)	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 losses on sales of securities	$	(324	)	Net investment gain (loss)
Defined benefit plan adjustments – actuarial losses		(97	)	⁽¹⁾
Total reclassifications for the period, before tax		(421	)
Tax benefit		103
Total reclassifications for the period, net of tax	$	(318	)

⁽¹⁾

^{Included in the computation of net periodic pension cost. See Note 5.}

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, 2019 and 2018:

	Three Months Ended									Three Months Ended
	June 30, 2019									June 30, 2018
(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	$	243		$	(63	)	$	180		$	(111	)	$	29		$	(82	)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss)		(99	)		26			(73	)		251			(65	)		186
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss)		217			(67	)		150			7			(2	)		5
Foreign currency translation adjustment		533			—			533			(3,424	)		—			(3,424	)
Total Other Comprehensive Income (Loss)	$	894		$	(104	)	$	790		$	(3,277	)	$	(38	)	$	(3,315	)

The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the six months ended June 30, 2019 and 2018:

	Six Months Ended									Six Months Ended
	June 30, 2019									June 30, 2018
(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	$	555		$	(144	)	$	411		$	(458	)	$	119		$	(339	)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss)		(161	)		42			(119	)		324			(73	)		251
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 defined benefit plan adjustments included in net income (loss)		393			(122	)		271			97			(30	)		67
Foreign currency translation adjustment		(627	)		—			(627	)		(2,582	)		—			(2,582	)
Total Other Comprehensive Income (Loss)	$	160		$	(224	)	$	(64	)	$	(5,839	)	$	16		$	(5,823	)

Earnings (Loss) Per Share (Tables)

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share

A summary of the calculation of basic and diluted earnings (loss) per share for the three and six months ended June 30, 2019 and 2018 is as follows:

	Three Months Ended					Six Months Ended
	June 30,					June 30,
(In thousands, except per share amounts)	2019		2018			2019		2018
Numerator
Net income (loss)	$	3,995	$	(7,670	)	$	4,765	$	(18,484	)
Denominator
Weighted average number of shares – basic		47,802		47,856			47,792		48,043
Effect of dilutive securities
Stock options		7		—			—		—
PSUs, RSUs and restricted stock		227		—			147		—
Weighted average number of shares – diluted		48,036		47,856			47,939		48,043
Earnings (loss) per share – basic	$	0.08	$	(0.16	)	$	0.10	$	(0.38	)
Earnings (loss) per share – diluted	$	0.08	$	(0.16	)	$	0.10	$	(0.38	)

Segment Information (Tables)

6 Months Ended

Jun. 30, 2019

Segment Reporting [Abstract]

Sales and Gross Profit of Reportable Segments

The following table presents information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2019 and 2018. We do not produce asset information by reportable segment; therefore, it is not reported.

	Three Months Ended
	June 30, 2019				June 30, 2018
(In thousands)	Sales		Gross Profit		Sales		Gross Profit
Network Solutions	$	139,167	$	58,992	$	115,063	$	45,434
Services & Support		17,224		6,023		12,985		4,562
Total	$	156,391	$	65,015	$	128,048	$	49,996

	Six Months Ended
	June 30, 2019				June 30, 2018
(In thousands)	Sales		Gross Profit		Sales		Gross Profit
Network Solutions	$	264,989	$	114,080	$	220,316	$	82,075
Services & Support		35,193		11,547		28,538		7,654
Total	$	300,182	$	125,627	$	248,854	$	89,729

Disaggregate of Revenue by Reportable Segment and Revenue Category

The following table disaggregates our revenue by reportable segment and revenue category for the three months ended June 30, 2019 and 2018:

	For the Three Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	96,262	$	13,159	$	109,421	$	75,222	$	9,520	$	84,742
Subscriber Solutions & Experience⁽¹⁾		38,444		2,058		40,502		33,306		1,254		34,560
Traditional & Other Products		4,461		2,007		6,468		6,535		2,211		8,746
Total	$	139,167	$	17,224	$	156,391	$	115,063	$	12,985	$	128,048

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

The following table disaggregates our revenue by reportable segment and revenue category for the six months ended June 30, 2019 and 2018:

	For the Six Months Ended
	June 30, 2019						June 30, 2018
(In thousands)	Network Solutions		Services & Support		Total		Network Solutions		Services & Support		Total
Access & Aggregation	$	181,935	$	27,264	$	209,199	$	144,607	$	21,815	$	166,422
Subscriber Solutions & Experience⁽¹⁾		73,163		4,092		77,255		62,083		2,578		64,661
Traditional & Other Products		9,891		3,837		13,728		13,626		4,145		17,771
Total	$	264,989	$	35,193	$	300,182	$	220,316	$	28,538	$	248,854

⁽¹⁾

^{Subscriber Solutions & Experience was formerly reported as Customer Devices. With the increasing focus on enhancing the customer experience for both our business and consumer broadband customers and the addition of SmartRG during the fourth quarter of 2018, Subscriber Solutions & Experience more accurately represents this revenue category.}

The table below presents sales information by category for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Access & Aggregation	$	109,421	$	84,742	$	209,199	$	166,422
Subscriber Solutions & Experience		40,502		34,560		77,255		64,661
Traditional & Other Products		6,468		8,746		13,728		17,771
Total	$	156,391	$	128,048	$	300,182	$	248,854

Sales Information by Geographic Area

The following table represents sales information by geographic area for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
United States	$	75,288	$	68,222	$	147,816	$	130,308
International		81,103		59,826		152,366		118,546
Total	$	156,391	$	128,048	$	300,182	$	248,854

Liability for Warranty Returns (Tables)

6 Months Ended

Jun. 30, 2019

Product Warranties Disclosures [Abstract]

Reconciliation of Beginning and Ending Warranty Accrual

A reconciliation of the beginning and ending warranty accrual for the three and six months ended June 30, 2019 and 2018 is as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In thousands)	2019			2018			2019			2018
Warranty accrual at beginning of period	$	8,802		$	9,687		$	8,623		$	9,724
Plus: Amounts charged to expense		1,849			4,860			2,980			6,683
Less: Deductions		(1,679	)		(4,436	)		(2,631	)		(6,296	)
Warranty accrual at end of period	$	8,972		$	10,111		$	8,972		$	10,111

Restructuring (Tables)

6 Months Ended

Jun. 30, 2019

Restructuring And Related Activities [Abstract]

Schedule of Reconciliation of Restructuring Liability

A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits on the Condensed Consolidated Balance Sheet, is as follows:

	Three Months Ended			Six Months Ended
	June 30,			June 30,
(In thousands)	2019			2019
Balance at beginning of period	$	1,971		$	185
Plus: Amounts charged to cost and expense		1,400			3,463
Less: Amounts paid		(716	)		(993	)
Balance at end of period	$	2,655		$	2,655

Schedule of Components of Restructuring Expense in Condensed Consolidated Statements of Income

The components of restructuring expense in the Condensed Consolidated Statements of Income are as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Selling, general and administrative expenses	$	703	$	634	$	1,547	$	2,400
Research and development expenses		647		—		1,231		1,814
Cost of sales		50		391		685		2,761
Total restructuring expenses	$	1,400	$	1,025	$	3,463	$	6,975

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019
Summary Of Significant Accounting Policy [Line Items]
Life insurance proceeds received				$ 1,000
Operating lease, right-of-use asset	$ 10,322	$ 8,838		8,838
Operating lease, right-of-use liability	10,322	8,863		8,863
ASU 2018-02 [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassification of tax effects related to adoption ASU	$ 400
Errors in Operating Activity [Member]
Summary Of Significant Accounting Policy [Line Items]
Amount of revision			$ 1,000
Out-of-Period Adjustment [Member]
Summary Of Significant Accounting Policy [Line Items]
Increase (decrease) in cost of goods sold		800		(200)
Increase (decrease) in excess and obsolete inventory reserve		$ 800		$ (200)

Business Combinations - Additional Information (Detail) - USD ($)		3 Months Ended			6 Months Ended		12 Months Ended
	Nov. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Gain on contingency		$ 1,230,000			$ 1,230,000
Goodwill					$ 7,000,000.0		$ 7,100,000
Bargain purchase gain net of income taxes						$ 11,322,000
SmartRG Inc [Member]
Business Acquisition [Line Items]
Date of acquisition					Nov. 30, 2018
Business acquisition, description					On November 30, 2018, we acquired SmartRG, Inc., a provider of carrier-class, open connected home platforms and cloud services for broadband service providers in exchange for cash consideration. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. The revenue from the SmartRG portfolio is included in the Subscriber Solutions & Experience category within the Network Solutions and Services & Support reportable segments.
Business combination, contingent consideration, liability	$ 1,200,000
Gain on contingency		1,200,000
Business combination escrow amount	2,800,000
Goodwill					$ 3,500,000
Acquisition and integration related expenses and amortization of acquired intangibles		$ 600,000	$ 0		$ 1,200,000	$ 0
SmartRG Inc [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Business combination potential release of funds	0
SmartRG Inc [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Business combination potential release of funds	$ 2,800,000
Sumitomo [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).
Bargain purchase gain net of income taxes				$ 11,300,000

Business Combinations - Final Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Nov. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Assets
Goodwill		$ 6,968	$ 7,106
SmartRG Inc [Member]
Assets
Tangible assets acquired	$ 8,594
Intangible assets	9,960
Goodwill	3,476
Total assets acquired	22,030
Liabilities
Liabilities assumed	(6,001)
Total liabilities assumed	(6,001)
Total purchase price	$ 16,029

Business Combinations - Details of the Acquired Intangible Assets (Detail) - SmartRG Inc [Member] $ in Thousands	Nov. 30, 2018 USD ($)
Business Acquisition [Line Items]
Total, Value	$ 9,960
Developed Technology [Member]
Business Acquisition [Line Items]
Total, Value	$ 7,400
Life (in years)	7 years
Customer Relationships [Member]
Business Acquisition [Line Items]
Total, Value	$ 1,790
Life (in years)	3 years
Licensing Agreements [Member]
Business Acquisition [Line Items]
Total, Value	$ 560
Trade Name [Member]
Business Acquisition [Line Items]
Total, Value	$ 210
Life (in years)	3 years
Licensing Agreements [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Life (in years)	5 years
Licensing Agreements [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Life (in years)	10 years

Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail) - Sumitomo [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Business Acquisition [Line Items]
Pro forma revenue	$ 250,114
Pro forma net loss	$ (31,020)

Revenue - Additional Information (Detail)	3 Months Ended	6 Months Ended
Revenue - Additional Information (Detail)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) Category
Revenue From Contract With Customer [Abstract]
Number of categories \| Category		3
Remaining performance obligations	$ 0	$ 0
Recognized revenue	$ 3,600,000	$ 10,500,000

Revenue - Disaggregate of Revenue by Reportable Segment and Revenue Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Revenue	$ 156,391	$ 128,048	$ 300,182	$ 248,854
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	109,421	84,742	209,199	166,422
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40,502	34,560	77,255	64,661
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	6,468	8,746	13,728	17,771
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	139,167	115,063	264,989	220,316
Network Solutions [Member] \| Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	96,262	75,222	181,935	144,607
Network Solutions [Member] \| Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	38,444	33,306	73,163	62,083
Network Solutions [Member] \| Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	4,461	6,535	9,891	13,626
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	17,224	12,985	35,193	28,538
Services & Support [Member] \| Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	13,159	9,520	27,264	21,815
Services & Support [Member] \| Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,058	1,254	4,092	2,578
Services & Support [Member] \| Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,007	$ 2,211	$ 3,837	$ 4,145

Revenue - Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Accounts receivable, net	$ 116,661	$ 99,385
Contract assets	2,251	3,766
Unearned revenue	12,910	17,940
Non-current unearned revenue	$ 4,265	$ 5,296

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate expense (benefit)	6.20%	20.10%
Effective tax rate reduction related to transfer pricing study	29.10%
Net deferred tax assets	$ 39.0

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 368	$ 303	$ 743	$ 611
Interest cost	159	185	321	372
Expected return on plan assets	(348)	(394)	(703)	(793)
Amortization of actuarial losses	199	63	402	127
Net periodic pension cost	$ 378	$ 157	$ 763	$ 317

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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,454	$ 1,784	$ 3,313	$ 3,603
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock	(332)	(340)	(775)	(724)
Total stock-based compensation expense, net of tax	1,122	1,444	2,538	2,879
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	85	102	189	197
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	662	995	1,725	2,030
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	707	687	1,399	1,376
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	$ 1,369	$ 1,682	$ 3,124	$ 3,406

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance	4,382
Number of Stock Options, Stock options exercised	(34)
Number of Stock Options, Stock options forfeited	(10)
Number of Stock Options, Stock options expired	(156)
Number of Stock Options, Stock options outstanding, Ending Balance	4,182	4,382
Number of Stock Options, Stock options exercisable	3,942
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance	$ 22.91
Weighted Avg. Exercise Price, Stock options exercised	15.53
Weighted Avg. Exercise Price, Stock options forfeited	15.67
Weighted Avg. Exercise Price, Stock options expired	24.50
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	22.93	$ 22.91
Weighted Avg. Exercise Price, Stock options exercisable	$ 23.39
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding	3 years 7 months 20 days	4 years 1 month 6 days
Weighted Avg. Remaining Contractual Life In Years, Stock options exercisable	3 years 5 months 19 days
Aggregate Intrinsic Value, Stock options outstanding	$ 0

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value based on fair market value	$ 0		$ 0
Total pre-tax intrinsic value of options exercised			$ 100
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	$ 300		$ 300
Recognition period of unvested compensation expense			4 months 24 days

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance \| shares	1,570
Number of Shares, PSUs, RSUs and restricted stock granted \| shares	59
Number of Shares, PSUs, RSUs and restricted stock vested \| shares	(1)
Number of Shares, PSUs, RSUs and restricted stock forfeited \| shares	(63)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance \| shares	1,565
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance \| $ / shares	$ 18.52
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted \| $ / shares	12.54
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested \| $ / shares	18.86
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited \| $ / shares	16.66
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance \| $ / shares	$ 18.37

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 1,454,000	$ 1,784,000	$ 3,313,000	$ 3,603,000
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	14,200,000		$ 14,200,000
Recognition period of unvested compensation expense			2 years 7 months 6 days
Performance-Based PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	8,300,000		$ 8,300,000
Recognition period of unvested compensation expense			6 months
Stock-based compensation expense	$ 0	$ 0	$ 0	$ 0
Stock Options, PSUs, RSUs or Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for grant under shareholders-approved equity plan	2.6		2.6

Investments - Debt Securities and Other Investments, Recorded at Either Fair Value or Cost (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 33,883	$ 41,042
Gross Unrealized Gains	173	27
Gross Unrealized Losses	(23)	(270)
Available-for-sale debt securities, Carrying Value	34,033	40,799
Restricted investment held at cost	25,600	25,600
Other investments held at cost	1,199	397
Total carrying value of available-for-sale investments	60,832	66,796
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,132	20,777
Gross Unrealized Gains	111	19
Gross Unrealized Losses	(4)	(112)
Available-for-sale debt securities, Carrying Value	14,239	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	930	1,339
Gross Unrealized Losses	(3)	(26)
Available-for-sale debt securities, Carrying Value	927	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,580	5,230
Gross Unrealized Gains	32	5
Gross Unrealized Losses	(3)	(14)
Available-for-sale debt securities, Carrying Value	6,609	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,362	3,833
Gross Unrealized Gains	23	2
Gross Unrealized Losses	(6)	(44)
Available-for-sale debt securities, Carrying Value	5,379	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,027	9,271
Gross Unrealized Gains	6	1
Gross Unrealized Losses	(6)	(66)
Available-for-sale debt securities, Carrying Value	5,027	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,852	592
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)	(8)
Available-for-sale debt securities, Carrying Value	$ 1,852	$ 584

Investments - Contractual Maturities of Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 34,033	$ 40,799
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,749
One to two years	8,460
Two to three years	3,030
Available-for-sale debt securities, Fair Value/Carrying Value	14,239	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	927
Available-for-sale debt securities, Fair Value/Carrying Value	927	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	96
One to two years	430
Two to three years	1,667
Three to five years	2,018
Five to ten years	1,772
More than ten years	626
Available-for-sale debt securities, Fair Value/Carrying Value	6,609	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	264
Two to three years	588
Three to five years	510
Five to ten years	425
More than ten years	3,592
Available-for-sale debt securities, Fair Value/Carrying Value	5,379	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,443
Two to three years	1,346
Three to five years	1,238
Available-for-sale debt securities, Fair Value/Carrying Value	5,027	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	891
Two to three years	961
Available-for-sale debt securities, Fair Value/Carrying Value	$ 1,852	$ 584

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Gross realized gains on debt securities	$ 8	$ 25	$ 49	$ 25
Gross realized losses on debt securities	(14)	(241)	(33)	(315)
Total gain (loss) recognized, net	$ (6)	$ (216)	$ 16	$ (290)

Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jan. 01, 2018
Schedule of Investments [Line Items]
Restricted certificate of deposit held		$ 25,600	$ 25,600
Transfer to investments	$ 3,400
Carrying value		$ 3,400
Other Receivables [Member]
Schedule of Investments [Line Items]
Note receivable			4,300
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. 01, 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		$ 25,600	25,600
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		$ 25,600	$ 25,400
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 Unrealized Gains and Losses for Marketable Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on equity securities sold	$ (49)	$ (52)	$ (63)	$ 347
Unrealized gains on equity securities held	2,540	1,258	8,458	836
Total gain recognized, net	$ 2,491	$ 1,206	$ 8,395	$ 1,183

Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 34,033	$ 40,799
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	4,310	1,554
Total debt and equity securities at fair value	87,994	86,071
Total other investments held at cost	3,375
Total	95,679	87,625
Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,337	1,554
Total debt and equity securities at fair value	58,988	54,478
Total	60,325	56,032
Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,973
Total debt and equity securities at fair value	29,006	31,593
Total	31,979	31,593
Money Market Funds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,337	1,554
Money Market Funds [Member] \| Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,337	1,554
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	14,239	20,684
Corporate Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	14,239	20,684
Corporate Bonds [Member] \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	14,239	20,684
Commercial Paper \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,973
Commercial Paper \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2,973
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	927	1,313
Municipal Fixed-Rate Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	927	1,313
Municipal Fixed-Rate Bonds [Member] \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	927	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,609	5,221
Asset-Backed Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,609	5,221
Asset-Backed Bonds [Member] \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,609	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,379	3,791
Mortgage/Agency-Backed Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,379	3,791
Mortgage/Agency-Backed Bonds [Member] \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,379	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,027	9,206
U.S. Government Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,027	9,206
U.S. Government Bonds [Member] \| Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	5,027	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,852	584
Foreign Government Bonds [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,852	584
Foreign Government Bonds [Member] \| Fair Value, Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	1,852	584
Marketable Equity Securities - Various Industries [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	32,548	26,763
Marketable Equity Securities - Various Industries [Member] \| Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	32,548	26,763
Deferred Compensation Plan Assets [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	21,228	18,256
Deferred Compensation Plan Assets [Member] \| Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	21,228	18,256
Equity in Escrow [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	185	253
Equity in Escrow [Member] \| Fair Value, Measurements [Member] \| Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	185	$ 253
Other Investments [Member] \| Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Total other investments held at cost	$ 3,375

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 38,844	$ 45,333
Work in process	1,383	1,638
Finished goods	54,883	52,877
Total	$ 95,110	$ 99,848

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventory valuation reserves	$ 31.0	$ 30.0

Goodwill - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill, relates to acquisition		$ 7.0	$ 7.1
SmartRG Inc [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition		3.5
Goodwill, reduced amount relates to acquisition		0.1
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition	$ 6.6	6.6	6.7
Services & Support [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition	$ 0.4	$ 0.4	$ 0.4

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Value	$ 42,654	$ 45,326
Accumulated Amortization	(12,151)	(12,143)
Net Value	30,503	33,183
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	22,414	22,455
Accumulated Amortization	(6,311)	(5,380)
Net Value	16,103	17,075
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	10,170	12,801
Accumulated Amortization	(2,810)	(4,867)
Net Value	7,360	7,934
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	5,900	5,900
Accumulated Amortization	(847)	(520)
Net Value	5,053	5,380
Supplier Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	2,800	2,800
Accumulated Amortization	(1,808)	(1,108)
Net Value	992	1,692
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	560	560
Accumulated Amortization	(43)	(5)
Net Value	517	555
Patent [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	500	500
Accumulated Amortization	(191)	(157)
Net Value	309	343
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Value	310	310
Accumulated Amortization	(141)	(106)
Net Value	$ 169	$ 204

Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Intangible Assets Net Excluding Goodwill [Abstract]
Amortization expense	$ 1.3	$ 1.0	$ 2.7	$ 1.5

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
Remainder of 2019	$ 2,665
2020	4,448
2021	4,099
2022	3,475
2023	3,322
Thereafter	12,494
Net Value	$ 30,503	$ 33,183

Leases - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
Leases - Additional Information (Detail) - USD ($)	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Lessor and Lessee Lease Description [Line Items]
Operating lease, option to extend, existence		true
Operating lease, option to terminate, existence		true
Short-term lease cost	$ 100,000	$ 300,000
Operating lease payments		797,000	$ 1,200,000
Allowance for credit losses for our investment in sales type leases	$ 0	$ 0	$ 0
Minimum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms		1 month
Operating lease, options to terminate term		3 months
Maximum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms		6 years
Operating lease, renewal term	3 years	3 years
Lessor sales type lease arrangement terms for network equipments		5 years

Leases - Schedule of Supplemental Balance Sheet Information Related to Operating Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
ASSETS
Operating lease asset	$ 8,838	$ 10,322
Operating lease, right-of-use asset, statement of financial position [extensible list]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Liabilities
Current operating lease liability	$ 2,514	$ 2,948
Operating lease, liability, current, statement of financial position [extensible list]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Non-current operating lease liability	$ 6,349	$ 7,374
Operating lease, liability, noncurrent, statement of financial position [extensible list]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total lease liability	$ 8,863	$ 10,322

Leases - Components of Lease Expense included in Condensed Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessor Lease Description [Line Items]
Total operating lease expense	$ 796	$ 1,615
Selling, General and Administrative Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	349	698
Research and Development Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	430	884
Cost of Sales [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	$ 17	$ 33

Leases - Schedule of Maturity of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2019	$ 1,583
2020	2,203
2021	2,047
2022	1,560
2023	1,173
Thereafter	756
Total lease payments	9,322
Less: Interest	(459)
Operating lease, right-of-use liability	$ 8,863	$ 10,322

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

Leases - Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate (Detail)	Jun. 30, 2019
USD
Weighted average remaining lease term (years)
Operating leases with functional currency	2 years 10 months 24 days
Weighted average discount rate
Operating leases with functional currency	4.61%
Euro
Weighted average remaining lease term (years)
Operating leases with functional currency	4 years 9 months 18 days
Weighted average discount rate
Operating leases with functional currency	1.85%

Leases - Schedule of Supplemental Cash Flow Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Cash paid for amounts included in the measurement of operating lease liabilities / assets
Cash used in operating activities related to operating leases	$ (797)	$ (1,200)
Right-of-use assets obtained in exchange for lease obligations	$ 10,396

Leases - Components of Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Sales Type Leases Net Investment In Leases [Abstract]
Current minimum lease payments receivable (included in other receivables)	$ 6,360	$ 11,339
Non-current minimum lease payments receivable (included in other assets)	1,286	1,670
Total minimum lease payments receivable	7,646	13,009
Less: Current unearned revenue	495	631
Less: Non-current unearned revenue	269	473
Net investment in sales-type leases	$ 6,882	$ 11,905

Leases - Schedule of Components of Sales-type Lease Gross Profit and Interest and Dividend Income Included in Condensed Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Sales [Member] \| Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 109	$ 1,621
Cost of Sales [Member] \| Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	44	635
Gross Profit [Member]
Lessor Lease Description [Line Items]
Sales type leases	65	986
Interest and Dividend Income [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 99	$ 186

Leases - Schedule of Future Minimum Lease Payments to be Received from Sales-Type Leases (Detail) $ in Thousands	Jun. 30, 2019 USD ($)
Sales Type And Direct Financing Leases Lease Receivable Fiscal Year Maturity [Abstract]
Remainder of 2019	$ 5,705
2020	1,112
2021	525
2022	220
2023	81
Thereafter	3
Total	$ 7,646

Stockholders' Equity - Additional Information (Detail)	6 Months Ended
Stockholders' Equity - Additional Information (Detail)	Jun. 30, 2019 $ / shares shares
Equity [Abstract]
Stock repurchased, shares	13,000,000
Shares repurchased, average price per share \| $ / shares	$ 14.06
Additional shares authorized for purchase	2,500,000
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	5,000,000.0

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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 443,547	$ 475,736	$ 446,279	$ 497,911
Other comprehensive income (loss) before reclassifications	713	(3,506)	(216)	(2,921)
Amounts reclassified from accumulated other comprehensive income (loss)	77	191	152	318
Amounts reclassified to retained earnings			385	(3,220)
Net current period other comprehensive income (loss)	790	(3,315)	321	(5,823)
Ending Balance	445,975	459,627	445,975	459,627
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	385
Amounts reclassified to retained earnings			385
Net current period other comprehensive income (loss)			385
Ending Balance	385		385
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(378)	(845)	(563)	2,567
Other comprehensive income (loss) before reclassifications	180	(82)	411	(339)
Amounts reclassified from accumulated other comprehensive income (loss)	(73)	186	(119)	251
Amounts reclassified to retained earnings				(3,220)
Net current period other comprehensive income (loss)	107	104	292	(3,308)
Ending Balance	(271)	(741)	(271)	(741)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,920)	(4,224)	(8,041)	(4,286)
Amounts reclassified from accumulated other comprehensive income (loss)	150	5	271	67
Net current period other comprehensive income (loss)	150	5	271	67
Ending Balance	(7,770)	(4,219)	(7,770)	(4,219)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,972)	(734)	(5,812)	(1,576)
Other comprehensive income (loss) before reclassifications	533	(3,424)	(627)	(2,582)
Net current period other comprehensive income (loss)	533	(3,424)	(627)	(2,582)
Ending Balance	(6,439)	(4,158)	(6,439)	(4,158)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(14,885)	(5,803)	(14,416)	(3,295)
Ending Balance	$ (14,095)	$ (9,118)	$ (14,095)	$ (9,118)

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	$ (91,376)		$ (78,052)		$ (174,555)	$ (159,125)
Income (Loss) Before Benefit for Income Taxes	3,407		(11,259)		4,485	(26,004)
Tax benefit	588		3,589		280	7,520
Net Income (Loss)	3,995	$ 770	(7,670)	$ (10,814)	4,765	(18,484)
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	(217)		(7)		(393)	(97)
Income (Loss) Before Benefit for Income Taxes	(118)		(258)		(232)	(421)
Tax benefit	41		67		80	103
Net Income (Loss)	(77)		(191)		(152)	(318)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] \| Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain (loss)	$ 99		$ (251)		$ 161	$ (324)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

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, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 243		$ (111)		$ 555	$ (458)
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(63)		29		(144)	119
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	180		(82)		411	(339)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Before-Tax Amount	(99)		251		(161)	324
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Tax (Expense) Benefit	26		(65)		42	(73)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Net-of-Tax Amount	(73)		186		(119)	251
Reclassification adjustment for amounts reclassed to retained earnings related of the adoption of ASU 2016-01, Before-Tax Amount						(3,220)
Reclassification adjustment for amounts reclassed to retained earnings related of the adoption of ASU 2016-01, Net-of-Tax Amount						(3,220)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Before-Tax Amount	217		7		393	97
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Tax (Expense) Benefit	(67)		(2)		(122)	(30)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Net-of-Tax Amount	150		5		271	67
Foreign currency translation adjustment, Before-Tax Amount	533		(3,424)		(627)	(2,582)
Foreign currency translation adjustment, Net-of-Tax Amount	533		(3,424)		(627)	(2,582)
Total Other Comprehensive Income (Loss), Before-Tax Amount	894		(3,277)		160	(5,839)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(104)		(38)		(224)	16
Other Comprehensive Income (Loss), net of tax	$ 790	$ (854)	$ (3,315)	$ (2,508)	$ (64)	$ (5,823)

Earnings (Loss) Per Share - Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator
Net Income (Loss)	$ 3,995	$ 770	$ (7,670)	$ (10,814)	$ 4,765	$ (18,484)
Denominator
Weighted average number of shares – basic	47,802		47,856		47,792	48,043
Effect of dilutive securities
Stock options	7
PSUs, RSUs and restricted stock	227				147
Weighted average number of shares – diluted	48,036		47,856		47,939	48,043
Earnings (loss) per share – basic	$ 0.08		$ (0.16)		$ 0.10	$ (0.38)
Earnings (loss) per share – diluted	$ 0.08		$ (0.16)		$ 0.10	$ (0.38)

Earnings (Loss) Per Share - Additional Information (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings (loss) per share	1,900	5,000	2,300	4,800
PSUs, RSUs and Restricted Stock Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings (loss) per share	15,000	100	100	100

Segment Information - Additional Information (Detail)	6 Months Ended
Segment Information - Additional Information (Detail)	Jun. 30, 2019 Category Segment
Segment Reporting [Abstract]
Number of reportable segments \| Segment	2
Number of categories \| Category	3

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Sales	$ 156,391	$ 128,048	$ 300,182	$ 248,854
Gross Profit	65,015	49,996	125,627	89,729
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	139,167	115,063	264,989	220,316
Gross Profit	58,992	45,434	114,080	82,075
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	17,224	12,985	35,193	28,538
Gross Profit	$ 6,023	$ 4,562	$ 11,547	$ 7,654

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Revenue	$ 156,391	$ 128,048	$ 300,182	$ 248,854
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	109,421	84,742	209,199	166,422
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40,502	34,560	77,255	64,661
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 6,468	$ 8,746	$ 13,728	$ 17,771

Segment Information- Sales Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from External Customer [Line Items]
Sales	$ 156,391	$ 128,048	$ 300,182	$ 248,854
United States [Member]
Revenue from External Customer [Line Items]
Sales	75,288	68,222	147,816	130,308
International [Member]
Revenue from External Customer [Line Items]
Sales	$ 81,103	$ 59,826	$ 152,366	$ 118,546

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Product Warranties Disclosures [Abstract]
Period of assurance-based warranty for product defects	90 days to five years
Liability for warranty obligations	$ 8,972	$ 8,802	$ 8,623	$ 10,111	$ 9,687	$ 9,724

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Product Warranties Disclosures [Abstract]
Warranty accrual at beginning of period	$ 8,802	$ 9,687	$ 8,623	$ 9,724
Plus: Amounts charged to expense	1,849	4,860	2,980	6,683
Less: Deductions	(1,679)	(4,436)	(2,631)	(6,296)
Warranty accrual at end of period	$ 8,972	$ 10,111	$ 8,972	$ 10,111

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Jun. 30, 2019 USD ($) EquityFund
Contingencies And Commitments [Line Items]
Number of private equity funds \| EquityFund	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

Restructuring - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2018
Restructuring And Related Activities [Abstract]
Cumulative amount incurred for restructuring program	$ 1.0	$ 7.0	$ 7.3

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring And Related Activities [Abstract]
Balance at beginning of period	$ 1,971		$ 185
Plus: Amounts charged to cost and expense	1,400	$ 1,025	3,463	$ 6,975
Less: Amounts paid	(716)		(993)
Balance at end of period	$ 2,655		$ 2,655

Restructuring - Schedule of Components of Restructuring Expense in Condensed Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,400	$ 1,025	$ 3,463	$ 6,975
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	703	634	1,547	2,400
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	647		1,231	1,814
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 50	$ 391	$ 685	$ 2,761

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended				6 Months Ended
	Sep. 19, 2019	Jul. 17, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Aug. 15, 2019	Jan. 01, 2019
Subsequent Event [Line Items]
Dividend payments			$ 0.09	$ 0.09	$ 0.09	$ 0.09
Operating lease, right-of-use asset			$ 8,838				$ 8,838		$ 10,322
Operating lease, right-of-use liability			$ 8,863				$ 8,863		$ 10,322
Operating lease, option to extend, existence							true
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declaration date		Jul. 17, 2019
Dividend payments		$ 0.09
Dividend record date		Aug. 01, 2019
Dividend payment date		Aug. 15, 2019
Subsequent Event [Member] \| India [Member]
Subsequent Event [Line Items]
Operating lease, remaining lease terms	5 years
Operating lease, renewal term	5 years
Operating lease, right-of-use asset	$ 10,200
Operating lease, right-of-use liability	$ 10,200
Operating lease, option to extend, existence	true
Scenario Forecast [Member]
Subsequent Event [Line Items]
Quarterly dividend payable subsequent to balance sheet date								$ 4,300