ADTRAN (ADTN) 10-Q 4 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 23, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	ADTN
Entity Registrant Name	ADTRAN INC
Entity Central Index Key	926,282
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		47,799,232

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 88,798	$ 79,895
Short-term investments	47,331	43,188
Accounts receivable, less allowance for doubtful accounts of $— at June 30, 2017 and December 31, 2016	79,891	92,346
Other receivables	14,561	15,137
Income tax receivable, net		760
Inventory, net	113,995	105,117
Prepaid expenses and other current assets	23,556	16,459
Total Current Assets	368,132	352,902
Property, plant and equipment, net	84,122	84,469
Deferred tax assets, net	40,296	38,036
Goodwill	3,492	3,492
Other assets	13,305	12,234
Long-term investments	159,634	176,102
Total Assets	668,981	667,235
Current Liabilities
Accounts payable	66,161	77,342
Unearned revenue	15,449	16,326
Accrued expenses	13,433	12,434
Accrued wages and benefits	16,303	20,433
Income tax payable, net	9,594
Total Current Liabilities	120,940	126,535
Non-current unearned revenue	5,351	6,333
Other non-current liabilities	32,527	28,050
Bonds payable	26,800	26,800
Total Liabilities	185,618	187,718
Commitments and contingencies (see Note 14)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 47,747 shares outstanding at June 30, 2017 and 79,652 shares issued and 48,472 shares outstanding at December 31, 2016	797	797
Additional paid-in capital	256,821	252,957
Accumulated other comprehensive loss	(6,816)	(12,188)
Retained earnings	931,044	921,942
Less treasury stock at cost: 31,905 and 31,180 shares at June 30, 2017 and December 31, 2016, respectively	(698,483)	(683,991)
Total Stockholders’ Equity	483,363	479,517
Total Liabilities and Stockholders’ Equity	$ 668,981	$ 667,235

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,652,000	79,652,000
Common stock, shares outstanding	47,747,000	48,472,000
Treasury stock, shares	31,905,000	31,180,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Sales
Products	$ 155,543	$ 138,549	$ 299,140	$ 262,432
Services	29,130	24,152	55,812	42,473
Total Sales	184,673	162,701	354,952	304,905
Cost of sales
Products	79,658	67,844	156,317	131,917
Services	20,383	15,902	40,288	28,239
Total Cost of Sales	100,041	83,746	196,605	160,156
Gross Profit	84,632	78,955	158,347	144,749
Selling, general and administrative expenses	34,683	32,866	69,450	63,651
Research and development expenses	33,501	31,277	65,417	60,765
Operating Income	16,448	14,812	23,480	20,333
Interest and dividend income	972	927	1,905	1,782
Interest expense	(137)	(142)	(278)	(287)
Net realized investment gain	1,390	1,110	1,860	2,838
Other expense, net	(804)	(251)	(753)	(132)
Income before provision for income taxes	17,869	16,456	26,214	24,534
Provision for income taxes	(5,468)	(6,228)	(7,162)	(9,292)
Net Income	$ 12,401	$ 10,228	$ 19,052	$ 15,242
Weighted average shares outstanding – basic	48,036	48,831	48,232	49,026
Weighted average shares outstanding – diluted	48,413	49,048	48,675	49,218
Earnings per common share – basic	$ 0.26	$ 0.21	$ 0.40	$ 0.31
Earnings per common share – diluted	0.26	0.21	0.39	0.31
Dividend per share	$ 0.09	$ 0.09	$ 0.18	$ 0.18

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 12,401	$ 10,228	$ 19,052	$ 15,242
Other Comprehensive Income (Loss), net of tax:
Net unrealized gains (losses) on available-for-sale securities	373	(165)	1,708	(420)
Net unrealized losses on cash flow hedges	(417)		(338)
Defined benefit plan adjustments	86	22	141	67
Foreign currency translation	2,619	(601)	3,861	627
Other Comprehensive Income (Loss), net of tax	2,661	(744)	5,372	274
Comprehensive Income, net of tax	$ 15,062	$ 9,484	$ 24,424	$ 15,516

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net Income	$ 19,052	$ 15,242
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,377	6,689
Amortization of net premium on available-for-sale investments	238	376
Net realized gain on long-term investments	(1,860)	(2,838)
Net (gain) loss on disposal of property, plant and equipment	(11)	5
Stock-based compensation expense	3,739	3,109
Deferred income taxes	(2,772)	(354)
Changes in operating assets and liabilities:
Accounts receivable, net	13,911	(17,192)
Other receivables	571	7,876
Inventory	(7,547)	4,938
Prepaid expenses and other assets	(9,853)	(4,263)
Accounts payable	(10,910)	10,354
Accrued expenses and other liabilities	(2,629)	1,474
Income tax payable/receivable, net	10,273	(4,799)
Net cash provided by operating activities	20,579	20,617
Cash flows from investing activities:
Purchases of property, plant and equipment	(7,509)	(6,679)
Proceeds from disposals of property, plant and equipment	16
Proceeds from sales and maturities of available-for-sale investments	81,891	109,993
Purchases of available-for-sale investments	(65,140)	(112,903)
Net cash provided by (used in) investing activities	9,258	(9,589)
Cash flows from financing activities:
Proceeds from stock option exercises	1,722	541
Purchases of treasury stock	(17,311)	(16,579)
Dividend payments	(8,719)	(8,860)
Net cash used in financing activities	(24,308)	(24,898)
Net increase (decrease) in cash and cash equivalents	5,529	(13,870)
Effect of exchange rate changes	3,374	234
Cash and cash equivalents, beginning of period	79,895	84,550
Cash and cash equivalents, end of period	88,798	70,914
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 454	$ 554

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2016, filed on February 24, 2017 with the SEC. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In March 2017, the FASB issued Accounting Standards Update No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost Compensation — Retirement Benefits During 2017, we adopted the following accounting standards, which had no material effect on our financial position, results of operations or cash flows: In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory Inventory In January 2017, we adopted ASU 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.

Business Combinations

Business Combinations	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Business Combinations	2. BUSINESS COMBINATIONS On September 13, 2016, we acquired key fiber access products, technologies and service relationships from subsidiaries of CommScope, Inc. for $0.9 million in cash. This acquisition will enhance our solutions for the cable MSO industry and will provide cable operators with the scalable solutions, services and support they require to compete in the multi-gigabit service delivery market. This transaction was accounted for as a business combination. We have included the financial results of this acquisition in our consolidated financial statements since the date of acquisition. These revenues are included in the Network Solutions reportable segment, and in the Access & Aggregation and Customer Devices categories. We recorded a bargain purchase gain of $3.5 million during the third quarter of 2016, net of income taxes, subject to customary working capital adjustments between the parties. The bargain purchase gain of $3.5 million represents the excess fair value of the net assets acquired over the consideration exchanged. We have assessed the recognition and measurement of the assets acquired and liabilities assumed based on historical and forecasted data for future periods and have concluded that our valuation procedures and resulting measures were appropriate. The allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date, subject to working capital adjustments, is as follows: (In Thousands) Assets Inventory $ 3,131 Property, plant and equipment 352 Intangible assets 4,700 Total assets acquired 8,183 Liabilities Accounts payable (1,250 ) Warranty payable (61 ) Accrued wages and benefits (122 ) Deferred income taxes (2,265 ) Total liabilities assumed (3,698 ) Total net assets 4,485 Gain on bargain purchase of a business, net of tax (3,542 ) Total purchase price $ 943 The details of the acquired intangible assets are as follows: In thousands Value Life (years) Supply agreement $ 1,400 0.8 Customer relationships 1,200 6.0 Developed technology 800 10.0 License 500 1.3 Patent 500 7.3 Non-compete 200 2.3 Trade name 100 2.0 Total $ 4,700 The following unaudited supplemental pro forma information presents the financial results as if the acquisition had occurred on January 1, 2015. 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, 2015, nor is it indicative of any future results. Aside from revising the 2015 net income for the effect of the bargain purchase gain, there were no material, non-recurring adjustments to this unaudited pro forma information. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Pro forma revenue $ 164,332 $ 160,562 $ 307,687 $ 304,542 Pro forma net income $ 10,022 $ 1,983 $ 14,907 $ 8,405 Pro forma earnings per share - basic $ 0.21 $ 0.04 $ 0.30 $ 0.16 Pro forma earnings per share - diluted $ 0.20 $ 0.04 $ 0.30 $ 0.16 For the three and six months ended June 30, 2017, we incurred acquisition and integration related expenses and amortization of acquired intangibles of $0.6 million and $1.4 million, respectively, related to this acquisition.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	3. INCOME TAXES Our effective tax rate decreased from 37.9% in the six months ended June 30, 2016 to 27.3% in the six months ended June 30, 2017. The decrease in the effective tax rate between the two periods is primarily attributable to a 6.3% effective rate reduction due to a greater mix of international revenues and a 3.2% effective rate reduction for a provision-to-return adjustment related to the assignment of research and development expenditures to specific company engineering locations.

Pension Benefit Plan

Pension Benefit Plan	6 Months Ended
	Jun. 30, 2017
Compensation And Retirement Disclosure [Abstract]
Pension Benefit Plan	4. 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, 2017 and 2016 Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Service cost $ 306 $ 310 $ 603 $ 607 Interest cost 147 184 290 360 Expected return on plan assets (307 ) (271 ) (606 ) (530 ) Amortization of actuarial losses 75 45 148 88 Net periodic pension cost $ 221 $ 268 $ 435 $ 525

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	5. STOCK-BASED COMPENSATION The following table summarizes the stock-based compensation expense related to stock options, performance stock units (PSUs), restricted stock units (RSUs) and restricted stock for the three and six months ended June 30, 2017 and 2016, which was recognized as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Stock-based compensation expense included in cost of sales $ 93 $ 95 $ 184 $ 194 Selling, general and administrative expense 1,008 788 2,024 1,557 Research and development expense 755 668 1,531 1,358 Stock-based compensation expense included in operating expenses 1,763 1,456 3,555 2,915 Total stock-based compensation expense 1,856 1,551 3,739 3,109 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (433 ) (213 ) (813 ) (425 ) Total stock-based compensation expense, net of tax $ 1,423 $ 1,338 $ 2,926 $ 2,684 Stock Options The following table is a summary of our stock options outstanding as of December 31, 2016 and June 30, 2017 and the changes that occurred during the six months ended June 30, 2017: (In thousands, except per share amounts) Number of Stock Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Stock options outstanding, December 31, 2016 6,338 $ 22.14 5.63 $ 16,972 Stock options granted — $ — Stock options exercised (103 ) $ 16.78 Stock options forfeited (32 ) $ 17.62 Stock options expired (55 ) $ 26.67 Stock options outstanding, June 30, 2017 6,148 $ 22.21 5.14 $ 11,232 Stock options vested and expected to vest, June 30, 2017 6,148 $ 22.21 5.14 $ 11,232 Options exercisable, June 30, 2017 4,601 $ 23.78 4.23 $ 5,862 The aggregate intrinsic values in the table above represent the total pre-tax intrinsic value (the difference between the closing price of our stock on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money stock options) that would have been received by the option holders had all option holders exercised their options on June 30, 2017. The aggregate intrinsic value will change based on the fair market value of our stock. The total pre-tax intrinsic value of options exercised during the three and six months ended June 30, 2017 was $0.1 million and $0.5, respectively. As of June 30, 2017, there was $5.2 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over an average remaining recognition period of 1.8 years. The fair value of our stock options is estimated using the Black-Scholes model. The determination of the fair value of stock options on the date of grant using the Black-Scholes model is affected by our stock price as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate. There were no stock options granted during the three or six months ended June 30, 2017. The weighted-average assumptions and value of options granted during the three and six months ended June 30, 2016 were as follows: Three and Six Months Ended June 30, 2016 Expected volatility 34.74 % Risk-free interest rate 1.33 % Expected dividend yield 1.91 % Expected life (in years) 6.26 Weighted-average estimated value $ 5.42 PSUs, RSUs and restricted stock The following table is a summary of our PSUs, RSUs and restricted stock outstanding as of December 31, 2016 and the changes that occurred during the six months ended June 30, 2017: (In thousands, except per share amounts) Number of Shares Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2016 519 $ 20.51 PSUs, RSUs and restricted stock granted 520 $ 22.24 PSUs, RSUs and restricted stock vested (2 ) $ 18.29 PSUs, RSUs and restricted stock forfeited (6 ) $ 20.00 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2017 1,031 $ 21.39 The fair value of our PSUs with market conditions is calculated using a Monte Carlo Simulation valuation method. The fair value of RSUs and restricted stock is equal to the closing price of our stock on the date of grant. During the first quarter of 2017, the Compensation Committee of the Board of Directors approved a PSU grant of 0.5 million shares that contain performance conditions. The fair value of these performance-based PSU awards was equal to the closing price of our stock on the date of grant. As of June 30, 2017, there was $7.9 million of unrecognized compensation expense related to unvested market-based PSUs, RSUs and restricted stock, which is expected to be recognized over an average remaining recognition period of 3.0 years. In addition, there was $11.5 million of unrecognized compensation expense related to unvested performance-based PSUs, which will be recognized over the requisite service period of three years as achievement of the performance objective becomes probable. For the three and six months ended June 30, 2017, no compensation expense was recognized related to these performance-based PSU awards.

Investments

Investments	6 Months Ended
	Jun. 30, 2017
Investments Debt And Equity Securities [Abstract]
Investments	6. INVESTMENTS At June 30, 2017, we held the following securities and investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 15,662 $ 2,389 $ (23 ) $ 18,028 Corporate bonds 72,954 132 (107 ) 72,979 Municipal fixed-rate bonds 7,596 7 (20 ) 7,583 Asset-backed bonds 13,313 11 (16 ) 13,308 Mortgage/Agency-backed bonds 9,549 14 (36 ) 9,527 U.S. government bonds 21,528 4 (132 ) 21,400 Foreign government bonds 2,700 3 (1 ) 2,702 Marketable equity securities 31,741 2,153 (929 ) 32,965 Available-for-sale securities held at fair value $ 175,043 $ 4,713 $ (1,264 ) $ 178,492 Restricted investment held at cost 27,800 Other investments held at cost 673 Total carrying value of available-for-sale investments $ 206,965 At December 31, 2016, we held the following securities and investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 12,367 $ 2,271 $ (42 ) $ 14,596 Corporate bonds 66,522 64 (174 ) 66,412 Municipal fixed-rate bonds 11,799 12 (37 ) 11,774 Asset-backed bonds 10,201 19 (14 ) 10,206 Mortgage/Agency-backed bonds 13,080 15 (91 ) 13,004 U.S. government bonds 30,022 15 (270 ) 29,767 Foreign government bonds 3,729 2 (1 ) 3,730 Variable rate demand notes 11,855 — — 11,855 Marketable equity securities 30,571 311 (1,503 ) 29,379 Available-for-sale securities held at fair value $ 190,146 $ 2,709 $ (2,132 ) $ 190,723 Restricted investment held at cost 27,800 Other investments held at cost 767 Total carrying value of available-for-sale investments $ 219,290 As of June 30, 2017, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, U.S. government bonds and foreign government bonds 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 $ 33,486 $ 4,101 $ — $ — $ 8,919 $ 825 One to two years 16,124 1,536 850 493 — 600 Two to three years 21,421 775 5,185 — 8,367 1,277 Three to five years 1,948 1,171 5,836 415 4,114 — Five to ten years — — 508 1,340 — — More than ten years — — 929 7,279 — — Total $ 72,979 $ 7,583 $ 13,308 $ 9,527 $ 21,400 $ 2,702 Actual maturities may differ from contractual maturities because some borrowers have the right to call or prepay obligations with or without call or prepayment penalties. 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, 2017, we held a $27.8 million restricted certificate of deposit, which 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 $27.8 million at June 30, 2017 and December 31, 2016. At June 30, 2017, the estimated fair value of the Bond using a level 2 valuation technique was approximately $28.0 million, based on a debt security with a comparable interest rate and maturity and a Standard and Poor’s credit rating of AAA. We have the right to set-off the balance of the Bond with the collateral deposit in order to reduce the balance of the indebtedness. The Bond matures on January 1, 2020, and bears interest at the rate of 2% per annum. In conjunction with this program, we are eligible to receive certain economic incentives from the state of Alabama that reduce the amount of payroll withholdings we are required to remit to the state for those employment positions that qualify under this program. We are required to make payments in the amounts necessary to pay the interest on the amounts currently outstanding. It is our intent to make annual principal payments in addition to the interest amounts that are due. We review our investment portfolio for potential “other-than-temporary” declines in value on an individual investment basis. We assess, on a quarterly basis, significant declines in value which may be considered other-than-temporary and, if necessary, recognize and record the appropriate charge to write-down the carrying value of such investments. In making this assessment, we take into consideration qualitative and quantitative information, including but not limited to the following: the magnitude and duration of historical declines in market prices, credit rating activity, assessments of liquidity, public filings, and statements made by the issuer. We generally begin our identification of potential other-than-temporary impairments by reviewing any security with a fair value that has declined from its original or adjusted cost basis by 25% or more for six or more consecutive months. We then evaluate the individual security based on the previously identified factors to determine the amount of the write-down, if any. For the three and six months ended June 30, 2017 and 2016, other-than-temporary impairment charges were not significant. Realized gains and losses on sales of securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our investments. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Gross realized gains $ 1,512 $ 1,517 $ 2,230 $ 3,881 Gross realized losses $ (122 ) $ (407 ) $ (370 ) $ (1,043 ) As of June 30, 2017 and 2016, gross unrealized losses related to individual securities in a continuous loss position for 12 months or longer were not significant. We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 - Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at June 30, 2017 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 6,487 $ 6,487 $ — $ — Commercial Paper 5,497 — 5,497 — Cash equivalents 11,984 6,487 5,497 — Available-for-sale securities Deferred compensation plan assets 18,028 18,028 — — Available-for-sale debt securities Corporate bonds 72,979 — 72,979 — Municipal fixed-rate bonds 7,583 — 7,583 — Asset-backed bonds 13,308 — 13,308 — Mortgage/Agency-backed bonds 9,527 — 9,527 — U.S. government bonds 21,400 21,400 — — Foreign government bonds 2,702 — 2,702 — Available-for-sale marketable equity securities Marketable equity securities – various industries 32,965 32,965 — — Available-for-sale securities 178,492 72,393 106,099 — Total $ 190,476 $ 78,880 $ 111,596 $ — Fair Value Measurements at December 31, 2016 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 6,878 $ 6,878 $ — $ — Commercial Paper 17,222 — 17,222 — Cash equivalents 24,100 6,878 17,222 — Available-for-sale securities Deferred compensation plan assets 14,596 14,596 — — Available-for-sale debt securities Corporate bonds 66,412 — 66,412 — Municipal fixed-rate bonds 11,774 — 11,774 — Asset-backed bonds 10,206 — 10,206 — Mortgage/Agency-backed bonds 13,004 — 13,004 — U.S. government bonds 29,767 29,767 — — Foreign government bonds 3,730 — 3,730 — Variable Rate Demand Notes 11,855 — 11,855 — Available-for-sale marketable equity securities Marketable equity securities – various industries 29,379 29,379 — — Available-for-sale securities 190,723 73,742 116,981 — Total $ 214,823 $ 80,620 $ 134,203 $ — The fair value of our Level 2 securities is calculated using a weighted average market price for each security. Market prices are obtained from a variety of industry standard data providers, security master files from large financial institutions, and other third-party sources. These multiple market prices are used as inputs into a distribution-curve-based algorithm to determine the daily market value of each security. Our variable rate demand notes have a structure that implies a standard expected market price. The frequent interest rate resets make it reasonable to expect the price to stay at par. These securities are priced at the expected market price.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	6 Months Ended
	Jun. 30, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	7. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES We participate in foreign exchange forward contracts in connection with the management of exposure to fluctuations in foreign exchange rates. Cash Flow Hedges Our cash flow hedging activities utilize foreign exchange forward contracts to reduce the risk that movements in exchange rates will adversely affect the net cash flows resulting from the planned purchase of products from foreign suppliers. Purchases of U.S. denominated inventory by our European subsidiary represent our primary exposure. Changes in the fair value of derivatives designated as cash flow hedges are not recognized in current operating results, but are recorded in accumulated other comprehensive income. Amounts related to cash flow hedges are reclassified from accumulated other comprehensive income when the underlying hedged item impacts earnings. This reclassification is recorded in the same line item of the consolidated statements of income as where the effects of the hedged item are recorded, which is cost of sales. Undesignated Hedges We have certain customers and suppliers who are invoiced or pay in a non-functional currency. Changes in the monetary exchange rates may adversely affect our results of operations and financial condition, as outstanding non-functional balances are revalued to the functional currency through profit and loss. When appropriate, we utilize foreign exchange forward contracts to help manage the volatility relating to these valuation exposures. All changes in the fair value of our derivative instruments that do not qualify for or are not designated for hedged accounting transactions are recognized as other income (expense) in the Consolidated Statements of Income. As of June 30, 2017, we had foreign exchange forward contracts outstanding with notional amounts totaling $20.0 million (€17.5 million), which hedge a portion of projected inventory purchases expected to be settled in the third and fourth quarters of 2017. We have determined that there was no hedge ineffectiveness for the quarter ended June 30, 2017 related to these contracts. We do not hold or issue derivative instruments for trading or other speculative purposes. Our derivative instruments are recorded in the Consolidated Balance Sheets at their fair values. Our derivative instruments are not subject to master netting arrangements and are not offset in the Consolidated Balance Sheets. The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2017 and December 31, 2016 were as follows: (In thousands) Balance Sheet Location June 30, 2017 December 31, 2016 Derivatives Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative liabilities Accounts payable $ 610 $ — Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative assets Other receivables — 159 Foreign exchange contracts – derivative liabilities Accounts payable 352 — Total derivatives $ 962 $ 159 The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and six months ended June 30, 2017 and 2016 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2017 2016 2017 2016 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ (451 ) $ 237 $ (485 ) $ 190 The change in our derivatives designated as hedging instruments recorded in other comprehensive income (OCI) and reclassified to income during the three and six months ended June 30, 2017 and 2016 were as follows: Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Three Months Ended Location of Gains Three Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2017 2016 from AOCI into Income 2017 2016 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ (571 ) $ — Cost of Sales $ (154 ) $ — Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Six Months Ended Location of Gains Six Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2017 2016 from AOCI into Income 2017 2016 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ (492 ) $ — Cost of Sales $ (154 ) $ —

Inventory

Inventory	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
Inventory	8. INVENTORY At June 30, 2017 and December 31, 2016, inventory consisted of the following: June 30, December 31, (In thousands) 2017 2016 Raw materials $ 42,218 $ 40,461 Work in process 2,443 4,003 Finished goods 69,334 60,653 Total $ 113,995 $ 105,117 We establish reserves for estimated excess, obsolete, or unmarketable inventory equal to the difference between the cost of the inventory and the estimated fair value of the inventory based upon assumptions about future demand and market conditions. At June 30, 2017 and December 31, 2016, raw materials reserves totaled $15.2 million and $14.6 million, respectively, and finished goods inventory reserves totaled $12.7 million and $10.6 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	9. GOODWILL AND INTANGIBLE ASSETS Goodwill, all of which relates to our acquisition of Bluesocket, Inc., was $3.5 million at June 30, 2017 and December 31, 2016, of which $3.1 million and $0.4 million is allocated to our Network Solutions and Services & Support reportable segments, respectively. We evaluate the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. We have elected to first assess the qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step impairment test. If we determine that it is more likely than not that its fair value is less than its carrying amount, then the two-step impairment test will be performed. Based on the results of our qualitative assessment in 2016, we concluded that it was not necessary to perform the two-step impairment test. There have been no impairment losses recognized since the acquisition in 2011. Intangible assets are included in other assets in the accompanying Consolidated Balance Sheets and include intangibles acquired in conjunction with our acquisitions of Bluesocket, Inc. on August 4, 2011, the NSN BBA business on May 4, 2012, and CommScope’s active fiber access business on September 13, 2016. The following table presents our intangible assets as of June 30, 2017 and December 31, 2016: (In thousands) June 30, 2017 December 31, 2016 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 7,249 $ (3,765 ) $ 3,484 $ 6,899 $ (3,208 ) $ 3,691 Developed technology 6,650 (5,609 ) 1,041 6,444 (5,061 ) 1,383 Intellectual property 2,340 (2,196 ) 144 2,340 (2,129 ) 211 Supply agreement 1,400 (1,400 ) — 1,400 (544 ) 856 License 500 (306 ) 194 500 (113 ) 387 Patent 500 (54 ) 446 500 (20 ) 480 Trade names 370 (310 ) 60 370 (285 ) 85 Non-compete 200 (70 ) 130 200 (26 ) 174 Total $ 19,209 $ (13,710 ) $ 5,499 $ 18,653 $ (11,386 ) $ 7,267 Amortization expense, all of which relates to business acquisitions, was $1.1 million and $0.4 million for the three months ended June 30, 2017 and 2016 $1.9 million and $0.9 million for the six months ended June 30, 2017 and 2016, respectively. As of June 30, 2017, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2017 $ 940 2018 1,195 2019 680 2020 644 2021 590 Thereafter 1,450 Total $ 5,499

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Stockholders' Equity	10. STOCKHOLDERS’ EQUITY A summary of the changes in stockholders’ equity for the six months ended June 30, 2017 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2016 $ 479,517 Net income 19,052 Dividend payments (8,719 ) Dividends accrued for unvested restricted stock units (19 ) Net unrealized gains on available-for-sale securities (net of tax) 1,708 Net unrealized losses on cash flow hedges (338 ) Defined benefit plan adjustments (net of tax) 141 Foreign currency translation adjustment 3,861 Proceeds from stock option exercises 1,722 Purchase of treasury stock (17,311 ) ASU 2016-09 adoption 10 Stock-based compensation expense 3,739 Balance, June 30, 2017 $ 483,363 Stock Repurchase Program Since 1997, our Board of Directors has approved multiple share repurchase programs that have authorized open market repurchase transactions of up to 50.0 million shares of our common stock, which will be implemented through open market or private purchases from time to time as conditions warrant. During the six months ended June 30, 2017, we repurchased 0.9 million shares of our common stock at an average price of $20.27 per share. As of June 30, 2017, we have the authority to purchase an additional 3.6 million shares of our common stock under the current plans approved by the Board of Directors. Stock Option Exercises We issued 0.1 million shares of treasury stock during the six months ended June 30, 2017 to accommodate employee stock option exercises. The stock options had exercise prices ranging from $15.29 to $23.02. We received proceeds totaling $1.7 million from the exercise of these stock options during the six months ended June 30, 2017. Dividend Payments During the six months ended June 30, 2017, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid February 2, 2017 February 16, 2017 $ 0.09 $ 4,369 May 4, 2017 May 18, 2017 $ 0.09 $ 4,350 Other Comprehensive Income Other comprehensive income consists of unrealized gains (losses) on available-for-sale securities, unrealized gains (losses) on cash flow hedges, reclassification adjustments for amounts included in net income related to impairments of available-for-sale securities, realized gains (losses) on available-for-sale securities, realized gains (losses) on cash flow hedges, and amortization of actuarial gains (losses) related to our defined benefit plan, defined benefit plan adjustments, and foreign currency translation adjustments. The following tables present the changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2017 and 2016: Three Months Ended June 30, 2017 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,739 $ 79 $ (4,962 ) $ (6,333 ) $ (9,477 ) Other comprehensive income (loss) before reclassifications 1,222 (571 ) — 2,619 3,270 Amounts reclassified from accumulated other comprehensive income (849 ) 154 86 — (609 ) Net current period other comprehensive income (loss) 373 (417 ) 86 2,619 2,661 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Three Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,677 $ (3,850 ) $ (5,778 ) $ (7,951 ) Other comprehensive income (loss) before reclassifications 481 — (601 ) (120 ) Amounts reclassified from accumulated other comprehensive income (646 ) 22 — (624 ) Net current period other comprehensive income (loss) (165 ) 22 (601 ) (744 ) Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) The following tables present the changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2017 and 2016: Six Months Ended June 30, 2017 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 404 $ — $ (5,017 ) $ (7,575 ) $ (12,188 ) Other comprehensive income (loss) before reclassifications 2,842 (492 ) — 3,861 6,211 Amounts reclassified from accumulated other comprehensive income (1,134 ) 154 141 — (839 ) Net current period other comprehensive income (loss) 1,708 (338 ) 141 3,861 5,372 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Six Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 1,239 — 627 1,866 Amounts reclassified from accumulated other comprehensive income (1,659 ) 67 — (1,592 ) Net current period other comprehensive income (loss) (420 ) 67 627 274 Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2017 and 2016: (In thousands) Three Months Ended June 30, 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,393 Net realized investment gain Impairment expense (2 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (124 ) (1) Total reclassifications for the period, before tax 1,113 Tax (expense) benefit (504 ) Total reclassifications for the period, net of tax $ 609 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,354 Net realized investment gain Impairment expense (295 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (33 ) (1) Total reclassifications for the period, before tax 1,026 Tax (expense) benefit (402 ) Total reclassifications for the period, net of tax $ 624 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2017 and 2016: (In thousands) Six Months Ended June 30, 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,965 Net realized investment gain Impairment expense (105 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (204 ) (1) Total reclassifications for the period, before tax 1,502 Tax (expense) benefit (663 ) Total reclassifications for the period, net of tax $ 839 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,115 Net realized investment gain Impairment expense (395 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,622 Tax (expense) benefit (1,030 ) Total reclassifications for the period, net of tax $ 1,592 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2017 and 2016: Three Months Ended Three Months Ended June 30, 2017 June 30, 2016 (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 $ 2,003 $ (781 ) $ 1,222 $ 789 $ (308 ) $ 481 Unrealized gains (losses) on cash flow hedges (571 ) — (571 ) — — — Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,391 ) 542 (849 ) (1,059 ) 413 (646 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 154 — 154 — — — Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 124 (38 ) 86 33 (11 ) 22 Foreign currency translation adjustment 2,619 — 2,619 (601 ) — (601 ) Total Other Comprehensive Income (Loss) $ 2,938 $ (277 ) $ 2,661 $ (838 ) $ 94 $ (744 ) The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2017 and 2016: Six Months Ended Six Months Ended June 30, 2017 June 30, 2016 (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 $ 4,659 $ (1,817 ) $ 2,842 $ 2,031 $ (792 ) $ 1,239 Unrealized gains (losses) on cash flow hedges (492 ) — (492 ) — — — Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,860 ) 726 (1,134 ) (2,720 ) 1,061 (1,659 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 154 — 154 — — — Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 204 (63 ) 141 98 (31 ) 67 Foreign currency translation adjustment 3,861 — 3,861 627 — 627 Total Other Comprehensive Income (Loss) $ 6,526 $ (1,154 ) $ 5,372 $ 36 $ 238 $ 274

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share	11. EARNINGS PER SHARE A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2017 2016 2017 2016 Numerator Net income $ 12,401 $ 10,228 $ 19,052 $ 15,242 Denominator Weighted average number of shares – basic 48,036 48,831 48,232 49,026 Effect of dilutive securities Stock options 279 161 348 138 PSUs, RSUs and restricted stock 98 56 95 54 Weighted average number of shares – diluted 48,413 49,048 48,675 49,218 Net income per share – basic $ 0.26 $ 0.21 $ 0.40 $ 0.31 Net income per share – diluted $ 0.26 $ 0.21 $ 0.39 $ 0.31 Anti-dilutive options to purchase common stock outstanding were excluded from the above calculations. Anti-dilutive options totaled 4.1 million and 5.6 million for the three months ended June 30, 2017 and 2016, respectively, and 4.1 million and 5.8 million for the six months ended June 30, 2017 and 2016, respectively.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Information	12. SEGMENT INFORMATION We operate in two reportable segments: (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes our suite of ProCloud ® We evaluate the performance of our segments based on gross profit; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net realized investment gain/loss, other income/expense and provision for taxes are reported on a company-wide, functional basis only. There are no inter-segment revenues. The following table presents information about the reported sales and gross profit of our reportable segments for the three and six months ended June 30, 2017 and 2016. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2017 June 30, 2016 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 155,543 $ 75,885 $ 138,549 $ 70,705 Services & Support 29,130 8,747 24,152 8,250 Total $ 184,673 $ 84,632 $ 162,701 $ 78,955 Six Months Ended June 30, 2017 June 30, 2016 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 299,140 $ 142,823 $ 262,432 $ 130,515 Services & Support 55,812 15,524 42,473 14,234 Total $ 354,952 $ 158,347 $ 304,905 $ 144,749 Sales by Category In addition to our reporting segments, we also report revenue for the following three categories – Access & Aggregation, Customer Devices, Traditional & Other Products. The table below presents sales information by category for the three and six months ended June 30, 2017 and 2016: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Access & Aggregation $ 138,639 $ 102,232 $ 258,782 $ 196,087 Customer Devices 33,833 40,876 70,101 73,229 Traditional & Other Products 12,201 19,593 26,069 35,589 Total $ 184,673 $ 162,701 $ 354,952 $ 304,905

Liability for Warranty Returns

Liability for Warranty Returns	6 Months Ended
	Jun. 30, 2017
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	13. 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 $9.2 million and $8.5 million at June 30, 2017 and December 31, 2016, respectively. During the three months ended March 31, 2017, we recorded a receivable and a reduction in warranty expense related to a settlement with a third party supplier for a defective component, the impact of which is reflected in the table below. These liabilities are included in accrued expenses in the accompanying Consolidated Balance Sheets. A summary of warranty expense and write-off activity for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Balance at beginning of period $ 8,988 $ 9,042 $ 8,548 $ 8,739 Plus: Amounts charged to cost and expenses 3,055 1,431 2,314 2,329 Less: Deductions (2,863 ) (1,538 ) (1,682 ) (2,133 ) Balance at end of period $ 9,180 $ 8,935 $ 9,180 $ 8,935

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. COMMITMENTS AND CONTINGENCIES In the ordinary course of business, we may be subject to various legal proceedings and claims, including employment disputes, patent claims, disputes over contract agreements and other commercial disputes. In some cases, claimants seek damages or other relief, such as royalty payments related to patents, which, if granted, could require significant expenditures. Although the outcome of any claim or litigation can never be certain, it is our opinion that the outcome of all contingencies of which we are currently aware will not materially affect our business, operations, financial condition or cash flows. We have committed to invest up to an aggregate of $7.9 million in two private equity funds, and we have contributed $8.4 million as of June 30, 2017, of which $7.7 million has been applied to these commitments.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	15. SUBSEQUENT EVENTS On July 18, 2017, 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 3, 2017. The payment date will be August 17, 2017. The quarterly dividend payment will be approximately $4.3 million. In July 2003, our Board of Directors elected to begin declaring quarterly dividends on our common stock considering the tax treatment of dividends and adequate levels of Company liquidity.

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim statements should be read in conjunction with the financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2016, filed on February 24, 2017 with the SEC.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. Our more significant estimates include the obsolete and excess inventory reserves, warranty reserves, customer rebates, determination of the deferred revenue components of multiple element sales agreements, estimated costs to complete obligations associated with deferred revenues, estimated income tax provision and income tax contingencies, the fair value of stock-based compensation, impairment of goodwill, valuation and estimated lives of intangible assets, estimated pension liability, fair value of investments, and the evaluation of other-than-temporary declines in the value of investments. Actual amounts could differ significantly from these estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In March 2017, the FASB issued Accounting Standards Update No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost Compensation — Retirement Benefits During 2017, we adopted the following accounting standards, which had no material effect on our financial position, results of operations or cash flows: In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory Inventory In January 2017, we adopted ASU 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.

Business Combinations (Tables)

Business Combinations (Tables)	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed Subject to Working Capital Adjustments	The allocation of the purchase price to the estimated fair value of the assets acquired and liabilities assumed at the acquisition date, subject to working capital adjustments, is as follows: (In Thousands) Assets Inventory $ 3,131 Property, plant and equipment 352 Intangible assets 4,700 Total assets acquired 8,183 Liabilities Accounts payable (1,250 ) Warranty payable (61 ) Accrued wages and benefits (122 ) Deferred income taxes (2,265 ) Total liabilities assumed (3,698 ) Total net assets 4,485 Gain on bargain purchase of a business, net of tax (3,542 ) Total purchase price $ 943
Details of the Acquired Intangible Assets	The details of the acquired intangible assets are as follows: In thousands Value Life (years) Supply agreement $ 1,400 0.8 Customer relationships 1,200 6.0 Developed technology 800 10.0 License 500 1.3 Patent 500 7.3 Non-compete 200 2.3 Trade name 100 2.0 Total $ 4,700
Summary of Unaudited Supplemental Pro Forma Information	The following unaudited supplemental pro forma information presents the financial results as if the acquisition had occurred on January 1, 2015. 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, 2015, nor is it indicative of any future results. Aside from revising the 2015 net income for the effect of the bargain purchase gain, there were no material, non-recurring adjustments to this unaudited pro forma information. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Pro forma revenue $ 164,332 $ 160,562 $ 307,687 $ 304,542 Pro forma net income $ 10,022 $ 1,983 $ 14,907 $ 8,405 Pro forma earnings per share - basic $ 0.21 $ 0.04 $ 0.30 $ 0.16 Pro forma earnings per share - diluted $ 0.20 $ 0.04 $ 0.30 $ 0.16

Pension Benefit Plan (Tables)

Pension Benefit Plan (Tables)	6 Months Ended
	Jun. 30, 2017
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, 2017 and 2016 Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Service cost $ 306 $ 310 $ 603 $ 607 Interest cost 147 184 290 360 Expected return on plan assets (307 ) (271 ) (606 ) (530 ) Amortization of actuarial losses 75 45 148 88 Net periodic pension cost $ 221 $ 268 $ 435 $ 525

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense Related to Stock Options, Performance Stock Units (PSUs), Restricted Stock Units (RSUs) and Restricted Stock	The following table summarizes the stock-based compensation expense related to stock options, performance stock units (PSUs), restricted stock units (RSUs) and restricted stock for the three and six months ended June 30, 2017 and 2016, which was recognized as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Stock-based compensation expense included in cost of sales $ 93 $ 95 $ 184 $ 194 Selling, general and administrative expense 1,008 788 2,024 1,557 Research and development expense 755 668 1,531 1,358 Stock-based compensation expense included in operating expenses 1,763 1,456 3,555 2,915 Total stock-based compensation expense 1,856 1,551 3,739 3,109 Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock (433 ) (213 ) (813 ) (425 ) Total stock-based compensation expense, net of tax $ 1,423 $ 1,338 $ 2,926 $ 2,684
Summary of Stock Options Outstanding	The following table is a summary of our stock options outstanding as of December 31, 2016 and June 30, 2017 and the changes that occurred during the six months ended June 30, 2017: (In thousands, except per share amounts) Number of Stock Options Weighted Avg. Exercise Price Weighted Avg. Remaining Contractual Life In Years Aggregate Intrinsic Value Stock options outstanding, December 31, 2016 6,338 $ 22.14 5.63 $ 16,972 Stock options granted — $ — Stock options exercised (103 ) $ 16.78 Stock options forfeited (32 ) $ 17.62 Stock options expired (55 ) $ 26.67 Stock options outstanding, June 30, 2017 6,148 $ 22.21 5.14 $ 11,232 Stock options vested and expected to vest, June 30, 2017 6,148 $ 22.21 5.14 $ 11,232 Options exercisable, June 30, 2017 4,601 $ 23.78 4.23 $ 5,862
Summary of Weighted-Average Assumptions and Value of Options Granted	The weighted-average assumptions and value of options granted during the three and six months ended June 30, 2016 were as follows: Three and Six Months Ended June 30, 2016 Expected volatility 34.74 % Risk-free interest rate 1.33 % Expected dividend yield 1.91 % Expected life (in years) 6.26 Weighted-average estimated value $ 5.42
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, 2016 and the changes that occurred during the six months ended June 30, 2017: (In thousands, except per share amounts) Number of Shares Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2016 519 $ 20.51 PSUs, RSUs and restricted stock granted 520 $ 22.24 PSUs, RSUs and restricted stock vested (2 ) $ 18.29 PSUs, RSUs and restricted stock forfeited (6 ) $ 20.00 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2017 1,031 $ 21.39

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2017
Investments Debt And Equity Securities [Abstract]
Securities and Investments, Recorded at Either Fair Value or Cost	At June 30, 2017, we held the following securities and investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 15,662 $ 2,389 $ (23 ) $ 18,028 Corporate bonds 72,954 132 (107 ) 72,979 Municipal fixed-rate bonds 7,596 7 (20 ) 7,583 Asset-backed bonds 13,313 11 (16 ) 13,308 Mortgage/Agency-backed bonds 9,549 14 (36 ) 9,527 U.S. government bonds 21,528 4 (132 ) 21,400 Foreign government bonds 2,700 3 (1 ) 2,702 Marketable equity securities 31,741 2,153 (929 ) 32,965 Available-for-sale securities held at fair value $ 175,043 $ 4,713 $ (1,264 ) $ 178,492 Restricted investment held at cost 27,800 Other investments held at cost 673 Total carrying value of available-for-sale investments $ 206,965 At December 31, 2016, we held the following securities and investments, recorded at either fair value or cost: Amortized Gross Unrealized Carrying (In thousands) Cost Gains Losses Value Deferred compensation plan assets $ 12,367 $ 2,271 $ (42 ) $ 14,596 Corporate bonds 66,522 64 (174 ) 66,412 Municipal fixed-rate bonds 11,799 12 (37 ) 11,774 Asset-backed bonds 10,201 19 (14 ) 10,206 Mortgage/Agency-backed bonds 13,080 15 (91 ) 13,004 U.S. government bonds 30,022 15 (270 ) 29,767 Foreign government bonds 3,729 2 (1 ) 3,730 Variable rate demand notes 11,855 — — 11,855 Marketable equity securities 30,571 311 (1,503 ) 29,379 Available-for-sale securities held at fair value $ 190,146 $ 2,709 $ (2,132 ) $ 190,723 Restricted investment held at cost 27,800 Other investments held at cost 767 Total carrying value of available-for-sale investments $ 219,290
Contractual Maturities of Corporate Bonds, Municipal Fixed-Rate Bonds, Asset-Backed Bonds, Mortgage/Agency-Backed Bonds, U.S. Government Bonds and Foreign Government Bonds	As of June 30, 2017, our corporate bonds, municipal fixed-rate bonds, asset-backed bonds, mortgage/agency-backed bonds, U.S. government bonds and foreign government bonds 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 $ 33,486 $ 4,101 $ — $ — $ 8,919 $ 825 One to two years 16,124 1,536 850 493 — 600 Two to three years 21,421 775 5,185 — 8,367 1,277 Three to five years 1,948 1,171 5,836 415 4,114 — Five to ten years — — 508 1,340 — — More than ten years — — 929 7,279 — — Total $ 72,979 $ 7,583 $ 13,308 $ 9,527 $ 21,400 $ 2,702
Gross Realized Gains and Losses on Sale of Securities	The following table presents gross realized gains and losses related to our investments. Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Gross realized gains $ 1,512 $ 1,517 $ 2,230 $ 3,881 Gross realized losses $ (122 ) $ (407 ) $ (370 ) $ (1,043 )
Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments	We have categorized our cash equivalents held in money market funds and our investments held at fair value into a three-level fair value hierarchy based on the priority of the inputs to the valuation technique for the cash equivalents and investments as follows: Level 1 - Values based on unadjusted quoted prices for identical assets or liabilities in an active market; Level 2 - Values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; Level 3 - Values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs include information supplied by investees. Fair Value Measurements at June 30, 2017 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 6,487 $ 6,487 $ — $ — Commercial Paper 5,497 — 5,497 — Cash equivalents 11,984 6,487 5,497 — Available-for-sale securities Deferred compensation plan assets 18,028 18,028 — — Available-for-sale debt securities Corporate bonds 72,979 — 72,979 — Municipal fixed-rate bonds 7,583 — 7,583 — Asset-backed bonds 13,308 — 13,308 — Mortgage/Agency-backed bonds 9,527 — 9,527 — U.S. government bonds 21,400 21,400 — — Foreign government bonds 2,702 — 2,702 — Available-for-sale marketable equity securities Marketable equity securities – various industries 32,965 32,965 — — Available-for-sale securities 178,492 72,393 106,099 — Total $ 190,476 $ 78,880 $ 111,596 $ — Fair Value Measurements at December 31, 2016 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 6,878 $ 6,878 $ — $ — Commercial Paper 17,222 — 17,222 — Cash equivalents 24,100 6,878 17,222 — Available-for-sale securities Deferred compensation plan assets 14,596 14,596 — — Available-for-sale debt securities Corporate bonds 66,412 — 66,412 — Municipal fixed-rate bonds 11,774 — 11,774 — Asset-backed bonds 10,206 — 10,206 — Mortgage/Agency-backed bonds 13,004 — 13,004 — U.S. government bonds 29,767 29,767 — — Foreign government bonds 3,730 — 3,730 — Variable Rate Demand Notes 11,855 — 11,855 — Available-for-sale marketable equity securities Marketable equity securities – various industries 29,379 29,379 — — Available-for-sale securities 190,723 73,742 116,981 — Total $ 214,823 $ 80,620 $ 134,203 $ —

Derivative Instruments and He27

Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet	The fair values of our derivative instruments recorded in the Consolidated Balance Sheet as of June 30, 2017 and December 31, 2016 were as follows: (In thousands) Balance Sheet Location June 30, 2017 December 31, 2016 Derivatives Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative liabilities Accounts payable $ 610 $ — Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative assets Other receivables — 159 Foreign exchange contracts – derivative liabilities Accounts payable 352 — Total derivatives $ 962 $ 159
Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income	The change in the fair values of our derivative instruments recorded in the Consolidated Statements of Income during the three and six months ended June 30, 2017 and 2016 were as follows: Three Months Ended Six Months Ended Income Statement June 30, June 30, (In thousands) Location 2017 2016 2017 2016 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other income (expense) $ (451 ) $ 237 $ (485 ) $ 190
Schedule of Change in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income (OCI) and Reclassified to Income	The change in our derivatives designated as hedging instruments recorded in other comprehensive income (OCI) and reclassified to income during the three and six months ended June 30, 2017 and 2016 were as follows: Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Three Months Ended Location of Gains Three Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2017 2016 from AOCI into Income 2017 2016 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ (571 ) $ — Cost of Sales $ (154 ) $ — Amount of Gains (Losses) Recognized in Amount of Gains (Losses) Reclassified OCI on Derivatives from AOCI into Income Six Months Ended Location of Gains Six Months Ended June 30, (Losses) Reclassified June 30, (In thousands) 2017 2016 from AOCI into Income 2017 2016 Derivatives Designated as Hedging Instruments: Foreign exchange contracts $ (492 ) $ — Cost of Sales $ (154 ) $ —

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
Components of Inventory	At June 30, 2017 and December 31, 2016, inventory consisted of the following: June 30, December 31, (In thousands) 2017 2016 Raw materials $ 42,218 $ 40,461 Work in process 2,443 4,003 Finished goods 69,334 60,653 Total $ 113,995 $ 105,117

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents our intangible assets as of June 30, 2017 and December 31, 2016: (In thousands) June 30, 2017 December 31, 2016 Gross Value Accumulated Amortization Net Value Gross Value Accumulated Amortization Net Value Customer relationships $ 7,249 $ (3,765 ) $ 3,484 $ 6,899 $ (3,208 ) $ 3,691 Developed technology 6,650 (5,609 ) 1,041 6,444 (5,061 ) 1,383 Intellectual property 2,340 (2,196 ) 144 2,340 (2,129 ) 211 Supply agreement 1,400 (1,400 ) — 1,400 (544 ) 856 License 500 (306 ) 194 500 (113 ) 387 Patent 500 (54 ) 446 500 (20 ) 480 Trade names 370 (310 ) 60 370 (285 ) 85 Non-compete 200 (70 ) 130 200 (26 ) 174 Total $ 19,209 $ (13,710 ) $ 5,499 $ 18,653 $ (11,386 ) $ 7,267
Estimated Future Amortization Expense Related to Intangible Assets	As of June 30, 2017, the estimated future amortization expense of our intangible assets is as follows: (In thousands) Amount Remainder of 2017 $ 940 2018 1,195 2019 680 2020 644 2021 590 Thereafter 1,450 Total $ 5,499

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Summary of Changes in Stockholders' Equity	A summary of the changes in stockholders’ equity for the six months ended June 30, 2017 is as follows: (In thousands) Stockholders’ Equity Balance, December 31, 2016 $ 479,517 Net income 19,052 Dividend payments (8,719 ) Dividends accrued for unvested restricted stock units (19 ) Net unrealized gains on available-for-sale securities (net of tax) 1,708 Net unrealized losses on cash flow hedges (338 ) Defined benefit plan adjustments (net of tax) 141 Foreign currency translation adjustment 3,861 Proceeds from stock option exercises 1,722 Purchase of treasury stock (17,311 ) ASU 2016-09 adoption 10 Stock-based compensation expense 3,739 Balance, June 30, 2017 $ 483,363
Cash Dividends	During the six months ended June 30, 2017, we paid cash dividends as follows (in thousands except per share amounts): Record Date Payment Date Per Share Amount Total Dividend Paid February 2, 2017 February 16, 2017 $ 0.09 $ 4,369 May 4, 2017 May 18, 2017 $ 0.09 $ 4,350
Changes in Accumulated Other Comprehensive Income, Net of Tax by Component	The following tables present the changes in accumulated other comprehensive income, net of tax, by component for the three months ended June 30, 2017 and 2016: Three Months Ended June 30, 2017 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,739 $ 79 $ (4,962 ) $ (6,333 ) $ (9,477 ) Other comprehensive income (loss) before reclassifications 1,222 (571 ) — 2,619 3,270 Amounts reclassified from accumulated other comprehensive income (849 ) 154 86 — (609 ) Net current period other comprehensive income (loss) 373 (417 ) 86 2,619 2,661 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Three Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,677 $ (3,850 ) $ (5,778 ) $ (7,951 ) Other comprehensive income (loss) before reclassifications 481 — (601 ) (120 ) Amounts reclassified from accumulated other comprehensive income (646 ) 22 — (624 ) Net current period other comprehensive income (loss) (165 ) 22 (601 ) (744 ) Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 ) The following tables present the changes in accumulated other comprehensive income, net of tax, by component for the six months ended June 30, 2017 and 2016: Six Months Ended June 30, 2017 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Unrealized Gains (Losses) on Cash Flow Hedges Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 404 $ — $ (5,017 ) $ (7,575 ) $ (12,188 ) Other comprehensive income (loss) before reclassifications 2,842 (492 ) — 3,861 6,211 Amounts reclassified from accumulated other comprehensive income (1,134 ) 154 141 — (839 ) Net current period other comprehensive income (loss) 1,708 (338 ) 141 3,861 5,372 Ending balance $ 2,112 $ (338 ) $ (4,876 ) $ (3,714 ) $ (6,816 ) Six Months Ended June 30, 2016 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments Total Beginning balance $ 1,932 $ (3,895 ) $ (7,006 ) $ (8,969 ) Other comprehensive income (loss) before reclassifications 1,239 — 627 1,866 Amounts reclassified from accumulated other comprehensive income (1,659 ) 67 — (1,592 ) Net current period other comprehensive income (loss) (420 ) 67 627 274 Ending balance $ 1,512 $ (3,828 ) $ (6,379 ) $ (8,695 )
Reclassifications Out of Accumulated Other Comprehensive Income	The following tables present the details of reclassifications out of accumulated other comprehensive income for the three months ended June 30, 2017 and 2016: (In thousands) Three Months Ended June 30, 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,393 Net realized investment gain Impairment expense (2 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (124 ) (1) Total reclassifications for the period, before tax 1,113 Tax (expense) benefit (504 ) Total reclassifications for the period, net of tax $ 609 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. (In thousands) Three Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,354 Net realized investment gain Impairment expense (295 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (33 ) (1) Total reclassifications for the period, before tax 1,026 Tax (expense) benefit (402 ) Total reclassifications for the period, net of tax $ 624 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. The following tables present the details of reclassifications out of accumulated other comprehensive income for the six months ended June 30, 2017 and 2016: (In thousands) Six Months Ended June 30, 2017 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 1,965 Net realized investment gain Impairment expense (105 ) Net realized investment gain Net losses on derivatives designated as hedging instruments (154 ) Cost of sales Defined benefit plan adjustments – actuarial losses (204 ) (1) Total reclassifications for the period, before tax 1,502 Tax (expense) benefit (663 ) Total reclassifications for the period, net of tax $ 839 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements. (In thousands) Six Months Ended June 30, 2016 Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for- sale securities: Net realized gain on sales of securities $ 3,115 Net realized investment gain Impairment expense (395 ) Net realized investment gain Defined benefit plan adjustments – actuarial losses (98 ) (1) Total reclassifications for the period, before tax 2,622 Tax (expense) benefit (1,030 ) Total reclassifications for the period, net of tax $ 1,592 (1) Included in the computation of net periodic pension cost. See Note 4 of Notes to Consolidated Financial Statements.
Other Comprehensive Income	The following table presents the tax effects related to the change in each component of other comprehensive income for the three months ended June 30, 2017 and 2016: Three Months Ended Three Months Ended June 30, 2017 June 30, 2016 (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 $ 2,003 $ (781 ) $ 1,222 $ 789 $ (308 ) $ 481 Unrealized gains (losses) on cash flow hedges (571 ) — (571 ) — — — Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,391 ) 542 (849 ) (1,059 ) 413 (646 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 154 — 154 — — — Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 124 (38 ) 86 33 (11 ) 22 Foreign currency translation adjustment 2,619 — 2,619 (601 ) — (601 ) Total Other Comprehensive Income (Loss) $ 2,938 $ (277 ) $ 2,661 $ (838 ) $ 94 $ (744 ) The following table presents the tax effects related to the change in each component of other comprehensive income for the six months ended June 30, 2017 and 2016: Six Months Ended Six Months Ended June 30, 2017 June 30, 2016 (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 $ 4,659 $ (1,817 ) $ 2,842 $ 2,031 $ (792 ) $ 1,239 Unrealized gains (losses) on cash flow hedges (492 ) — (492 ) — — — Reclassification adjustment for amounts related to available-for-sale investments included in net income (1,860 ) 726 (1,134 ) (2,720 ) 1,061 (1,659 ) Reclassification adjustment for amounts related to cash flow hedges included in net income 154 — 154 — — — Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income 204 (63 ) 141 98 (31 ) 67 Foreign currency translation adjustment 3,861 — 3,861 627 — 627 Total Other Comprehensive Income (Loss) $ 6,526 $ (1,154 ) $ 5,372 $ 36 $ 238 $ 274

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings Per Share	A summary of the calculation of basic and diluted earnings per share for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2017 2016 2017 2016 Numerator Net income $ 12,401 $ 10,228 $ 19,052 $ 15,242 Denominator Weighted average number of shares – basic 48,036 48,831 48,232 49,026 Effect of dilutive securities Stock options 279 161 348 138 PSUs, RSUs and restricted stock 98 56 95 54 Weighted average number of shares – diluted 48,413 49,048 48,675 49,218 Net income per share – basic $ 0.26 $ 0.21 $ 0.40 $ 0.31 Net income per share – diluted $ 0.26 $ 0.21 $ 0.39 $ 0.31

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
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, 2017 and 2016. We do not produce asset information by reportable segment; therefore, it is not reported. Three Months Ended June 30, 2017 June 30, 2016 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 155,543 $ 75,885 $ 138,549 $ 70,705 Services & Support 29,130 8,747 24,152 8,250 Total $ 184,673 $ 84,632 $ 162,701 $ 78,955 Six Months Ended June 30, 2017 June 30, 2016 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 299,140 $ 142,823 $ 262,432 $ 130,515 Services & Support 55,812 15,524 42,473 14,234 Total $ 354,952 $ 158,347 $ 304,905 $ 144,749
Sales Information by Category	The table below presents sales information by category for the three and six months ended June 30, 2017 and 2016: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Access & Aggregation $ 138,639 $ 102,232 $ 258,782 $ 196,087 Customer Devices 33,833 40,876 70,101 73,229 Traditional & Other Products 12,201 19,593 26,069 35,589 Total $ 184,673 $ 162,701 $ 354,952 $ 304,905

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	6 Months Ended
	Jun. 30, 2017
Product Warranties Disclosures [Abstract]
Summary of Warranty Expense and Write-Off Activity	A summary of warranty expense and write-off activity for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2017 2016 2017 2016 Balance at beginning of period $ 8,988 $ 9,042 $ 8,548 $ 8,739 Plus: Amounts charged to cost and expenses 3,055 1,431 2,314 2,329 Less: Deductions (2,863 ) (1,538 ) (1,682 ) (2,133 ) Balance at end of period $ 9,180 $ 8,935 $ 9,180 $ 8,935

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Jan. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policy [Line Items]
Retained earnings	$ 931,044		$ 921,942
ASU 2016-09 [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in additional paid in capital		$ 100
Retained earnings		100
ASU 2016-09 [Member] | Non-qualified Stock Options and RSUs [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in deferred tax assets		$ 10

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - CommScope, Inc. Subsidiaries Fiber Access Products, Technologies and Service Relationships [Member] - USD ($) $ in Thousands	Sep. 13, 2016	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2017
Business Acquisition [Line Items]
Date of acquisition				Sep. 13, 2016
Business acquisition, description				On September 13, 2016, we acquired key fiber access products, technologies and service relationships from subsidiaries of CommScope, Inc. for $0.9 million in cash. This acquisition will enhance our solutions for the cable MSO industry and will provide cable operators with the scalable solutions, services and support they require to compete in the multi-gigabit service delivery market.
Cash consideration	$ 943
Bargain purchase gain net of income taxes	$ 3,542		$ 3,500
Acquisition and integration related expenses and amortization of acquired intangibles		$ 600		$ 1,400

Business Combinations - Allocat

Business Combinations - Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed Subject to Working Capital Adjustments (Detail) - CommScope, Inc. Subsidiaries Fiber Access Products, Technologies and Service Relationships [Member] - USD ($) $ in Thousands	Sep. 13, 2016	Sep. 30, 2016
Assets
Inventory	$ 3,131
Property, plant and equipment	352
Intangible assets	4,700
Total assets acquired	8,183
Liabilities
Accounts payable	(1,250)
Warranty payable	(61)
Accrued wages and benefits	(122)
Deferred income taxes	(2,265)
Total liabilities assumed	(3,698)
Total net assets	4,485
Gain on bargain purchase of a business, net of tax	(3,542)	$ (3,500)
Total purchase price	$ 943

Business Combinations - Details

Business Combinations - Details of the Acquired Intangible Assets (Detail) - CommScope, Inc. Subsidiaries Fiber Access Products, Technologies and Service Relationships [Member] $ in Thousands	Sep. 13, 2016USD ($)
Business Acquisition [Line Items]
Total, Value	$ 4,700
Supply Agreement [Member]
Business Acquisition [Line Items]
Total, Value	$ 1,400
Life (years)	9 months 18 days
Customer Relationships [Member]
Business Acquisition [Line Items]
Total, Value	$ 1,200
Life (years)	6 years
Developed Technology [Member]
Business Acquisition [Line Items]
Total, Value	$ 800
Life (years)	10 years
License [Member]
Business Acquisition [Line Items]
Total, Value	$ 500
Life (years)	1 year 3 months 18 days
Patent [Member]
Business Acquisition [Line Items]
Total, Value	$ 500
Life (years)	7 years 3 months 18 days
Non-compete [Member]
Business Acquisition [Line Items]
Total, Value	$ 200
Life (years)	2 years 3 months 18 days
Trade Name [Member]
Business Acquisition [Line Items]
Total, Value	$ 100
Life (years)	2 years

Business Combinations - Summary

Business Combinations - Summary of Unaudited Supplemental Pro Forma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Business Combinations [Abstract]
Pro forma revenue	$ 164,332	$ 160,562	$ 307,687	$ 304,542
Pro forma net income	$ 10,022	$ 1,983	$ 14,907	$ 8,405
Pro forma earnings per share - basic	$ 0.21	$ 0.04	$ 0.30	$ 0.16
Pro forma earnings per share - diluted	$ 0.20	$ 0.04	$ 0.30	$ 0.16

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Effective tax rate	27.30%	37.90%
Effective tax rate reduction for provision to return adjustment	3.20%
Effective tax rate reduction due to international revenues	6.30%

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 306	$ 310	$ 603	$ 607
Interest cost	147	184	290	360
Expected return on plan assets	(307)	(271)	(606)	(530)
Amortization of actuarial losses	75	45	148	88
Net periodic pension cost	$ 221	$ 268	$ 435	$ 525

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, Performance Stock Units (PSUs), Restricted Stock Units (RSUs) and Restricted Stock (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,856	$ 1,551	$ 3,739	$ 3,109
Tax benefit for expense associated with non-qualified options, PSUs, RSUs and restricted stock	(433)	(213)	(813)	(425)
Total stock-based compensation expense, net of tax	1,423	1,338	2,926	2,684
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	93	95	184	194
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,008	788	2,024	1,557
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	755	668	1,531	1,358
Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,763	$ 1,456	$ 3,555	$ 2,915

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance		6,338,000
Number of Stock Options, Stock options granted	0	0
Number of Stock Options, Stock options exercised		(103,000)
Number of Stock Options, Stock options forfeited		(32,000)
Number of Stock Options, Stock options expired		(55,000)
Number of Stock Options, Stock options outstanding, Ending Balance	6,148,000	6,148,000	6,338,000
Number of Stock Options, Stock options vested and expected to vest	6,148,000	6,148,000
Number of Stock Options, Options exercisable	4,601,000	4,601,000
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance		$ 22.14
Weighted Avg. Exercise Price, Stock options exercised		16.78
Weighted Avg. Exercise Price, Stock options forfeited		17.62
Weighted Avg. Exercise Price, Stock options expired		26.67
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	$ 22.21	22.21	$ 22.14
Weighted Avg. Exercise Price, Stock options vested and expected to vest	22.21	22.21
Weighted Avg. Exercise Price, Options exercisable	$ 23.78	$ 23.78
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding		5 years 1 month 20 days	5 years 7 months 17 days
Weighted Avg. Remaining Contractual Life In Years, Stock options vested and expected to vest		5 years 1 month 20 days
Weighted Avg. Remaining Contractual Life In Years, Options exercisable		4 years 2 months 23 days
Aggregate Intrinsic Value, Stock options outstanding	$ 11,232	$ 11,232	$ 16,972
Aggregate Intrinsic Value, Stock options vested and expected to vest	11,232	11,232
Aggregate Intrinsic Value, Options exercisable	$ 5,862	$ 5,862

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) - Additional Information (Detail) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)shares	Jun. 30, 2017USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pre-tax intrinsic value of options exercised	$ 0.1	$ 0.5
Number of Stock options, granted | shares	0	0
Unvested Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 5.2	$ 5.2
Recognition period of unvested compensation expense		1 year 9 months 18 days

Stock-Based Compensation - Su44

Stock-Based Compensation - Summary of Weighted-Average Assumptions and Value of Options Granted (Detail) - Stock Options [Member] - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	34.74%	34.74%
Risk-free interest rate	1.33%	1.33%
Expected dividend yield	1.91%	1.91%
Expected life (in years)	6 years 3 months 4 days	6 years 3 months 4 days
Weighted-average estimated value	$ 5.42	$ 5.42

Stock-Based Compensation - Su45

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	519
Number of Shares, PSUs, RSUs and restricted stock granted | shares	520
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(2)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(6)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,031
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance | $ / shares	$ 20.51
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	22.24
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	18.29
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	20
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 21.39

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU shares grant approved by board of directors				520
Compensation expense recognized	$ 1,856,000		$ 1,551,000	$ 3,739,000	$ 3,109,000
Performance Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU shares grant approved by board of directors		500
Market-Based PSUs, RSUs and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	7,900,000			$ 7,900,000
Recognition period of unvested compensation expense				3 years
Performance-Based PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	11,500,000			$ 11,500,000
Recognition period of unvested compensation expense				3 years
Performance-Based PSU Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized	$ 0			$ 0

Investments - Securities and In

Investments - Securities and Investments, Recorded at Either Fair Value or Cost (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 175,043	$ 190,146
Gross Unrealized Gains	4,713	2,709
Gross Unrealized Losses	(1,264)	(2,132)
Available-for-sale-securities, Carrying Value	178,492	190,723
Restricted investment held at cost	27,800	27,800
Other investments held at cost	673	767
Total carrying value of available-for-sale investments	206,965	219,290
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,662	12,367
Gross Unrealized Gains	2,389	2,271
Gross Unrealized Losses	(23)	(42)
Available-for-sale-securities, Carrying Value	18,028	14,596
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	72,954	66,522
Gross Unrealized Gains	132	64
Gross Unrealized Losses	(107)	(174)
Available-for-sale-securities, Carrying Value	72,979	66,412
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,596	11,799
Gross Unrealized Gains	7	12
Gross Unrealized Losses	(20)	(37)
Available-for-sale-securities, Carrying Value	7,583	11,774
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,313	10,201
Gross Unrealized Gains	11	19
Gross Unrealized Losses	(16)	(14)
Available-for-sale-securities, Carrying Value	13,308	10,206
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,549	13,080
Gross Unrealized Gains	14	15
Gross Unrealized Losses	(36)	(91)
Available-for-sale-securities, Carrying Value	9,527	13,004
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,528	30,022
Gross Unrealized Gains	4	15
Gross Unrealized Losses	(132)	(270)
Available-for-sale-securities, Carrying Value	21,400	29,767
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,700	3,729
Gross Unrealized Gains	3	2
Gross Unrealized Losses	(1)	(1)
Available-for-sale-securities, Carrying Value	2,702	3,730
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		11,855
Available-for-sale-securities, Carrying Value		11,855
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,741	30,571
Gross Unrealized Gains	2,153	311
Gross Unrealized Losses	(929)	(1,503)
Available-for-sale-securities, Carrying Value	$ 32,965	$ 29,379

Investments - Contractual Matur

Investments - Contractual Maturities of Corporate Bonds, Municipal Fixed-Rate Bonds, Asset-Backed Bonds, Mortgage/Agency-Backed Bonds, U.S. Government Bonds and Foreign Government Bonds (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale-securities, Fair Value/Carrying Value	$ 178,492	$ 190,723
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	33,486
One to two years	16,124
Two to three years	21,421
Three to five years	1,948
Available-for-sale-securities, Fair Value/Carrying Value	72,979	66,412
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	4,101
One to two years	1,536
Two to three years	775
Three to five years	1,171
Available-for-sale-securities, Fair Value/Carrying Value	7,583	11,774
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	850
Two to three years	5,185
Three to five years	5,836
Five to ten years	508
More than ten years	929
Available-for-sale-securities, Fair Value/Carrying Value	13,308	10,206
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	493
Three to five years	415
Five to ten years	1,340
More than ten years	7,279
Available-for-sale-securities, Fair Value/Carrying Value	9,527	13,004
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	8,919
Two to three years	8,367
Three to five years	4,114
Available-for-sale-securities, Fair Value/Carrying Value	21,400	29,767
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	825
One to two years	600
Two to three years	1,277
Available-for-sale-securities, Fair Value/Carrying Value	$ 2,702	$ 3,730

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Restricted certificate of deposit held	$ 27,800	$ 27,800
Identification of potential other-than-temporary impairments	25.00%
Alabama State Industrial Development Authority [Member]
Schedule of Investments [Line Items]
Maturity date of bond	Jan. 1, 2020
Percentage of interest on bond	2.00%
Alabama State Industrial Development Authority [Member] | Taxable Revenue Bond [Member]
Schedule of Investments [Line Items]
Collateral deposit against outstanding principal amount	$ 27,800	$ 27,800
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	$ 28,000
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member]
Schedule of Investments [Line Items]
Investment concentration risk percentage	5.00%

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Investments Debt And Equity Securities [Abstract]
Gross realized gains	$ 1,512	$ 1,517	$ 2,230	$ 3,881
Gross realized losses	$ (122)	$ (407)	$ (370)	$ (1,043)

Investments - Fair Value Measur

Investments - Fair Value Measurements of Cash Equivalents Held in Money Market Funds and Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 178,492	$ 190,723
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	11,984	24,100
Available-for-sale securities	178,492	190,723
Total	190,476	214,823
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	6,487	6,878
Available-for-sale securities	72,393	73,742
Total	78,880	80,620
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	5,497	17,222
Available-for-sale securities	106,099	116,981
Total	111,596	134,203
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	6,487	6,878
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	6,487	6,878
Commercial Paper [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	5,497	17,222
Commercial Paper [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	5,497	17,222
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	18,028	14,596
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	18,028	14,596
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	18,028	14,596
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	72,979	66,412
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	72,979	66,412
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	72,979	66,412
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	7,583	11,774
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	7,583	11,774
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	7,583	11,774
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,308	10,206
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	13,308	10,206
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	13,308	10,206
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,527	13,004
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,527	13,004
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	9,527	13,004
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	21,400	29,767
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	21,400	29,767
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	21,400	29,767
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,702	3,730
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,702	3,730
Foreign Government Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	2,702	3,730
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		11,855
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		11,855
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities		11,855
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	32,965	29,379
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 32,965	$ 29,379

Derivative Instruments and He52

Derivative Instruments and Hedging Activities - Additional Information (Detail) - Jun. 30, 2017	USD ($)	EUR (€)
Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Derivative, notional amount	$ 20,000,000	€ 17,500,000

Derivative Instruments and He53

Derivative Instruments and Hedging Activities - Schedule of Fair Values of Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) - Significant Other Observable Inputs (Level 2) [Member] - Foreign Exchange Contracts [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives Not Designated as Hedging Instruments (Level 2):
Total derivatives, assets fair value	$ 962	$ 159
Accounts Payable [Member]
Derivatives Designated as Hedging Instruments (Level 2):
Derivatives liabilities, fair value	610
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives liabilities, fair value	$ 352
Other Receivables [Member]
Derivatives Not Designated as Hedging Instruments (Level 2):
Derivatives asset, fair value		$ 159

Derivative Instruments and He54

Derivative Instruments and Hedging Activities - Schedule of Change in Fair Values of Derivative Instruments Recorded in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Foreign Exchange Contracts [Member] | Other Income (Expense) [Member]
Derivatives Not Designated as Hedging Instruments:
Derivative instrument, gain or loss	$ (451)	$ 237	$ (485)	$ 190

Derivative Instruments and He55

Derivative Instruments and Hedging Activities - Schedule of Change in Derivatives Designated Hedging Instruments Recorded in Other Comprehensive Income (OCI) and Reclassified to Income (Detail) - Foreign Exchange Contracts [Member] - Derivatives Designated as Hedging Instruments [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Derivative [Line Items]
Amount of Gains (Losses) Recognized in OCI on Derivatives	$ (571)	$ (492)
Cost of Sales [Member]
Derivative [Line Items]
Amount of Gains (Losses) Reclassified from AOCI into Income	$ (154)	$ (154)

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 42,218	$ 40,461
Work in process	2,443	4,003
Finished goods	69,334	60,653
Total	$ 113,995	$ 105,117

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Raw Materials [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 15.2	$ 14.6
Finished Goods [Member]
Inventory [Line Items]
Inventory valuation reserves	$ 12.7	$ 10.6

Goodwill and Intangible Asset58

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, relates to acquisition			$ 3,500,000		$ 3,500,000
Impairment losses			0
Amortization expense	$ 1,100,000	$ 400,000	1,900,000	$ 900,000
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition			3,100,000
Services & Support [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition			$ 400,000

Goodwill and Intangible Asset59

Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Goodwill [Line Items]
Gross Value	$ 19,209	$ 18,653
Accumulated Amortization	(13,710)	(11,386)
Net Value	5,499	7,267
Customer Relationships [Member]
Goodwill [Line Items]
Gross Value	7,249	6,899
Accumulated Amortization	(3,765)	(3,208)
Net Value	3,484	3,691
Developed Technology [Member]
Goodwill [Line Items]
Gross Value	6,650	6,444
Accumulated Amortization	(5,609)	(5,061)
Net Value	1,041	1,383
Intellectual Property [Member]
Goodwill [Line Items]
Gross Value	2,340	2,340
Accumulated Amortization	(2,196)	(2,129)
Net Value	144	211
Supply Agreement [Member]
Goodwill [Line Items]
Gross Value	1,400	1,400
Accumulated Amortization	(1,400)	(544)
Net Value		856
License [Member]
Goodwill [Line Items]
Gross Value	500	500
Accumulated Amortization	(306)	(113)
Net Value	194	387
Trade Names [Member]
Goodwill [Line Items]
Gross Value	370	370
Accumulated Amortization	(310)	(285)
Net Value	60	85
Patent [Member]
Goodwill [Line Items]
Gross Value	500	500
Accumulated Amortization	(54)	(20)
Net Value	446	480
Non-compete [Member]
Goodwill [Line Items]
Gross Value	200	200
Accumulated Amortization	(70)	(26)
Net Value	$ 130	$ 174

Goodwill and Intangible Asset60

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Remainder of 2017	$ 940
2,018	1,195
2,019	680
2,020	644
2,021	590
Thereafter	1,450
Net Value	$ 5,499	$ 7,267

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Beginning Balance			$ 479,517
Net Income	$ 12,401	$ 10,228	19,052	$ 15,242
Dividend payments			(8,719)
Dividends accrued for unvested restricted stock units			(19)
Net unrealized gains on available-for-sale securities (net of tax)	373	(165)	1,708	(420)
Net unrealized losses on cash flow hedges	(417)		(338)
Defined benefit plan adjustments (net of tax)	86	22	141	67
Foreign currency translation adjustment	2,619	$ (601)	3,861	627
Proceeds from stock option exercises			1,722	$ 541
Purchase of treasury stock			(17,311)
ASU 2016-09 adoption			10
Stock-based compensation expense			3,739
Ending Balance	$ 483,363		$ 483,363

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	50,000,000
Stock repurchased, shares	900,000
Shares repurchased, average price per share	$ 20.27
Additional shares authorized for purchase	3,600,000
Number of Options, exercised	103,000
Exercise price of stock options, lower range limit	$ 15.29
Exercise price of stock options, upper range limit	$ 23.02
Proceeds from stock option exercises	$ 1,722	$ 541

Stockholders' Equity - Cash Div

Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Dividends Payable [Line Items]
Record Date			Aug. 3, 2017
Payment Date			Aug. 17, 2017
Per Share Amount	$ 0.09	$ 0.09	$ 0.18	$ 0.18
Total Dividend Paid			$ 8,719	$ 8,860
Cash Dividends Paid in February [Member]
Dividends Payable [Line Items]
Record Date			Feb. 2, 2017
Payment Date			Feb. 16, 2017
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,369
Cash Dividends Paid in May [Member]
Dividends Payable [Line Items]
Record Date			May 4, 2017
Payment Date			May 18, 2017
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,350

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 479,517
Other comprehensive income (loss) before reclassifications	$ 3,270	$ (120)	6,211	$ 1,866
Amounts reclassified from accumulated other comprehensive income	(609)	(624)	(839)	(1,592)
Other Comprehensive Income (Loss), net of tax	2,661	(744)	5,372	274
Ending Balance	483,363		483,363
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,739	1,677	404	1,932
Other comprehensive income (loss) before reclassifications	1,222	481	2,842	1,239
Amounts reclassified from accumulated other comprehensive income	(849)	(646)	(1,134)	(1,659)
Other Comprehensive Income (Loss), net of tax	373	(165)	1,708	(420)
Ending Balance	2,112	1,512	2,112	1,512
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	79
Other comprehensive income (loss) before reclassifications	(571)		(492)
Amounts reclassified from accumulated other comprehensive income	154		154
Other Comprehensive Income (Loss), net of tax	(417)		(338)
Ending Balance	(338)		(338)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4,962)	(3,850)	(5,017)	(3,895)
Amounts reclassified from accumulated other comprehensive income	86	22	141	67
Other Comprehensive Income (Loss), net of tax	86	22	141	67
Ending Balance	(4,876)	(3,828)	(4,876)	(3,828)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,333)	(5,778)	(7,575)	(7,006)
Other comprehensive income (loss) before reclassifications	2,619	(601)	3,861	627
Other Comprehensive Income (Loss), net of tax	2,619	(601)	3,861	627
Ending Balance	(3,714)	(6,379)	(3,714)	(6,379)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,477)	(7,951)	(12,188)	(8,969)
Ending Balance	$ (6,816)	$ (8,695)	$ (6,816)	$ (8,695)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	$ (79,658)	$ (67,844)	$ (156,317)	$ (131,917)
Income before provision for income taxes	17,869	16,456	26,214	24,534
Tax (expense) benefit	(5,468)	(6,228)	(7,162)	(9,292)
Total reclassifications for the period, net of tax	12,401	10,228	19,052	15,242
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit plan adjustments – actuarial losses	(124)	(33)	(204)	(98)
Income before provision for income taxes	1,113	1,026	1,502	2,622
Tax (expense) benefit	(504)	(402)	(663)	(1,030)
Total reclassifications for the period, net of tax	609	624	839	1,592
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gain	1,393	1,354	1,965	3,115
Impairment Expense [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gain	(2)	$ (295)	(105)	$ (395)
Net Losses on Derivatives Designated as Hedging Instruments [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	$ (154)		$ (154)

Stockholders' Equity - Tax Effe

Stockholders' Equity - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, Before-Tax Amount	$ 2,003	$ 789	$ 4,659	$ 2,031
Unrealized gains (losses) on available-for-sale securities, Tax (Expense) Benefit	(781)	(308)	(1,817)	(792)
Unrealized gains (losses) on available-for-sale securities, Net-of-Tax Amount	1,222	481	2,842	1,239
Unrealized gains (losses) on cash flow hedges, Before-Tax Amount	(571)		(492)
Unrealized gains (losses) on cash flow hedges, Net-of-Tax Amount	(571)		(492)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Before-Tax Amount	(1,391)	(1,059)	(1,860)	(2,720)
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Tax (Expense) Benefit	542	413	726	1,061
Reclassification adjustment for amounts related to available-for-sale investments included in net income, Net-of-Tax Amount	(849)	(646)	(1,134)	(1,659)
Reclassification adjustment for amounts related to cash flow hedges included in net income, Before-Tax Amount	154		154
Reclassification adjustment for amounts related to cash flow hedges included in net income, Net-of-Tax Amount	154		154
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Before-Tax Amount	124	33	204	98
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Tax (Expense) Benefit	(38)	(11)	(63)	(31)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income, Net-of-Tax Amount	86	22	141	67
Foreign currency translation adjustment, Before-Tax Amount	2,619	(601)	3,861	627
Foreign currency translation adjustment, Net-of-Tax Amount	2,619	(601)	3,861	627
Total Other Comprehensive Income (Loss), Before-Tax Amount	2,938	(838)	6,526	36
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(277)	94	(1,154)	238
Other Comprehensive Income (Loss), net of tax	$ 2,661	$ (744)	$ 5,372	$ 274

Earnings Per Share - Summary of

Earnings Per Share - Summary of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator
Net Income	$ 12,401	$ 10,228	$ 19,052	$ 15,242
Denominator
Weighted average number of shares – basic	48,036	48,831	48,232	49,026
Effect of dilutive securities
Stock options	279	161	348	138
PSUs, RSUs and restricted stock	98	56	95	54
Weighted average number of shares – diluted	48,413	49,048	48,675	49,218
Net income per share – basic	$ 0.26	$ 0.21	$ 0.40	$ 0.31
Net income per share – diluted	$ 0.26	$ 0.21	$ 0.39	$ 0.31

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Anti-dilutive options, Total	4.1	5.6	4.1	5.8

Segment Information - Additiona

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016SegmentCategory
Segment Reporting [Abstract]
Number of reportable segments | Segment	2
Number of categories | Category	3

Segment Information - Sales and

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Sales	$ 184,673	$ 162,701	$ 354,952	$ 304,905
Gross Profit	84,632	78,955	158,347	144,749
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	155,543	138,549	299,140	262,432
Gross Profit	75,885	70,705	142,823	130,515
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	29,130	24,152	55,812	42,473
Gross Profit	$ 8,747	$ 8,250	$ 15,524	$ 14,234

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue from External Customer [Line Items]
Sales	$ 184,673	$ 162,701	$ 354,952	$ 304,905
Access & Aggregation [Member]
Revenue from External Customer [Line Items]
Sales	138,639	102,232	258,782	196,087
Customer Devices [Member]
Revenue from External Customer [Line Items]
Sales	33,833	40,876	70,101	73,229
Traditional & Other Products [Member]
Revenue from External Customer [Line Items]
Sales	$ 12,201	$ 19,593	$ 26,069	$ 35,589

Liability for Warranty Return72

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Product Warranties Disclosures [Abstract]
Period of warranty for product defects	90 days to five years
Liability for warranty obligations	$ 9,180	$ 8,988	$ 8,548	$ 8,935	$ 9,042	$ 8,739

Liability for Warranty Return73

Liability for Warranty Returns - Summary of Warranty Expense and Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 8,988	$ 9,042	$ 8,548	$ 8,739
Plus: Amounts charged to cost and expenses	3,055	1,431	2,314	2,329
Less: Deductions	(2,863)	(1,538)	(1,682)	(2,133)
Balance at end of period	$ 9,180	$ 8,935	$ 9,180	$ 8,935

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Jun. 30, 2017USD ($)EquityUnit
Contingencies And Commitments [Line Items]
Number of private equity funds | EquityUnit	2
Commitments towards private equity funds	$ 7.7
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds	7.9
Private Equity Funds [Member]
Contingencies And Commitments [Line Items]
Contribution to private equity funds	$ 8.4

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jul. 18, 2017	Jun. 30, 2017	Aug. 17, 2017
Subsequent Event [Line Items]
Dividend declaration date		Jul. 18, 2017
Dividend record date		Aug. 3, 2017
Dividend payment date		Aug. 17, 2017
Scenario Forecast [Member]
Subsequent Event [Line Items]
Quarterly dividend payable subsequent to balance sheet date			$ 4.3
Subsequent Events [Member]
Subsequent Event [Line Items]
Common stock dividends per share declared	$ 0.09