Teradyne (TER) 10-Q 9 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 05, 2018
Document Information
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	TER
Entity Registrant Name	TERADYNE, INC
Entity Central Index Key	97,210
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		179,249,910
Entity Emerging Growth Company	false
Entity Small Company	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018		Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 814,019		$ 429,843
Marketable securities	418,410		1,347,979
Accounts receivable, less allowance for doubtful accounts of $2,214 and $2,219 at September 30, 2018 and December 31, 2017, respectively	352,476		272,783
Inventories, net	154,705		107,525
Prepayments and other current assets	139,785		112,151
Total current assets	1,879,395		2,270,281
Property, plant and equipment, net	278,071		268,447
Marketable securities	91,982		125,926
Deferred tax assets	70,772		84,026
Retirement plans assets	17,885		17,491
Other assets	11,421		12,275
Acquired intangible assets, net	139,963		79,088
Goodwill	392,998		252,011
Total assets	2,882,487	[1]	3,109,545
Current liabilities:
Accounts payable	107,890		86,393
Accrued employees' compensation and withholdings	116,546		141,694
Deferred revenue and customer advances	77,953		83,614
Other accrued liabilities	95,888		59,083
Contingent consideration	35,532		24,497
Income taxes payable	24,603		59,055
Total current liabilities	458,412		454,336
Retirement plans liabilities	127,037		119,776
Long-term deferred revenue and customer advances	29,387		30,127
Deferred tax liabilities	21,748		6,720
Long-term other accrued liabilities	28,956		10,273
Long-term contingent consideration	25,410		20,605
Long-term incomes taxes payable	147,360		148,075
Long-term debt	376,417		365,987
Total liabilities	1,214,727		1,155,899
Commitments and contingencies (See Note Q)
Shareholders' equity
Common stock, $0.125 par value, 1,000,000 shares authorized; 183,289 and 195,548 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	22,911		24,444
Additional paid-in capital	1,664,568		1,638,413
Accumulated other comprehensive income	3,524		18,776
(Accumulated deficit) Retained earnings	(23,243)		272,013
Total shareholders' equity	1,667,760		1,953,646
Total liabilities and shareholders' equity	$ 2,882,487		$ 3,109,545
[1]	Total business assets are directly attributable to each business. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable, less allowance for doubtful accounts	$ 2,214	$ 2,219
Common stock, par value	$ 0.125	$ 0.125
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	183,289,000	195,548,000
Common stock, shares outstanding	183,289,000	195,548,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Revenues:
Total revenues	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	233,155	208,509	670,385	706,667
Gross profit	333,693	294,869	910,859	950,524
Operating expenses:
Selling and administrative	100,199	86,130	290,115	261,034
Engineering and development	77,049	76,986	226,799	235,235
Acquired intangible assets amortization	11,142	7,028	28,633	23,145
Restructuring and other	1,710	(4,407)	3,785	392
Total operating expenses	190,100	165,737	549,332	519,806
Income from operations	143,593	129,132	361,527	430,718
Non-operating (income) expense:
Interest income	(6,213)	(4,517)	(17,620)	(11,329)
Interest expense	5,557	5,372	18,087	16,283
Other (income) expense, net	3,405	840	4,385	(565)
Income before income taxes	140,844	127,437	356,675	426,329
Income tax provision	20,863	24,017	48,684	62,713
Net income	$ 119,981	$ 103,420	$ 307,991	$ 363,616
Net income per common share:
Basic	$ 0.65	$ 0.52	$ 1.62	$ 1.83
Diluted	$ 0.63	$ 0.52	$ 1.57	$ 1.81
Weighted average common shares-basic	185,744	197,485	190,576	198,755
Weighted average common shares-diluted	190,505	200,775	196,300	201,413
Cash dividend declared per common share	$ 0.09	$ 0.07	$ 0.27	$ 0.21
Product [Member]
Revenues:
Total revenues	$ 470,994	$ 412,854	$ 1,308,969	$ 1,396,413
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	195,339	169,661	557,074	592,294
Service [Member]
Revenues:
Total revenues	95,854	90,524	272,275	260,778
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 37,816	$ 38,848	$ 113,311	$ 114,373

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Net income	$ 119,981	$ 103,420	$ 307,991	$ 363,616
Other comprehensive income, net of tax:
Foreign currency translation adjustment	7,213	9,291	(11,568)	34,235
Available-for-sale marketable securities:
Unrealized gains (losses) on marketable securities arising during period, net of tax of $(62), $481, $(806), $1,666, respectively	(66)	950	(2,555)	2,448
Less: Reclassification adjustment for (gains) losses included in net income, net of tax of $(17), $(67), $(6), $(173), respectively	(57)	(87)	1,411	(264)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	(123)	863	(1,144)	2,184
Defined benefit pension and post-retirement plans:
Amortization of prior service benefit included in net periodic pension and post-retirement benefit, net of tax of $(18), $(38), $(53), $(115), respectively	(61)	(68)	(184)	(204)
Other comprehensive income (loss)	7,029	10,086	(12,896)	36,215
Comprehensive income	$ 127,010	$ 113,506	$ 295,095	$ 399,831

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Unrealized (losses) gains on marketable securities arising during period, tax	$ (62)	$ 481	$ (806)	$ 1,666
Reclassification adjustment for gains included in net income, tax	(17)	(67)	(6)	(173)
Amortization of prior service benefit included in net periodic pension and post-retirement benefit, tax	$ (18)	$ (38)	$ (53)	$ (115)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017
Cash flows from operating activities:
Net income	$ 307,991	$ 363,616
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	49,930	49,243
Amortization	32,909	32,313
Stock-based compensation	25,327	25,620
Deferred taxes	24,442	(679)
Provision for excess and obsolete inventory	9,522	7,154
Contingent consideration adjustment	(9,236)	1,847
Retirement plan actuarial losses (gains)	196	(2,504)
Property insurance recovery		(4,309)
Other	516	429
Changes in operating assets and liabilities, net of businesses acquired:
Accounts receivable	(77,807)	(75,623)
Inventories	(34,117)	23,770
Prepayments and other assets	(28,719)	7,362
Accounts payable and other accrued expenses	16,124	5,298
Deferred revenue and customer advances	9,823	34,535
Retirement plans contributions	(3,244)	(4,858)
Income taxes	(33,152)	15,808
Net cash provided by operating activities	290,505	479,022
Cash flows from investing activities:
Purchases of property, plant and equipment	(88,269)	(73,247)
Proceeds from government subsidy for property, plant and equipment	7,920
Purchases of marketable securities	(809,521)	(1,036,523)
Proceeds from sales of marketable securities	843,164	443,169
Proceeds from maturities of marketable securities	934,100	473,255
Proceeds from life insurance	1,126
Proceeds from property insurance		5,064
Acquisition of businesses, net of cash acquired	(169,474)
Net cash provided by (used for) investing activities	719,046	(188,282)
Cash flows from financing activities:
Issuance of common stock under stock purchase and stock option plans	20,959	24,462
Repurchase of common stock	(562,263)	(151,821)
Dividend payments	(51,320)	(41,730)
Payments related to net settlement of employee stock compensation awards	(19,841)	(12,584)
Payments of contingent consideration	(13,571)	(1,050)
Net cash used for financing activities	(626,036)	(182,723)
Effects of exchange rate changes on cash and cash equivalents	661	2,776
Increase in cash and cash equivalents	384,176	110,793
Cash and cash equivalents at beginning of period	429,843	307,884
Cash and cash equivalents at end of period	$ 814,019	$ 418,677

The Company

The Company	9 Months Ended
	Sep. 30, 2018
The Company	A. THE COMPANY Teradyne, Inc. (“Teradyne”) is a leading global supplier of automation equipment for test and industrial applications. Teradyne designs, develops, manufactures and sells automatic test systems used to test semiconductors, wireless products, data storage and complex electronics systems in the consumer electronics, wireless, automotive, industrial, computing, communications, and aerospace and defense industries. Teradyne’s industrial automation products include collaborative robotic arms, autonomous mobile robots, and advanced robotic control software used by global manufacturing and light industrial customers to improve quality, increase manufacturing and material handling efficiency and decrease manufacturing costs. Teradyne’s automatic test equipment and industrial automation products and services include: • semiconductor test (“Semiconductor Test”) systems; • defense/aerospace (“Defense/Aerospace”) test instrumentation and systems, storage test (“Storage Test”) systems, and circuit-board test and inspection (“Production Board Test”) systems (collectively these products represent “System Test”); • industrial automation (“Industrial Automation”) products; and • wireless test (“Wireless Test”) systems.

Accounting Policies

Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies	B. ACCOUNTING POLICIES Basis of Presentation The consolidated interim financial statements include the accounts of Teradyne and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated. These interim financial statements are unaudited and reflect all normal recurring adjustments that are, in the opinion of management, necessary for the fair statement of such interim financial statements. Certain prior year amounts were reclassified to conform to the current year presentation. The December 31, 2017 condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The accompanying financial information should be read in conjunction with the consolidated financial statements and notes thereto contained in Teradyne’s Annual Report on Form 10-K, Preparation of Financial Statements and Use of Estimates The preparation of consolidated financial statements requires management to make estimates and judgments that affect the amounts reported in the financial statements. Actual results may differ significantly from these estimates. Revenue from Contracts with Customers Teradyne adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers” (“ASC 606”) “Revenue Recognition” (“ASC 605”) 10-K In accordance with ASC 606, Teradyne recognizes revenues, when or as control is transferred to a customer. Teradyne’s determination of revenue is dependent upon a five step process outlined below. Step 1: Identify the contract with the customer Teradyne accounts for a contract with a customer when there is written approval, the contract is committed, the rights of the parties, including payment terms, are identified, the contract has commercial substance and consideration is probable of collection. Step 2: Identify the performance obligations in the contract Teradyne periodically enters into contracts with its customers in which a customer may purchase a combination of goods and services, such as products with extended warranty obligations. Teradyne determines performance obligations by assessing whether the products or services are distinct from the other elements of the contract. In order to be distinct, the product or service must perform either on its own or with readily available resources and must be separate within the context of the contract. Step 3: Determine the transaction price Teradyne considers the amount stated on the face of the purchase order to be the transaction price. Teradyne does not have material variable consideration which could impact the stated purchase price agreed to by Teradyne and the customer. Step 4: Allocate the transaction price to the performance obligations in the contract Transaction price is allocated to each individual performance obligation based on the standalone selling price of that performance obligation. Teradyne uses standalone transactions when available to value each performance obligation. If standalone transactions are not available, Teradyne will estimate the standalone selling price through market assessments or cost plus a reasonable margin analysis. Any discounts from standalone selling price are spread proportionally to each performance obligation. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation In order to determine the appropriate timing for revenue recognition, Teradyne first determines if the transaction meets any of three criteria for over time recognition. If the transaction meets the criteria for over time recognition, Teradyne recognizes revenue as the good or service is delivered. Teradyne uses input variables such as hours or months utilized or costs incurred to determine the amount of revenue to recognize in a given period. Input variables are used as they best align consumption with benefit to the customer. For transactions that do not meet the criteria for over time recognition, Teradyne will recognize revenue at a point in time based on an assessment of the five criteria for transfer of control. Teradyne has concluded that revenue should be recognized when shipped or delivered based on contractual terms. Typically acceptance of Teradyne’s products and services is a formality as Teradyne delivers similar systems, instruments and robots to standard specifications. In cases where acceptance is not deemed a formality, Teradyne will defer revenue recognition until customer acceptance. Revenue recognized in accordance with ASC 606 was $564.5 million and $1,571.0 million for the three and nine months ended September 30, 2018, respectively. For the three and nine months ended September 30, 2018, Teradyne also recognized $2.3 million and $10.2 million, respectively, in revenue on leases of Teradyne systems, which are accounted for outside of ASC 606. Disaggregation of Revenue The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Three Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated System on a chip Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 8,866 $ 4,600 $ 15,423 $ — $ 2,625 $ 17,834 $ 1,810 $ 104 $ 3,820 $ (272 ) $ 54,810 Over Time 8,810 686 6,037 — 789 190 — 167 146 — 16,825 Europe, Middle East and Africa Point in Time 9,728 2,080 161 — 3,223 26,445 2,647 — 1,504 — 45,788 Over Time 5,336 301 505 — 1,510 282 — 457 318 — 8,709 Asia Pacific Point in Time 258,898 76,429 931 9,916 5,201 13,656 2,087 10 26,851 — 393,979 Over Time 36,722 2,794 212 2,116 885 145 — 79 1,494 — 44,447 Lease Revenue 2,047 — — — 72 — — — 171 — 2,290 Total $ 330,407 $ 86,890 $ 23,269 $ 12,032 $ 14,305 $ 58,552 $ 6,544 $ 817 $ 34,304 $ (272 ) $ 566,848 For the Nine Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated SOC Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 30,577 $ 10,291 $ 42,276 $ 284 $ 5,814 $ 48,025 $ 3,009 $ 104 $ 13,515 $ (602 ) $ 153,293 Over Time 26,536 2,092 18,462 — 2,342 431 — 578 379 — 50,820 Europe, Middle East and Africa Point in Time 32,079 3,066 2,104 — 12,109 75,631 4,647 — 2,570 — 132,206 Over Time 16,240 824 1,596 — 4,781 675 — 732 802 — 25,650 Asia Pacific Point in Time 702,097 202,336 1,417 51,863 10,804 39,135 3,397 10 68,180 — 1,079,239 Over Time 108,011 7,401 678 5,077 2,364 350 — 79 5,893 — 129,853 Lease Revenue 9,162 — — — 337 — — — 684 — 10,183 Total $ 924,702 $ 226,010 $ 66,533 $ 57,224 $ 38,551 $ 164,247 $ 11,053 $ 1,503 $ 92,023 $ (602 ) $ 1,581,244 Performance Obligations Hardware Teradyne hardware consists primarily of semiconductor test systems and instruments, defense/aerospace test instrumentation and systems, storage test systems and instruments, circuit-board test and inspection systems and instruments, collaborative robots, autonomous mobile robots and wireless test systems. The hardware includes a standard 12-month Extended Warranty Customers have the option to purchase an extended warranty, which extends the warranty period for systems and robots beyond the one-year Training and Applications Support Teradyne sells training and applications support to customers either in standalone transactions or included with system purchases. The training and support allow the customer to use Teradyne’s systems efficiently and effectively. Training and applications support included in system orders are valued based on their standalone selling price and all training and applications support is recognized over time as the customer receives and consumes the benefit associated with each. Both are recognized using an input method of hours consumed as this best depicts the transfer of services to the customer. Service Agreements Service agreements are recognized ratably over the period of agreement based on months completed. Post-Contract Customer Support (“PCS”) Teradyne provides support services for certain systems and robots outside of warranty. These services include telephone support, bug fixes, and when-and-if Teradyne does not allow customer returns or provide refunds to customers for any products or services. Contract Balances The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. September 30, January 1, 2018 (as adjusted) Increase/ Decrease (in thousands) Deferred revenue and customer advances $ 77,953 $ 76,638 $ 1,315 Long-term deferred revenue and customer advances 29,387 20,848 8,539 The amount of revenue recognized during the three and nine months ended September 30, 2018 that was previously included within the deferred revenue and customer advances was $24.5 million and $70.9 million, respectively, and primarily relates to extended warranties, training, application support, and PCS. Each of these represents a distinct performance obligation. Customers typically pay for these services net 30 to 60 days from the date that transfer of control of the associated system or product occurs. Remaining Performance Obligations Teradyne does not have material remaining performance obligations from contracts with an original expected duration of greater than one year. Significant Judgments Teradyne makes no significant judgments in determining the amount or timing of revenue recognition. Practical Expedients Teradyne has adopted the practical expedients available within ASC 340 “Other Assets and Deferred Costs” Teradyne has adopted the practical expedient, which states an entity need not adjust the promised amount of consideration for the effects of a significant financing component if the entity expects, at contract inception, that the period between when the entity transfers a promised good or service to the customer and when the customer pays for that good or service will be one year or less. Teradyne does not have material payments associated with performance obligations outside this one-year Impacts The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: September 30, 2018 As Adjustments to Legacy (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 352,476 $ (31,205 ) $ 321,271 Inventories, net 154,705 11,708 166,413 Deferred tax assets 70,772 (3,684 ) 67,088 Liabilities Deferred revenue and customer advances $ 77,953 $ (4,825 ) $ 73,128 Income taxes payable 24,603 (4,271 ) 20,332 Long-term deferred revenue and customer advances 29,387 (9,968 ) 19,419 Shareholders’ equity Accumulated deficit $ (23,243 ) $ (4,117 ) $ (27,360 ) Condensed Consolidated Statement of Operation: For the Three Months ended September 30, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 566,848 $ 59,738 $ 626,586 Total cost of revenues 233,155 21,702 254,857 Income tax provision 20,863 4,771 25,634 Net income 119,981 33,265 153,246 Net income per common share: Basic $ 0.65 $ 0.18 $ 0.83 Diluted $ 0.63 $ 0.17 $ 0.80 For the Nine Months ended September, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 1,581,244 $ (32,668 ) $ 1,548,576 Total cost of revenues 670,385 (11,708 ) 658,677 Income tax provision 48,684 (4,163 ) 44,521 Net income 307,991 (16,797 ) 291,194 Net income per common share: Basic $ 1.62 $ (0.09 ) $ 1.53 Diluted $ 1.57 $ (0.09 ) $ 1.48 Retirement Benefits In March 2017, the Financial Accounting Standards Board (“FASB”) issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost non-service non-service non-operating non-operating Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Contingencies and Litigation Teradyne may be subject to certain legal proceedings, lawsuits and other claims as discussed in Note Q: “Commitments and Contingencies.” Teradyne accrues for a loss contingency, including legal proceedings, lawsuits, pending claims and other legal matters, when the likelihood of a loss is probable and the amount of the loss can be reasonably estimated. When the reasonable estimate of the loss is within a range of amounts, and no amount in the range constitutes a better estimate than any other amount, Teradyne accrues the amount at the low end of the range. Teradyne adjusts the accruals from time to time as additional information is received, but the loss incurred may be significantly greater than or less than the amount accrued. Loss contingencies are disclosed when they are material and there is at least a reasonable possibility that a loss has been incurred. Attorney fees related to legal matters are expensed as incurred.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
Recently Issued Accounting Pronouncements	C. RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS On January 26, 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment.” one-step In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” “Leases.” of-use 2018-11, “Leases 2016-02. non-lease 2016-02.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2018
Acquisitions	D. ACQUISITIONS Mobile Industrial Robots On April 25, 2018, Teradyne acquired all the issued and outstanding shares of Mobile Industrial Robots ApS (“MiR”), a Danish limited liability company located in Odense, Denmark. MiR is the leading maker of collaborative autonomous mobile robots for industrial applications. MiR is part of Teradyne’s Industrial Automation segment. The total preliminary purchase price of $196.6 million consisted of $145.2 million of cash paid and $51.4 million of contingent consideration, measured at fair value. The contingent consideration is payable in Euros upon the achievement of certain thresholds and targets for revenue and earnings before interest and taxes for periods from January 1, 2018 to December 31, 2018; January 1, 2018 to December 31, 2019; and January 1, 2018 to December 31, 2020. At September 30, 2018, the maximum amount of contingent consideration that could be paid is $118.9 million. The valuation of the contingent consideration is dependent on the following assumptions: forecasted revenues, revenue volatility, earnings before interest and taxes, and discount rate. These assumptions were estimated based on a review of the historical and projected results. The MiR acquisition was accounted for as a business combination and, accordingly, the results have been included in Teradyne’s consolidated results of operations from the date of acquisition. The allocation of the preliminary total purchase price to MiR’s net tangible liabilities and identifiable intangible assets was based on their estimated fair values as of the acquisition date. The excess of the purchase price over the identifiable intangible assets and net tangible liabilities in the amount of $134.7 million was allocated to goodwill, which is not deductible for tax purposes. The purchase price and purchase price allocation are preliminary pending the final determination of the fair value of contingent consideration, acquired assets and assumed liabilities. Teradyne expects to finalize the purchase price calculation in the fourth quarter of 2018. MiR’s results have been included in Teradyne’s Industrial Automation segment from the date of acquisition. The following table represents the allocation of the preliminary purchase price: Purchase Price Allocation (in thousands) Goodwill $ 134,737 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current 299 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (17,779 ) Total purchase price $ 196,630 Teradyne estimated the fair value of intangible assets using the income and cost approaches with the following key assumptions: (1) forecasted cash flows and (2) discount rate. Acquired intangible assets are amortized on a straight-line basis over their estimated useful lives. Components of these intangible assets and their estimated useful lives at the acquisition date are as follows: Fair Value Estimated Useful Life (in thousands) (in years) Developed technology $ 58,900 7.0 Trademarks and tradenames 13,240 11.0 Customer relationships 8,500 2.5 Backlog 30 0.2 Total intangible assets $ 80,670 7.2 For the three months ended September 30, 2018, MiR contributed $6.5 million of revenues and had a $(3.8) million loss from operations before income taxes. For the period from April 25, 2018 to September 30, 2018, MiR contributed $11.1 million of revenues and had a $(5.4) million loss from operations before income taxes. The following unaudited pro forma information gives effect to the acquisition of MiR as if the acquisition occurred on January 1, 2017. The unaudited pro forma results are not necessarily indicative of what actually would have occurred had the acquisition been in effect for the periods presented: For the Three Months For the Nine Months Ended October 1, 2017 September 30, October 1, (in thousands) Revenue $ 507,982 $ 1,588,042 $ 1,666,075 Net income 100,339 306,768 351,626 Net income per common share: Basic $ 0.51 $ 1.61 $ 1.77 Diluted $ 0.50 $ 1.56 $ 1.75 Pro forma results for the nine months ended September 30, 2018 were adjusted to exclude $2.9 million of acquisition related costs, and $0.4 million of non-recurring Pro forma results for the nine months ended October 1, 2017 were adjusted to include $2.9 million of acquisition related costs and $0.4 million of non-recurring Energid Technologies Corporation On February 26, 2018, Teradyne acquired all of the issued and outstanding shares of Energid Technologies Corporation (“Energid”) for a total purchase price of approximately $27.6 million. Energid’s technology enables and simplifies the programming of complex robotic motions used in a wide variety of end markets, ranging from heavy industry to healthcare, utilizing both traditional robots and collaborative robots. The Energid acquisition was accounted for as a business combination and, accordingly, Energid’s results have been included in Teradyne’s Industrial Automation segment from the date of acquisition. As of the acquisition date, Teradyne’s purchase price allocation was goodwill of $14.4 million, acquired intangible assets of $12.3 million with an average estimated useful life of 7.7 years, and $1.0 million of net tangible assets. The acquisition was not material to Teradyne’s condensed consolidated financial statements.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2018
Inventories	E. INVENTORIES Inventories, net consisted of the following at September 30, 2018 and December 31, 2017: September 30, December 31, (in thousands) Raw material $ 87,124 $ 62,668 Work-in-process 33,788 19,464 Finished Goods 33,793 25,393 $ 154,705 $ 107,525 Inventory reserves at September 30, 2018 and December 31, 2017 were $104.3 million and $102.9 million, respectively.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2018
Financial Instruments	F. FINANCIAL INSTRUMENTS Cash Equivalents Teradyne considers all highly liquid investments with maturities of three months or less at the date of acquisition to be cash equivalents. Marketable Securities Effective January 1, 2018, Teradyne adopted ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): On a quarterly basis, Teradyne reviews its investments to identify and evaluate those that have an indication of a potential other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include: • The length of time and the extent to which the market value has been less than cost; • The financial condition and near-term prospects of the issuer; and • The intent and ability to retain the investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. Teradyne uses the market and income approach techniques to value its financial instruments and there were no changes in valuation techniques during the three and nine months ended September 30, 2018 and October 1, 2017. As defined in ASC 820-10, Fair Value Measurements and Disclosures, 820-10 Level 1: Quoted prices in active markets for identical assets as of the reporting date; Level 2: Inputs other than Level 1, that are observable either directly or indirectly as of the reporting date. For example, a common approach for valuing fixed income securities is the use of matrix pricing. Matrix pricing is a mathematical technique used to value securities by relying on the securities’ relationship to other benchmark quoted prices, and is considered a Level 2 input; or Level 3: Unobservable inputs that are not supported by market data. Unobservable inputs are developed based on the best information available, which might include Teradyne’s own data. Teradyne’s available-for-sale During the three and nine months ended September 30, 2018 and October 1, 2017, there were no transfers in or out of Level 1, Level 2, or Level 3 financial instruments. Realized gains related to available-for-sale available-for-sale available-for-sale available-for-sale Realized gains related to available-for-sale available-for-sale Unrealized gains related to equity securities held at September 30, 2018 recorded in the three and nine months ended September 30, 2018 were $1.0 million and $1.4 million, respectively. Unrealized and realized gains related to equity securities are included in interest income and unrealized and realized losses are included in interest expense. The cost of securities sold is based on the specific identification method. The following table sets forth by fair value hierarchy Teradyne’s financial assets and liabilities that were measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017. September 30, 2018 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 275,614 $ — $ — $ 275,614 Cash equivalents 477,869 60,536 — 538,405 Available-for-sale U.S. Treasury securities — 363,414 — 363,414 Commercial paper — 67,202 — 67,202 Corporate debt securities — 40,271 — 40,271 U.S. government agency securities — 9,004 — 9,004 Debt mutual funds 3,055 — — 3,055 Certificates of deposit and time deposits — 2,218 — 2,218 Non-U.S. — 543 — 543 Equity securities: Mutual Funds 24,685 — — 24,685 $ 781,223 $ 543,188 $ — $ 1,324,411 Derivative assets — 3 — 3 Total $ 781,223 $ 543,191 $ — $ 1,324,414 Liabilities Contingent consideration $ — $ — $ 60,942 $ 60,942 Derivative liabilities — 455 — 455 Total $ — $ 455 $ 60,942 $ 61,397 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 753,483 $ 60,536 $ — $ 814,019 Marketable securities — 418,410 — 418,410 Long-term marketable securities 27,740 64,242 — 91,982 Prepayments — 3 — 3 Total $ 781,223 $ 543,191 $ — $ 1,324,414 Liabilities Other current liabilities $ — $ 455 $ — $ 455 Contingent consideration — — 35,532 35,532 Long-term contingent consideration — — 25,410 25,410 Total $ — $ 455 $ 60,942 $ 61,397 December 31, 2017 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 197,955 $ — $ — $ 197,955 Cash equivalents 206,335 25,553 — 231,888 Available for sale securities: U.S. Treasury securities — 855,795 — 855,795 Commercial paper — 282,840 — 282,840 Certificates of deposit and time deposits — 167,342 — 167,342 Corporate debt securities — 133,186 — 133,186 Equity and debt mutual funds 23,430 — — 23,430 U.S. government agency securities — 10,726 — 10,726 Non-U.S. — 586 — 586 $ 427,720 $ 1,476,028 $ — $ 1,903,748 Derivative assets — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Contingent consideration $ — $ — $ 45,102 $ 45,102 Derivative liabilities — 446 — 446 Total $ — $ 446 $ 45,102 $ 45,548 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 404,290 $ 25,553 $ — $ 429,843 Marketable securities — 1,347,979 — 1,347,979 Long-term marketable securities 23,430 102,496 — 125,926 Prepayments — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Other accrued liabilities $ — $ 446 $ — $ 446 Contingent consideration — — 24,497 24,497 Long-term contingent consideration — — 20,605 20,605 Total $ — $ 446 $ 45,102 $ 45,548 Changes in the fair value of Level 3 contingent consideration for the three and nine months ended September 30, 2018 and October 1, 2017 were as follows: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, 2018 2017 2018 2017 (in thousands) Balance at beginning of period $ 60,914 $ 39,415 $ 45,102 $ 38,332 Acquisition of MiR — — 51,399 — Foreign currency impact 796 — (1,770 ) — Payments (a) — — (24,553 ) (1,050 ) Fair value adjustment (b) (768 ) (286 ) (9,236 ) 1,847 Balance at end of period $ 60,942 $ 39,129 $ 60,942 $ 39,129 (a) In the nine months ended September 30, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out earn-out (b) In the three and nine months ended September 30, 2018, the fair value of contingent consideration for the earn-out earn-out The following table provides quantitative information associated with the fair value measurement of Teradyne’s Level 3 financial instruments: Liability September 30, Value Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (Universal Robots) $11,314 Monte Carlo Simulation Revenue volatility 12.9% Discount Rate 3.7% Contingent consideration (Mobile Industrial Robots) $49,628 Monte Carlo Simulation Revenue volatility 18.0% Discount Rate 0.5% As of September 30, 2018, the significant unobservable inputs used in the Monte Carlo simulation to fair value the Universal Robots contingent consideration include forecasted revenue, revenue volatility, and discount rate. Increases or decreases in the inputs would result in a higher or lower fair value measurement. The maximum payment for the remaining Universal Robots revenue earn-out As of September 30, 2018, the significant unobservable inputs used in the Monte Carlo simulation to fair value the MiR contingent consideration include forecasted revenue, revenue volatility, earnings before interest and taxes, and discount rate. Increases or decreases in the inputs would result in a higher or lower fair value measurement. As of September 30, 2018, the maximum amount of contingent consideration that could be paid in connection with the acquisition of MiR is $118.9 million. The earn-out The carrying amounts and fair values of Teradyne’s financial instruments at September 30, 2018 and December 31, 2017 were as follows: September 30, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 814,019 $ 814,019 $ 429,843 $ 429,843 Marketable securities 510,392 510,392 1,473,905 1,473,905 Derivative assets 3 3 389 389 Liabilities Contingent consideration 60,942 60,942 45,102 45,102 Derivative liabilities 455 455 446 446 Convertible debt (1) 376,417 599,438 365,987 659,525 (1) The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note, which includes the equity conversion features. The fair values of accounts receivable, net and accounts payable approximate the carrying value due to the short-term nature of these instruments. The following table summarizes the composition of available-for-sale September 30, 2018 Available-for-Sale Fair Market Value of Investments with Unrealized Losses Cost Unrealized Gain Unrealized (Loss) Fair Market Value (in thousands) U.S. Treasury securities $ 365,701 $ — $ (2,287 ) $ 363,414 $ 362,167 Commercial paper 67,208 7 (13 ) 67,202 66,186 Corporate debt securities 40,669 537 (935 ) 40,271 22,030 U.S. government agency securities 9,065 — (61 ) 9,004 9,004 Debt mutual funds 3,128 — (73 ) 3,055 1,786 Certificates of deposit and time deposits 2,218 — — 2,218 — Non-U.S. 543 — — 543 176 $ 488,532 $ 544 $ (3,369 ) $ 485,707 $ 461,349 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 418,554 $ 52 $ (196 ) $ 418,410 $ 405,959 Long-term marketable securities 69,978 492 (3,173 ) 67,297 55,390 $ 488,532 $ 544 $ (3,369 ) $ 485,707 $ 461,349 The following table summarizes the composition of available-for-sale December 31, 2017 Available-for-Sale Fair Market Value of Investments with Unrealized Losses Cost Unrealized Gain Unrealized (Loss) Fair Market Value (in thousands) U.S. Treasury securities $ 858,258 $ 72 $ (2,535 ) $ 855,795 $ 850,163 Commercial paper 283,009 18 (187 ) 282,840 258,933 Certificates of deposit and time deposits 167,523 6 (187 ) 167,342 138,340 Corporate debt securities 131,179 2,380 (373 ) 133,186 91,010 Equity and debt mutual funds 19,403 4,102 (75 ) 23,430 1,723 U.S. government agency securities 10,775 — (49 ) 10,726 10,726 Non-U.S. 582 4 — 586 — $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 1,349,970 $ 38 $ (2,029 ) $ 1,347,979 $ 1,288,844 Long-term marketable securities 120,759 6,544 (1,377 ) 125,926 62,052 $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 As of September 30, 2018, the fair market value of investments in available-for-sale As of December 31, 2017, the fair market value of investments with unrealized losses totaled $1,350.9 million. Of this value, $141.0 million had unrealized losses of $1.2 million for greater than one year and $1,209.9 million had unrealized losses of $2.2 million for less than one year. Teradyne reviews its investments to identify and evaluate investments that have an indication of possible impairment. Based on this review, Teradyne determined that the unrealized losses related to these investments at September 30, 2018 and December 31, 2017 were temporary. The contractual maturities of investments in available-for-sale September 30, 2018 Cost Fair Market Value (in thousands) Due within one year $ 418,554 $ 418,410 Due after 1 year through 5 years 11,477 11,368 Due after 5 years through 10 years 14,906 13,949 Due after 10 years 40,467 38,925 Total $ 485,404 $ 482,652 Contractual maturities of investments in available-for-sale Derivatives Teradyne conducts business in a number of foreign countries, with certain transactions denominated in local currencies. The purpose of Teradyne’s foreign currency management is to minimize the effect of exchange rate fluctuations on certain foreign currency denominated monetary assets and liabilities. Teradyne does not use derivative financial instruments for trading or speculative purposes. To minimize the effect of exchange rate fluctuations associated with the remeasurement of monetary assets and liabilities denominated in foreign currencies, Teradyne enters into foreign currency forward contracts. The change in fair value of these derivatives is recorded directly in earnings, and is used to offset the change in value of monetary assets and liabilities denominated in foreign currencies. The notional amount of foreign currency forward contracts at September 30, 2018 and December 31, 2017 was $166.6 million and $116.8 million, respectively. Gains and losses on foreign currency forward contracts and foreign currency remeasurement gains and losses on monetary assets and liabilities are included in other (income) expense, net. The following table summarizes the fair value of derivative instruments as of September 30, 2018 and December 31, 2017: Balance Sheet Location September 30, December 31, 2017 (in thousands) Derivatives not designated as hedging instruments: Foreign currency forward contracts assets Prepayments $ 3 $ 389 Foreign currency forward contracts liabilities Other current liabilities (455 ) (446 ) Total derivatives $ (452 ) $ (57 ) The following table summarizes the effect of derivative instruments recognized in the statement of operations for the three and nine months ended September 30, 2018 and October 1, 2017. Location of Losses (Gains) Recognized in For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Derivatives not designated as hedging instruments: Foreign currency forward contracts Other (income) expense, net $ (899 ) $ (939 ) $ 2,502 $ (1,514 ) (1) The table does not reflect the corresponding gains and losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies. (2) For the three and nine months ended September 30, 2018, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $3.7 million and $1.2 million, respectively. (3) For the three and nine months ended October 1, 2017, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.4 million and $2.3 million, respectively. See Note G: “Debt” regarding derivatives related to the convertible senior notes.

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt	G. DEBT Convertible Senior Notes On December 12, 2016, Teradyne completed a private offering of $460.0 million convertible senior unsecured notes (the “Notes”). The Notes will mature on December 15, 2023, unless earlier repurchased or converted. The Notes bear interest from December 12, 2016 at a rate of 1.25% per year payable semi-annually in arrears on June 15 and December 15 of each year, beginning on June 15, 2017. The Notes will be convertible at the option of the noteholders at any time prior to the close of business on the business day immediately preceding September 15, 2023, under the following circumstances: (1) during any calendar quarter beginning after March 31, 2017 (and only during such calendar quarter), if the closing sale price of Teradyne’s common stock, for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined in the Indenture) per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the closing sale price of the Teradyne’s common stock and the conversion rate on each such trading day; and (3) upon the occurrence of specified corporate events. On or after September 15, 2023 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their Notes at any time, regardless of the foregoing circumstances. Teradyne may satisfy its conversion obligation by paying or delivering cash, shares of its common stock or a combination of cash and shares of its common stock, at Teradyne’s election. The conversion rate for the Notes is 31.4463 shares per $1,000 principal amount, which is equivalent to a conversion price of approximately $31.80 per share of Teradyne’s common stock. The conversion rate is subject to adjustment under certain circumstances. Concurrent with the offering of the Notes, Teradyne entered into convertible note hedge transactions (the “Note Hedge Transactions”) with the initial purchasers or their affiliates (the “Option Counterparties”). The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, the number of shares of the common stock that underlie the Notes, with a strike price equal to the conversion price of the Notes of approximately $31.80. The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, approximately 14.5 million shares of Teradyne’s common stock. The convertible note hedge is considered indexed to Teradyne’s stock as the terms of the Note Hedge Transactions do not contain an exercise contingency and the settlement amount equals the difference between the fair value of a fixed number of Teradyne’s shares and a fixed strike price. Because the only variable that can affect the settlement amount is Teradyne’s stock price, which is an input to the fair value of a fixed-for-fixed Separately and concurrent with the pricing of the Notes, Teradyne entered into warrant transactions with the Option Counterparties (the “Warrant Transactions”) in which it sold net-share-settled The Note Hedge Transactions are expected to reduce the potential dilution to Teradyne’s common stock upon any conversion of the Notes. However, the Warrant Transactions could separately have a dilutive effect to the extent that the market value per share of Teradyne’s common stock exceeds the applicable strike price of the warrant. The net cost of the Notes Hedge Transactions, after being partially offset by the proceeds from the sale of the warrants, was approximately $33 million. In connection with establishing their initial hedge of these convertible note hedge and warrant transactions, the Option Counterparties have entered into various derivative transactions with respect to Teradyne’s common stock and/or purchased shares of Teradyne’s common stock or other securities, including the Notes, concurrent with, or shortly after, the pricing of the Notes. In addition, the Option Counterparties may modify their hedge positions by entering into or unwinding various derivative transactions with respect to Teradyne’s common stock or by selling Teradyne’s common stock or other securities, including the Notes, in secondary market transactions (and may do so during any observation period related to the conversion of the Notes). These activities could adversely affect the value of Teradyne’s common stock and the Notes. Teradyne’s effective annual interest rate on the Notes will be approximately 5.0%. The Notes are classified as long-term debt in the balance sheet based on their December 15, 2023 maturity date. Debt issuance costs of approximately $7.2 million are being amortized to interest expense using the effective interest method over the seven year term of the Notes. As of September 30, 2018, unamortized debt issuance costs were approximately $5.6 million. The below tables represent the key components of Teradyne’s convertible senior notes: September 30, 2018 December 31, 2017 (in thousands) Debt Principal $ 460,000 $ 460,000 Unamortized discount 83,583 94,013 Net Carrying amount of convertible debt $ 376,417 $ 365,987 For the Three Months Ended For the Nine Months Ended September 30, 2018 October 1, 2017 September 30, 2018 October 1, 2017 (in thousands) Contractual interest expense on the coupon $ 1,438 $ 1,422 $ 4,313 $ 4,297 Amortization of the discount component and debt issue fees recognized as interest expense 3,520 3,350 10,431 9,926 Total interest expense on the convertible debt $ 4,958 $ 4,772 $ 14,744 $ 14,223 As of September 30, 2018, the remaining unamortized discount was $83.6 million, which will be amortized over 5.3 years using the effective interest rate method. The carrying amount of the equity component was $100.8 million. As of September 30, 2018, the if-converted Revolving Credit Facility On April 27, 2015, Teradyne entered into a Credit Agreement (the “Credit Agreement”) with Barclays Bank PLC, as administrative agent and collateral agent, and the lenders party thereto. The Credit Agreement provides for a five-year, senior secured revolving credit facility of up to $350 million (the “Credit Facility”). The Credit Agreement further provides that, subject to customary conditions, Teradyne may seek to obtain from existing or new lenders incremental commitments under the Credit Facility in an aggregate principal amount not to exceed $150 million. Proceeds from the Credit Facility may be used for general corporate purposes and working capital. Teradyne incurred $2.3 million in costs related to the revolving credit facility. These costs are being amortized over the five-year term of the revolving credit facility and are included in interest expense in the statements of operations. As of November 9, 2018, Teradyne has not borrowed any funds under the Credit Facility. The interest rates applicable to loans under the Credit Facility are, at Teradyne’s option, equal to either a base rate plus a margin ranging from 0.00% to 1.00% per annum or LIBOR plus a margin ranging from 1.00% to 2.00% per annum, based on the Consolidated Leverage Ratio of Teradyne and its Restricted Subsidiaries. In addition, Teradyne will pay a commitment fee on the unused portion of the commitments under the Credit Facility ranging from 0.125% to 0.350% per annum, based on the then applicable Consolidated Leverage Ratio. Teradyne is not required to repay any loans under the Credit Facility prior to maturity, subject to certain customary exceptions. Teradyne is permitted to prepay all or any portion of the loans under the Credit Facility prior to maturity without premium or penalty, other than customary LIBOR breakage costs. The Credit Agreement contains customary events of default, representations, warranties and affirmative and negative covenants that, among other things, limit Teradyne’s and its Restricted Subsidiaries’ ability to sell assets, grant liens on assets, incur other secured indebtedness and make certain investments and restricted payments, all subject to exceptions set forth in the Credit Agreement. The Credit Agreement also requires Teradyne to satisfy two financial ratios measured as of the end of each fiscal quarter: a consolidated leverage ratio and an interest coverage ratio. As of November 9, 2018, Teradyne was in compliance with all covenants. The Credit Facility is guaranteed by certain of Teradyne’s domestic subsidiaries and collateralized by assets of Teradyne and such subsidiaries, including a pledge of 65% of the capital stock of certain foreign subsidiaries.

Prepayments

Prepayments	9 Months Ended
	Sep. 30, 2018
Prepayments	H. PREPAYMENTS Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: September 30, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 102,652 $ 82,503 Prepaid taxes 10,709 5,039 Prepaid maintenance and other services 7,802 8,189 Other prepayments 12,439 12,386 Total prepayments $ 133,602 $ 108,117

Deferred Revenue and Customer A

Deferred Revenue and Customer Advances	9 Months Ended
	Sep. 30, 2018
Deferred Revenue and Customer Advances	I. DEFERRED REVENUE AND CUSTOMER ADVANCES Deferred revenue and customer advances consist of the following and are included in short and long-term deferred revenue and customer advances on the balance sheet: September 30, December 31, (in thousands) Maintenance and training $ 59,681 $ 57,256 Extended warranty 27,617 24,438 Customer advances, undelivered elements and other 20,042 32,047 Total deferred revenue and customer advances $ 107,340 $ 113,741

Product Warranty

Product Warranty	9 Months Ended
	Sep. 30, 2018
Product Warranty	J. PRODUCT WARRANTY Teradyne generally provides a one-year For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Balance at beginning of period $ 7,136 $ 9,093 $ 8,200 $ 7,203 Acquisition — — 41 — Accruals for warranties issued during the period 2,760 2,734 9,171 11,049 Adjustments related to pre-existing 282 (35 ) 109 (499 ) Settlements made during the period (2,675 ) (3,055 ) (10,018 ) (9,016 ) Balance at end of period $ 7,503 $ 8,737 $ 7,503 $ 8,737 When Teradyne receives revenue for extended warranties, beyond one year, it is deferred and recognized on a straight-line basis over the contract period. Related costs are expensed as incurred. The balance below is included in short and long-term deferred revenue and customer advances on the balance sheet. For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Balance at beginning of period $ 25,971 $ 29,377 $ 24,438 $ 28,200 Deferral of new extended warranty revenue 7,232 2,636 19,072 17,126 Recognition of extended warranty deferred revenue (5,586 ) (5,521 ) (15,893 ) (18,834 ) Balance at end of period $ 27,617 $ 26,492 $ 27,617 $ 26,492

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Stock-Based Compensation	K. STOCK-BASED COMPENSATION Under Teradyne’s stock compensation plans, Teradyne grants stock options, restricted stock units and performance-based restricted stock units, and employees are eligible to purchase Teradyne’s common stock through its Employee Stock Purchase Plan (“ESPP”). Time-based restricted stock unit awards granted to employees vest in equal annual installments over four years. Restricted stock unit awards granted to non-employee Commencing in January 2014, Teradyne granted performance-based restricted stock units (“PRSUs”) to its executive officers with a performance metric based on relative total shareholder return (“TSR”). For TSR grants issued in 2018 and 2017, Teradyne’s three-year TSR performance is measured against the New York Stock Exchange (“NYSE”) Composite Index. The final number of TSR PRSUs that vest will vary based upon the level of performance achieved from 200% to 0% of the target shares capped at four times the grant date value. The TSR PRSUs will vest upon the three-year anniversary of the grant date. The TSR PRSUs are valued using a Monte Carlo simulation model. The number of units expected to be earned, based upon the achievement of the TSR market condition, is factored into the grant date Monte Carlo valuation. Compensation expense is recognized on a straight-line basis over the shorter of the three-year service period or the period from the grant date to the date described in the retirement provisions below. Compensation expense for employees meeting the retirement provisions prior to the grant date will be recognized in full on the date of the grant. Compensation expense is recognized regardless of the eventual number of units that are earned based upon the market condition, provided the executive officer remains an employee at the end of the three-year period. Compensation expense is reversed if at any time during the three-year service period the executive officer is no longer an employee, subject to the retirement and termination eligibility provisions noted below. In January 2018 and 2017, Teradyne granted PRSUs to its executive officers with a performance metric based on three-year cumulative non-GAAP Non-GAAP non-cash non-recurring Beginning with PRSUs granted in January 2014, if the recipient’s employment ends prior to the determination of the performance percentage due to (1) permanent disability or death or (2) retirement or termination other than for cause, after attaining both at least age sixty and at least ten years of service, then all or a portion of the recipient’s PRSUs (based on the actual performance percentage achieved on the determination date) will vest on the date the performance percentage is determined. Except as set forth in the preceding sentence, no PRSUs will vest if the executive officer is no longer an employee at the end of the three-year period. During the nine months ended September 30, 2018 and October 1, 2017, Teradyne granted 0.1 million and 0.1 million TSR PRSUs, respectively, with a grant date fair value of $54.85 and $35.66, respectively. The fair value was estimated using the Monte Carlo simulation model with the following assumptions: For the Nine Months Ended September 30, October 1, Risk-free interest rate 2.2 % 1.5 % Teradyne volatility-historical 26.8 % 26.6 % NYSE Composite Index volatility-historical 12.4 % 13.4 % Dividend yield 0.8 % 1.0 % Expected volatility was based on the historical volatility of Teradyne’s stock and the NYSE Composite Index for the 2018 and 2017 grant over the most recent three-year period. The risk-free interest rate was determined using the U.S. Treasury yield curve in effect at the time of grant. Dividend yield was based upon an estimated annual dividend amount of $0.36 per share for 2018 grants and $0.28 per share for 2017 grants, divided by Teradyne’s stock price on the grant date of $47.70 for the 2018 grant and $28.56 for the 2017 grant. During the nine months ended September 30, 2018 and October 1, 2017, Teradyne granted 0.1 million and 0.1 million, respectively, of PBIT PRSUs with a grant date fair value of $46.62 and $27.72, respectively. During the nine months ended September 30, 2018, Teradyne granted 0.6 million of service-based restricted stock unit awards to employees at a weighted average grant date fair value of $46.25, 0.1 million of service-based restricted stock unit awards to non-employee During the nine months ended October 1, 2017, Teradyne granted 0.8 million of service-based restricted stock unit awards to employees at a weighted average grant date fair value of $28.03, 0.1 million of service-based restricted stock unit awards to non- employee directors at a weighted average grant date fair value of $34.48, and 0.1 million of service-based stock options to executive officers at a weighted average grant date fair value of $7.13. Restricted stock unit awards granted to employees vest in equal annual installments over four years. Stock options to purchase Teradyne’s common stock at 100% of the fair market value on the grant date vest in equal annual installments over four years from the grant date and have a maximum term of seven years. The fair value of stock options was estimated using the Black-Scholes option-pricing model with the following assumptions: For the Nine Months Ended September 30, October 1, Expected life (years) 5.0 5.0 Risk-free interest rate 2.4 % 2.0 % Volatility-historical 26.4 % 27.8 % Dividend yield 0.8 % 1.0 % Teradyne determined the stock options’ expected life based upon historical exercise data for executive officers, the age of the executive officers and the terms of the stock option grant. Volatility was determined using historical volatility for a period equal to the expected life. The risk-free interest rate was determined using the U.S. Treasury yield curve in effect at the time of grant. Dividend yield was based upon an estimated annual dividend amount of $0.36 per share for 2018 grants and $0.28 per share for 2017 grants divided by Teradyne’s stock price on the grant date of $47.70 for the 2018 grant and $28.56 for the 2017 grant.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss)	L. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Changes in accumulated other comprehensive income (loss), which are presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains (Losses) on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Nine Months Ended September 30, 2018 Balance at December 31, 2017, net of tax of $0, $1,815, $(932), respectively $ 15,919 $ 1,362 $ 1,495 $ 18,776 Other comprehensive loss before reclassifications, net of tax of $0, $(806), $0, respectively (11,568 ) (2,555 ) — (14,123 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(6), $(53), respectively — 1,411 (184 ) 1,227 Net current period other comprehensive loss, net of tax of $0, $(812), $(53), respectively (11,568 ) (1,144 ) (184 ) (12,896 ) Reclassification of tax effects resulting of the Tax Reform Act, $0, $(691), $(78), respectively (a) — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax $0, $(902), $0, respectively (b) — (3,125 ) — (3,125 ) Balance at September 30, 2018, net of tax of $0, $(590), $(1,063), respectively $ 4,351 $ (2,216 ) $ 1,389 $ 3,524 (a) In the nine months ended September 30, 2018, Teradyne early adopted the ASU 2018-02, “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” (b) In the nine months ended September 30, 2018, Teradyne adopted the ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Foreign Currency Translation Adjustments Unrealized Gains (Losses) on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Nine Months Ended October 1, 2017 Balance at December 31, 2016, net of tax of $0, $209, $(778), respectively $ (21,921 ) $ (60 ) $ 1,767 $ (20,214 ) Other comprehensive income before reclassifications, net of tax of $0, $1,666, $0, respectively 34,235 2,448 — 36,683 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(173), $(115), respectively — (264 ) (204 ) (468 ) Net current period other comprehensive income (loss), net of tax of $0, $1,493, $(115), respectively 34,235 2,184 (204 ) 36,215 Balance as October 1, 2017, net of tax of $0, $1,702, $(893), respectively $ 12,314 $ 2,124 $ 1,563 $ 16,001 Reclassifications out of accumulated other comprehensive income (loss) to the statement of operations for the three and nine months ended September 30, 2018 and October 1, 2017 were as follows: Details about Accumulated Other Comprehensive Income For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations September 30, October 1, September 30, October 1, 2017 (in thousands) Available-for-sale Unrealized gains (losses), net of tax of $17, $67, $6, $173, respectively $ 57 $ 87 $ (1,411 ) $ 264 Interest income (expense) Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $18, $38, $53, $115, respectively 61 68 184 204 (a) Total reclassifications, net of tax of $35, $105, $59, $288, respectively $ 118 $ 155 $ (1,227 ) $ 468 Net income (a) The amortization of prior service benefit is included in the computation of net periodic pension cost and postretirement benefit. See Note P: “Retirement Plans.”

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Acquired Intangible Assets	M. GOODWILL AND ACQUIRED INTANGIBLE ASSETS Goodwill Teradyne performs its annual goodwill impairment test as required under the provisions of ASC 350-10, “Intangibles—Goodwill and Other” The changes in the carrying amount of goodwill by reportable segments for the nine months ended September 30, 2018, were as follows: Wireless Test Industrial Automation System Test Semiconductor Test Total (in thousands) Balance at December 31, 2017 Goodwill $ 361,819 $ 233,519 $ 158,699 $ 260,540 $ 1,014,577 Accumulated impairment losses (353,843 ) — (148,183 ) (260,540 ) (762,566 ) 7,976 233,519 10,516 — 252,011 MiR acquisition — 134,737 — — 134,737 Energid acquisition — 14,394 — — 14,394 Foreign currency translation adjustment — (8,144 ) — — (8,144 ) Balance at September 30, 2018 Goodwill 361,819 374,506 158,699 260,540 1,155,564 Accumulated impairment losses (353,843 ) — (148,183 ) (260,540 ) (762,566 ) $ 7,976 $ 374,506 $ 10,516 $ — $ 392,998 Intangible Assets Teradyne reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable or that the useful lives of these assets are no longer appropriate. Amortizable intangible assets consist of the following and are included in intangible assets, net on the balance sheet: September 30, 2018 Gross Carrying Amount (1)(2) Accumulated Amortization (2) Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 336,306 $ (244,833 ) $ (1,117 ) $ 90,356 Customer relationships 105,622 (89,848 ) (83 ) 15,691 Tradenames and trademarks 64,420 (30,408 ) (96 ) 33,916 Non-compete 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 506,698 $ (365,439 ) $ (1,296 ) $ 139,963 December 31, 2017 Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 270,877 $ (226,190 ) $ 1,618 $ 46,305 Customer relationships 92,741 (83,585 ) 171 9,327 Tradenames and trademarks 50,100 (27,120 ) 416 23,396 Non-compete 320 (260 ) — 60 Total intangible assets $ 414,038 $ (337,155 ) $ 2,205 $ 79,088 (1) Includes intangible assets acquired in 2018, $80.7 million from the MiR acquisition and $12.3 million from the Energid acquisition. (2) In 2018, $0.3 million of amortizable intangible assets became fully amortized and have been eliminated from the gross carrying amount and accumulated amortization. Aggregate intangible asset amortization expense was $11.1 million and $28.6 million, respectively, for the three and nine months ended September 30, 2018 and $7.0 million and $23.1 million, respectively, for the three and nine months ended October 1, 2017. Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2018 (remainder) 10,731 2019 39,610 2020 24,928 2021 14,343 2022 13,450 Thereafter 36,901

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Sep. 30, 2018
Net Income Per Common Share	N. NET INCOME PER COMMON SHARE The following table sets forth the computation of basic and diluted net income per common share: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 119,981 $ 103,420 $ 307,991 $ 363,616 Weighted average common shares-basic 185,744 197,485 190,576 198,755 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 3,025 1,144 3,356 632 Convertible note hedge warrant shares (2) 108 — 646 — Restricted stock units 1,331 1,832 1,406 1,663 Stock options 275 306 290 337 Employee stock purchase plan 22 8 26 26 Dilutive potential common shares 4,761 3,290 5,724 2,658 Weighted average common shares-diluted 190,505 200,775 196,300 201,413 Net income per common share-basic $ 0.65 $ 0.52 $ 1.62 $ 1.83 Net income per common share-diluted $ 0.63 $ 0.52 $ 1.57 $ 1.81 (1) Incremental shares from assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.80, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period. (2) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.91, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period. The computation of diluted net income per common share for the three and nine months ended September 30, 2018 excludes the effect of the potential vesting of 0.5 million of restricted stock units because the effect would have been anti-dilutive. The computation of diluted net income per common share for the three and nine months ended October 1, 2017 excludes the effect of the potential exercise of stock options to purchase approximately 0.1 million shares because the effect would have been anti-dilutive.

Restructuring and Other

Restructuring and Other	9 Months Ended
	Sep. 30, 2018
Restructuring and Other	O. RESTRUCTURING AND OTHER During the three months ended September 30, 2018, Teradyne recorded $1.7 million for employee severance charges, primarily in Semiconductor Test, and $0.8 million of acquisition related compensation, partially offset by a $0.8 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability. During the nine months ended September 30, 2018, Teradyne recorded $7.9 million for employee severance charges, primarily in Semiconductor Test, and $4.1 million for acquisition related expenses and compensation, partially offset by a $9.2 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability. During the three months ended October 1, 2017, Teradyne recorded $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to a previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, which was terminated in September 2017, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million recorded for employee severance charges, primarily in Semiconductor Test. During the nine months ended October 1, 2017, Teradyne recorded $2.0 million for employee severance charges, primarily in Industrial Automation and Corporate, $1.8 million for the increase in the fair value of the Universal Robots contingent consideration liability, $0.9 million for a lease impairment of a Wireless Test facility in Sunnyvale, CA, which was terminated in September 2017, and $0.8 million of Japan earthquake related expenses, partially offset by $5.1 million of property insurance recovery related to the Japan earthquake.

Retirement Plans

Retirement Plans	9 Months Ended
	Sep. 30, 2018
Defined Benefit Pension Plans
Retirement Plans	P. RETIREMENT PLANS ASC 715, “Compensation—Retirement Benefits” Defined Benefit Pension Plans Teradyne has defined benefit pension plans covering a portion of domestic employees and employees of certain non-U.S. During the nine months ended September 30, 2018, Teradyne purchased a group annuity contract for its retiree participants in the U.S. qualified pension plan. Under the group annuity, the accrued pension obligations for approximately 1,700 retiree participants were transferred to an insurance company. The reduction in the pension benefit obligation and pension assets was $151.3 million. During the three and nine months ended September 30, 2018, Teradyne recorded a settlement loss of $0.3 million related to the retiree group annuity transaction. In the nine months ended September 30, 2018, Teradyne contributed $1.9 million to the U.S. supplemental executive defined benefit pension plan and $0.6 million to certain qualified pension plans for non-U.S. For the three and nine months ended September 30, 2018 and October 1, 2017, Teradyne’s net periodic pension cost was comprised of the following: For the Three Months Ended September 30, 2018 October 1, 2017 United States Foreign United States Foreign (in thousands) Service cost $ 538 $ 203 $ 560 $ 215 Interest cost 1,750 177 3,288 186 Expected return on plan assets (1,551 ) (5 ) (3,002 ) (6 ) Amortization of prior service cost 14 — 18 — Settlement loss 267 — — — Total net periodic pension cost $ 1,018 $ 375 $ 864 $ 395 For the Nine Months Ended September 30, 2018 October 1, 2017 United States Foreign United States Foreign (in thousands) Service cost $ 1,657 $ 609 $ 1,679 $ 606 Interest cost 7,188 532 9,863 527 Expected return on plan assets (7,484 ) (15 ) (9,006 ) (19 ) Amortization of prior service cost 43 — 53 — Net actuarial gain (189 ) — (2,732 ) 243 Settlement loss 345 — — — Total net periodic pension cost (benefit) $ 1,560 $ 1,126 $ (143 ) $ 1,357 Postretirement Benefit Plan In addition to receiving pension benefits, Teradyne employees in the United States who meet early retirement eligibility requirements as of their termination dates may participate in Teradyne’s Welfare Plan, which includes medical and dental benefits up to age 65. Death benefits provide a fixed sum to retirees’ survivors and are available to all retirees. Substantially all of Teradyne’s current U.S. employees could become eligible for these benefits, and the existing benefit obligation relates primarily to those employees. For the three and nine months ended September 30, 2018 and October 1, 2017, Teradyne’s net periodic postretirement benefit cost (income) was comprised of the following: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Service cost $ 10 $ 8 $ 29 $ 25 Interest cost 49 50 147 151 Amortization of prior service credit (93 ) (124 ) (280 ) (372 ) Net actuarial loss (gain) — — 40 (15 ) Special termination benefits 601 — 3,419 — Total net periodic postretirement benefit cost (income) $ 567 $ (66 ) $ 3,355 $ (211 )

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies	Q. COMMITMENTS AND CONTINGENCIES Purchase Commitments As of September 30, 2018, Teradyne had entered into purchase commitments for certain components and materials. The purchase commitments covered by the agreements aggregate to approximately $275.6 million, of which $263.3 million is for less than one year. Legal Claims Teradyne is subject to various legal proceedings and claims which have arisen in the ordinary course of business. In the opinion of management, the ultimate disposition of these matters will not have a material adverse effect on Teradyne’s results of operations, financial condition or cash flows.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Taxes	R. INCOME TAXES The effective tax rate for the three months ended September 30, 2018 and October 1, 2017 was 14.8% and 18.8%, respectively. The effective tax rate for the nine months ended September 30, 2018 and October 1, 2017 was 13.6% and 14.7%, respectively. The decrease in the effective tax rate from the three and nine months ended October 1, 2017 to the three and nine months ended September 30, 2018 primarily resulted from the benefit of the U.S. foreign derived intangible income deduction. The tax rate effect of a projected shift in the geographic distribution of income, which increases the income subject to taxation in the U.S. relative to lower tax rate jurisdictions, was substantially offset by the reduction in the U.S. corporate tax rate from 35% to 21%. The effective tax rate for the three and nine months ended September 30, 2018 and October 1, 2017 was lower than the expected federal statutory rate primarily because of the favorable effect of statutory rates applicable to income earned outside the United States and the benefit from U.S. research and development tax credits, partially offset by additions to the uncertain tax positions for transfer pricing. The effective rate for the three and nine months ended September 30, 2018 was also reduced by the benefit of the U.S. foreign derived intangible income deduction. Discrete tax items recorded in the three and nine months ended September 30, 2018 amounted to $0.2 million of expense and $6.5 million of benefit, respectively. The $0.2 million of discrete tax expense recorded in the three months ended September 30, 2018 consisted of $1.1 million of expense related to non-taxable Discrete tax items recorded in the three and nine months ended October 1, 2017 amounted to expense of $0.3 million and benefit of $6.1 million, respectively. The $0.3 million of discrete tax expense recorded in the three months ended October 1, 2017 was primarily composed of $0.8 million of expense related to non-taxable non-taxable On a quarterly basis, Teradyne evaluates the realizability of the deferred tax assets by jurisdiction and assesses the need for a valuation allowance. As of September 30, 2018, Teradyne believes that it will ultimately realize the deferred tax assets recorded on the condensed consolidated balance sheet. However, should Teradyne believe that it is more-likely-than-not As of September 30, 2018 and December 31, 2017, Teradyne had $38.6 million and $36.3 million, respectively, of reserves for uncertain tax positions. The $2.3 million net increase in reserves for uncertain tax positions is primarily composed of additions related to transfer pricing and U.S. research and development tax credits. Teradyne is currently under examination by the U.S. Internal Revenue Service and the Inland Revenue Authority of Singapore. The timing of resolution and closure of these tax audits is highly unpredictable. Given the uncertainty, it is reasonably possible that the balance of unrecognized tax benefits could significantly change within the next twelve months. However, an estimate of the range of reasonably possible adjustments cannot presently be made. Teradyne recognizes interest and penalties related to income tax matters in income tax expense. As of September 30, 2018 and December 31, 2017, $0.3 million and $0.3 million, respectively, of interest and penalties were accrued for uncertain tax positions. For the nine months ended September 30, 2018, an expense of $0.1 million was recorded for interest and penalties related to income tax items. For the nine months ended October 1, 2017, a benefit of $0.1 million was recorded for interest and penalties related to income tax items. Teradyne qualifies for a tax holiday in Singapore by fulfilling the requirements of an agreement with the Singapore Economic Development Board under which certain headcount and spending requirements must be met. The tax savings due to the tax holiday for the nine months ended September 30, 2018 was $8.9 million, or $0.05 per diluted share. The tax savings due to the tax holiday for the nine months ended October 1, 2017 was $20.5 million, or $0.10 per diluted share. The tax holiday is scheduled to expire on December 31, 2020. In the fourth quarter of 2017, Teradyne recorded a provisional amount of $186.0 million of additional income tax expense, which represents Teradyne’s best estimate of the impact of the Tax Cuts and Jobs Act of 2017 (the “Tax Reform Act”) in accordance with Teradyne’s understanding of the Tax Reform Act and guidance available at that time. The $186.0 million is composed of expense of $161.0 million related to the one-time

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Information	S. SEGMENT INFORMATION Teradyne has four reportable segments (Semiconductor Test, System Test, Industrial Automation and Wireless Test). Each of the Semiconductor Test, System Test, and Wireless Test segments is also an individual operating segment. The Industrial Automation reportable segment consists of operating segments with discrete financial information, which have been combined into one reportable segment as they share similar economic characteristics, types of products, production processes, distribution channels, and currency risks. The Semiconductor Test segment includes operations related to the design, manufacturing and marketing of semiconductor test products and services. The System Test segment includes operations related to the design, manufacturing and marketing of products and services for defense/aerospace instrumentation test, storage test and circuit-board test. The Industrial Automation segment includes operations related to the design, manufacturing and marketing of collaborative robotic arms, autonomous mobile robots and advanced robotic control software. The Wireless Test segment includes operations related to the design, manufacturing and marketing of wireless test products and services. Teradyne evaluates performance based on several factors, of which the primary financial measure is business segment income (loss) before income taxes. The accounting policies of the business segments in effect are described in Note B: “Accounting Policies” in Teradyne’s Annual Report on Form 10-K Segment information for the three and nine months ended September 30, 2018 and October 1, 2017 is as follows: Semiconductor Test Industrial Automation System Test Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended September 30, 2018 Revenues $ 417,297 $ 65,913 $ 49,606 $ 34,304 $ (272 ) $ 566,848 Income (loss) before income taxes (1)(2) 126,638 940 9,056 7,843 (3,633 ) 140,844 Total assets (3) 709,616 617,741 83,160 79,986 1,391,984 2,882,487 Three Months Ended October 1, 2017 Revenues $ 396,881 $ 40,063 $ 35,569 $ 30,865 $ — $ 503,378 Income (loss) before income taxes (1)(2) 116,836 3,373 (3,344 ) 7,461 3,111 127,437 Total assets (3) 598,925 508,943 100,083 61,206 1,820,170 3,089,327 Nine Months Ended September 30, 2018 Revenues $ 1,150,712 $ 176,803 $ 162,308 $ 92,023 $ (602 ) $ 1,581,244 Income (loss) before income taxes (1)(2) 305,876 (1,198 ) 35,296 18,615 (1,914 ) 356,675 Total assets (3) 709,616 617,741 83,160 79,986 1,391,984 2,882,487 Nine Months Ended October 1, 2017 Revenues $ 1,345,560 $ 115,672 $ 112,147 $ 83,812 $ — $ 1,657,191 Income (loss) before income taxes (1)(2) 426,081 (279 ) (11,795 ) 13,508 (1,186 ) 426,329 Total assets (3) 598,925 508,943 100,083 61,206 1,820,170 3,089,327 (1) Included in Corporate and Other are: contingent consideration adjustments, severance charges, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges. (2) Included in the income (loss) before income taxes for each of the segments are charges and credits related to restructuring and other and inventory charges. (3) Total business assets are directly attributable to each business. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets. Included in the Semiconductor Test segment are charges in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 2,071 $ 743 $ 5,851 $ 3,686 Restructuring and other—employee severance 1,716 375 7,657 242 Included in the System Test segment are charges in the following line item in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 237 $ 251 $ 812 $ 1,609 Included in the Industrial Automation segment are charges in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Restructuring and other—acquisition related expenses and compensation $ 811 $ — $ 811 $ — Cost of revenues—inventory charge 323 130 680 130 Restructuring and other—employee severance — 206 288 1,150 Included in the Wireless Test segment are charges and credits in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 716 $ 735 $ 2,179 $ 1,729 Restructuring and other—lease impairment — (393 ) — 900 Included in Corporate and Other are charges and credits in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Restructuring and other—Universal Robots contingent consideration adjustment $ (768 ) $ (286 ) $ (9,236 ) $ 1,847 Restructuring and other—acquisition related expenses — — 3,318 — Restructuring and other — — 872 — Restructuring and other—property insurance recovery — (5,064 ) — (5,064 ) Restructuring and other—expenses related to Japan earthquake and impairment of fixed assets — 755 — 755 Restructuring and other—employee severance — — — 530

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2018
Shareholders' Equity	T. SHAREHOLDERS’ EQUITY Stock Repurchase Program In January 2018, Teradyne’s Board of Directors cancelled the December 2016 stock repurchase program and authorized a new stock repurchase program for up to $1.5 billion of common stock. Teradyne intends to repurchase $750 million in 2018. During the nine months ended September 30, 2018, Teradyne repurchased 13.8 million shares of common stock for $562.3 million at an average price of $40.62 per share. In December 2016, the Board of Directors approved a $500 million share repurchase authorization which commenced on January 1, 2017. During the nine months ended October 1, 2017, Teradyne repurchased 4.6 million shares of common stock for $151.8 million at an average price of $32.66 per share. The total price includes commissions and is recorded as a reduction to retained earnings. Dividend Holders of Teradyne’s common stock are entitled to receive dividends when they are declared by Teradyne’s Board of Directors. In January 2018, May 2018 and August 2018, Teradyne’s Board of Directors declared a quarterly cash dividend of $0.09 per share. Dividend payments for the three and nine months ended September 30, 2018 were $16.6 million and $51.3 million, respectively. In January 2017, May 2017 and August 2017, Teradyne’s Board of Directors declared a quarterly cash dividend of $0.07 per share. Dividend payments for the three and nine months ended October 1, 2017 were $13.8 million and $41.7 million, respectively. While Teradyne declared a quarterly cash dividend and authorized a share repurchase program, it may reduce or eliminate the cash dividend or share repurchase program in the future. Future cash dividends and stock repurchases are subject to the discretion of Teradyne’s Board of Directors, which will consider, among other things, Teradyne’s earnings, capital requirements and financial condition.

Accounting Policies (Policies)

Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Basis of Presentation	Basis of Presentation The consolidated interim financial statements include the accounts of Teradyne and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated. These interim financial statements are unaudited and reflect all normal recurring adjustments that are, in the opinion of management, necessary for the fair statement of such interim financial statements. Certain prior year amounts were reclassified to conform to the current year presentation. The December 31, 2017 condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The accompanying financial information should be read in conjunction with the consolidated financial statements and notes thereto contained in Teradyne’s Annual Report on Form 10-K,
Preparation of Financial Statements and Use of Estimates	Preparation of Financial Statements and Use of Estimates The preparation of consolidated financial statements requires management to make estimates and judgments that affect the amounts reported in the financial statements. Actual results may differ significantly from these estimates.
Revenue from Contracts with Customers	Revenue from Contracts with Customers Teradyne adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers” (“ASC 606”) “Revenue Recognition” (“ASC 605”) 10-K In accordance with ASC 606, Teradyne recognizes revenues, when or as control is transferred to a customer. Teradyne’s determination of revenue is dependent upon a five step process outlined below. Step 1: Identify the contract with the customer Teradyne accounts for a contract with a customer when there is written approval, the contract is committed, the rights of the parties, including payment terms, are identified, the contract has commercial substance and consideration is probable of collection. Step 2: Identify the performance obligations in the contract Teradyne periodically enters into contracts with its customers in which a customer may purchase a combination of goods and services, such as products with extended warranty obligations. Teradyne determines performance obligations by assessing whether the products or services are distinct from the other elements of the contract. In order to be distinct, the product or service must perform either on its own or with readily available resources and must be separate within the context of the contract. Step 3: Determine the transaction price Teradyne considers the amount stated on the face of the purchase order to be the transaction price. Teradyne does not have material variable consideration which could impact the stated purchase price agreed to by Teradyne and the customer. Step 4: Allocate the transaction price to the performance obligations in the contract Transaction price is allocated to each individual performance obligation based on the standalone selling price of that performance obligation. Teradyne uses standalone transactions when available to value each performance obligation. If standalone transactions are not available, Teradyne will estimate the standalone selling price through market assessments or cost plus a reasonable margin analysis. Any discounts from standalone selling price are spread proportionally to each performance obligation. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation In order to determine the appropriate timing for revenue recognition, Teradyne first determines if the transaction meets any of three criteria for over time recognition. If the transaction meets the criteria for over time recognition, Teradyne recognizes revenue as the good or service is delivered. Teradyne uses input variables such as hours or months utilized or costs incurred to determine the amount of revenue to recognize in a given period. Input variables are used as they best align consumption with benefit to the customer. For transactions that do not meet the criteria for over time recognition, Teradyne will recognize revenue at a point in time based on an assessment of the five criteria for transfer of control. Teradyne has concluded that revenue should be recognized when shipped or delivered based on contractual terms. Typically acceptance of Teradyne’s products and services is a formality as Teradyne delivers similar systems, instruments and robots to standard specifications. In cases where acceptance is not deemed a formality, Teradyne will defer revenue recognition until customer acceptance. Revenue recognized in accordance with ASC 606 was $564.5 million and $1,571.0 million for the three and nine months ended September 30, 2018, respectively. For the three and nine months ended September 30, 2018, Teradyne also recognized $2.3 million and $10.2 million, respectively, in revenue on leases of Teradyne systems, which are accounted for outside of ASC 606. Disaggregation of Revenue The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Three Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated System on a chip Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 8,866 $ 4,600 $ 15,423 $ — $ 2,625 $ 17,834 $ 1,810 $ 104 $ 3,820 $ (272 ) $ 54,810 Over Time 8,810 686 6,037 — 789 190 — 167 146 — 16,825 Europe, Middle East and Africa Point in Time 9,728 2,080 161 — 3,223 26,445 2,647 — 1,504 — 45,788 Over Time 5,336 301 505 — 1,510 282 — 457 318 — 8,709 Asia Pacific Point in Time 258,898 76,429 931 9,916 5,201 13,656 2,087 10 26,851 — 393,979 Over Time 36,722 2,794 212 2,116 885 145 — 79 1,494 — 44,447 Lease Revenue 2,047 — — — 72 — — — 171 — 2,290 Total $ 330,407 $ 86,890 $ 23,269 $ 12,032 $ 14,305 $ 58,552 $ 6,544 $ 817 $ 34,304 $ (272 ) $ 566,848 For the Nine Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated SOC Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 30,577 $ 10,291 $ 42,276 $ 284 $ 5,814 $ 48,025 $ 3,009 $ 104 $ 13,515 $ (602 ) $ 153,293 Over Time 26,536 2,092 18,462 — 2,342 431 — 578 379 — 50,820 Europe, Middle East and Africa Point in Time 32,079 3,066 2,104 — 12,109 75,631 4,647 — 2,570 — 132,206 Over Time 16,240 824 1,596 — 4,781 675 — 732 802 — 25,650 Asia Pacific Point in Time 702,097 202,336 1,417 51,863 10,804 39,135 3,397 10 68,180 — 1,079,239 Over Time 108,011 7,401 678 5,077 2,364 350 — 79 5,893 — 129,853 Lease Revenue 9,162 — — — 337 — — — 684 — 10,183 Total $ 924,702 $ 226,010 $ 66,533 $ 57,224 $ 38,551 $ 164,247 $ 11,053 $ 1,503 $ 92,023 $ (602 ) $ 1,581,244 Performance Obligations Hardware Teradyne hardware consists primarily of semiconductor test systems and instruments, defense/aerospace test instrumentation and systems, storage test systems and instruments, circuit-board test and inspection systems and instruments, collaborative robots, autonomous mobile robots and wireless test systems. The hardware includes a standard 12-month Extended Warranty Customers have the option to purchase an extended warranty, which extends the warranty period for systems and robots beyond the one-year Training and Applications Support Teradyne sells training and applications support to customers either in standalone transactions or included with system purchases. The training and support allow the customer to use Teradyne’s systems efficiently and effectively. Training and applications support included in system orders are valued based on their standalone selling price and all training and applications support is recognized over time as the customer receives and consumes the benefit associated with each. Both are recognized using an input method of hours consumed as this best depicts the transfer of services to the customer. Service Agreements Service agreements are recognized ratably over the period of agreement based on months completed. Post-Contract Customer Support (“PCS”) Teradyne provides support services for certain systems and robots outside of warranty. These services include telephone support, bug fixes, and when-and-if Teradyne does not allow customer returns or provide refunds to customers for any products or services. Contract Balances The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. September 30, January 1, 2018 (as adjusted) Increase/ Decrease (in thousands) Deferred revenue and customer advances $ 77,953 $ 76,638 $ 1,315 Long-term deferred revenue and customer advances 29,387 20,848 8,539 The amount of revenue recognized during the three and nine months ended September 30, 2018 that was previously included within the deferred revenue and customer advances was $24.5 million and $70.9 million, respectively, and primarily relates to extended warranties, training, application support, and PCS. Each of these represents a distinct performance obligation. Customers typically pay for these services net 30 to 60 days from the date that transfer of control of the associated system or product occurs. Remaining Performance Obligations Teradyne does not have material remaining performance obligations from contracts with an original expected duration of greater than one year. Significant Judgments Teradyne makes no significant judgments in determining the amount or timing of revenue recognition. Practical Expedients Teradyne has adopted the practical expedients available within ASC 340 “Other Assets and Deferred Costs” Teradyne has adopted the practical expedient, which states an entity need not adjust the promised amount of consideration for the effects of a significant financing component if the entity expects, at contract inception, that the period between when the entity transfers a promised good or service to the customer and when the customer pays for that good or service will be one year or less. Teradyne does not have material payments associated with performance obligations outside this one-year Impacts The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: September 30, 2018 As Adjustments to Legacy (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 352,476 $ (31,205 ) $ 321,271 Inventories, net 154,705 11,708 166,413 Deferred tax assets 70,772 (3,684 ) 67,088 Liabilities Deferred revenue and customer advances $ 77,953 $ (4,825 ) $ 73,128 Income taxes payable 24,603 (4,271 ) 20,332 Long-term deferred revenue and customer advances 29,387 (9,968 ) 19,419 Shareholders’ equity Accumulated deficit $ (23,243 ) $ (4,117 ) $ (27,360 ) Condensed Consolidated Statement of Operation: For the Three Months ended September 30, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 566,848 $ 59,738 $ 626,586 Total cost of revenues 233,155 21,702 254,857 Income tax provision 20,863 4,771 25,634 Net income 119,981 33,265 153,246 Net income per common share: Basic $ 0.65 $ 0.18 $ 0.83 Diluted $ 0.63 $ 0.17 $ 0.80 For the Nine Months ended September, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 1,581,244 $ (32,668 ) $ 1,548,576 Total cost of revenues 670,385 (11,708 ) 658,677 Income tax provision 48,684 (4,163 ) 44,521 Net income 307,991 (16,797 ) 291,194 Net income per common share: Basic $ 1.62 $ (0.09 ) $ 1.53 Diluted $ 1.57 $ (0.09 ) $ 1.48
Retirement Benefits	Retirement Benefits In March 2017, the Financial Accounting Standards Board (“FASB”) issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost non-service non-service non-operating non-operating
Financial Assets and Financial Liabilities	Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10):
Contingencies and Litigation	Contingencies and Litigation Teradyne may be subject to certain legal proceedings, lawsuits and other claims as discussed in Note Q: “Commitments and Contingencies.” Teradyne accrues for a loss contingency, including legal proceedings, lawsuits, pending claims and other legal matters, when the likelihood of a loss is probable and the amount of the loss can be reasonably estimated. When the reasonable estimate of the loss is within a range of amounts, and no amount in the range constitutes a better estimate than any other amount, Teradyne accrues the amount at the low end of the range. Teradyne adjusts the accruals from time to time as additional information is received, but the loss incurred may be significantly greater than or less than the amount accrued. Loss contingencies are disclosed when they are material and there is at least a reasonable possibility that a loss has been incurred. Attorney fees related to legal matters are expensed as incurred.

Accounting Policies (Tables)

Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition	The following table provides information about disaggregated revenue by primary geographical market, major product line and timing of revenue recognition. For the Three Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated System on a chip Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 8,866 $ 4,600 $ 15,423 $ — $ 2,625 $ 17,834 $ 1,810 $ 104 $ 3,820 $ (272 ) $ 54,810 Over Time 8,810 686 6,037 — 789 190 — 167 146 — 16,825 Europe, Middle East and Africa Point in Time 9,728 2,080 161 — 3,223 26,445 2,647 — 1,504 — 45,788 Over Time 5,336 301 505 — 1,510 282 — 457 318 — 8,709 Asia Pacific Point in Time 258,898 76,429 931 9,916 5,201 13,656 2,087 10 26,851 — 393,979 Over Time 36,722 2,794 212 2,116 885 145 — 79 1,494 — 44,447 Lease Revenue 2,047 — — — 72 — — — 171 — 2,290 Total $ 330,407 $ 86,890 $ 23,269 $ 12,032 $ 14,305 $ 58,552 $ 6,544 $ 817 $ 34,304 $ (272 ) $ 566,848 For the Nine Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Other Consolidated SOC Memory Defense/ Aerospace Storage Production Universal Mobile Energid (in thousands) Americas Point in Time $ 30,577 $ 10,291 $ 42,276 $ 284 $ 5,814 $ 48,025 $ 3,009 $ 104 $ 13,515 $ (602 ) $ 153,293 Over Time 26,536 2,092 18,462 — 2,342 431 — 578 379 — 50,820 Europe, Middle East and Africa Point in Time 32,079 3,066 2,104 — 12,109 75,631 4,647 — 2,570 — 132,206 Over Time 16,240 824 1,596 — 4,781 675 — 732 802 — 25,650 Asia Pacific Point in Time 702,097 202,336 1,417 51,863 10,804 39,135 3,397 10 68,180 — 1,079,239 Over Time 108,011 7,401 678 5,077 2,364 350 — 79 5,893 — 129,853 Lease Revenue 9,162 — — — 337 — — — 684 — 10,183 Total $ 924,702 $ 226,010 $ 66,533 $ 57,224 $ 38,551 $ 164,247 $ 11,053 $ 1,503 $ 92,023 $ (602 ) $ 1,581,244
Information about Contract Liabilities	The following table provides information about contract liabilities. Teradyne does not have material contract assets on the balance sheet. September 30, January 1, 2018 (as adjusted) Increase/ Decrease (in thousands) Deferred revenue and customer advances $ 77,953 $ 76,638 $ 1,315 Long-term deferred revenue and customer advances 29,387 20,848 8,539
ASU 2014-09
Summarize Impact of ASC 606 to Consolidated Financial Statements	The following tables summarize the impact of ASC 606 to Teradyne’s consolidated financial statements. Differences are the result of timing differences between the recognition of revenue under ASC 606 and ASC 605 primarily with respect to software transactions deferred due to lack of vendor specific objective evidence of price under ASC 605 and Teradyne’s assessment of acceptance under ASC 606. Under Legacy GAAP, Teradyne did not recognize revenue prior to acceptance if payment, title, or risk of loss was tied to acceptance. Under ASC 606, Teradyne recognizes revenue prior to receipt of acceptance if acceptance is deemed a formality. Condensed Consolidated Balance Sheet: September 30, 2018 As Adjustments to Legacy (in thousands, except per share amount) Assets Accounts receivable, less allowance for doubtful accounts $ 352,476 $ (31,205 ) $ 321,271 Inventories, net 154,705 11,708 166,413 Deferred tax assets 70,772 (3,684 ) 67,088 Liabilities Deferred revenue and customer advances $ 77,953 $ (4,825 ) $ 73,128 Income taxes payable 24,603 (4,271 ) 20,332 Long-term deferred revenue and customer advances 29,387 (9,968 ) 19,419 Shareholders’ equity Accumulated deficit $ (23,243 ) $ (4,117 ) $ (27,360 ) Condensed Consolidated Statement of Operation: For the Three Months ended September 30, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 566,848 $ 59,738 $ 626,586 Total cost of revenues 233,155 21,702 254,857 Income tax provision 20,863 4,771 25,634 Net income 119,981 33,265 153,246 Net income per common share: Basic $ 0.65 $ 0.18 $ 0.83 Diluted $ 0.63 $ 0.17 $ 0.80 For the Nine Months ended September, 2018 As Reported Adjustments to Legacy (in thousands, except per share amount) Total revenues $ 1,581,244 $ (32,668 ) $ 1,548,576 Total cost of revenues 670,385 (11,708 ) 658,677 Income tax provision 48,684 (4,163 ) 44,521 Net income 307,991 (16,797 ) 291,194 Net income per common share: Basic $ 1.62 $ (0.09 ) $ 1.53 Diluted $ 1.57 $ (0.09 ) $ 1.48

Acquisitions (Tables)

Acquisitions (Tables) - Mobile Industrial Robots (MiR)	9 Months Ended
	Sep. 30, 2018
Allocation of Preliminary Purchase Price	The following table represents the allocation of the preliminary purchase price: Purchase Price Allocation (in thousands) Goodwill $ 134,737 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current 299 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (17,779 ) Total purchase price $ 196,630
Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date	Components of these intangible assets and their estimated useful lives at the acquisition date are as follows: Fair Value Estimated Useful Life (in thousands) (in years) Developed technology $ 58,900 7.0 Trademarks and tradenames 13,240 11.0 Customer relationships 8,500 2.5 Backlog 30 0.2 Total intangible assets $ 80,670 7.2
Pro Forma Results Under Acquisitions	The unaudited pro forma results are not necessarily indicative of what actually would have occurred had the acquisition been in effect for the periods presented: For the Three Months For the Nine Months Ended October 1, 2017 September 30, October 1, (in thousands) Revenue $ 507,982 $ 1,588,042 $ 1,666,075 Net income 100,339 306,768 351,626 Net income per common share: Basic $ 0.51 $ 1.61 $ 1.77 Diluted $ 0.50 $ 1.56 $ 1.75

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2018
Composition of Inventories, Net	Inventories, net consisted of the following at September 30, 2018 and December 31, 2017: September 30, December 31, (in thousands) Raw material $ 87,124 $ 62,668 Work-in-process 33,788 19,464 Finished Goods 33,793 25,393 $ 154,705 $ 107,525

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following table sets forth by fair value hierarchy Teradyne’s financial assets and liabilities that were measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017. September 30, 2018 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 275,614 $ — $ — $ 275,614 Cash equivalents 477,869 60,536 — 538,405 Available-for-sale U.S. Treasury securities — 363,414 — 363,414 Commercial paper — 67,202 — 67,202 Corporate debt securities — 40,271 — 40,271 U.S. government agency securities — 9,004 — 9,004 Debt mutual funds 3,055 — — 3,055 Certificates of deposit and time deposits — 2,218 — 2,218 Non-U.S. — 543 — 543 Equity securities: Mutual Funds 24,685 — — 24,685 $ 781,223 $ 543,188 $ — $ 1,324,411 Derivative assets — 3 — 3 Total $ 781,223 $ 543,191 $ — $ 1,324,414 Liabilities Contingent consideration $ — $ — $ 60,942 $ 60,942 Derivative liabilities — 455 — 455 Total $ — $ 455 $ 60,942 $ 61,397 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 753,483 $ 60,536 $ — $ 814,019 Marketable securities — 418,410 — 418,410 Long-term marketable securities 27,740 64,242 — 91,982 Prepayments — 3 — 3 Total $ 781,223 $ 543,191 $ — $ 1,324,414 Liabilities Other current liabilities $ — $ 455 $ — $ 455 Contingent consideration — — 35,532 35,532 Long-term contingent consideration — — 25,410 25,410 Total $ — $ 455 $ 60,942 $ 61,397 December 31, 2017 Quoted Prices in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 197,955 $ — $ — $ 197,955 Cash equivalents 206,335 25,553 — 231,888 Available for sale securities: U.S. Treasury securities — 855,795 — 855,795 Commercial paper — 282,840 — 282,840 Certificates of deposit and time deposits — 167,342 — 167,342 Corporate debt securities — 133,186 — 133,186 Equity and debt mutual funds 23,430 — — 23,430 U.S. government agency securities — 10,726 — 10,726 Non-U.S. — 586 — 586 $ 427,720 $ 1,476,028 $ — $ 1,903,748 Derivative assets — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Contingent consideration $ — $ — $ 45,102 $ 45,102 Derivative liabilities — 446 — 446 Total $ — $ 446 $ 45,102 $ 45,548 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 404,290 $ 25,553 $ — $ 429,843 Marketable securities — 1,347,979 — 1,347,979 Long-term marketable securities 23,430 102,496 — 125,926 Prepayments — 389 — 389 Total $ 427,720 $ 1,476,417 $ — $ 1,904,137 Liabilities Other accrued liabilities $ — $ 446 $ — $ 446 Contingent consideration — — 24,497 24,497 Long-term contingent consideration — — 20,605 20,605 Total $ — $ 446 $ 45,102 $ 45,548
Schedule of Changes in Fair Value of Level 3 Contingent Consideration	Changes in the fair value of Level 3 contingent consideration for the three and nine months ended September 30, 2018 and October 1, 2017 were as follows: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, 2018 2017 2018 2017 (in thousands) Balance at beginning of period $ 60,914 $ 39,415 $ 45,102 $ 38,332 Acquisition of MiR — — 51,399 — Foreign currency impact 796 — (1,770 ) — Payments (a) — — (24,553 ) (1,050 ) Fair value adjustment (b) (768 ) (286 ) (9,236 ) 1,847 Balance at end of period $ 60,942 $ 39,129 $ 60,942 $ 39,129 (a) In the nine months ended September 30, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out earn-out (b) In the three and nine months ended September 30, 2018, the fair value of contingent consideration for the earn-out earn-out
Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument	The following table provides quantitative information associated with the fair value measurement of Teradyne’s Level 3 financial instruments: Liability September 30, Value Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (Universal Robots) $11,314 Monte Carlo Simulation Revenue volatility 12.9% Discount Rate 3.7% Contingent consideration (Mobile Industrial Robots) $49,628 Monte Carlo Simulation Revenue volatility 18.0% Discount Rate 0.5%
Schedule of Carrying Amounts and Fair Values of Financial Instruments	The carrying amounts and fair values of Teradyne’s financial instruments at September 30, 2018 and December 31, 2017 were as follows: September 30, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 814,019 $ 814,019 $ 429,843 $ 429,843 Marketable securities 510,392 510,392 1,473,905 1,473,905 Derivative assets 3 3 389 389 Liabilities Contingent consideration 60,942 60,942 45,102 45,102 Derivative liabilities 455 455 446 446 Convertible debt (1) 376,417 599,438 365,987 659,525 (1) The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note, which includes the equity conversion features.
Schedule of Available-for-Sale Marketable Securities	The following table summarizes the composition of available-for-sale September 30, 2018 Available-for-Sale Fair Market Value of Investments with Unrealized Losses Cost Unrealized Gain Unrealized (Loss) Fair Market Value (in thousands) U.S. Treasury securities $ 365,701 $ — $ (2,287 ) $ 363,414 $ 362,167 Commercial paper 67,208 7 (13 ) 67,202 66,186 Corporate debt securities 40,669 537 (935 ) 40,271 22,030 U.S. government agency securities 9,065 — (61 ) 9,004 9,004 Debt mutual funds 3,128 — (73 ) 3,055 1,786 Certificates of deposit and time deposits 2,218 — — 2,218 — Non-U.S. 543 — — 543 176 $ 488,532 $ 544 $ (3,369 ) $ 485,707 $ 461,349 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 418,554 $ 52 $ (196 ) $ 418,410 $ 405,959 Long-term marketable securities 69,978 492 (3,173 ) 67,297 55,390 $ 488,532 $ 544 $ (3,369 ) $ 485,707 $ 461,349 The following table summarizes the composition of available-for-sale December 31, 2017 Available-for-Sale Fair Market Value of Investments with Unrealized Losses Cost Unrealized Gain Unrealized (Loss) Fair Market Value (in thousands) U.S. Treasury securities $ 858,258 $ 72 $ (2,535 ) $ 855,795 $ 850,163 Commercial paper 283,009 18 (187 ) 282,840 258,933 Certificates of deposit and time deposits 167,523 6 (187 ) 167,342 138,340 Corporate debt securities 131,179 2,380 (373 ) 133,186 91,010 Equity and debt mutual funds 19,403 4,102 (75 ) 23,430 1,723 U.S. government agency securities 10,775 — (49 ) 10,726 10,726 Non-U.S. 582 4 — 586 — $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 1,349,970 $ 38 $ (2,029 ) $ 1,347,979 $ 1,288,844 Long-term marketable securities 120,759 6,544 (1,377 ) 125,926 62,052 $ 1,470,729 $ 6,582 $ (3,406 ) $ 1,473,905 $ 1,350,896
Contractual Maturities of Investments in Debt Securities Held	The contractual maturities of investments in available-for-sale September 30, 2018 Cost Fair Market Value (in thousands) Due within one year $ 418,554 $ 418,410 Due after 1 year through 5 years 11,477 11,368 Due after 5 years through 10 years 14,906 13,949 Due after 10 years 40,467 38,925 Total $ 485,404 $ 482,652
Schedule of Derivative Instruments in Statement of Financial Position at Fair Value	The following table summarizes the fair value of derivative instruments as of September 30, 2018 and December 31, 2017: Balance Sheet Location September 30, December 31, 2017 (in thousands) Derivatives not designated as hedging instruments: Foreign currency forward contracts assets Prepayments $ 3 $ 389 Foreign currency forward contracts liabilities Other current liabilities (455 ) (446 ) Total derivatives $ (452 ) $ (57 )
Schedule of Effect of Derivative Instruments on Statement of Operations Recognized	The following table summarizes the effect of derivative instruments recognized in the statement of operations for the three and nine months ended September 30, 2018 and October 1, 2017. Location of Losses (Gains) Recognized in For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Derivatives not designated as hedging instruments: Foreign currency forward contracts Other (income) expense, net $ (899 ) $ (939 ) $ 2,502 $ (1,514 ) (1) The table does not reflect the corresponding gains and losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies. (2) For the three and nine months ended September 30, 2018, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $3.7 million and $1.2 million, respectively. (3) For the three and nine months ended October 1, 2017, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.4 million and $2.3 million, respectively.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Components of Convertible Senior Notes	The below tables represent the key components of Teradyne’s convertible senior notes: September 30, 2018 December 31, 2017 (in thousands) Debt Principal $ 460,000 $ 460,000 Unamortized discount 83,583 94,013 Net Carrying amount of convertible debt $ 376,417 $ 365,987 For the Three Months Ended For the Nine Months Ended September 30, 2018 October 1, 2017 September 30, 2018 October 1, 2017 (in thousands) Contractual interest expense on the coupon $ 1,438 $ 1,422 $ 4,313 $ 4,297 Amortization of the discount component and debt issue fees recognized as interest expense 3,520 3,350 10,431 9,926 Total interest expense on the convertible debt $ 4,958 $ 4,772 $ 14,744 $ 14,223

Prepayments (Tables)

Prepayments (Tables)	9 Months Ended
	Sep. 30, 2018
Schedule of Prepayments and other assets	Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: September 30, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 102,652 $ 82,503 Prepaid taxes 10,709 5,039 Prepaid maintenance and other services 7,802 8,189 Other prepayments 12,439 12,386 Total prepayments $ 133,602 $ 108,117

Deferred Revenue and Customer_2

Deferred Revenue and Customer Advances (Tables)	9 Months Ended
	Sep. 30, 2018
Deferred Revenue and Customer Advances	Deferred revenue and customer advances consist of the following and are included in short and long-term deferred revenue and customer advances on the balance sheet: September 30, December 31, (in thousands) Maintenance and training $ 59,681 $ 57,256 Extended warranty 27,617 24,438 Customer advances, undelivered elements and other 20,042 32,047 Total deferred revenue and customer advances $ 107,340 $ 113,741

Product Warranty (Tables)

Product Warranty (Tables)	9 Months Ended
	Sep. 30, 2018
Other Accrued Liabilities	The warranty balance below is included in other accrued liabilities on the balance sheet. For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Balance at beginning of period $ 7,136 $ 9,093 $ 8,200 $ 7,203 Acquisition — — 41 — Accruals for warranties issued during the period 2,760 2,734 9,171 11,049 Adjustments related to pre-existing 282 (35 ) 109 (499 ) Settlements made during the period (2,675 ) (3,055 ) (10,018 ) (9,016 ) Balance at end of period $ 7,503 $ 8,737 $ 7,503 $ 8,737
Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances	When Teradyne receives revenue for extended warranties, beyond one year, it is deferred and recognized on a straight-line basis over the contract period. Related costs are expensed as incurred. The balance below is included in short and long-term deferred revenue and customer advances on the balance sheet. For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Balance at beginning of period $ 25,971 $ 29,377 $ 24,438 $ 28,200 Deferral of new extended warranty revenue 7,232 2,636 19,072 17,126 Recognition of extended warranty deferred revenue (5,586 ) (5,521 ) (15,893 ) (18,834 ) Balance at end of period $ 27,617 $ 26,492 $ 27,617 $ 26,492

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions	The fair value was estimated using the Monte Carlo simulation model with the following assumptions: For the Nine Months Ended September 30, October 1, Risk-free interest rate 2.2 % 1.5 % Teradyne volatility-historical 26.8 % 26.6 % NYSE Composite Index volatility-historical 12.4 % 13.4 % Dividend yield 0.8 % 1.0 %
Fair Value of Stock Options Using Assumptions	The fair value of stock options was estimated using the Black-Scholes option-pricing model with the following assumptions: For the Nine Months Ended September 30, October 1, Expected life (years) 5.0 5.0 Risk-free interest rate 2.4 % 2.0 % Volatility-historical 26.4 % 27.8 % Dividend yield 0.8 % 1.0 %

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2018
Changes in Accumulated Other Comprehensive Income (Loss)	Changes in accumulated other comprehensive income (loss), which are presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains (Losses) on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Nine Months Ended September 30, 2018 Balance at December 31, 2017, net of tax of $0, $1,815, $(932), respectively $ 15,919 $ 1,362 $ 1,495 $ 18,776 Other comprehensive loss before reclassifications, net of tax of $0, $(806), $0, respectively (11,568 ) (2,555 ) — (14,123 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(6), $(53), respectively — 1,411 (184 ) 1,227 Net current period other comprehensive loss, net of tax of $0, $(812), $(53), respectively (11,568 ) (1,144 ) (184 ) (12,896 ) Reclassification of tax effects resulting of the Tax Reform Act, $0, $(691), $(78), respectively (a) — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax $0, $(902), $0, respectively (b) — (3,125 ) — (3,125 ) Balance at September 30, 2018, net of tax of $0, $(590), $(1,063), respectively $ 4,351 $ (2,216 ) $ 1,389 $ 3,524 (a) In the nine months ended September 30, 2018, Teradyne early adopted the ASU 2018-02, “Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” (b) In the nine months ended September 30, 2018, Teradyne adopted the ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Foreign Currency Translation Adjustments Unrealized Gains (Losses) on Marketable Securities Retirement Plans Prior Service Credit Total (in thousands) Nine Months Ended October 1, 2017 Balance at December 31, 2016, net of tax of $0, $209, $(778), respectively $ (21,921 ) $ (60 ) $ 1,767 $ (20,214 ) Other comprehensive income before reclassifications, net of tax of $0, $1,666, $0, respectively 34,235 2,448 — 36,683 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(173), $(115), respectively — (264 ) (204 ) (468 ) Net current period other comprehensive income (loss), net of tax of $0, $1,493, $(115), respectively 34,235 2,184 (204 ) 36,215 Balance as October 1, 2017, net of tax of $0, $1,702, $(893), respectively $ 12,314 $ 2,124 $ 1,563 $ 16,001
Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations	Reclassifications out of accumulated other comprehensive income (loss) to the statement of operations for the three and nine months ended September 30, 2018 and October 1, 2017 were as follows: Details about Accumulated Other Comprehensive Income For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations September 30, October 1, September 30, October 1, 2017 (in thousands) Available-for-sale Unrealized gains (losses), net of tax of $17, $67, $6, $173, respectively $ 57 $ 87 $ (1,411 ) $ 264 Interest income (expense) Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $18, $38, $53, $115, respectively 61 68 184 204 (a) Total reclassifications, net of tax of $35, $105, $59, $288, respectively $ 118 $ 155 $ (1,227 ) $ 468 Net income (a) The amortization of prior service benefit is included in the computation of net periodic pension cost and postretirement benefit. See Note P: “Retirement Plans.”

Goodwill and Acquired Intangi_2

Goodwill and Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Changes in Carrying Amount of Goodwill by Segment	The changes in the carrying amount of goodwill by reportable segments for the nine months ended September 30, 2018, were as follows: Wireless Test Industrial Automation System Test Semiconductor Test Total (in thousands) Balance at December 31, 2017 Goodwill $ 361,819 $ 233,519 $ 158,699 $ 260,540 $ 1,014,577 Accumulated impairment losses (353,843 ) — (148,183 ) (260,540 ) (762,566 ) 7,976 233,519 10,516 — 252,011 MiR acquisition — 134,737 — — 134,737 Energid acquisition — 14,394 — — 14,394 Foreign currency translation adjustment — (8,144 ) — — (8,144 ) Balance at September 30, 2018 Goodwill 361,819 374,506 158,699 260,540 1,155,564 Accumulated impairment losses (353,843 ) — (148,183 ) (260,540 ) (762,566 ) $ 7,976 $ 374,506 $ 10,516 $ — $ 392,998
Schedule of Estimated Intangible Asset Amortization Expense	Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2018 (remainder) 10,731 2019 39,610 2020 24,928 2021 14,343 2022 13,450 Thereafter 36,901
Wireless Test
Schedule of Amortizable Intangible Assets	Amortizable intangible assets consist of the following and are included in intangible assets, net on the balance sheet: September 30, 2018 Gross Carrying Amount (1)(2) Accumulated Amortization (2) Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 336,306 $ (244,833 ) $ (1,117 ) $ 90,356 Customer relationships 105,622 (89,848 ) (83 ) 15,691 Tradenames and trademarks 64,420 (30,408 ) (96 ) 33,916 Non-compete 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 506,698 $ (365,439 ) $ (1,296 ) $ 139,963 December 31, 2017 Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 270,877 $ (226,190 ) $ 1,618 $ 46,305 Customer relationships 92,741 (83,585 ) 171 9,327 Tradenames and trademarks 50,100 (27,120 ) 416 23,396 Non-compete 320 (260 ) — 60 Total intangible assets $ 414,038 $ (337,155 ) $ 2,205 $ 79,088 (1) Includes intangible assets acquired in 2018, $80.7 million from the MiR acquisition and $12.3 million from the Energid acquisition. (2) In 2018, $0.3 million of amortizable intangible assets became fully amortized and have been eliminated from the gross carrying amount and accumulated amortization.

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Computation of Basic and Diluted Net Income Per Common Share	The following table sets forth the computation of basic and diluted net income per common share: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 119,981 $ 103,420 $ 307,991 $ 363,616 Weighted average common shares-basic 185,744 197,485 190,576 198,755 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 3,025 1,144 3,356 632 Convertible note hedge warrant shares (2) 108 — 646 — Restricted stock units 1,331 1,832 1,406 1,663 Stock options 275 306 290 337 Employee stock purchase plan 22 8 26 26 Dilutive potential common shares 4,761 3,290 5,724 2,658 Weighted average common shares-diluted 190,505 200,775 196,300 201,413 Net income per common share-basic $ 0.65 $ 0.52 $ 1.62 $ 1.83 Net income per common share-diluted $ 0.63 $ 0.52 $ 1.57 $ 1.81 (1) Incremental shares from assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.80, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period. (2) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.91, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.

Retirement Plans (Tables)

Retirement Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Defined Benefit Pension Plans
Net Periodic Pension and Postretirement benefit Cost (Income)	For the three and nine months ended September 30, 2018 and October 1, 2017, Teradyne’s net periodic pension cost was comprised of the following: For the Three Months Ended September 30, 2018 October 1, 2017 United States Foreign United States Foreign (in thousands) Service cost $ 538 $ 203 $ 560 $ 215 Interest cost 1,750 177 3,288 186 Expected return on plan assets (1,551 ) (5 ) (3,002 ) (6 ) Amortization of prior service cost 14 — 18 — Settlement loss 267 — — — Total net periodic pension cost $ 1,018 $ 375 $ 864 $ 395 For the Nine Months Ended September 30, 2018 October 1, 2017 United States Foreign United States Foreign (in thousands) Service cost $ 1,657 $ 609 $ 1,679 $ 606 Interest cost 7,188 532 9,863 527 Expected return on plan assets (7,484 ) (15 ) (9,006 ) (19 ) Amortization of prior service cost 43 — 53 — Net actuarial gain (189 ) — (2,732 ) 243 Settlement loss 345 — — — Total net periodic pension cost (benefit) $ 1,560 $ 1,126 $ (143 ) $ 1,357
Postretirement Benefit Plans
Net Periodic Pension and Postretirement benefit Cost (Income)	For the three and nine months ended September 30, 2018 and October 1, 2017, Teradyne’s net periodic postretirement benefit cost (income) was comprised of the following: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Service cost $ 10 $ 8 $ 29 $ 25 Interest cost 49 50 147 151 Amortization of prior service credit (93 ) (124 ) (280 ) (372 ) Net actuarial loss (gain) — — 40 (15 ) Special termination benefits 601 — 3,419 — Total net periodic postretirement benefit cost (income) $ 567 $ (66 ) $ 3,355 $ (211 )

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Information	Segment information for the three and nine months ended September 30, 2018 and October 1, 2017 is as follows: Semiconductor Test Industrial Automation System Test Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended September 30, 2018 Revenues $ 417,297 $ 65,913 $ 49,606 $ 34,304 $ (272 ) $ 566,848 Income (loss) before income taxes (1)(2) 126,638 940 9,056 7,843 (3,633 ) 140,844 Total assets (3) 709,616 617,741 83,160 79,986 1,391,984 2,882,487 Three Months Ended October 1, 2017 Revenues $ 396,881 $ 40,063 $ 35,569 $ 30,865 $ — $ 503,378 Income (loss) before income taxes (1)(2) 116,836 3,373 (3,344 ) 7,461 3,111 127,437 Total assets (3) 598,925 508,943 100,083 61,206 1,820,170 3,089,327 Nine Months Ended September 30, 2018 Revenues $ 1,150,712 $ 176,803 $ 162,308 $ 92,023 $ (602 ) $ 1,581,244 Income (loss) before income taxes (1)(2) 305,876 (1,198 ) 35,296 18,615 (1,914 ) 356,675 Total assets (3) 709,616 617,741 83,160 79,986 1,391,984 2,882,487 Nine Months Ended October 1, 2017 Revenues $ 1,345,560 $ 115,672 $ 112,147 $ 83,812 $ — $ 1,657,191 Income (loss) before income taxes (1)(2) 426,081 (279 ) (11,795 ) 13,508 (1,186 ) 426,329 Total assets (3) 598,925 508,943 100,083 61,206 1,820,170 3,089,327 (1) Included in Corporate and Other are: contingent consideration adjustments, severance charges, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges. (2) Included in the income (loss) before income taxes for each of the segments are charges and credits related to restructuring and other and inventory charges. (3) Total business assets are directly attributable to each business. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.
Semiconductor Test
Schedule of Segment Reporting Information by Segment Charges	Included in the Semiconductor Test segment are charges in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 2,071 $ 743 $ 5,851 $ 3,686 Restructuring and other—employee severance 1,716 375 7,657 242
System Test
Schedule of Segment Reporting Information by Segment Charges	Included in the System Test segment are charges in the following line item in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 237 $ 251 $ 812 $ 1,609
Industrial Automation
Schedule of Segment Reporting Information by Segment Charges	Included in the Industrial Automation segment are charges in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Restructuring and other—acquisition related expenses and compensation $ 811 $ — $ 811 $ — Cost of revenues—inventory charge 323 130 680 130 Restructuring and other—employee severance — 206 288 1,150
Wireless Test
Schedule of Segment Reporting Information by Segment Charges	Included in the Wireless Test segment are charges and credits in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Cost of revenues—inventory charge $ 716 $ 735 $ 2,179 $ 1,729 Restructuring and other—lease impairment — (393 ) — 900
Corporate and Other
Schedule of Segment Reporting Information by Segment Charges	Included in Corporate and Other are charges and credits in the following line items in the statements of operations: For the Three Months Ended For the Nine Months Ended September 30, October 1, September 30, October 1, (in thousands) Restructuring and other—Universal Robots contingent consideration adjustment $ (768 ) $ (286 ) $ (9,236 ) $ 1,847 Restructuring and other—acquisition related expenses — — 3,318 — Restructuring and other — — 872 — Restructuring and other—property insurance recovery — (5,064 ) — (5,064 ) Restructuring and other—expenses related to Japan earthquake and impairment of fixed assets — 755 — 755 Restructuring and other—employee severance — — — 530

Accounting Policies - Additiona

Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Jan. 01, 2018
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized in accordance with ASC 606	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Revenue on leases	2,300		$ 10,200
Standard warranty period			12 months
Deferred revenue and customer advances balance	24,500		$ 70,900
ASU 2014-09
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized in accordance with ASC 606	$ 564,500		$ 1,571,000
ASU 2017-07
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in income from operations		$ 400		$ (1,300)
Retained Earnings | ASU 2014-09
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in adoption of new accounting guidance amount					$ 12,700
Retained Earnings | ASU 2016-01
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in adoption of new accounting guidance amount					3,100
Accumulated Other Comprehensive Income (Loss) | ASU 2016-01
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in adoption of new accounting guidance amount					$ (3,100)

Disaggregated Revenue by Primar

Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Disaggregation of Revenue [Line Items]
Total	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	417,297	396,881	1,150,712	1,345,560
System Test
Disaggregation of Revenue [Line Items]
Total	65,913	40,063	176,803	115,672
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	49,606	35,569	162,308	112,147
Wireless Test
Disaggregation of Revenue [Line Items]
Total	34,304	$ 30,865	92,023	$ 83,812
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(272)		(602)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total	54,810		153,293
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	3,820		13,515
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(272)		(602)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total	16,825		50,820
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	146		379
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total	45,788		132,206
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,504		2,570
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total	8,709		25,650
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	318		802
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	2,290		10,183
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	171		684
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total	393,979		1,079,239
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	26,851		68,180
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total	44,447		129,853
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,494		5,893
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	330,407		924,702
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,866		30,577
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,810		26,536
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	9,728		32,079
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	5,336		16,240
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,047		9,162
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	258,898		702,097
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	36,722		108,011
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	86,890		226,010
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	4,600		10,291
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	686		2,092
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,080		3,066
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	301		824
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	76,429		202,336
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,794		7,401
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total	23,269		66,533
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	15,423		42,276
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	6,037		18,462
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	161		2,104
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	505		1,596
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	931		1,417
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	212		678
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total	12,032		57,224
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total			284
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	9,916		51,863
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,116		5,077
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total	14,305		38,551
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,625		5,814
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	789		2,342
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	3,223		12,109
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,510		4,781
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	72		337
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	5,201		10,804
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	885		2,364
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	58,552		164,247
Universal Robots (UR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	17,834		48,025
Universal Robots (UR) | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	190		431
Universal Robots (UR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	26,445		75,631
Universal Robots (UR) | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	282		675
Universal Robots (UR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	13,656		39,135
Universal Robots (UR) | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	145		350
Mobile Industrial Robots (MiR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	6,544		11,053
Mobile Industrial Robots (MiR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,810		3,009
Mobile Industrial Robots (MiR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,647		4,647
Mobile Industrial Robots (MiR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,087		3,397
Energid Technologies Corporation | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	817		1,503
Energid Technologies Corporation | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	104		104
Energid Technologies Corporation | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	167		578
Energid Technologies Corporation | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	457		732
Energid Technologies Corporation | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	10		10
Energid Technologies Corporation | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 79		$ 79

Information about Contract Liab

Information about Contract Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	$ 77,953		$ 83,614
Long-term deferred revenue and customer advances	29,387		$ 30,127
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	73,128	$ 76,638
Long-term deferred revenue and customer advances	19,419	20,848
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue and customer advances	(4,825)	1,315
Long-term deferred revenue and customer advances	$ (9,968)	$ 8,539

Summarize Impact of ASC 606 to

Summarize Impact of ASC 606 to Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
ASSETS
Accounts receivable, less allowance for doubtful accounts	$ 352,476		$ 272,783
Inventories, net	154,705		107,525
Deferred tax assets	70,772		84,026
LIABILITIES
Deferred revenue and customer advances	77,953		83,614
Income taxes payable	24,603		59,055
Long-term deferred revenue and customer advances	29,387		30,127
Shareholders' equity
Accumulated deficit	(23,243)		$ 272,013
ASU 2014-09
ASSETS
Accounts receivable, less allowance for doubtful accounts	321,271
Inventories, net	166,413
Deferred tax assets	67,088
LIABILITIES
Deferred revenue and customer advances	73,128	$ 76,638
Income taxes payable	20,332
Long-term deferred revenue and customer advances	19,419	20,848
Shareholders' equity
Accumulated deficit	(27,360)
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
ASSETS
Accounts receivable, less allowance for doubtful accounts	(31,205)
Inventories, net	11,708
Deferred tax assets	(3,684)
LIABILITIES
Deferred revenue and customer advances	(4,825)	1,315
Income taxes payable	(4,271)
Long-term deferred revenue and customer advances	(9,968)	$ 8,539
Shareholders' equity
Accumulated deficit	$ (4,117)

Summarize Impact of ASC 606 t_2

Summarize Impact of ASC 606 to Condensed Consolidated Statement of Operation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Total cost of revenues	233,155		670,385
Income tax provision	20,863	24,017	48,684	62,713
Net income	$ 119,981	$ 103,420	$ 307,991	$ 363,616
Net income per common share:
Basic	$ 0.65	$ 0.52	$ 1.62	$ 1.83
Diluted	$ 0.63	$ 0.52	$ 1.57	$ 1.81
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 564,500		$ 1,571,000
ASU 2014-09 | Adjustments to Recognize Under Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	59,738		(32,668)
Total cost of revenues	21,702		(11,708)
Income tax provision	4,771		(4,163)
Net income	$ 33,265		$ (16,797)
Net income per common share:
Basic	$ 0.18		$ (0.09)
Diluted	$ 0.17		$ (0.09)
ASU 2014-09 | Legacy GAAP
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 626,586		$ 1,548,576
Total cost of revenues	254,857		658,677
Income tax provision	25,634		44,521
Net income	$ 153,246		$ 291,194
Net income per common share:
Basic	$ 0.83		$ 1.53
Diluted	$ 0.80		$ 1.48

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($)	Apr. 25, 2018	Feb. 26, 2018	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Revenues			$ 6,500,000		$ 11,100,000
Income (loss) before income taxes			(3,800,000)		(5,400,000)
Goodwill			392,998,000		392,998,000	$ 392,998,000		$ 252,011,000
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Total preliminary purchase price	$ 196,630,000
Cash paid to acquire outstanding common and preferred stock	145,200,000
Contingent consideration	51,400,000
Arrangement range of outcomes value high			$ 118,900,000		$ 118,900,000	118,900,000
Goodwill, not deductible for tax purposes	134,700,000
Net income				$ 100,339,000		306,768,000	$ 351,626,000
Goodwill	$ 134,737,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 2 months 12 days
Mobile Industrial Robots (MiR) | Fair Value Adjustment to Inventory
Business Acquisition [Line Items]
Net income						400,000	2,900,000
Mobile Industrial Robots (MiR) | Acquisition Related Costs
Business Acquisition [Line Items]
Net income						$ 2,900,000	$ 400,000
Energid Technologies Corporation
Business Acquisition [Line Items]
Total preliminary purchase price		$ 27,600,000
Goodwill		14,400,000
Acquired value of intangible assets		$ 12,300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		7 years 8 months 12 days
Net tangible assets		$ 1,000,000

Allocation of Preliminary Purch

Allocation of Preliminary Purchase Price (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Apr. 25, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 392,998		$ 252,011
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Goodwill		$ 134,737
Intangible assets		80,670
Current assets		6,039
Non-current assets		299
Accounts payable and current liabilities		(7,336)
Long-term deferred tax liabilities		(17,779)
Total purchase price		$ 196,630

Components of Intangible Assets

Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date (Detail) - Mobile Industrial Robots (MiR) - USD ($) $ in Thousands	Apr. 25, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 80,670	$ 80,700
Total intangible assets, estimated useful life, years	7 years 2 months 12 days
Developed technology
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 58,900
Total intangible assets, estimated useful life, years	7 years
Trademarks and tradenames
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 13,240
Total intangible assets, estimated useful life, years	11 years
Customer Relationships
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 8,500
Total intangible assets, estimated useful life, years	2 years 6 months
Customer backlog
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 30
Total intangible assets, estimated useful life, years	2 months 12 days

Pro Forma Results Under Acquisi

Pro Forma Results Under Acquisition (Detail) - Mobile Industrial Robots (MiR) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Business Acquisition [Line Items]
Revenue	$ 507,982	$ 1,588,042	$ 1,666,075
Net income	$ 100,339	$ 306,768	$ 351,626
Net income per common share, basic	$ 0.51	$ 1.61	$ 1.77
Net income per common share, diluted	$ 0.50	$ 1.56	$ 1.75

Composition of Inventories, Net

Composition of Inventories, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory [Line Items]
Raw material	$ 87,124	$ 62,668
Work-in-process	33,788	19,464
Finished Goods	33,793	25,393
Inventories, net	$ 154,705	$ 107,525

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Inventory [Line Items]
Inventory reserves	$ 104.3	$ 102.9

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Financial Instruments and Fair Value [Line Items]
Available-for-sale securities, realized gain	$ 200,000	$ 200,000	$ 600,000	$ 700,000
Available-for-sale securities, realized loss			1,600,000	$ 300,000
Unrealized gains related to equity securities	1,000,000		1,400,000
Available-for-sale marketable securities, Fair Market Value of Investments in debt securities with Unrealized Losses	461,349,000		461,349,000		$ 1,350,896,000
Fair market value of investments with unrealized losses greater than one year	76,100,000		76,100,000		141,000,000
Aggregate loss of investments with unrealized losses greater than one year	2,100,000		2,100,000		1,200,000
Fair market value of investments with unrealized losses less than one year	385,300,000		385,300,000		1,209,900,000
Aggregate loss of investments with unrealized losses less than one year	1,300,000		1,300,000		2,200,000
Debt Mutual Funds
Financial Instruments and Fair Value [Line Items]
Available-for-sale marketable securities, Fair Market Value of Investments in debt securities with Unrealized Losses	1,786,000		1,786,000
Available for sale securities with out contractual maturity date	3,100,000		3,100,000
Universal Robots (UR)
Financial Instruments and Fair Value [Line Items]
Maximum payment per earn-out			25,000,000
Mobile Industrial Robots (MiR)
Financial Instruments and Fair Value [Line Items]
Maximum amount of contingent consideration paid for acquisition	118,900,000		118,900,000
Foreign Exchange Contracts
Financial Instruments and Fair Value [Line Items]
Notional amount of foreign currency forward contracts	$ 166,600,000		$ 166,600,000		$ 116,800,000

Schedule of Fair Value of Finan

Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 485,707	$ 1,473,905
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	363,414	855,795
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	67,202	282,840
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	40,271	133,186
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,004	10,726
Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	2,218	167,342
Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,055
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	543	586
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,324,411	1,903,748
Derivative assets	3	389
Total	1,324,414	1,904,137
Contingent consideration	60,942	45,102
Derivative liabilities	455	446
Total	61,397	45,548
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	275,614	197,955
Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	538,405	231,888
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	363,414
Available for sale securities		855,795
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	67,202
Available for sale securities		282,840
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	40,271
Available for sale securities		133,186
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	9,004
Available for sale securities		10,726
Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	2,218
Available for sale securities		167,342
Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	3,055
Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	543
Available for sale securities		586
Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	24,685
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	781,223	427,720
Total	781,223	427,720
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	275,614	197,955
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	477,869	206,335
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	3,055
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	24,685
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	543,188	1,476,028
Derivative assets	3	389
Total	543,191	1,476,417
Derivative liabilities	455	446
Total	455	446
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	60,536	25,553
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	363,414
Available for sale securities		855,795
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	67,202
Available for sale securities		282,840
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	40,271
Available for sale securities		133,186
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	9,004
Available for sale securities		10,726
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	2,218
Available for sale securities		167,342
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	543
Available for sale securities		586
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration	60,942	45,102
Total	$ 60,942	$ 45,102

Schedule of Reported Financial

Schedule of Reported Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	$ 1,324,414	$ 1,904,137
Liabilities	61,397	45,548
Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	455	446
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	814,019	429,843
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	418,410	1,347,979
Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	91,982	125,926
Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	3	389
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	35,532	24,497
Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	25,410	20,605
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	781,223	427,720
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	753,483	404,290
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	27,740	23,430
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	543,191	1,476,417
Liabilities	455	446
Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	455	446
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	60,536	25,553
Significant Other Observable Inputs (Level 2) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	418,410	1,347,979
Significant Other Observable Inputs (Level 2) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	64,242	102,496
Significant Other Observable Inputs (Level 2) | Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	3	389
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	60,942	45,102
Significant Unobservable Inputs (Level 3) | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	35,532	24,497
Significant Unobservable Inputs (Level 3) | Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	$ 25,410	$ 20,605

Schedule of Changes in Fair Val

Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 60,914	$ 39,415	$ 45,102	$ 38,332
Acquisition of MiR				51,399
Foreign currency impact		796		(1,770)
Payments	[1]			(24,553)	(1,050)
Fair value adjustment	[2]	(768)	(286)	(9,236)	1,847
Balance at end of period		$ 60,942	$ 39,129	$ 60,942	$ 39,129
[1]	In the nine months ended September 30, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out in connection with the acquisition of Universal Robots A/S ("Universal Robots"). In the nine months ended October 1, 2017, Teradyne paid $1.1 million of contingent consideration for the earn-out in connection with the acquisition of Avionics Interface Technology, LLC ("AIT").
[2]	In the three and nine months ended September 30, 2018, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was decreased by $0.8 million and $9.2 million, respectively, primarily due to a decrease in forecasted revenue. In the nine months ended October 1, 2017, the fair value of contingent consideration for the earn-out in connection with the acquisition of Universal Robots was increased by $1.8 million due to an increase in forecasted revenue.

Schedule of Changes in Fair V_2

Schedule of Changes in Fair Value of Level 3 Contingent Consideration (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			$ 13,571	$ 1,050
Increase (decrease) in contingent consideration			(9,236)	1,847
Universal Robots (UR)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			24,600
Increase (decrease) in contingent consideration	$ (800)	$ (300)	$ (9,200)	1,800
Avionics Interface Technologies, LLC
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration				$ 1,100

Quantitative Information Associ

Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Apr. 25, 2018
Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 51,400
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility	12.90%
Discount Rate	3.70%
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 11,314
Monte Carlo Simulation | Revenue for the period July 1, 2018-December 31, 2018 | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility	18.00%
Discount Rate	0.50%
Monte Carlo Simulation | Revenue for the period July 1, 2018-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 49,628

Schedule of Carrying Amounts an

Schedule of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Marketable securities		$ 485,707	$ 1,473,905
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		814,019	429,843
Marketable securities		510,392	1,473,905
Derivative assets		3	389
Contingent consideration		60,942	45,102
Derivative liabilities		455	446
Convertible debt	[1]	376,417	365,987
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		814,019	429,843
Marketable securities		510,392	1,473,905
Derivative assets		3	389
Contingent consideration		60,942	45,102
Derivative liabilities		455	446
Convertible debt	[1]	$ 599,438	$ 659,525
[1]	The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note, which includes the equity conversion features.

Schedule of Available for Sale

Schedule of Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 488,532	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	544	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(3,369)	(3,406)
Available-for-sale marketable securities, Fair Market Value	485,707	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	461,349	1,350,896
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	365,701	858,258
Available-for-sale marketable securities, Unrealized Gain		72
Available-for-sale marketable securities, Unrealized (Loss)	(2,287)	(2,535)
Available-for-sale marketable securities, Fair Market Value	363,414	855,795
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	362,167	850,163
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	67,208	283,009
Available-for-sale marketable securities, Unrealized Gain	7	18
Available-for-sale marketable securities, Unrealized (Loss)	(13)	(187)
Available-for-sale marketable securities, Fair Market Value	67,202	282,840
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	66,186	258,933
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	40,669	131,179
Available-for-sale marketable securities, Unrealized Gain	537	2,380
Available-for-sale marketable securities, Unrealized (Loss)	(935)	(373)
Available-for-sale marketable securities, Fair Market Value	40,271	133,186
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	22,030	91,010
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	9,065	10,775
Available-for-sale marketable securities, Unrealized (Loss)	(61)	(49)
Available-for-sale marketable securities, Fair Market Value	9,004	10,726
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	9,004	10,726
Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	3,128
Available-for-sale marketable securities, Unrealized (Loss)	(73)
Available-for-sale marketable securities, Fair Market Value	3,055
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	1,786
Equity and Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost		19,403
Available-for-sale marketable securities, Unrealized Gain		4,102
Available-for-sale marketable securities, Unrealized (Loss)		(75)
Available-for-sale marketable securities, Fair Market Value		23,430
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		1,723
Certificates of Deposit and Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	2,218	167,523
Available-for-sale marketable securities, Unrealized Gain		6
Available-for-sale marketable securities, Unrealized (Loss)		(187)
Available-for-sale marketable securities, Fair Market Value	2,218	167,342
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		138,340
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	543	582
Available-for-sale marketable securities, Unrealized Gain		4
Available-for-sale marketable securities, Fair Market Value	543	$ 586
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 176

Schedule of Reported Available

Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 488,532	$ 1,470,729
Available-for-sale marketable securities, Unrealized Gain	544	6,582
Available-for-sale marketable securities, Unrealized (Loss)	(3,369)	(3,406)
Available-for-sale marketable securities, Fair Market Value	485,707	1,473,905
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	461,349	1,350,896
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	418,554	1,349,970
Available-for-sale marketable securities, Unrealized Gain	52	38
Available-for-sale marketable securities, Unrealized (Loss)	(196)	(2,029)
Available-for-sale marketable securities, Fair Market Value	418,410	1,347,979
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	405,959	1,288,844
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	69,978	120,759
Available-for-sale marketable securities, Unrealized Gain	492	6,544
Available-for-sale marketable securities, Unrealized (Loss)	(3,173)	(1,377)
Available-for-sale marketable securities, Fair Market Value	67,297	125,926
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 55,390	$ 62,052

Contractual Maturities of Inves

Contractual Maturities of Investments in Debt Securities Held (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Schedule of Available-for-sale Securities
Due within one year, cost	$ 418,554
Due after 1 year through 5 years, cost	11,477
Due after 5 years through 10 years, cost	14,906
Due after 10 years, cost	40,467
Total, cost	485,404
Due within one year, fair market value	418,410
Due after 1 year through 5 years, fair market value	11,368
Due after 5 years through 10 years, fair market value	13,949
Due after 10 years, fair maket value	38,925
Total, fair market value	$ 482,652

Schedule of Derivative Instrume

Schedule of Derivative Instruments in Statement of Financial Position at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	$ (452)	$ (57)
Not Designated as Hedging Instrument | Foreign currency forward contracts | Prepayments
Derivatives, Fair Value [Line Items]
Derivative assets	3	389
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ (455)	$ (446)

Schedule of Effect of Derivativ

Schedule of Effect of Derivative Instruments in Statement of Operations Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses (Gains) on derivatives recognized in statements of operations	$ (899)	$ (939)	$ 2,502	$ (1,514)

Schedule of Effect of Derivat_2

Schedule of Effect of Derivative Instruments in Statement of Operations Recognized (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on foreign currency transactions	$ 3.7	$ 1.4	$ 1.2	$ 2.3

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, shares in Millions	Dec. 12, 2016USD ($)d$ / shares	Apr. 27, 2015USD ($)	Sep. 30, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)
Debt Instrument
Term of loan, years		5 years
Pledge percentage of capital stock		65.00%
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Aggregate principal amount	$ 460,000,000		$ 460,000,000	$ 460,000,000
Debt instrument, interest rate, stated percentage	1.25%
Senior notes maturity date	Dec. 15, 2023
Debt instrument, frequency of periodic payment	Payable semi-annually in arrears on June 15 and December 15 of each year
Debt instrument, date of first required payment	Jun. 15, 2017
Debt instrument, conversion option expiration date	Sep. 15, 2023
Debt instrument conversion rate, shares	0.314463
Debt instrument conversion price | $ / shares	$ 31.80		$ 31.80
Shares that would be issued upon conversion | shares			14.5
Strike price per share of warrant | $ / shares			$ 39.91
Payment for net cost of convertible note hedges net of warrant proceeds			$ 33,000,000
Debt instrument, effective annual interest rate			5.00%
Financing cost	$ 7,200,000		$ 5,600,000
Debt issuance costs, amortization period			7 years
Unamortized discount			$ 83,600,000
Debt Instrument, convertible, remaining discount amortization period			5 years 3 months 18 days
Debt instrument, convertible, carrying amount of equity component			$ 100,800,000
Value of notes converted			534,900,000
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option one
Debt Instrument
Trading days measurement period | d	20
Consecutive trading days measurement period | d	30
Percentage of conversion price	130.00%
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option two
Debt Instrument
Trading days measurement period | d	5
Consecutive trading days measurement period | d	5
Percentage of closing sale price of common stock and conversion rate product	98.00%
Maximum
Debt Instrument
Aggregate principal amount		$ 150,000,000
Commitment fee percentage of unused portion of credit facility		0.35%
Minimum
Debt Instrument
Commitment fee percentage of unused portion of credit facility		0.125%
Base Rate | Maximum
Debt Instrument
Debt instrument, basis spread on variable rate		1.00%
Base Rate | Minimum
Debt Instrument
Debt instrument, basis spread on variable rate		0.00%
London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument
Debt instrument, basis spread on variable rate		2.00%
London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument
Debt instrument, basis spread on variable rate		1.00%
Revolving Credit Facility
Debt Instrument
Financing cost			$ 2,300,000
Financing cost, amortization term			5 years
Revolving Credit Facility | Maximum
Debt Instrument
Credit facility, borrowing capacity		$ 350,000,000

Components of Convertible Senio

Components of Convertible Senior Notes (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 12, 2016
Debt Instrument
Net Carrying amount of convertible debt	$ 376,417	$ 365,987
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Debt Principal	460,000	460,000	$ 460,000
Unamortized discount	83,583	94,013
Net Carrying amount of convertible debt	$ 376,417	$ 365,987

Interest Expense on Convertible

Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Debt Instrument
Contractual interest expense on the coupon	$ 1,438	$ 1,422	$ 4,313	$ 4,297
Amortization of the discount component and debt issue fees recognized as interest expense	3,520	3,350	10,431	9,926
Total interest expense on the convertible debt	$ 4,958	$ 4,772	$ 14,744	$ 14,223

Schedule of Prepayments and Oth

Schedule of Prepayments and Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Prepaid And Other Current Assets [Line Items]
Contract manufacturer and supplier prepayments	$ 102,652	$ 82,503
Prepaid taxes	10,709	5,039
Prepaid maintenance and other services	7,802	8,189
Other prepayments	12,439	12,386
Total prepayments	$ 133,602	$ 108,117

Deferred Revenue and Customer_3

Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jul. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Dec. 31, 2016
Deferred Revenue Arrangement
Maintenance and training	$ 59,681		$ 57,256
Extended warranty	27,617	$ 25,971	24,438	$ 26,492	$ 29,377	$ 28,200
Customer advances, undelivered elements and other	20,042		32,047
Total deferred revenue and customer advances	$ 107,340		$ 113,741

Warranty Accrual Included in Ot

Warranty Accrual Included in Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 7,136	$ 9,093	$ 8,200	$ 7,203
Acquisition			41
Accruals for warranties issued during the period	2,760	2,734	9,171	11,049
Adjustments related to pre-existing warranties	282	(35)	109	(499)
Settlements made during the period	(2,675)	(3,055)	(10,018)	(9,016)
Balance at end of period	$ 7,503	$ 8,737	$ 7,503	$ 8,737

Extended Product Warranty of Sh

Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 25,971	$ 29,377	$ 24,438	$ 28,200
Deferral of new extended warranty revenue	7,232	2,636	19,072	17,126
Recognition of extended warranty deferred revenue	(5,586)	(5,521)	(15,893)	(18,834)
Balance at end of period	$ 27,617	$ 26,492	$ 27,617	$ 26,492

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - $ / shares shares in Millions	1 Months Ended			9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2014	Sep. 30, 2018	Oct. 01, 2017
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal annual installments				4 years
Percentage of common stock price paid				100.00%
Stock options term				7 years
Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal annual installments				4 years
Restricted Stock Units | Director
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal annual installments				1 year
Percentage of awards vesting on the first anniversary of grant date				100.00%
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period		3 years
Minimum age of retirement to be eligible for PRSUs			60 years
Minimum years of service for retirement to be eligible for PRSUs			10 years
Restricted stock unit awards granted				0.1	0.1
Weighted average grant date fair value of restricted stock units granted				$ 54.85	$ 35.66
Stock price				47.70	28.56
TSR Performance-Based Restricted Stock Units | Measurement Input, Expected Dividend Payment [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Estimated annual dividend amount per share				$ 0.36	$ 0.28
TSR Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved		200.00%
TSR Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved		0.00%
PBIT Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period	3 years
Restricted stock unit awards granted				0.1	0.1
Weighted average grant date fair value of restricted stock units granted				$ 46.62	$ 27.72
PBIT Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved	200.00%
PBIT Performance-Based Restricted Stock Units | Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved	0.00%
Service-Based Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted				0.6	0.8
Weighted average grant date fair value of restricted stock units granted				$ 46.25	$ 28.03
Service-Based Restricted Stock Units | Director
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted				0.1	0.1
Weighted average grant date fair value of restricted stock units granted				$ 35.81	$ 34.48
Service-Based Restricted Stock Units | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted				0.1	0.1
Weighted average grant date fair value of restricted stock units granted				$ 12.17	$ 7.13

Schedule of Estimated Fair Valu

Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions (Detail) - TSR Performance-Based Restricted Stock Units	9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Risk-free interest rate	2.20%	1.50%
Expected historical volatility	26.80%	26.60%
Dividend yield	0.80%	1.00%
New York Stock Exchange Composite Index
Share-based Compensation Arrangement by Share-based Payment Award
Expected historical volatility	12.40%	13.40%

Schedule of Estimated Fair Va_2

Schedule of Estimated Fair Value of Stock Options Grant Using Black Scholes Option Pricing Model (Detail) - Stock Options	9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	5 years	5 years
Risk-free interest rate	2.40%	2.00%
Volatility-historical	26.40%	27.80%
Dividend yield	0.80%	1.00%

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			$ 1,953,646
Other comprehensive income (loss) before reclassifications, net of tax			(14,123)	$ 36,683
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			1,227	(468)
Other comprehensive income (loss)	$ 7,029	$ 10,086	(12,896)	36,215
Reclassification of income tax effects from the Tax Reform Act, net of tax			769
Reclassification of unrealized gains on equity securities, net of tax	(57)	(87)	1,411	(264)
Balance	1,667,760		1,667,760
ASU 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax			(3,125)
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			15,919	(21,921)
Other comprehensive income (loss) before reclassifications, net of tax			(11,568)	34,235
Other comprehensive income (loss)			(11,568)	34,235
Balance	4,351	12,314	4,351	12,314
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			1,362	(60)
Other comprehensive income (loss) before reclassifications, net of tax			(2,555)	2,448
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			1,411	(264)
Other comprehensive income (loss)			(1,144)	2,184
Reclassification of income tax effects from the Tax Reform Act, net of tax			691
Balance	(2,216)	2,124	(2,216)	2,124
Unrealized Gains (Losses) on Marketable Securities | ASU 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax			(3,125)
Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			1,495	1,767
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(61)	(68)	(184)	(204)
Other comprehensive income (loss)			(184)	(204)
Reclassification of income tax effects from the Tax Reform Act, net of tax			78
Balance	1,389	1,563	1,389	1,563
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			18,776	(20,214)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(118)	(155)	1,227	(468)
Balance	$ 3,524	$ 16,001	$ 3,524	$ 16,001

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss), tax	$ (35)	$ (105)	$ (59)	$ (288)
Foreign currency translation adjustments, tax	0	0	0	0	$ 0	$ 0
Unrealized gains on marketable securities, tax	(902)	1,702	(902)	1,702	1,815	209
Retirement plans prior service benefit, tax	0	(893)	0	(893)	$ (932)	$ (778)
Reclassification of unrealized gains on equity securities, net of tax	17	67	6	173
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax			0	0
Amounts reclassified from accumulated other comprehensive income (loss), tax			0	0
Other comprehensive income (loss), tax			0	0
Reclassification of income tax effects from the Tax Reform Act, net of tax			0
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax			(806)	1,666
Amounts reclassified from accumulated other comprehensive income (loss), tax	(17)	(67)	(6)	(173)
Other comprehensive income (loss), tax			(812)	1,493
Reclassification of income tax effects from the Tax Reform Act, net of tax			(691)
Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax			0	0
Amounts reclassified from accumulated other comprehensive income (loss), tax	$ (18)	$ (38)	(53)	(115)
Other comprehensive income (loss), tax			(53)	$ (115)
Reclassification of income tax effects from the Tax Reform Act, net of tax			(78)
ASU 2016-01 | Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax			0
ASU 2016-01 | Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax			(902)
ASU 2016-01 | Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized gains on equity securities, net of tax			$ 0

Reclassifications Out of Accumu

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and interest expense	$ (6,213)	$ (4,517)	$ (17,620)	$ (11,329)
Reclassifications, net of tax			(1,227)	468
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			(1,411)	264
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	61	68	184	204
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	118	155	(1,227)	468
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and interest expense	$ 57	$ 87	$ (1,411)	$ 264

Reclassifications Out of Accu_2

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 35	$ 105	$ 59	$ 288
Unrealized Gains (Losses) on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	17	67	6	173
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 18	$ 38	$ 53	$ 115

Changes in Carrying Amount of G

Changes in Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Apr. 25, 2018	Feb. 26, 2018	Dec. 31, 2017
Goodwill [Line Items]
Foreign currency translation adjustment	$ (8,144)
Goodwill	1,155,564			$ 1,014,577
Accumulated impairment losses	(762,566)			(762,566)
Goodwill	392,998			252,011
Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition	134,737
Goodwill		$ 134,737
Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition	14,394
Goodwill			$ 14,400
Wireless Test
Goodwill [Line Items]
Goodwill	361,819			361,819
Accumulated impairment losses	(353,843)			(353,843)
Goodwill	7,976			7,976
Industrial Automation
Goodwill [Line Items]
Foreign currency translation adjustment	(8,144)
Goodwill	374,506			233,519
Goodwill	374,506			233,519
Industrial Automation | Mobile Industrial Robots (MiR)
Goodwill [Line Items]
Goodwill acquisition	134,737
Industrial Automation | Energid Technologies Corporation
Goodwill [Line Items]
Goodwill acquisition	14,394
System Test
Goodwill [Line Items]
Goodwill	158,699			158,699
Accumulated impairment losses	(148,183)			(148,183)
Goodwill	10,516			10,516
Semiconductor Test
Goodwill [Line Items]
Goodwill	260,540			260,540
Accumulated impairment losses	$ (260,540)			$ (260,540)

Schedule of Amortizable Intangi

Schedule of Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 506,698	$ 414,038
Accumulated Amortization	(365,439)	(337,155)
Foreign Currency Translation Adjustment	(1,296)	2,205
Net Carrying Amount	139,963	79,088
Developed technology
Finite-Lived Intangible Assets
Gross Carrying Amount	336,306	270,877
Accumulated Amortization	(244,833)	(226,190)
Foreign Currency Translation Adjustment	(1,117)	1,618
Net Carrying Amount	90,356	46,305
Customer Relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	105,622	92,741
Accumulated Amortization	(89,848)	(83,585)
Foreign Currency Translation Adjustment	(83)	171
Net Carrying Amount	15,691	9,327
Trademarks and tradenames
Finite-Lived Intangible Assets
Gross Carrying Amount	64,420	50,100
Accumulated Amortization	(30,408)	(27,120)
Foreign Currency Translation Adjustment	(96)	416
Net Carrying Amount	33,916	23,396
Non-compete Agreements
Finite-Lived Intangible Assets
Gross Carrying Amount	320	320
Accumulated Amortization	(320)	(260)
Net Carrying Amount		$ 60
Customer backlog
Finite-Lived Intangible Assets
Gross Carrying Amount	30
Accumulated Amortization	$ (30)

Schedule of Amortizable Intan_2

Schedule of Amortizable Intangible Assets (Parenthetical) (Detail) - USD ($) $ in Thousands	Apr. 25, 2018	Sep. 30, 2018
Finite-Lived Intangible Assets
Impairment of intangible assets		$ 300
Mobile Industrial Robots (MiR)
Finite-Lived Intangible Assets
Intangible assets acquired	$ 80,670	80,700
Energid Technologies Corporation
Finite-Lived Intangible Assets
Intangible assets acquired		$ 12,300

Goodwill and Acquired Intangi_3

Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Goodwill and Intangible Assets Disclosure [Line Items]
Acquired intangible assets amortization	$ 11,142	$ 7,028	$ 28,633	$ 23,145

Schedule of Estimated Intangibl

Schedule of Estimated Intangible Asset Amortization Expense (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Finite-Lived Intangible Assets
2018 (remainder)	$ 10,731
2,019	39,610
2,020	24,928
2,021	14,343
2,022	13,450
Thereafter	$ 36,901

Computation of Basic and Dilute

Computation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 119,981	$ 103,420	$ 307,991	$ 363,616
Weighted average common shares-basic		185,744	197,485	190,576	198,755
Incremental shares from assumed conversion of convertible notes	[1]	3,025	1,144	3,356	632
Convertible note hedge warrant shares	[2]	108		646
Employee stock purchase plan		22	8	26	26
Dilutive potential common shares		4,761	3,290	5,724	2,658
Weighted average common shares-diluted		190,505	200,775	196,300	201,413
Net income per common share-basic		$ 0.65	$ 0.52	$ 1.62	$ 1.83
Net income per common share-diluted		$ 0.63	$ 0.52	$ 1.57	$ 1.81
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,331	1,832	1,406	1,663
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		275	306	290	337
[1]	Incremental shares from assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.80, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period.
[2]	Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.91, multiplied by 14.5 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.

Computation of Basic and Dilu_2

Computation of Basic and Diluted Net Income Per Common Share (Parenthetical) (Detail) shares in Millions	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Convertible Notes
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 31.80
Shares that would be issued upon conversion | shares	14.5
Convertible Notes Hedge Warrant
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 39.91
Shares that would be issued upon conversion | shares	14.5

Net Income Per Common Share - A

Net Income Per Common Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Net Income Loss Per Common Share
Exercise of stock options		0.1		0.1
Restricted Stock Units
Net Income Loss Per Common Share
Dilutive securities excluded from earning per share	0.5		0.5

Restructuring and Other - Addit

Restructuring and Other - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Restructuring Cost and Reserve
Contingent consideration adjustment			$ (9,236)	$ 1,847
Acquisition related expenses	$ 800		4,100
Lease termination year		2017-09
Lease termination period				2017-09
Semiconductor Test and Wireless Test
Restructuring Cost and Reserve
Severance benefit and charges		$ 600
Industrial Automation
Restructuring Cost and Reserve
Severance benefit and charges				$ 2,000
Earthquake Related Expenses
Restructuring Cost and Reserve
Impairment of fixed assets and other expenses		800		800
Wireless Test
Restructuring Cost and Reserve
Lease termination		400
Lease impairment				900
Semiconductor Test
Restructuring Cost and Reserve
Severance benefit and charges	1,700
Semiconductor Test and Industrial Automation [Member]
Restructuring Cost and Reserve
Severance benefit and charges			7,900
Impairment of Fixed Assets and Expenses Related to the Japan Earthquake
Restructuring Cost and Reserve
Property insurance, recovery		5,100		5,100
Universal Robots (UR)
Restructuring Cost and Reserve
Contingent consideration adjustment	$ (800)	$ (300)	$ (9,200)	$ 1,800

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)Participant
Defined Benefit Plan Disclosure
Number of retiree participants | Participant		1,700
Defined Benefit Plan, decrease in benefit obligation		$ (151.3)
Defined Benefit Plan, decrease in plan assets		(151.3)
Gain (Loss) Due to Settlement	$ (0.3)	(0.3)
U.S. Supplemental Executive Defined Benefit Pension Plan
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans		1.9
Non-United States Subsidiaries
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans		$ 0.6

Schedule of Net Periodic Pensio

Schedule of Net Periodic Pension and Postretirement benefit Cost (Income) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Defined Benefit Plan Disclosure
Net actuarial loss (gain)			$ 196	$ (2,504)
Settlement loss	$ 300		300
UNITED STATES
Defined Benefit Plan Disclosure
Service cost	538	$ 560	1,657	1,679
Interest cost	1,750	3,288	7,188	9,863
Expected return on plan assets	(1,551)	(3,002)	(7,484)	(9,006)
Amortization of prior service cost	14	18	43	53
Net actuarial loss (gain)			(189)	(2,732)
Settlement loss	267		345
Total	1,018	864	1,560	(143)
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Service cost	203	215	609	606
Interest cost	177	186	532	527
Expected return on plan assets	(5)	(6)	(15)	(19)
Net actuarial loss (gain)				243
Total	375	395	1,126	1,357
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Service cost	10	8	29	25
Interest cost	49	50	147	151
Amortization of prior service credit	(93)	(124)	(280)	(372)
Net actuarial loss (gain)			40	(15)
Special termination benefits	601		3,419
Total	$ 567	$ (66)	$ 3,355	$ (211)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Sep. 30, 2018USD ($)
Purchase Commitment, Excluding Long-term Commitment
Aggregate purchase commitments	$ 275.6
Purchase commitments less than one year	$ 263.3

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Income Taxes [Line Items]
Effective tax rate	14.80%		18.80%	13.60%	14.70%
U.S. statutory federal tax rate				21.00%		35.00%
Discrete tax expense	$ 0.2		$ 0.3	$ 2.4
Discrete tax benefits				6.5	$ 6.1
Discrete tax benefits, non-taxable foregn exchange gain (loss)	(1.1)		(0.8)		1.1
Discrete tax benefit, Other	0.4			0.6
Discrete tax benefits, net				8.9
Discrete tax benefits, stock based compensation			0.2	7.8	6.7
Discrete tax expense, remeasurement of deferred tax assets				1.7
Discrete tax expenses, Other				0.7
Discrete tax benefits, U.S research and development tax credits					0.7
Discrete tax expense, actuarial gains					1
Uncertain tax positions	38.6	$ 36.3		38.6		$ 36.3
Net Increase in uncertain tax positions				2.3
Accrued interest and penalties	0.3	0.3		0.3		$ 0.3
Interest and penalties related to income tax, expense (benefit)				0.1	0.1
Tax savings due to the tax holiday				$ 8.9	$ 20.5
Tax savings due to the tax holiday, per share				$ 0.05	$ 0.10
Tax holiday expiration date				December 31, 2020
Provisional amount of additional income tax expense		186
Transition tax on mandatory deemed repatriation of foreign earnings		161
Expense related to remeasurement of deferred tax assets and liabilities		33.6
Benefit associated with impact of correlative adjustments on tax positions		10.3
Expense related to remeasurement of certain deferred		$ 1.7
Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Discrete tax offset amount	$ 0.5		$ 0.2	$ 0.5	$ 0.5

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018Segment
Segment Reporting Information [Line Items]
Reportable segments	4

Schedule of Segment Information

Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2018		Oct. 01, 2017		Sep. 30, 2018		Oct. 01, 2017		Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues		$ 566,848		$ 503,378		$ 1,581,244		$ 1,657,191
Income (loss) before income taxes	[1],[2]	140,844		127,437		356,675		426,329
Total assets		2,882,487	[3]	3,089,327	[3]	2,882,487	[3]	3,089,327	[3]	$ 3,109,545
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		417,297		396,881		1,150,712		1,345,560
Income (loss) before income taxes	[1],[2]	126,638		116,836		305,876		426,081
Total assets	[3]	709,616		598,925		709,616		598,925
System Test
Segment Reporting Information [Line Items]
Revenues		65,913		40,063		176,803		115,672
Income (loss) before income taxes	[1],[2]	940		3,373		(1,198)		(279)
Total assets	[3]	617,741		508,943		617,741		508,943
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		49,606		35,569		162,308		112,147
Income (loss) before income taxes	[1],[2]	9,056		(3,344)		35,296		(11,795)
Total assets	[3]	83,160		100,083		83,160		100,083
Wireless Test
Segment Reporting Information [Line Items]
Revenues		34,304		30,865		92,023		83,812
Income (loss) before income taxes	[1],[2]	7,843		7,461		18,615		13,508
Total assets	[3]	79,986		61,206		79,986		61,206
Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenues		(272)				(602)
Income (loss) before income taxes	[1],[2]	(3,633)		3,111		(1,914)		(1,186)
Total assets	[3]	$ 1,391,984		$ 1,820,170		$ 1,391,984		$ 1,820,170
[1]	Included in Corporate and Other are: contingent consideration adjustments, severance charges, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations and acquisition related charges.
[2]	Included in the income (loss) before income taxes for each of the segments are charges and credits related to restructuring and other and inventory charges.
[3]	Total business assets are directly attributable to each business. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

Schedule of Segment Reporting I

Schedule of Segment Reporting Information by Segment Charges (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Segment Reporting Information [Line Items]
Contingent consideration adjustment			$ (9,236)	$ 1,847
Acquisition related expenses	$ 800		4,100
Property insurance recovery				4,309
Restructuring and other - employee severance	1,710	$ (4,407)	3,785	392
Universal Robots (UR)
Segment Reporting Information [Line Items]
Contingent consideration adjustment	(800)	(300)	(9,200)	1,800
Semiconductor Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge	2,071	743	5,851	3,686
Semiconductor Test | Severance And Benefits
Segment Reporting Information [Line Items]
Restructuring and other - employee severance	1,716	375	7,657	242
System Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge	237	251	812	1,609
Industrial Automation
Segment Reporting Information [Line Items]
Acquisition related expenses	811		811
Cost of revenues-inventory charge	323	130	680	130
Restructuring and other - employee severance		206	288	1,150
Wireless Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge	716	735	2,179	1,729
Restructuring and other-lease impairment		(393)		900
Corporate and Eliminations
Segment Reporting Information [Line Items]
Acquisition related expenses			3,318
Restructuring and other			872
Property insurance recovery		(5,064)		(5,064)
Restructuring and other - employee severance				530
Corporate and Eliminations | Universal Robots (UR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment	$ (768)	(286)	$ (9,236)	1,847
Corporate and Eliminations | Impairment of Fixed Assets and Expenses Related to the Japan Earthquake
Segment Reporting Information [Line Items]
Building impairment and other expenses		$ 755		$ 755

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2018

Oct. 01, 2017

Sep. 30, 2018

Oct. 01, 2017

Dec. 31, 2018

Aug. 31, 2018

May 31, 2018

Jan. 31, 2018

Aug. 31, 2017

May 31, 2017

Jan. 31, 2017

Dec. 31, 2016

Stockholders Equity Note Disclosure [Line Items]

Stock repurchase program, authorized amount

$ 500,000,000

Cumulative repurchases, value

$ 562,300

$ 151,800,000

Cumulative repurchases, shares

13.8

4.6

Common stock average price

$ 40.62

$ 32.66

Dividends payable, amount per share

$ 0.09

$ 0.09

$ 0.09

$ 0.07

$ 0.07

$ 0.07

Dividend payment

$ 16,600,000

$ 13,800,000

$ 51,320,000

$ 41,730,000

Scenario, Forecast

Stockholders Equity Note Disclosure [Line Items]

Cumulative repurchases, value

$ 750,000,000

Maximum

Stockholders Equity Note Disclosure [Line Items]

Stock repurchase program, authorized amount

$ 1,500,000,000