Teradyne (TER) 10-Q 8 Nov 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 29, 2019	Nov. 04, 2019
Cover [Abstract]
Amendment Flag	false
Document Type	10-Q
Document Fiscal Year Focus	2019
Entity Central Index Key	0000097210
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Document Period End Date	Sep. 29, 2019
Entity Registrant Name	TERADYNE, INC
Entity Filer Category	Large Accelerated Filer
Trading Symbol	TER
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity File Number	001-06462
Entity Incorporation, State or Country Code	MA
Entity Tax Identification Number	04-2272148
Entity Address, Address Line One	600 Riverpark Drive
Entity Address, City or Town	North Reading
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01864
City Area Code	978
Local Phone Number	370-2700
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		167,577,669

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 29, 2019		Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 593,939		$ 926,752
Marketable securities	342,538		190,096
Accounts receivable, less allowance for doubtful accounts of $1,770 and $1,673 at September 29, 2019 and December 31, 2018, respectively	357,886		291,267
Inventories, net	178,203		153,541
Prepayments and other current assets	182,013		170,826
Total current assets	1,654,579		1,732,482
Property, plant and equipment, net	307,567		279,821
Operating lease right-of-use assets, net	57,595
Marketable securities	103,558		87,731
Deferred tax assets	69,120		70,848
Other assets	22,724		11,509
Retirement plans assets	16,358		16,883
Acquired intangible assets, net	96,573		125,482
Goodwill	370,717		381,850
Total assets	2,698,791	[1]	2,706,606
Current liabilities:
Accounts payable	117,936		100,688
Accrued employees' compensation and withholdings	127,912		148,566
Deferred revenue and customer advances	95,936		77,711
Other accrued liabilities	93,736		78,272
Operating lease liabilities	18,386
Contingent consideration	6,297		34,865
Income taxes payable	33,508		36,185
Total current liabilities	493,711		476,287
Retirement plans liabilities	121,340		117,456
Long-term deferred revenue and customer advances	42,592		32,750
Deferred tax liabilities	15,390		20,662
Long-term other accrued liabilities	9,803		37,547
Long-term contingent consideration	11,783		35,678
Long-term operating lease liabilities	46,813
Long-term income taxes payable	83,782		83,891
Debt	390,942		379,981
Total liabilities	1,216,156		1,184,252
Commitments and contingencies (See Note S)
SHAREHOLDERS' EQUITY
Common stock, $0.125 par value, 1,000,000 shares authorized; 168,490 and 175,522 shares issued and outstanding at September 29, 2019 and December 31, 2018, respectively	21,061		21,940
Additional paid-in capital	1,712,185		1,671,645
Accumulated other comprehensive loss	(24,221)		(13,040)
Accumulated deficit	(226,390)		(158,191)
Total shareholders' equity	1,482,635		1,522,354
Total liabilities and shareholders' equity	$ 2,698,791		$ 2,706,606
[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. 29, 2019	Dec. 31, 2018
Accounts receivable, less allowance for doubtful accounts	$ 1,770	$ 1,673
Common stock, par value	$ 0.125	$ 0.125
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	168,490,000	175,522,000
Common stock, shares outstanding	168,490,000	175,522,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 582,038	$ 566,848	$ 1,640,315	$ 1,581,244
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	237,000	233,155	683,724	670,385
Gross profit	345,038	333,693	956,591	910,859
Operating expenses:
Selling and administrative	109,166	100,199	319,990	290,115
Engineering and development	77,804	77,049	236,030	226,799
Acquired intangible assets amortization	9,647	11,142	30,363	28,633
Restructuring and other	(6,500)	1,710	(11,792)	3,785
Total operating expenses	190,117	190,100	574,591	549,332
Income from operations	154,921	143,593	382,000	361,527
Non-operating (income) expense:
Interest income	(5,159)	(6,213)	(18,641)	(17,620)
Interest expense	5,682	5,557	17,195	18,087
Other (income) expense, net	2,665	3,405	6,557	4,385
Income before income taxes	151,733	140,844	376,889	356,675
Income tax provision	15,873	20,863	34,494	48,684
Net income	$ 135,860	$ 119,981	$ 342,395	$ 307,991
Net income per common share:
Basic	$ 0.80	$ 0.65	$ 2	$ 1.62
Diluted	$ 0.75	$ 0.63	$ 1.92	$ 1.57
Weighted average common shares-basic	169,641	185,744	171,471	190,576
Weighted average common shares-diluted	180,494	190,505	178,685	196,300
Product [Member]
Revenues:
Total revenues	$ 488,170	$ 470,994	$ 1,339,123	$ 1,308,969
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	197,196	195,339	555,863	557,074
Service [Member]
Revenues:
Total revenues	93,868	95,854	301,192	272,275
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 39,804	$ 37,816	$ 127,861	$ 113,311

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Net income	$ 135,860	$ 119,981	$ 342,395	$ 307,991
Other comprehensive income, net of tax:
Foreign currency translation adjustment, net of tax of $0	(18,002)	7,213	(17,019)	(11,568)
Available-for-sale marketable securities:
Unrealized gains (losses) on marketable securities arising during period, net of tax of $507, $(62), $1,762, $(806), respectively	1,754	(66)	6,391	(2,555)
Less: Reclassification adjustment for (gains) losses included in net income, net of tax of $(99), $(17), $(125), $(6), respectively	(345)	(57)	(442)	1,411
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	1,409	(123)	5,949	(1,144)
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 $(11), $(18), $(32), $(53), respectively	(37)	(61)	(111)	(184)
Other comprehensive (loss) income	(16,630)	7,029	(11,181)	(12,896)
Comprehensive income	$ 119,230	$ 127,010	$ 331,214	$ 295,095

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Foreign currency translation adjustments, tax	$ 0
Unrealized gains (losses) on marketable securities arising during period, net of tax	507	$ (62)	$ 1,762	$ (806)
Reclassification adjustment for (gains) losses included in net income, net of tax	(99)	(17)	(125)	(6)
Amortization of prior service benefit included in net periodic pension and post-retirement benefit, net of tax	$ (11)	$ (18)	$ (32)	$ (53)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Balance at Dec. 31, 2017	$ 1,953,646	$ 24,444	$ 1,638,413	$ 18,776	$ 272,013
Balance, Shares at Dec. 31, 2017		195,548
Net issuance of common stock under stock-based plans	2,010	$ 197	1,813
Net issuance of common stock under stock-based plans (in shares)		1,584
Stock-based compensation expense	24,342		24,342
Repurchase of common stock	(568,660)	$ (1,730)			(566,930)
Repurchase of common stock (in shares)		(13,843)
Cash dividends	(51,352)				(51,352)
Net income	307,991				307,991
Other comprehensive loss	(12,896)			(12,896)
Reclassification of unrealized gains on equity securities				(3,125)	3,125
Reclassification of tax effects resulting from the Tax Reform Act				769	(769)
Balance at Sep. 30, 2018	1,667,760	$ 22,911	1,664,568	3,524	(23,243)
Balance, Shares at Sep. 30, 2018		183,289
Balance at Jul. 01, 2018	1,739,940	$ 23,495	1,645,679	(3,504)	74,270
Balance, Shares at Jul. 01, 2018		187,962
Net issuance of common stock under stock-based plans	10,098	$ 42	10,056
Net issuance of common stock under stock-based plans (in shares)		332
Stock-based compensation expense	8,833		8,833
Repurchase of common stock	(201,472)	$ (626)			(200,846)
Repurchase of common stock (in shares)		(5,005)
Cash dividends	(16,648)				(16,648)
Net income	119,981				119,981
Other comprehensive loss	7,029			7,028
Reclassification of tax effects resulting from the Tax Reform Act				118
Balance at Sep. 30, 2018	1,667,760	$ 22,911	1,664,568	3,524	(23,243)
Balance, Shares at Sep. 30, 2018		183,289
Cumulative effect of changes in accounting principle related to revenue recognition	12,679				12,679
Balance at Dec. 31, 2018	1,522,354	$ 21,940	1,671,645	(13,040)	(158,191)
Balance, Shares at Dec. 31, 2018		175,522
Net issuance of common stock under stock-based plans	14,731	$ 220	14,511
Net issuance of common stock under stock-based plans (in shares)		1,762
Stock-based compensation expense	26,029		26,029
Repurchase of common stock	(365,386)	$ (1,099)			(364,287)
Repurchase of common stock (in shares)		(8,794)
Cash dividends	(46,307)				(46,307)
Net income	342,395				342,395
Other comprehensive loss	(11,181)			(11,181)
Reclassification of tax effects resulting from the Tax Reform Act				553
Balance at Sep. 29, 2019	1,482,635	$ 21,061	1,712,185	(24,221)	(226,390)
Balance, Shares at Sep. 29, 2019		168,490
Balance at Jun. 30, 2019	1,479,412	$ 21,305	1,688,211	(7,591)	(222,513)
Balance, Shares at Jun. 30, 2019		170,436
Net issuance of common stock under stock-based plans	14,087	$ 46	14,041
Net issuance of common stock under stock-based plans (in shares)		377
Stock-based compensation expense	9,933		9,933
Repurchase of common stock	(124,763)	$ (290)			(124,473)
Repurchase of common stock (in shares)		(2,323)
Cash dividends	(15,264)				(15,264)
Net income	135,860				135,860
Other comprehensive loss	(16,630)			(16,630)
Reclassification of tax effects resulting from the Tax Reform Act				382
Balance at Sep. 29, 2019	$ 1,482,635	$ 21,061	$ 1,712,185	$ (24,221)	$ (226,390)
Balance, Shares at Sep. 29, 2019		168,490

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Common Stock, Dividends, Per Share, Cash Paid	$ 0.09	$ 0.09	$ 0.09	$ 0.09

CONDENSED CONSOLIDATED STATEM_6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 342,395	$ 307,991
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	51,508	49,930
Amortization	36,849	32,909
Stock-based compensation	28,822	25,327
Deferred taxes	(2,977)	24,442
Provision for excess and obsolete inventory	8,848	9,522
Contingent consideration fair value adjustment	(16,460)	(9,236)
Gains on marketable securities	(4,158)	(420)
Retirement plans actuarial losses	448	196
Other	610	936
Changes in operating assets and liabilities, net of businesses acquired:
Accounts receivable	(66,789)	(77,807)
Inventories	(14,143)	(34,117)
Prepayments and other assets	(16,118)	(28,719)
Accounts payable and other liabilities	20,807	16,124
Deferred revenue and customer advances	27,779	9,823
Retirement plans contributions	(3,775)	(3,244)
Income taxes	(31,224)	(33,152)
Net cash provided by operating activities	362,422	290,505
Cash flows from investing activities:
Purchases of property, plant and equipment	(96,048)	(88,269)
Proceeds from government subsidy for property, plant and equipment		7,920
Purchases of marketable securities	(605,539)	(809,521)
Proceeds from sales of marketable securities	60,274	843,164
Proceeds from maturities of marketable securities	393,472	934,100
Proceeds from life insurance	2,912	1,126
Purchase of investment and acquisition of businesses, net of cash acquired	(21,970)	(169,474)
Net cash (used for) provided by investing activities	(266,899)	719,046
Cash flows from financing activities:
Issuance of common stock under stock purchase and stock option plans	29,280	20,959
Repurchase of common stock	(368,782)	(562,263)
Dividend payments	(46,269)	(51,320)
Payments related to net settlement of employee stock compensation awards	(14,550)	(19,841)
Payments of contingent consideration	(27,615)	(13,571)
Net cash used for financing activities	(427,936)	(626,036)
Effects of exchange rate changes on cash and cash equivalents	(400)	661
(Decrease) increase in cash and cash equivalents	(332,813)	384,176
Cash and cash equivalents at beginning of period	926,752	429,843
Cash and cash equivalents at end of period	$ 593,939	$ 814,019

The Company

The Company	9 Months Ended
	Sep. 29, 2019
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; • industrial automation (“Industrial Automation”) products; • 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”); and • wireless test (“Wireless Test”) systems.

Accounting Policies

Accounting Policies	9 Months Ended
	Sep. 29, 2019
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, 2018 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. Investment in Other Company Teradyne holds an investment in a private company that develops and sells advanced wearable technology. Teradyne does not have the ability to exert significant influence over the company. The investment was recorded at cost and is evaluated for impairment or an indication of changes in fair value resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer on a quarterly basis. See Note D: “Acquisitions and Investment in Other Company.” Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” right-of-use 2018-11, “Leases (Topic 842): Targeted Improvements,” Under ASC 842, a contract is or contains a lease when Teradyne has the right to control the use of an identified asset. Teradyne determines if an arrangement is a lease at inception of the contract, which is the date on which the terms of the contract are agreed to and the agreement creates enforceable rights and obligations. The commencement date of the lease is the date that the lessor makes an underlying asset available for use by Teradyne. As of September 29, 2019, Teradyne does not have material leases that have not yet commenced. Teradyne determines if the lease is operating or finance at the lease commencement date based upon the terms of the lease and the nature of the asset. The lease term used to calculate the lease liability includes options to extend or terminate the lease when it is reasonably certain that the option will be exercised. For leases commencing after January 1, 2019, the lease liability is measured at the present value of future lease payments, discounted using the discount rate for the lease at the commencement date. As Teradyne is typically unable to determine the implicit rate, Teradyne uses an incremental borrowing rate based on the lease term and economic environment at commencement date. Teradyne initially measures payments based on an index by using the applicable rate at lease commencement. Variable payments that do not depend on an index are not included in the lease liability and are recognized as they are incurred. The ROU asset is initially measured as the amount of lease liability, adjusted for any initial lease costs, prepaid lease payments, and reduced by any lease incentives. Teradyne’s contracts often include non-lease non-lease

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	9 Months Ended
	Sep. 29, 2019
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

Acquisitions and Investment In

Acquisitions and Investment In Other Company	9 Months Ended
	Sep. 29, 2019
Acquisitions and Investment In Other Company	D. ACQUISITIONS AND INVESTMENT IN OTHER COMPANY Acquisitions Lemsys SA On January 30, 2019, Teradyne acquired all of the issued and outstanding shares of Lemsys SA (“Lemsys”) for a total purchase price of approximately $9.1 million. Lemsys strengthens Teradyne’s position in the electrification trends of vehicles, solar, wind, and industrial applications. The Lemsys acquisition was accounted for as a business combination and, accordingly, the results have been included in Teradyne’s Semiconductor Test segment from the date of acquisition. Teradyne’s final allocation of the purchase price was goodwill of $1.4 million, which is not deductible for tax purposes, acquired intangible assets of $4.6 million with an average estimated useful life of 5.2 years, and $3.1 million of net tangible assets. The acquisition was not material to Teradyne’s condensed consolidated financial statements. Mobile Industrial Robots On April 25, 2018, Teradyne acquired all of 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 purchase price of $197.8 million included $145.2 million of cash paid and $52.6 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. The contingent consideration related to revenue for the period from January 1, 2018 to December 31, 2018 in the amount of $30.8 million was paid in March 2019. The remaining maximum contingent consideration that could be paid is $81.0 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. MiR’s products will help expand the Industrial Automation segment, which is a key component of Teradyne’s growth strategy. The allocation of the 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 $136.0 million was allocated to goodwill, which is not deductible for tax purposes. MiR’s results have been included in Teradyne’s Industrial Automation segment from the date of acquisition. The following table represents the final allocation of the purchase price: Purchase Price Allocation (in thousands) Goodwill $ 135,976 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current 1,336 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (18,007 ) Other long-term liabilities (900 ) Total purchase price $ 197,778 Teradyne estimated the fair value of intangible assets using the income and cost approaches. 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 The following unaudited pro forma information gives effect to the acquisition of MiR as if the acquisition occurred on January 1, 2018. 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 Nine Months September 30, 2018 (in thousands) Revenue $ 1,588,042 Net income 306,768 Net income per common share: Basic $ 1.61 Diluted $ 1.56 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 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 which is deductible for tax purposes, 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. Investment in Other Company On June 3, 2019, Teradyne invested $15.0 million in RealWear, Inc. (“RealWear”). RealWear, a private company, develops and sells advanced wearable technology including industrial, hands-free, head-mounted augmented reality devices that make the workplace safer and more productive. Teradyne’s investment in RealWear aligns with its strategy of bringing the power of advanced automation to companies of all sizes to improve the productivity of their employees and the quality of their products and services. The investment was recorded at cost and is evaluated for impairment or an indication of changes in fair value resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer on a quarterly basis. At September 29, 2019 , , which was unchanged in the three months ended September 30, 2019 .

Revenue

Revenue	9 Months Ended
	Sep. 29, 2019
Revenue from Contract with Customer [Abstract]
Revenue	E. REVENUE For the three and nine months ended September 29, 2019, revenues recognized in accordance with ASC 606: “ Revenue from Contracts with Customers” For the three and nine months ended September 30, 2018, revenues recognized in accordance with ASC 606: “ Revenue from Contracts with Customers” 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 29, 2019 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated System chip (“SOC”) Memory Defense/ Aerospace Storage Production Universal M iR Energid (in thousands) Americas Point in time $ 6,307 $ 3,464 $ 22,861 $ 2,232 $ 2,165 $ 16,294 $ 2,820 $ — $ 5,621 $ (160 ) $ 61,604 Over time 8,497 621 5,814 — 796 293 — 188 723 — 16,932 Europe, Middle East Point in time 6,894 274 742 — 4,354 25,557 5,011 — 1,220 — 44,052 Over time 5,189 255 469 — 1,613 459 — 615 48 — 8,648 Asia Pacific Point in time 259,909 63,483 99 22,696 6,751 15,575 1,800 — 33,032 — 403,345 Over time 37,680 3,874 299 1,496 830 280 — — 1,545 — 46,004 Lease Revenue 1,290 — — — 88 — — — 75 — 1,453 Total $ 325,766 $ 71,971 $ 30,284 $ 26,424 $ 16,597 $ 58,458 $ 9,631 $ 803 $ 42,264 $ (160 ) $ 582,038 For the Three Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR 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 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 29, 2019 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR Energid (in thousands) Americas Point in time $ 21,830 $ 19,574 $ 54,870 $ 7,528 $ 6,760 $ 48,529 $ 9,152 $ — $ 12,961 $ (402 ) $ 180,802 Over time 24,862 2,056 19,116 — 2,317 793 — 1,235 1,550 — 51,929 Europe, Middle East Point in time 27,934 2,443 992 — 12,391 78,007 13,883 — 2,575 — 138,225 Over time 15,681 819 1,442 — 4,782 1,274 — 1,381 140 — 25,519 Asia Pacific Point in time 727,035 143,163 525 66,974 17,235 48,284 6,208 — 91,029 — 1,100,453 Over time 113,158 10,447 1,391 5,860 2,526 786 — 221 4,146 — 138,535 Lease Revenue 4,487 — — — 225 — — — 140 — 4,852 Total $ 934,987 $ 178,502 $ 78,336 $ 80,362 $ 46,236 $ 177,673 $ 29,243 $ 2,837 $ 112,541 $ (402 ) $ 1,640,315 For the Nine Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR 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 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 Contract Balances During the three and nine months ended September 29, 2019, Teradyne recognized $14.2 million and $47.6 million, respectively, that was previously included within the deferred revenue and customer advances balances. During the three and nine months ended September 30, 2018, Teradyne recognized $24.5 million and $70.9 million, respectively, that was previously included within the deferred revenue and customer advances balances. This revenue primarily relates to undelivered hardware , 1-3 Accounts Receivable Teradyne sells certain trade accounts receivables on a non-recourse in are a

Inventories

Inventories	9 Months Ended
	Sep. 29, 2019
Inventories	F. INVENTORIES Inventories, net consisted of the following at September 29, 2019 and December 31, 2018: September 29, December 31, (in thousands) Raw material $ 114,162 $ 89,365 Work-in-process 28,460 31,014 Finished goods 35,581 33,162 $ 178,203 $ 153,541 Inventory reserves at September 29, 2019 and December 31, 2018 were $101.2 million and $100.8 million, respectively.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 29, 2019
Financial Instruments	G. 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 Teradyne’s available-for-sale During the three and nine months ended September 29, 2019 and September 30, 2018, there were no transfers in or out of Level 1, Level 2, or Level 3 financial instruments. Realized gains recorded in the three and nine months ended September 29, 2019 were $0.5 million and $0.7 million, respectively. Realized losses recorded in the nine months ended September 29, 2019 were $0.2 million. Realized gains recorded in the three and nine months ended September 30, 2018 were $0.2 million and $0.6 million, respectively. Realized losses recorded in the nine months ended September 30, 2018 were $1.6 million. Realized gains are included in interest income and realized losses are included in interest expense. Unrealized gains on equity securities recorded in the three and nine months ended September 29, 2019 were $0.1 million and $3.8 million, respectively. Unrealized losses on equity securities recorded in the three and nine months ended September 29, 2019 were $0.2 million. Unrealized gains on equity securities recorded in the three and nine months ended September 30, 2018 were $1.0 million and $1.4 million, respectively. Unrealized gains on equity securities are included in interest income and unrealized losses are included in interest expense. available-for-sale 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 29, 2019 and December 31, 2018. September 29, 2019 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 $ 257,235 $ — $ — $ 257,235 Cash equivalents 198,519 138,185 — 336,704 Available-for-sale U.S. Treasury securities — 185,025 — 185,025 Commercial paper — 117,714 — 117,714 Corporate debt securities — 90,898 — 90,898 Certificates of deposit and time deposits — 14,086 — 14,086 U.S. government agency securities — 8,024 — 8,024 Debt mutual funds 3,968 — — 3,968 Non-U.S. — 380 — 380 Equity securities: Mutual funds 26,001 — — 26,001 $ 485,723 $ 554,312 $ — $ 1,040,035 Derivative assets — 119 — 119 Total $ 485,723 $ 554,431 $ — $ 1,040,154 Liabilities Contingent consideration $ — $ — $ 18,080 $ 18,080 Derivative liabilities — 489 — 489 Total $ — $ 489 $ 18,080 $ 18,569 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 455,754 $ 138,185 $ — $ 593,939 Marketable securities — 342,538 — 342,538 Long-term marketable securities 29,969 73,589 — 103,558 Prepayments — 119 — 119 Total $ 485,723 $ 554,431 $ — $ 1,040,154 Liabilities Other current liabilities $ — $ 489 $ — $ 489 Contingent consideration — — 6,297 6,297 Long-term contingent consideration — — 11,783 11,783 Total $ — $ 489 $ 18,080 $ 18,569 December 31, 2018 Quoted in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 312,512 $ — $ — $ 312,512 Cash equivalents 253,525 360,715 — 614,240 Available-for-sale U.S. Treasury securities — 109,721 — 109,721 Commercial paper — 86,117 — 86,117 Corporate debt securities — 40,020 — 40,020 U.S. government agency securities — 9,611 — 9,611 Certificates of deposit and time deposits — 7,604 — 7,604 Debt mutual funds 3,187 — — 3,187 Non-U.S. — 376 — 376 Equity securities: — Mutual funds 21,191 — — 21,191 $ 590,415 $ 614,164 $ — $ 1,204,579 Derivative assets — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Contingent consideration $ — $ — $ 70,543 $ 70,543 Derivative liabilities — 514 — 514 Total $ — $ 514 $ 70,543 $ 71,057 Reported as follows: ) Total (in thousands) Assets Cash and cash equivalents $ 566,037 $ 360,715 $ — $ 926,752 Marketable securities — 190,096 — 190,096 Long-term marketable securities 24,378 63,353 — 87,731 Prepayments — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Other accrued liabilities $ — $ 514 $ — $ 514 Contingent consideration — — 34,865 34,865 Long-term contingent consideration — — 35,678 35,678 Total $ — $ 514 $ 70,543 $ 71,057 Changes in the fair value of Level 3 contingent consideration for the three and nine months ended September 29, 2019 and September 30, 2018 were as follows: For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Balance at beginning of period $ 26,847 $ 60,914 $ 70,543 $ 45,102 Fair value adjustment (a) (7,759 ) (768 ) (16,460 ) (9,236 ) Foreign currency impact (1,008 ) 796 (1,413 ) (1,770 ) Payments (b) — — (34,590 ) (24,553 ) Acquisition of MiR — — — 51,399 Balance at end of period $ 18,080 $ 60,942 $ 18,080 $ 60,942 (a) In the three and nine months ended September 29, 2019, the fair value of contingent consideration for the earn-out , partially offset by impact from the modification, in the three months ended September 29, 2019, of the earn-out structure earn-out (b) In the nine months ended September 29, 2019, Teradyne paid $30.8 million and $3.8 million of contingent consideration for the earn-outs in connection with the acquisition of MiR and Universal Robots, respectively. In the nine months ended September 30, 2018, Teradyne paid $24.6 million of contingent consideration for the earn-out The following table provides quantitative information associated with the fair value measurement of Teradyne’s Level 3 financial instruments: Liability September 29, Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (MiR) $ 18,080 Monte Carl o s Revenue volatility 15.0 % Discount r 0.1 % As of September 29, 2019, the significant unobservable inputs used in the Monte Carlo simulation to fair value the MiR contingent consideration include forecasted revenues, 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 29, 2019, the maximum amount of contingent consideration that could be paid in connection with the acquisition of MiR is $81.0 million. The remaining earn-out The carrying amounts and fair values of Teradyne’s financial instruments at September 29, 2019 and December 31, 2018 were as follows: September 29, 2019 December 31, 2018 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 593,939 $ 593,939 $ 926,752 $ 926,752 Marketable securities 446,096 446,096 277,827 277,827 Derivative assets 119 119 79 79 Liabilities Contingent consideration 18,080 18,080 70,543 70,543 Derivative liabilities 489 489 514 514 Convertible debt (1) 390,942 867,388 379,981 547,113 (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 29, 2019 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 184,229 $ 847 $ (51 ) $ 185,025 $ 25,814 Commercial paper 117,618 99 (3 ) 117,714 30,704 Corporate debt securities 86,718 4,229 (49 ) 90,898 3,079 Certificates of deposit and time deposits 14,083 3 — 14,086 — U.S. government agency securities 8,009 17 (2 ) 8,024 1,150 Debt mutual funds 3,820 148 — 3,968 — Non-U.S. 380 — — 380 — $ 414,857 $ 5,343 $ (105 ) $ 420,095 $ 60,747 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 342,234 $ 313 $ (9 ) $ 342,538 $ 46,115 Long-term marketable securities 72,623 5,030 (96 ) 77,557 14,632 $ 414,857 $ 5,343 $ (105 ) $ 420,095 $ 60,747 The following table summarizes the composition of available-for-sale December 31, 2018 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 110,969 $ 112 $ (1,360 ) $ 109,721 $ 75,040 Commercial paper 86,130 13 (26 ) 86,117 85,094 Corporate debt securities 41,133 432 (1,545 ) 40,020 24,767 U.S. government agency securities 9,646 1 (36 ) 9,611 7,077 Certificates of deposit and time deposits 7,604 — — 7,604 — Debt mutual funds 3,153 34 — 3,187 — Non-U.S. 376 — — 376 — $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 190,100 $ 88 $ (92 ) $ 190,096 $ 140,262 Long-term marketable securities 68,911 504 (2,875 ) 66,540 51,716 $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 As of September 29, 2019, the fair market value of investments in available-for-sale As of December 31, 2018, the fair market value of investments with unrealized losses totaled $192.0 million. Of this value, $28.5 million had unrealized losses of $1.6 million greater than one year and $163.5 million had unrealized losses of $1.4 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 29, 2019 and December 31, 2018 were temporary. The contractual maturities of investments in available-for-sale September 29, 2019 Cost Fair Market Value (in thousands) Due within one year $ 342,234 $ 342,538 Due after 1 year through 5 years 16,609 16,718 Due after 5 years through 10 years 15,002 15,297 Due after 10 years 37,192 41,574 Total $ 411,037 $ 416,127 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 29, 2019 and December 31, 2018 was $114.9 million and $163.1 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 29, 2019 and December 31, 2018: Balance Sheet Location September 29, December 31, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts - derivative assets Prepayments $ 119 $ 79 Foreign exchange contracts - derivative liabilities Other current liabilities (489 ) (514 ) Total derivatives $ (370 ) $ (435 ) The following table summarizes the effect of derivative instruments recognized in the statement of operations for the three and nine months ended September 29, 2019 and September 30, 2018. Location of Losses (Gains) Recognized in Statement of Operations For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 3,699 $ (899 ) $ 7,872 $ 2,502 (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 months ended September 29, 2019, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.5 million. For the nine months ended September 29, 2019, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $3.4 million. (3) 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. See Note I: “Debt” regarding derivatives related to the convertible senior notes.

Leases

Leases	9 Months Ended
	Sep. 29, 2019
Lease	H. LEASES On January 1, 2019, Teradyne adopted ASC 842 using the modified retrospective approach. Under this method of adoption, the comparative information in the consolidated financial statements has not been revised and continues to be reported under the previously applicable lease accounting guidance (ASC 840). Adoption of ASC 842 resulted in recording ROU assets and lease liabilities of approximately $50.1 million and $54.3 million, respectively. The adoption of ASC 842 did not have a material impact on beginning retained earnings, the consolidated statement of operations, cash flows, or earnings per share. Teradyne has facility and auto leases, which are accounted for as operating leases. Teradyne’s facility leases are primarily used for administrative functions, research and development, manufacturing, and storage and distribution. Remaining lease terms range from less than one year to ten years. Total lease expense for the three months ended September 29, 2019 was $9.1 million and included $3.0 million of variable lease costs and $0.7 million of costs related to short-term leases which are not recorded on the consolidated balance sheets. Total lease expense for the nine months ended September 29, 2019 was $26.6 million and included $8.3 million of variable lease costs and $2.2 million of costs related to short-term leases which are not recorded on the consolidated balance sheets. At September 29, 2019, the weighted average remaining lease term and weighted average discount rate for operating leases was 4.7 years and 5.0%, respectively. Supplemental cash flow information related to leases was as follows: For the Three Months For the Nine Months September 29, 2019 September 29, 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows: $ 4,946 $ 14,998 Right-of-use 8,315 23,727 Maturities of lease liabilities as of September 29, 2019 were as follows: Operating Lease (in thousands) 2019 $ 5,520 2020 20,368 2021 16,045 2022 11,603 2023 6,135 Thereafter 13,285 Total lease payments 72,956 Less imputed interest (7,757 ) Total lease liabilities $ 65,199 As of December 31, 2018, future non-cancelable Operating Lease (in thousands) 2019 $ 19,570 2020 18,293 2021 13,578 2022 9,693 2023 5,449 Thereafter 9,472 Total lease payments $ 76,055

Debt

Debt	9 Months Ended
	Sep. 29, 2019
Debt	I. DEBT Convertible Senior Notes On December 12, 2016, Teradyne completed a private offering of $460.0 million aggregate principal amount of 1.25% convertible senior unsecured notes (the “Notes”) due December 15, 2023 and received net proceeds, after issuance costs, of approximately $450.8 million, $33.0 million of which was used to pay the net cost of the convertible note hedge transactions and $50.1 million of which was used to repurchase 2.0 million shares of Teradyne’s common stock under its existing stock repurchase program from purchasers of the Notes in privately negotiated transactions effected through one of the initial purchasers or its affiliates conducted concurrently with the pricing of the Note offering. 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 semiannually 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, only 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. As of September 29, 2019, the conversion price was approximately $31.70 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 $31.70. The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, approximately 14.5 million shares of Teradyne’s common stock. 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 Note Hedge Transactions, after being partially offset by the proceeds from the sale of the warrants, was approximately $33.0 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 considered the guidance of ASC 815-40, “Derivatives and Hedging—Contracts in Entity’s Own Equity,” fixed-for-fixed Teradyne assessed whether the convertible note hedge should be classified as equity under ASC 815-40. 815-40 Teradyne analyzed the Warrant Transactions under ASC 815-40, “Derivatives and Hedging—Contracts in Entity’s Own Equity,” paid-in The provisions of ASC 470-20, Debt with Conversion and Other Options, 470-20 The below tables represent the key components of Teradyne’s convertible senior notes: September 29, December 31, (in thousands) Debt Principal $ 460,000 $ 460,000 Unamortized discount 69,058 80,019 Net Carrying amount of convertible debt $ 390,942 $ 379,981 For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Contractual interest expense on the coupon $ 1,438 $ 1,438 $ 4,313 $ 4,313 Amortization of the discount component recognized as interest expense 3,699 3,520 10,961 10,431 Total interest expense on the convertible debt $ 5,137 $ 4,958 $ 15,274 $ 14,744 As of September 29, 2019, the remaining unamortized discount was $69.1 million, which will be amortized over 4.3 years using the effective interest rate method. The carrying amount of the equity component was $100.8 million. As of September 29, 2019, the if-converted Revolving Credit Facility On June 27, 2019, Teradyne terminated its credit agreement, which Teradyne entered into with Barclays Bank PLC, on April 27, 2015. The terminated credit agreement provided for a five-year, senior secured revolving credit facility of up to $350 million.

Prepayments

Prepayments	9 Months Ended
	Sep. 29, 2019
Prepayments	J. PREPAYMENTS Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: September 29, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 136,470 $ 131,642 Prepaid taxes 9,754 9,646 Prepaid maintenance and other services 8,310 8,487 Other prepayments 17,180 12,744 Total prepayments $ 171,714 $ 162,519

Deferred Revenue and Customer A

Deferred Revenue and Customer Advances	9 Months Ended
	Sep. 29, 2019
Deferred Revenue and Customer Advances	K. 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 29, December 31, (in thousands) Maintenance and training $ 61,048 $ 58,362 Extended warranty 29,937 27,422 Customer advances, undelivered performance obligations and other 47,543 24,677 Total deferred revenue and customer advances $ 138,528 $ 110,461

Product Warranty

Product Warranty	9 Months Ended
	Sep. 29, 2019
Product Warranty	L. PRODUCT WARRANTY Teradyne generally provides a one-year For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, 2019 2018 2019 2018 (in thousands) Balance at beginning of period $ 8,133 $ 7,136 $ 7,909 $ 8,200 Acquisition — — 14 41 Accruals for warranties issued during the period 3,508 2,760 10,008 9,171 Accruals related to pre-existing 1,132 282 3,156 109 Settlements made during the period (4,265 ) (2,675 ) (12,579 ) (10,018 ) Balance at end of period $ 8,508 $ 7,503 $ 8,508 $ 7,503 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 29, September 30, September 29, September 30, (in thousands) Balance at beginning of period $ 28,716 $ 25,971 $ 27,422 $ 24,438 Deferral of new extended warranty revenue 5,666 7,232 16,962 19,072 Recognition of extended warranty deferred revenue (4,445 ) (5,586 ) (14,447 ) (15,893 ) Balance at end of period $ 29,937 $ 27,617 $ 29,937 $ 27,617

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 29, 2019
Stock-Based Compensation	M. STOCK-BASED COMPENSATION On July 17, 2019 (the “Retirement Date”), former Chief Financial Officer Gregory Beecher retired as Vice President and Senior Advisor of Teradyne, and Teradyne entered into an agreement (the “Retirement Agreement”) with Mr. Beecher. Under the Retirement Agreement, Mr. Beecher’s unvested time-based restricted stock units and stock options granted prior to 2019 were modified to allow continued vesting; unvested time-based restricted stock units and stock options granted in 2019 were modified to allow continued vesting through January 31, 2023 (the “Non-Competition Period”) in a pro-rated amount based on the number of days that Mr. Beecher was employed during 2019;​​​​​​​ unvested, performance-based restricted stock units awarded in 2019 will vest on the date the amount of shares underlying the performance-based restricted stock units are determined in a pro-rated amount of shares based on the number of days that Mr. Beecher was employed during 2019; vested options or options that vest during the Non-Competition Period may be exercised for the remainder of the applicable option term. During the three and nine months ended September 29, 2019, Teradyne recorded a stock based compensation expense of $2.1 million related to the Retirement Agreement . 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 Performance-based restricted stock units (“PRSUs”) granted to Teradyne’s executive officers have a performance metric based on relative total shareholder return (“TSR”). Teradyne’s three Compensation expense is recognized on a straight-line basis over the shorter of the three-year service period or the period from the grant 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. During the nine months ended September 29, 2019 and September 30, 2018, Teradyne granted PRSUs to its executive officers with a performance metric based on three-year cumulative non-GAAP Non-GAAP convertible debt interest expense; and other non-recurring gains and charges. The final number of PBIT PRSUs that vest will vary based upon the level of performance achieved from % to % of the target shares. The PBIT PRSUs will vest upon the three-year anniversary of the grant date. Compensation expense is recognized on a straight-line basis over the shorter of the 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 grant. Compensation expense is recognized based on the number of units that are earned based upon the three-year Teradyne PBIT as a percent of Teradyne’s revenue, provided the executive officer remains an employee at the end of the three-year period subject to the retirement and termination eligibility provisions noted below. If a PRSU 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 During the nine months ended September 29, 2019 and September 30, 2018, Teradyne granted 0.1 million and 0.1 million TSR PRSUs, respectively, with a grant date fair value of $51.51 and $54.85, respectively. For the Nine Months Ended September 29, September 30, Risk-free interest rate 2.6 % 2.2 % Teradyne volatility-historical 31.9 % 26.8 % NYSE Composite Index volatility-historical 11.9 % 12.4 % Dividend yield 1.0 % 0.8 % Expected volatility was based on the historical volatility of Teradyne’s stock and the NYSE Composite Index for each of the 2019 and 2018 grants 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 each of the grants. Dividend yield was based upon an estimated annual dividend amount of $0.36 per share, divided by Teradyne’s stock price on the grant date of $37.95 for the s During the nine months ended September 29, 2019 and September 30, 2018, Teradyne granted 0.1 million and 0.1 million, respectively, of PBIT PRSUs with a grant date fair value of $36.88 and $46.62, respectively. During the nine months ended September 29, 2019, Teradyne granted 0.7 million of service-based restricted stock unit awards to employees at a weighted average grant date fair value of $36.85, 0.1 million of service-based restricted stock unit awards to non-employee , 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 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 29, September 30, Expected life (years) 5.0 5.0 Risk-free interest rate 2.5 % 2.4 % Volatility-historical 30.1 % 26.4 % Dividend yield 1.0 % 0.8 % 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 divided by Teradyne’s stock price on the grant date of $37.95 for the s

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 29, 2019
Accumulated Other Comprehensive Income (Loss)	N. 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 29, 2019 Balance at December 31, 2018, net of tax of $0, $(521), $(1,081), $ (12,523 ) $ (1,845 ) $ 1,328 $ (13,040 ) Other comprehensive loss (17,019 ) 6,391 — (10,628 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $( 125 — (442 ) (111 ) (553 ) Net current period other comprehensive income (loss), net of tax of $0, $1,637, $(32), respectively (17,019 ) 5,949 (111 ) (11,181 ) Balance at September 29, 2019, net of tax of $0, $1,116, $(1,113), $ (29,542 ) $ 4,104 $ 1,217 $ (24,221 ) Foreign Currency Translation Adjustments 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 income (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 income (loss), net of tax of $0, $(812), $(53), respectively (11,568 ) (1,144 ) (184 ) (12,896 ) Reclassification of income tax effects from the Tax Reform Act, net of tax of $0, $(691), $(78), respectively — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax of $0, $(902), $0, respectively — (3,125 ) — (3,125 ) Balance a t $ 4,351 $ (2,216 ) $ 1,389 $ 3,524 Reclassifications out of accumulated other comprehensive income (loss) to the statement of operations for the three and nine months ended September 29 , and September , were as follows: For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations September 29, September 30, September 29, September 30, Details about Accumulated Other Comprehensive Income (in thousands) Available-for-sale Unrealized gains (losses), net of tax of $99, $17, $125, $6, respectively $ 345 $ 57 $ 442 $ (1,411 ) Interest income Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $11, $18, $32, $53 respectively 37 61 111 184 (a) Total reclassifications, net of tax of $110, $35, $157, $59, respectively $ 382 $ 118 $ 553 $ (1,227 ) Net income (a) The amortization of prior service benefit is included in the computation of net periodic pension cost and postretirement benefit. See Note R: “Retirement Plans.”

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	9 Months Ended
	Sep. 29, 2019
Goodwill and Intangible Assets	O. 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 29, 2019 were as follows: Industrial Automation System Test Wireless Test Semiconductor Test Total (in thousands) Balance at December 31, 2018 Goodwill $ 363,358 $ 158,699 $ 361,819 $ 260,540 $ 1,144,416 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 363,358 10,516 7,976 — 381,850 Lemsys acquisition — — — 1,428 1,428 Foreign currency translation adjustment (12,572 ) — — 11 (12,561 ) Balance at September 29, 2019 Goodwill 350,786 158,699 361,819 261,979 1,133,283 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 350,786 $ 10,516 $ 7,976 $ 1,439 $ 370,717 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 29, 2019 Gross Carrying Amount (1) Accumulated Amortization (2) Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 337,198 $ (272,317 ) $ (6,461 ) $ 58,420 Customer relationships 100,313 (89,540 ) (562 ) 10,211 Tradenames and trademarks 64,670 (35,368 ) (1,360 ) 27,942 Total intangible assets $ 502,181 $ (397,225 ) $ (8,383 ) $ 96,573 December 31, 2018 Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 336,308 $ (252,080 ) $ (4,079 ) $ 80,149 Customer relationships 97,153 (83,448 ) (340 ) 13,365 Tradenames and trademarks 64,420 (31,653 ) (799 ) 31,968 Non-compete 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 498,231 $ (367,531 ) $ (5,218 ) $ 125,482 (1) $4.6 million of intangible assets from Lemsys acquisition have been added in January 2019 (2) $0.7 million of amortizable intangible assets became fully amortized and have been removed Aggregate intangible asset amortization expense was $9.6 million and $30.4 million, respectively, for the three and nine months ended September 29, 2019 and $11.1 million and $28.6 million, respectively, for the three and nine months ended September 30, 2018. Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Amortization Expense Year (in thousands) 2019 (remainder) 8,694 2020 24,232 2021 14,340 2022 13,447 2023 12,976 Thereafter 22,884

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Sep. 29, 2019
Net Income per Common Share	P. 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 29, September 30, September 29, September 30, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 135,860 $ 119,981 $ 342,395 $ 307,991 Weighted average common shares-basic 169,641 185,744 171,471 190,576 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 5,800 3,025 4,117 3,356 Convertible note hedge warrant shares (2) 3,580 108 1,786 646 Restricted stock units 1,313 1,331 1,112 1,406 Stock options 155 275 186 290 Employee stock purchase plan 5 22 13 26 Dilutive potential common shares 10,853 4,761 7,214 5,724 Weighted average common shares-diluted 180,494 190,505 178,685 196,300 Net income per common share-basic $ 0.80 $ 0.65 $ 2.00 $ 1.62 Net income per common share-diluted $ 0.75 $ 0.63 $ 1.92 $ 1.57 (1) Incremental shares from assumed conversion of the convertible notes were calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, 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 note hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, 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 29, 2019 excludes the effect of the potential vesting of 0.1 million of stock options , The computation of diluted net income per share for the nine months ended September 29, 2019 excludes the effect of the potential vesting of 0.2 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 September 30, 2018 excludes the effect of the potential vesting of 0.5 million shares of restricted stock units because the effect would have been anti-dilutive.

Restructuring and Other

Restructuring and Other	9 Months Ended
	Sep. 29, 2019
Restructuring and Other	Q. RESTRUCTURING AND OTHER During the three months ended September 29, 2019, Teradyne recorded a $7.8 million gain employee severance charges primarily in Industrial Automation, $0.5 million f or , and $0.3 million of fixed assets impairment in Wireless Test . 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 f o r During the nine months ended September 29, 2019, Teradyne recorded a $16.5 million gain for the decrease in the fair value of the MiR contingent consideration liability, partially offset by $2.1 million recorded for employee severance charges primarily in Semiconductor Test and Industrial Automation, $2.3 million for acquisition related expenses and compensation, and $0.3 million of fixed assets impairment in Wireless Test. 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 compensation and expenses , partially offset by a $9.2 million gain for the decrease in the fair value of the Universal Robots contingent consideration liability.

Retirement Plans

Retirement Plans	9 Months Ended
	Sep. 29, 2019
Retirement Plans	R. 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. In the nine months ended September 29, 2019, Teradyne contributed $2.1 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 29, 2019 and September 30, 2018, Teradyne’s net periodic pension cost was comprised of the following: For the Three Months Ended September September 30, 2018 United States Foreign United States Foreign (in thousands) Service cost $ 402 $ 183 $ 538 $ 203 Interest cost 1,797 168 1,750 177 Expected return on plan assets (1,510 ) (7 ) (1,551 ) (5 ) Amortization of prior service cost — — 14 — Settlement loss — — 267 — Total net periodic pension cost $ 689 $ 344 $ 1,018 $ 375 For the Nine Months Ended September 29, 2019 September 30, 2018 United States Foreign United States Foreign (in thousands) Service cost $ 1,206 $ 550 $ 1,657 $ 609 Interest cost 5,392 505 7,188 532 Expected return on plan assets (4,531 ) (21 ) (7,484 ) (15 ) Amortization of prior service cost — — 43 — Net actuarial loss (gain) 252 — (189 ) — Settlement loss — — 345 — Total net periodic pension cost $ 2,319 $ 1,034 $ 1,560 $ 1,126 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 29, 2019 and September 30, 2018, Teradyne’s net periodic postretirement benefit cost was comprised of the following: For the Three Months For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Service cost $ 10 $ 10 $ 31 $ 29 Interest cost 87 49 260 147 Amortization of prior service credit (48 ) (93 ) (143 ) (280 ) Net actuarial loss — — 196 40 Special termination benefits — 601 — 3,419 Total net periodic postretirement benefit cost $ 49 $ 567 $ 344 $ 3,355

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 29, 2019
Commitments and Contingencies	S. COMMITMENTS AND CONTINGENCIES Purchase Commitments As of September 29, 2019, Teradyne had entered into purchase commitments for certain components and materials. The purchase commitments covered by the agreements aggregate to approximately $360.3 million, of which $354.2 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. 29, 2019
Income Taxes	T. INCOME TAXES A reconciliation of the United States federal statutory corporate tax rate to Teradyne’s effective tax rate was as follows: For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, US statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % Discrete expense related to U.S. transition tax — — 3.9 0.0 Foreign taxes (5.1 ) (4.4 ) (4.9 ) (3.7 ) International provisions of the U.S. Tax Cuts and Jobs (2.8 ) (1.4 ) (0.6 ) (1.4 ) Tax credits (1.8 ) (1.9 ) (2.2 ) (2.1 ) Discrete benefit related to equity compensation (0.7 ) (0.1 ) (1.5 ) (2.2 ) Discrete benefit related to release of reserves for uncertain tax positions — (0.1 ) (6.9 ) — Other, net (0.1 ) 1.7 0.4 2.0 Effective tax rate 10.5 % 14.8 % 9.2 % 13.6 % 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 29, 2019, 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 29, 2019 and December 31, 2018, Teradyne had $13.6 million and $43.4 million, respectively, of reserves for uncertain tax positions. The $29.8 million net decrease in reserves for uncertain tax positions is primarily composed of reductions in uncertain tax positions amounting to $22.4 million related to transfer pricing and $7.2 million associated with U.S. research and development tax credits. These reductions primarily resulted from the conclusion of the U.S. Federal income tax audit for the year ended December 31, 2015. As of September 29 On July 27, 2015, in Altera Corp. v. Commissioner (“Altera”), the U.S. Tax Court issued an opinion invalidating the regulations relating to the treatment of stock-based compensation expense in an intercompany cost-sharing arrangement. A final decision was issued by the Tax Court in December 2015. The IRS appealed the decision in June 2016. On July 24, 2018, the Ninth Circuit Federal Court issued a decision that was subsequently withdrawn and a reconstituted panel has conferred on the appeal. On June 7, 2019, the Ninth Circuit Federal Court upheld the cost-sharing regulations. Due to the uncertainty surrounding the status of the current regulations, questions related to the scope of potential benefits or obligations, the outcome of the appeals process, and questions regarding jurisdiction, Teradyne has not established any income tax reserves as of September 29 Teradyne recognizes interest and penalties related to income tax matters in income tax expense. As of September 29, 2019 and December 31, 2018, $0.5 million and $0.3 million, respectively, of interest and penalties were accrued for uncertain tax positions. For the nine months ended September 29, 2019 and September 30, 2018, expense of $0.2 million and $0.1 million, respectively, 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 29, 2019 was $12.0 million, or $0.07 per diluted share. 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 holiday is scheduled to expire on December 31, 2020.

Segment Information

Segment Information	9 Months Ended
	Sep. 29, 2019
Segment Reporting [Abstract]
Segment Information	U. 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 29, 2019 and September 30, 2018 is as follows: Semiconductor Test Industrial Automation System Test Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended September 29, 2019 Revenues $ 397,737 $ 68,892 $ 73,305 $ 42,264 $ (160 ) $ 582,038 Income (loss) before income taxes (1)(2) 116,633 (1,645 ) 24,381 11,182 1,182 151,733 Total assets (3) 757,422 580,635 126,452 94,789 1,139,493 2,698,791 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 Nine Months Ended September 29, 2019 Revenues $ 1,113,489 $ 209,753 $ 204,934 $ 112,541 $ (402 ) $ 1,640,315 Income (loss) before income taxes (1)(2) 291,037 (10,670 ) 63,254 25,740 7,528 376,889 Total assets (3) 757,422 580,635 126,452 94,789 1,139,493 2,698,791 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 (1) Included in (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 each 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 29, September 30, September 29, September 30, 2019 2018 2019 2018 (in thousands) Semiconductor Test: Cost of revenues—inventory charge $ 1,867 $ 2,071 $ 5,319 $ 5,851 Restructuring and other—employee severance — 1,716 1,009 7,657 Industrial Automation: Restructuring and other—acquisition related expenses $ — $ 811 $ 1,330 $ 811 Restructuring and other—employee severance — — 604 — Cost of revenues—inventory charge — — 508 680 System Test: Cost of revenues—inventory charge $ — $ — $ 1,129 $ 812 Wireless Test: Cost of revenues—inventory charge $ 724 $ 716 $ 1,892 $ 2,179 Corporate and Other: Restructuring and other—MiR contingent consideration adjustment $ (7,759 ) $ — $ (16,427 ) $ — Selling and administrative – equity modification charge 2,108 — 2,108 — Restructuring and other—acquisition related expenses and compensation 816 — 928 3,318 Restructuring and other—Universal Robots contingent consideration adjustment — (768 ) — (9,236 )

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 29, 2019
Equity [Abstract]
Shareholders' Equity	V. 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 $500 million in 2019. During the nine months ended September 29, 2019, Teradyne repurchased 8.8 million shares of common stock for $368.8 million at an average price of $41.93 per share. The cumulative repurchases under the $1.5 billion stock repurchase program as of September 29, 2019 totaled 30.4 million shares of common stock for $1.2 billion at an average price per share of $39.18. 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. 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 2019 , In January 2018 , 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.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 29, 2019
Subsequent Events	W. SUBSEQUENT EVENTS On October 18, 2019, Teradyne entered into an agreement to acquire 100% of the equity of AutoGuide, LLC (“AutoGuide”), a maker of high-payload autonomous mobile robots (AMRs), an emerging and fast growing segment of the global forklift market for $58 million of cash and up to $107 million in earn-outs potentially through 2022. AutoGuide is based in Chelmsford, MA. AutoGuide’s AMRs are used for material transport of payloads up to 4,500 kg in manufacturing, warehouse and logistics applications. These products complement MiR’s lower payload products. The acquisition of AutoGuide is expected to close in the fourth quarter of 2019, subject to customary closing conditions and regulatory approval. AutoGuide will be included in Teradyne’s Industrial Automation segment.

Accounting Policies (Policies)

Accounting Policies (Policies)	9 Months Ended
	Sep. 29, 2019
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, 2018 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.
Investment in Other Company	Investment in Other Company Teradyne holds an investment in a private company that develops and sells advanced wearable technology. Teradyne does not have the ability to exert significant influence over the company. The investment was recorded at cost and is evaluated for impairment or an indication of changes in fair value resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer on a quarterly basis. See Note D: “Acquisitions and Investment in Other Company.”
Leases	Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” right-of-use 2018-11, “Leases (Topic 842): Targeted Improvements,” Under ASC 842, a contract is or contains a lease when Teradyne has the right to control the use of an identified asset. Teradyne determines if an arrangement is a lease at inception of the contract, which is the date on which the terms of the contract are agreed to and the agreement creates enforceable rights and obligations. The commencement date of the lease is the date that the lessor makes an underlying asset available for use by Teradyne. As of September 29, 2019, Teradyne does not have material leases that have not yet commenced. Teradyne determines if the lease is operating or finance at the lease commencement date based upon the terms of the lease and the nature of the asset. The lease term used to calculate the lease liability includes options to extend or terminate the lease when it is reasonably certain that the option will be exercised. For leases commencing after January 1, 2019, the lease liability is measured at the present value of future lease payments, discounted using the discount rate for the lease at the commencement date. As Teradyne is typically unable to determine the implicit rate, Teradyne uses an incremental borrowing rate based on the lease term and economic environment at commencement date. Teradyne initially measures payments based on an index by using the applicable rate at lease commencement. Variable payments that do not depend on an index are not included in the lease liability and are recognized as they are incurred. The ROU asset is initially measured as the amount of lease liability, adjusted for any initial lease costs, prepaid lease payments, and reduced by any lease incentives. Teradyne’s contracts often include non-lease non-lease

Acquisitions and Investment I_2

Acquisitions and Investment In Other Company (Tables)	9 Months Ended
	Sep. 29, 2019
Final Allocation of Purchase Price	The following table represents the final allocation of the purchase price: Purchase Price Allocation (in thousands) Goodwill $ 135,976 Intangible assets 80,670 Tangible assets acquired and liabilities assumed: Current assets 6,039 Non-current 1,336 Accounts payable and current liabilities (7,336 ) Long-term deferred tax liabilities (18,007 ) Other long-term liabilities (900 ) Total purchase price $ 197,778
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 Nine Months September 30, 2018 (in thousands) Revenue $ 1,588,042 Net income 306,768 Net income per common share: Basic $ 1.61 Diluted $ 1.56

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 29, 2019
Revenue from Contract with Customer [Abstract]
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 29, 2019 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated System chip (“SOC”) Memory Defense/ Aerospace Storage Production Universal M iR Energid (in thousands) Americas Point in time $ 6,307 $ 3,464 $ 22,861 $ 2,232 $ 2,165 $ 16,294 $ 2,820 $ — $ 5,621 $ (160 ) $ 61,604 Over time 8,497 621 5,814 — 796 293 — 188 723 — 16,932 Europe, Middle East Point in time 6,894 274 742 — 4,354 25,557 5,011 — 1,220 — 44,052 Over time 5,189 255 469 — 1,613 459 — 615 48 — 8,648 Asia Pacific Point in time 259,909 63,483 99 22,696 6,751 15,575 1,800 — 33,032 — 403,345 Over time 37,680 3,874 299 1,496 830 280 — — 1,545 — 46,004 Lease Revenue 1,290 — — — 88 — — — 75 — 1,453 Total $ 325,766 $ 71,971 $ 30,284 $ 26,424 $ 16,597 $ 58,458 $ 9,631 $ 803 $ 42,264 $ (160 ) $ 582,038 For the Three Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR 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 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 29, 2019 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR Energid (in thousands) Americas Point in time $ 21,830 $ 19,574 $ 54,870 $ 7,528 $ 6,760 $ 48,529 $ 9,152 $ — $ 12,961 $ (402 ) $ 180,802 Over time 24,862 2,056 19,116 — 2,317 793 — 1,235 1,550 — 51,929 Europe, Middle East Point in time 27,934 2,443 992 — 12,391 78,007 13,883 — 2,575 — 138,225 Over time 15,681 819 1,442 — 4,782 1,274 — 1,381 140 — 25,519 Asia Pacific Point in time 727,035 143,163 525 66,974 17,235 48,284 6,208 — 91,029 — 1,100,453 Over time 113,158 10,447 1,391 5,860 2,526 786 — 221 4,146 — 138,535 Lease Revenue 4,487 — — — 225 — — — 140 — 4,852 Total $ 934,987 $ 178,502 $ 78,336 $ 80,362 $ 46,236 $ 177,673 $ 29,243 $ 2,837 $ 112,541 $ (402 ) $ 1,640,315 For the Nine Months Ended September 30, 2018 Semiconductor Test System Test Industrial Automation Wireless Corporate Consolidated SOC Memory Defense/ Aerospace Storage Production Universal M iR 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 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

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 29, 2019
Composition of Inventories, Net	Inventories, net consisted of the following at September 29, 2019 and December 31, 2018: September 29, December 31, (in thousands) Raw material $ 114,162 $ 89,365 Work-in-process 28,460 31,014 Finished goods 35,581 33,162 $ 178,203 $ 153,541

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 29, 2019
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 29, 2019 and December 31, 2018. September 29, 2019 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 $ 257,235 $ — $ — $ 257,235 Cash equivalents 198,519 138,185 — 336,704 Available-for-sale U.S. Treasury securities — 185,025 — 185,025 Commercial paper — 117,714 — 117,714 Corporate debt securities — 90,898 — 90,898 Certificates of deposit and time deposits — 14,086 — 14,086 U.S. government agency securities — 8,024 — 8,024 Debt mutual funds 3,968 — — 3,968 Non-U.S. — 380 — 380 Equity securities: Mutual funds 26,001 — — 26,001 $ 485,723 $ 554,312 $ — $ 1,040,035 Derivative assets — 119 — 119 Total $ 485,723 $ 554,431 $ — $ 1,040,154 Liabilities Contingent consideration $ — $ — $ 18,080 $ 18,080 Derivative liabilities — 489 — 489 Total $ — $ 489 $ 18,080 $ 18,569 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 455,754 $ 138,185 $ — $ 593,939 Marketable securities — 342,538 — 342,538 Long-term marketable securities 29,969 73,589 — 103,558 Prepayments — 119 — 119 Total $ 485,723 $ 554,431 $ — $ 1,040,154 Liabilities Other current liabilities $ — $ 489 $ — $ 489 Contingent consideration — — 6,297 6,297 Long-term contingent consideration — — 11,783 11,783 Total $ — $ 489 $ 18,080 $ 18,569 December 31, 2018 Quoted in Active Markets for Identical Instruments (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in thousands) Assets Cash $ 312,512 $ — $ — $ 312,512 Cash equivalents 253,525 360,715 — 614,240 Available-for-sale U.S. Treasury securities — 109,721 — 109,721 Commercial paper — 86,117 — 86,117 Corporate debt securities — 40,020 — 40,020 U.S. government agency securities — 9,611 — 9,611 Certificates of deposit and time deposits — 7,604 — 7,604 Debt mutual funds 3,187 — — 3,187 Non-U.S. — 376 — 376 Equity securities: — Mutual funds 21,191 — — 21,191 $ 590,415 $ 614,164 $ — $ 1,204,579 Derivative assets — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Contingent consideration $ — $ — $ 70,543 $ 70,543 Derivative liabilities — 514 — 514 Total $ — $ 514 $ 70,543 $ 71,057 Reported as follows: ) Total (in thousands) Assets Cash and cash equivalents $ 566,037 $ 360,715 $ — $ 926,752 Marketable securities — 190,096 — 190,096 Long-term marketable securities 24,378 63,353 — 87,731 Prepayments — 79 — 79 Total $ 590,415 $ 614,243 $ — $ 1,204,658 Liabilities Other accrued liabilities $ — $ 514 $ — $ 514 Contingent consideration — — 34,865 34,865 Long-term contingent consideration — — 35,678 35,678 Total $ — $ 514 $ 70,543 $ 71,057
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 29, 2019 and September 30, 2018 were as follows: For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Balance at beginning of period $ 26,847 $ 60,914 $ 70,543 $ 45,102 Fair value adjustment (a) (7,759 ) (768 ) (16,460 ) (9,236 ) Foreign currency impact (1,008 ) 796 (1,413 ) (1,770 ) Payments (b) — — (34,590 ) (24,553 ) Acquisition of MiR — — — 51,399 Balance at end of period $ 18,080 $ 60,942 $ 18,080 $ 60,942 (a) In the three and nine months ended September 29, 2019, the fair value of contingent consideration for the earn-out , partially offset by impact from the modification, in the three months ended September 29, 2019, of the earn-out structure earn-out (b) In the nine months ended September 29, 2019, Teradyne paid $30.8 million and $3.8 million of contingent consideration for the earn-outs in connection with the acquisition of MiR and Universal Robots, respectively. In the nine months ended September 30, 2018, Teradyne paid $24.6 million of contingent consideration for the 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 29, Valuation Technique Unobservable Inputs Weighted Average (in thousands) Contingent consideration (MiR) $ 18,080 Monte Carl o s Revenue volatility 15.0 % Discount r 0.1 %
Schedule of Carrying Amounts and Fair Values of Financial Instruments	The carrying amounts and fair values of Teradyne’s financial instruments at September 29, 2019 and December 31, 2018 were as follows: September 29, 2019 December 31, 2018 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 593,939 $ 593,939 $ 926,752 $ 926,752 Marketable securities 446,096 446,096 277,827 277,827 Derivative assets 119 119 79 79 Liabilities Contingent consideration 18,080 18,080 70,543 70,543 Derivative liabilities 489 489 514 514 Convertible debt (1) 390,942 867,388 379,981 547,113 (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 29, 2019 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 184,229 $ 847 $ (51 ) $ 185,025 $ 25,814 Commercial paper 117,618 99 (3 ) 117,714 30,704 Corporate debt securities 86,718 4,229 (49 ) 90,898 3,079 Certificates of deposit and time deposits 14,083 3 — 14,086 — U.S. government agency securities 8,009 17 (2 ) 8,024 1,150 Debt mutual funds 3,820 148 — 3,968 — Non-U.S. 380 — — 380 — $ 414,857 $ 5,343 $ (105 ) $ 420,095 $ 60,747 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 342,234 $ 313 $ (9 ) $ 342,538 $ 46,115 Long-term marketable securities 72,623 5,030 (96 ) 77,557 14,632 $ 414,857 $ 5,343 $ (105 ) $ 420,095 $ 60,747 The following table summarizes the composition of available-for-sale December 31, 2018 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) U.S. Treasury securities $ 110,969 $ 112 $ (1,360 ) $ 109,721 $ 75,040 Commercial paper 86,130 13 (26 ) 86,117 85,094 Corporate debt securities 41,133 432 (1,545 ) 40,020 24,767 U.S. government agency securities 9,646 1 (36 ) 9,611 7,077 Certificates of deposit and time deposits 7,604 — — 7,604 — Debt mutual funds 3,153 34 — 3,187 — Non-U.S. 376 — — 376 — $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 190,100 $ 88 $ (92 ) $ 190,096 $ 140,262 Long-term marketable securities 68,911 504 (2,875 ) 66,540 51,716 $ 259,011 $ 592 $ (2,967 ) $ 256,636 $ 191,978
Contractual Maturities of Investments Held	The contractual maturities of investments in available-for-sale September 29, 2019 Cost Fair Market Value (in thousands) Due within one year $ 342,234 $ 342,538 Due after 1 year through 5 years 16,609 16,718 Due after 5 years through 10 years 15,002 15,297 Due after 10 years 37,192 41,574 Total $ 411,037 $ 416,127
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 29, 2019 and December 31, 2018: Balance Sheet Location September 29, December 31, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts - derivative assets Prepayments $ 119 $ 79 Foreign exchange contracts - derivative liabilities Other current liabilities (489 ) (514 ) Total derivatives $ (370 ) $ (435 )
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 29, 2019 and September 30, 2018. Location of Losses (Gains) Recognized in Statement of Operations For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 3,699 $ (899 ) $ 7,872 $ 2,502 (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 months ended September 29, 2019, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.5 million. For the nine months ended September 29, 2019, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $3.4 million. (3) 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.

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 29, 2019
Supplemental cash flow information related to leases	Supplemental cash flow information related to leases was as follows: For the Three Months For the Nine Months September 29, 2019 September 29, 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows: $ 4,946 $ 14,998 Right-of-use 8,315 23,727
Schedule of operating lease, maturity	Maturities of lease liabilities as of September 29, 2019 were as follows: Operating Lease (in thousands) 2019 $ 5,520 2020 20,368 2021 16,045 2022 11,603 2023 6,135 Thereafter 13,285 Total lease payments 72,956 Less imputed interest (7,757 ) Total lease liabilities $ 65,199
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	As of December 31, 2018, future non-cancelable Operating Lease (in thousands) 2019 $ 19,570 2020 18,293 2021 13,578 2022 9,693 2023 5,449 Thereafter 9,472 Total lease payments $ 76,055

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 29, 2019
Components of Convertible Senior Notes	The below tables represent the key components of Teradyne’s convertible senior notes: September 29, December 31, (in thousands) Debt Principal $ 460,000 $ 460,000 Unamortized discount 69,058 80,019 Net Carrying amount of convertible debt $ 390,942 $ 379,981 For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Contractual interest expense on the coupon $ 1,438 $ 1,438 $ 4,313 $ 4,313 Amortization of the discount component recognized as interest expense 3,699 3,520 10,961 10,431 Total interest expense on the convertible debt $ 5,137 $ 4,958 $ 15,274 $ 14,744

Prepayments (Tables)

Prepayments (Tables)	9 Months Ended
	Sep. 29, 2019
Schedule of Prepayments and other assets	Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: September 29, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 136,470 $ 131,642 Prepaid taxes 9,754 9,646 Prepaid maintenance and other services 8,310 8,487 Other prepayments 17,180 12,744 Total prepayments $ 171,714 $ 162,519

Deferred Revenue and Customer_2

Deferred Revenue and Customer Advances (Tables)	9 Months Ended
	Sep. 29, 2019
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 29, December 31, (in thousands) Maintenance and training $ 61,048 $ 58,362 Extended warranty 29,937 27,422 Customer advances, undelivered performance obligations and other 47,543 24,677 Total deferred revenue and customer advances $ 138,528 $ 110,461

Product Warranty (Tables)

Product Warranty (Tables)	9 Months Ended
	Sep. 29, 2019
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 29, September 30, September 29, September 30, 2019 2018 2019 2018 (in thousands) Balance at beginning of period $ 8,133 $ 7,136 $ 7,909 $ 8,200 Acquisition — — 14 41 Accruals for warranties issued during the period 3,508 2,760 10,008 9,171 Accruals related to pre-existing 1,132 282 3,156 109 Settlements made during the period (4,265 ) (2,675 ) (12,579 ) (10,018 ) Balance at end of period $ 8,508 $ 7,503 $ 8,508 $ 7,503
Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances	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 29, September 30, September 29, September 30, (in thousands) Balance at beginning of period $ 28,716 $ 25,971 $ 27,422 $ 24,438 Deferral of new extended warranty revenue 5,666 7,232 16,962 19,072 Recognition of extended warranty deferred revenue (4,445 ) (5,586 ) (14,447 ) (15,893 ) Balance at end of period $ 29,937 $ 27,617 $ 29,937 $ 27,617

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 29, 2019
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 29, September 30, Risk-free interest rate 2.6 % 2.2 % Teradyne volatility-historical 31.9 % 26.8 % NYSE Composite Index volatility-historical 11.9 % 12.4 % Dividend yield 1.0 % 0.8 %
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 29, September 30, Expected life (years) 5.0 5.0 Risk-free interest rate 2.5 % 2.4 % Volatility-historical 30.1 % 26.4 % Dividend yield 1.0 % 0.8 %

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 29, 2019
Changes in Accumulated Other Comprehensive (Loss) Income	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 29, 2019 Balance at December 31, 2018, net of tax of $0, $(521), $(1,081), $ (12,523 ) $ (1,845 ) $ 1,328 $ (13,040 ) Other comprehensive loss (17,019 ) 6,391 — (10,628 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $( 125 — (442 ) (111 ) (553 ) Net current period other comprehensive income (loss), net of tax of $0, $1,637, $(32), respectively (17,019 ) 5,949 (111 ) (11,181 ) Balance at September 29, 2019, net of tax of $0, $1,116, $(1,113), $ (29,542 ) $ 4,104 $ 1,217 $ (24,221 ) Foreign Currency Translation Adjustments 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 income (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 income (loss), net of tax of $0, $(812), $(53), respectively (11,568 ) (1,144 ) (184 ) (12,896 ) Reclassification of income tax effects from the Tax Reform Act, net of tax of $0, $(691), $(78), respectively — 691 78 769 Reclassification of unrealized gains on equity securities, net of tax of $0, $(902), $0, respectively — (3,125 ) — (3,125 ) Balance a t $ 4,351 $ (2,216 ) $ 1,389 $ 3,524
Reclassifications Out of Accumulated Other Comprehensive Income 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 29 , and September , were as follows: For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations September 29, September 30, September 29, September 30, Details about Accumulated Other Comprehensive Income (in thousands) Available-for-sale Unrealized gains (losses), net of tax of $99, $17, $125, $6, respectively $ 345 $ 57 $ 442 $ (1,411 ) Interest income Defined benefit pension and postretirement plans: Amortization of prior service benefit, net of tax of $11, $18, $32, $53 respectively 37 61 111 184 (a) Total reclassifications, net of tax of $110, $35, $157, $59, respectively $ 382 $ 118 $ 553 $ (1,227 ) Net income (a) The amortization of prior service benefit is included in the computation of net periodic pension cost and postretirement benefit. See Note R: “Retirement Plans.”

Goodwill and Acquired Intangi_2

Goodwill and Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 29, 2019
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 29, 2019 were as follows: Industrial Automation System Test Wireless Test Semiconductor Test Total (in thousands) Balance at December 31, 2018 Goodwill $ 363,358 $ 158,699 $ 361,819 $ 260,540 $ 1,144,416 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 363,358 10,516 7,976 — 381,850 Lemsys acquisition — — — 1,428 1,428 Foreign currency translation adjustment (12,572 ) — — 11 (12,561 ) Balance at September 29, 2019 Goodwill 350,786 158,699 361,819 261,979 1,133,283 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 350,786 $ 10,516 $ 7,976 $ 1,439 $ 370,717
Schedule of Estimated Intangible Assets Amortization Expense	Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Amortization Expense Year (in thousands) 2019 (remainder) 8,694 2020 24,232 2021 14,340 2022 13,447 2023 12,976 Thereafter 22,884
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 29, 2019 Gross Carrying Amount (1) Accumulated Amortization (2) Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 337,198 $ (272,317 ) $ (6,461 ) $ 58,420 Customer relationships 100,313 (89,540 ) (562 ) 10,211 Tradenames and trademarks 64,670 (35,368 ) (1,360 ) 27,942 Total intangible assets $ 502,181 $ (397,225 ) $ (8,383 ) $ 96,573 December 31, 2018 Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount (in thousands) Developed technology $ 336,308 $ (252,080 ) $ (4,079 ) $ 80,149 Customer relationships 97,153 (83,448 ) (340 ) 13,365 Tradenames and trademarks 64,420 (31,653 ) (799 ) 31,968 Non-compete 320 (320 ) — — Backlog 30 (30 ) — — Total intangible assets $ 498,231 $ (367,531 ) $ (5,218 ) $ 125,482

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Sep. 29, 2019
Computation of Basic and Diluted Net Income (Loss) 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 29, September 30, September 29, September 30, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 135,860 $ 119,981 $ 342,395 $ 307,991 Weighted average common shares-basic 169,641 185,744 171,471 190,576 Effect of dilutive potential common shares: Incremental shares from assumed conversion of convertible notes (1) 5,800 3,025 4,117 3,356 Convertible note hedge warrant shares (2) 3,580 108 1,786 646 Restricted stock units 1,313 1,331 1,112 1,406 Stock options 155 275 186 290 Employee stock purchase plan 5 22 13 26 Dilutive potential common shares 10,853 4,761 7,214 5,724 Weighted average common shares-diluted 180,494 190,505 178,685 196,300 Net income per common share-basic $ 0.80 $ 0.65 $ 2.00 $ 1.62 Net income per common share-diluted $ 0.75 $ 0.63 $ 1.92 $ 1.57 (1) Incremental shares from assumed conversion of the convertible notes were calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, 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 note hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, 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. 29, 2019
Defined Benefit Pension Plans
Net Periodic Pension and Postretirement Benefit Costs	For the three and nine months ended September 29, 2019 and September 30, 2018, Teradyne’s net periodic pension cost was comprised of the following: For the Three Months Ended September September 30, 2018 United States Foreign United States Foreign (in thousands) Service cost $ 402 $ 183 $ 538 $ 203 Interest cost 1,797 168 1,750 177 Expected return on plan assets (1,510 ) (7 ) (1,551 ) (5 ) Amortization of prior service cost — — 14 — Settlement loss — — 267 — Total net periodic pension cost $ 689 $ 344 $ 1,018 $ 375 For the Nine Months Ended September 29, 2019 September 30, 2018 United States Foreign United States Foreign (in thousands) Service cost $ 1,206 $ 550 $ 1,657 $ 609 Interest cost 5,392 505 7,188 532 Expected return on plan assets (4,531 ) (21 ) (7,484 ) (15 ) Amortization of prior service cost — — 43 — Net actuarial loss (gain) 252 — (189 ) — Settlement loss — — 345 — Total net periodic pension cost $ 2,319 $ 1,034 $ 1,560 $ 1,126
Postretirement Benefit Plans
Net Periodic Pension and Postretirement Benefit Costs	For the three and nine months ended September 29, 2019 and September 30, 2018, Teradyne’s net periodic postretirement benefit cost was comprised of the following: For the Three Months For the Nine Months Ended September 29, September 30, September 29, September 30, (in thousands) Service cost $ 10 $ 10 $ 31 $ 29 Interest cost 87 49 260 147 Amortization of prior service credit (48 ) (93 ) (143 ) (280 ) Net actuarial loss — — 196 40 Special termination benefits — 601 — 3,419 Total net periodic postretirement benefit cost $ 49 $ 567 $ 344 $ 3,355

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 29, 2019
Reconciliation of Effective Tax Rate	A reconciliation of the United States federal statutory corporate tax rate to Teradyne’s effective tax rate was as follows: For the Three Months Ended For the Nine Months Ended September 29, September 30, September 29, September 30, US statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % Discrete expense related to U.S. transition tax — — 3.9 0.0 Foreign taxes (5.1 ) (4.4 ) (4.9 ) (3.7 ) International provisions of the U.S. Tax Cuts and Jobs (2.8 ) (1.4 ) (0.6 ) (1.4 ) Tax credits (1.8 ) (1.9 ) (2.2 ) (2.1 ) Discrete benefit related to equity compensation (0.7 ) (0.1 ) (1.5 ) (2.2 ) Discrete benefit related to release of reserves for uncertain tax positions — (0.1 ) (6.9 ) — Other, net (0.1 ) 1.7 0.4 2.0 Effective tax rate 10.5 % 14.8 % 9.2 % 13.6 %

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 29, 2019
Segment Information	Segment information for the three and nine months ended September 29, 2019 and September 30, 2018 is as follows: Semiconductor Test Industrial Automation System Test Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended September 29, 2019 Revenues $ 397,737 $ 68,892 $ 73,305 $ 42,264 $ (160 ) $ 582,038 Income (loss) before income taxes (1)(2) 116,633 (1,645 ) 24,381 11,182 1,182 151,733 Total assets (3) 757,422 580,635 126,452 94,789 1,139,493 2,698,791 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 Nine Months Ended September 29, 2019 Revenues $ 1,113,489 $ 209,753 $ 204,934 $ 112,541 $ (402 ) $ 1,640,315 Income (loss) before income taxes (1)(2) 291,037 (10,670 ) 63,254 25,740 7,528 376,889 Total assets (3) 757,422 580,635 126,452 94,789 1,139,493 2,698,791 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 (1) Included in (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 Information by Segment Charges	Included in each 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 29, September 30, September 29, September 30, 2019 2018 2019 2018 (in thousands) Semiconductor Test: Cost of revenues—inventory charge $ 1,867 $ 2,071 $ 5,319 $ 5,851 Restructuring and other—employee severance — 1,716 1,009 7,657 Industrial Automation: Restructuring and other—acquisition related expenses $ — $ 811 $ 1,330 $ 811 Restructuring and other—employee severance — — 604 — Cost of revenues—inventory charge — — 508 680 System Test: Cost of revenues—inventory charge $ — $ — $ 1,129 $ 812 Wireless Test: Cost of revenues—inventory charge $ 724 $ 716 $ 1,892 $ 2,179 Corporate and Other: Restructuring and other—MiR contingent consideration adjustment $ (7,759 ) $ — $ (16,427 ) $ — Selling and administrative – equity modification charge 2,108 — 2,108 — Restructuring and other—acquisition related expenses and compensation 816 — 928 3,318 Restructuring and other—Universal Robots contingent consideration adjustment — (768 ) — (9,236 )

Acquisitions and Investment I_3

Acquisitions and Investment In Other Company - Additional Information (Detail) - USD ($)	Apr. 25, 2018	Feb. 26, 2018	Jan. 30, 2019	Sep. 30, 2018	Sep. 29, 2019	Jun. 03, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Contingent consideration							$ 30,800,000
Goodwill					$ 370,717,000		381,850,000
Estimate of Fair Value Measurement [Member]
Business Acquisition [Line Items]
Contingent consideration					18,080,000		$ 70,543,000
Revenues				$ 400,000
Real War In [Member]
Business Acquisition [Line Items]
Equity Method Investments						$ 15,000,000
Investments, Fair Value Disclosure					15,000,000
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Total preliminary purchase price	$ 197,778,000
Cash paid to acquire outstanding common and preferred stock	145,200,000
Contingent consideration	52,600,000
Arrangement range of outcomes value high					$ 81,000,000
Goodwill, not deductible for tax purposes	136,000,000
Net income				306,768,000
Goodwill	$ 135,976,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 2 months 12 days
Mobile Industrial Robots (MiR) | Acquisition Related Costs
Business Acquisition [Line Items]
Net income				$ 2,900,000
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
Lemsys [Member]
Business Acquisition [Line Items]
Total preliminary purchase price			$ 1,400,000
Total preliminary purchase price			9,100,000
Acquired value of intangible assets			$ 4,600,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			5 years 2 months 12 days
Net tangible assets			$ 3,100,000

Final Allocation of Purchase Pr

Final Allocation of Purchase Price (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018	Apr. 25, 2018
Business Acquisition [Line Items]
Goodwill	$ 370,717	$ 381,850
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Goodwill			$ 135,976
Intangible assets			80,670
Current assets			6,039
Non-current assets			1,336
Accounts payable and current liabilities			(7,336)
Long-term deferred tax liabilities			(18,007)
Other long-term liabilities			(900)
Total purchase price			$ 197,778

Components of Intangible Assets

Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date (Detail) - Mobile Industrial Robots (MiR) $ in Thousands	Apr. 25, 2018USD ($)
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 80,670
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) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)$ / shares
Business Acquisition [Line Items]
Revenue | $	$ 1,588,042
Net income | $	$ 306,768
Net income per common share, basic | $ / shares	$ 1.61
Net income per common share, diluted | $ / shares	$ 1.56

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Revenue recognized in accordance with ASC 606	$ 582,038	$ 566,848	$ 1,640,315	$ 1,581,244
Revenue on leases	1,500	2,300	4,900	10,200
Deferred Revenue And Customer Advances	14,200	24,500	47,600	70,900
Trade Accounts Receivable	$ 113,400	$ 10,600	$ 113,400	$ 10,600
Short-term Contract with Customer [Member]
Revenue, Remaining Performance Obligation, Percentage	69.00%		69.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period			12 months
Long-term Contract with Customer [Member]
Revenue, Remaining Performance Obligation, Percentage	26.00%		26.00%
Long-term Contract with Customer [Member] | Maximum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period			3 years
Long-term Contract with Customer [Member] | Minimum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period			1 year
Accounting Standards Update 2014-09 [Member]
Revenue recognized in accordance with ASC 606	$ 580,600		$ 1,635,500

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total	$ 582,038	$ 566,848	$ 1,640,315	$ 1,581,244
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	397,737	417,297	1,113,489	1,150,712
System Test
Disaggregation of Revenue [Line Items]
Total	73,305	49,606	204,934	162,308
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	68,892	65,913	209,753	176,803
Wireless Test
Disaggregation of Revenue [Line Items]
Total	42,264	34,304	112,541	92,023
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(160)	(272)	(402)	(602)
Americas | Point in Time
Disaggregation of Revenue [Line Items]
Total	61,604	54,810	180,802	153,293
Americas | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	5,621	3,820	12,961	13,515
Americas | Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(160)	(272)	(402)	(602)
Americas | Over Time
Disaggregation of Revenue [Line Items]
Total	16,932	16,825	51,929	50,820
Americas | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	723	146	1,550	379
Europe, Middle East and Africa | Point in Time
Disaggregation of Revenue [Line Items]
Total	44,052	45,788	138,225	132,206
Europe, Middle East and Africa | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,220	1,504	2,575	2,570
Europe, Middle East and Africa | Over Time
Disaggregation of Revenue [Line Items]
Total	8,648	8,709	25,519	25,650
Europe, Middle East and Africa | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	48	318	140	802
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	1,453	2,290	4,852	10,183
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	75	171	140	684
Asia Pacific | Point in Time
Disaggregation of Revenue [Line Items]
Total	403,345	393,979	1,100,453	1,079,239
Asia Pacific | Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	33,032	26,851	91,029	68,180
Asia Pacific | Over Time
Disaggregation of Revenue [Line Items]
Total	46,004	44,447	138,535	129,853
Asia Pacific | Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	1,545	1,494	4,146	5,893
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	325,766	330,407	934,987	924,702
SOC | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	6,307	8,866	21,830	30,577
SOC | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	8,497	8,810	24,862	26,536
SOC | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	6,894	9,728	27,934	32,079
SOC | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	5,189	5,336	15,681	16,240
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	1,290	2,047	4,487	9,162
SOC | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	259,909	258,898	727,035	702,097
SOC | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	37,680	36,722	113,158	108,011
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	71,971	86,890	178,502	226,010
Memory | Americas | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	3,464	4,600	19,574	10,291
Memory | Americas | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	621	686	2,056	2,092
Memory | Europe, Middle East and Africa | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	274	2,080	2,443	3,066
Memory | Europe, Middle East and Africa | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	255	301	819	824
Memory | Asia Pacific | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	63,483	76,429	143,163	202,336
Memory | Asia Pacific | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	3,874	2,794	10,447	7,401
Defense/Aerospace | System Test
Disaggregation of Revenue [Line Items]
Total	30,284	23,269	78,336	66,533
Defense/Aerospace | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	22,861	15,423	54,870	42,276
Defense/Aerospace | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	5,814	6,037	19,116	18,462
Defense/Aerospace | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	742	161	992	2,104
Defense/Aerospace | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	469	505	1,442	1,596
Defense/Aerospace | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	99	931	525	1,417
Defense/Aerospace | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	299	212	1,391	678
Storage Test | System Test
Disaggregation of Revenue [Line Items]
Total	26,424	12,032	80,362	57,224
Storage Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,232	0	7,528	284
Storage Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	22,696	9,916	66,974	51,863
Storage Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,496	2,116	5,860	5,077
Production Board Test | System Test
Disaggregation of Revenue [Line Items]
Total	16,597	14,305	46,236	38,551
Production Board Test | Americas | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	2,165	2,625	6,760	5,814
Production Board Test | Americas | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	796	789	2,317	2,342
Production Board Test | Europe, Middle East and Africa | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	4,354	3,223	12,391	12,109
Production Board Test | Europe, Middle East and Africa | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	1,613	1,510	4,782	4,781
Production Board Test | Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	88	72	225	337
Production Board Test | Asia Pacific | Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	6,751	5,201	17,235	10,804
Production Board Test | Asia Pacific | Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	830	885	2,526	2,364
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	58,458	58,552	177,673	164,247
Universal Robots (UR) | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	16,294	17,834	48,529	48,025
Universal Robots (UR) | Americas | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	293	190	793	431
Universal Robots (UR) | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	25,557	26,445	78,007	75,631
Universal Robots (UR) | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	459	282	1,274	675
Universal Robots (UR) | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	15,575	13,656	48,284	39,135
Universal Robots (UR) | Asia Pacific | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	280	145	786	350
MiR | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	9,631	6,544	29,243	11,053
MiR | Americas | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,820	1,810	9,152	3,009
MiR | Europe, Middle East and Africa | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	5,011	2,647	13,883	4,647
MiR | Asia Pacific | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,800	2,087	6,208	3,397
Energid Technologies Corporation | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	803	817	2,837	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	188	167	1,235	578
Energid Technologies Corporation | Europe, Middle East and Africa | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 615	457	1,381	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	$ 221	$ 79

Composition of Inventories, Net

Composition of Inventories, Net (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Inventory [Line Items]
Raw material	$ 114,162	$ 89,365
Work-in-process	28,460	31,014
Finished goods	35,581	33,162
Inventories, net	$ 178,203	$ 153,541

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Sep. 29, 2019	Dec. 31, 2018
Inventory [Line Items]
Inventory reserves	$ 101.2	$ 100.8

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2018
Financial Instruments and Fair Value [Line Items]
Available-for-sale securities, realized gain	$ 500,000	$ 200,000	$ 700,000	$ 600,000
Available-for-sale securities, realized loss			200,000	1,600,000
Available-for-sale marketable securities, Fair Market Value of Investments in debt securities with Unrealized Losses	60,747,000		60,747,000		$ 191,978,000
Fair market value of investments with unrealized losses greater than one year	4,900,000		4,900,000		28,500,000
Aggregate loss of investments with unrealized losses greater than one year	100,000		100,000		1,600,000
Fair market value of investments with unrealized losses less than one year	55,800,000		55,800,000		163,500,000
Aggregate loss of investments with unrealized losses less than one year	100,000		100,000		1,400,000
Unrealized Gain (loss) on contracts	1,500,000	3,700,000	3,400,000	1,200,000
Equity securities unrealized gain loss		$ 1,000,000		$ 1,400,000
Equity securities unrealized gain	100,000		3,800,000
Equity securities unrealized loss	200,000		200,000
Debt Mutual Funds
Financial Instruments and Fair Value [Line Items]
Available for sale securities with out contractual maturity date	4,000,000		4,000,000
Mobile Industrial Robots (MiR)
Financial Instruments and Fair Value [Line Items]
Maximum amount of contingent consideration paid for acquisition	$ 81,000,000		81,000,000
Foreign Exchange Contracts
Financial Instruments and Fair Value [Line Items]
Unrealized Gain (loss) on contracts			$ 114,900,000		$ 163,100,000

Schedule of Fair Value of Finan

Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 420,095	$ 256,636
Contingent consideration		30,800
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	185,025	109,721
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	117,714	86,117
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	90,898	40,020
Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	14,086	7,604
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	8,024	9,611
Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,968	3,187
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	380	376
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,040,035	1,204,579
Derivative assets	119	79
Total	1,040,154	1,204,658
Contingent consideration	18,080	70,543
Derivative liabilities	489	514
Total	18,569	71,057
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	257,235	312,512
Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	336,704	614,240
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	185,025	109,721
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	117,714	86,117
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	90,898	40,020
Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	14,086	7,604
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	8,024	9,611
Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	3,968	3,187
Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	380	376
Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	26,001	21,191
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	485,723	590,415
Total	485,723	590,415
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	257,235	312,512
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	198,519	253,525
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 securities	3,968	3,187
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	26,001	21,191
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	554,312	614,164
Derivative assets	119	79
Total	554,431	614,243
Derivative liabilities	489	514
Total	489	514
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	138,185	360,715
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 securities	185,025	109,721
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 securities	117,714	86,117
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 securities	90,898	40,020
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 securities	14,086	7,604
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 securities	8,024	9,611
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 securities	380	376
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration	18,080	70,543
Total	$ 18,080	$ 70,543

Schedule of Reported Financial

Schedule of Reported Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	$ 1,040,154	$ 1,204,658
Liabilities	18,569	71,057
Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	489	514
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	593,939	926,752
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	342,538	190,096
Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	103,558	87,731
Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	119	79
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	6,297	34,865
Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	11,783	35,678
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	485,723	590,415
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	455,754	566,037
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	29,969	24,378
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	554,431	614,243
Liabilities	489	514
Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	489	514
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	138,185	360,715
Significant Other Observable Inputs (Level 2) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	342,538	190,096
Significant Other Observable Inputs (Level 2) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	73,589	63,353
Significant Other Observable Inputs (Level 2) | Prepayments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	119	79
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	18,080	70,543
Significant Unobservable Inputs (Level 3) | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	6,297	34,865
Significant Unobservable Inputs (Level 3) | Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	$ 11,783	$ 35,678

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 26,847	$ 60,914	$ 70,543	$ 45,102
Acquisition of MiR	[1]	(7,759)	(768)	(16,460)	(9,236)
Foreign currency impact		(1,008)	796	(1,413)	(1,770)
Payments	[2]			(34,590)	(24,553)
Fair value adjustment					51,399
Balance at end of period		$ 18,080	$ 60,942	$ 18,080	$ 60,942
[1]	In the three and nine months ended September 29, 2019, the fair value of contingent consideration for the earn-out in connection with the acquisition of MiR was decreased by $7.8 million and $16.5 million, respectively, primarily due to a decrease in the forecasted revenue, partially offset by impact from the modification, in the three months ended September 29, 2019, of the earn-out structure. 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 A/S (“Universal Robots”) was decreased by $0.8 million and $9.2 million, respectively, primarily due to a decrease in forecasted revenue.
[2]	In the nine months ended September 29, 2019, Teradyne paid $30.8 million and $3.8 million of contingent consideration for the earn-outs in connection with the acquisition of MiR and Universal Robots, respectively. 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.

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			$ 27,615	$ 13,571
Increase (decrease) in contingent consideration	$ 7,800	$ 800	(16,460)	$ (9,236)
Universal Robots (UR)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration	800		9,200
Increase (decrease) in contingent consideration		$ 24,600
Universal Robots (UR) | Payment One [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			7,800
Universal Robots (UR) | Payment Two [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			16,500
MiR
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Increase (decrease) in contingent consideration	$ 30,800		3,800
MiR | Payment One [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			7,800
MiR | Payment Two [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			$ 16,500

Quantitative Information Associ

Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 29, 2019	Dec. 31, 2018	Apr. 25, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 30,800
Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration			$ 52,600
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility	15.00%
Discount rate	0.10%
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 18,080

Schedule of Carrying Amounts an

Schedule of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Sep. 29, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Marketable securities		$ 420,095	$ 256,636
Contingent consideration			30,800
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		593,939	926,752
Marketable securities		446,096	277,827
Derivative assets		119	79
Contingent consideration		18,080	70,543
Derivative liabilities		489	514
Convertible debt	[1]	390,942	379,981
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		593,939	926,752
Marketable securities		446,096	277,827
Derivative assets		119	79
Contingent consideration		18,080	70,543
Derivative liabilities		489	514
Convertible debt	[1]	$ 867,388	$ 547,113
[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. 29, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 414,857	$ 259,011
Available-for-sale marketable securities, Unrealized Gain	5,343	592
Available-for-sale marketable securities, Unrealized (Loss)	(105)	(2,967)
Available-for-sale marketable securities, Fair Market Value	420,095	256,636
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	60,747	191,978
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	184,229	110,969
Available-for-sale marketable securities, Unrealized Gain	847	112
Available-for-sale marketable securities, Unrealized (Loss)	(51)	(1,360)
Available-for-sale marketable securities, Fair Market Value	185,025	109,721
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	25,814	75,040
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	117,618	86,130
Available-for-sale marketable securities, Unrealized Gain	99	13
Available-for-sale marketable securities, Unrealized (Loss)	(3)	(26)
Available-for-sale marketable securities, Fair Market Value	117,714	86,117
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	30,704	85,094
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	86,718	41,133
Available-for-sale marketable securities, Unrealized Gain	4,229	432
Available-for-sale marketable securities, Unrealized (Loss)	(49)	(1,545)
Available-for-sale marketable securities, Fair Market Value	90,898	40,020
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	3,079	24,767
Certificates of Deposit and Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	14,083	7,604
Available-for-sale marketable securities, Unrealized Gain	3
Available-for-sale marketable securities, Fair Market Value	14,086	7,604
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	8,009	9,646
Available-for-sale marketable securities, Unrealized Gain	17	1
Available-for-sale marketable securities, Unrealized (Loss)	(2)	(36)
Available-for-sale marketable securities, Fair Market Value	8,024	9,611
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	1,150	7,077
Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	3,820	3,153
Available-for-sale marketable securities, Unrealized Gain	148	34
Available-for-sale marketable securities, Fair Market Value	3,968	3,187
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	380	376
Available-for-sale marketable securities, Fair Market Value	$ 380	$ 376

Schedule of Reported Available

Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 414,857	$ 259,011
Available-for-sale marketable securities, Unrealized Gain	5,343	592
Available-for-sale marketable securities, Unrealized (Loss)	(105)	(2,967)
Available-for-sale marketable securities, Fair Market Value	420,095	256,636
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	60,747	191,978
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	342,234	190,100
Available-for-sale marketable securities, Unrealized Gain	313	88
Available-for-sale marketable securities, Unrealized (Loss)	(9)	(92)
Available-for-sale marketable securities, Fair Market Value	342,538	190,096
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	46,115	140,262
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	72,623	68,911
Available-for-sale marketable securities, Unrealized Gain	5,030	504
Available-for-sale marketable securities, Unrealized (Loss)	(96)	(2,875)
Available-for-sale marketable securities, Fair Market Value	77,557	66,540
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 14,632	$ 51,716

Contractual Maturities of Inves

Contractual Maturities of Investments in Debt Securities Held (Detail) $ in Thousands	Sep. 29, 2019USD ($)
Schedule of Available-for-sale Securities
Due within one year, cost	$ 342,234
Due after 1 year through 5 years, cost	16,609
Due after 5 years through 10 years, cost	15,002
Due after 10 years, cost	37,192
Total, cost	411,037
Due within one year, fair market value	342,538
Due after 1 year through 5 years, fair market value	16,718
Due after 5 years through 10 years, fair market value	15,297
Due after 10 years, fair maket value	41,574
Total, fair market value	$ 416,127

Schedule of Derivative Instrume

Schedule of Derivative Instruments in Statement of Financial Position at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	$ (370)	$ (435)
Not Designated as Hedging Instrument | Foreign currency forward contracts | Prepayments
Derivatives, Fair Value [Line Items]
Derivative assets	119	79
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ (489)	$ (514)

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses (Gains) on derivatives recognized in statements of operations	$ 3,699	$ (899)	$ 7,872	$ 2,502

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on foreign currency transactions	$ 1.5	$ 3.7	$ 3.4	$ 1.2

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 29, 2019	Sep. 29, 2019	Jan. 01, 2019	Feb. 28, 2016
Total lease expense	$ 9,100	$ 26,600
Variable lease costs	3,000	8,300
Operating Lease, Right-of-Use Asset	57,595	57,595	$ 50,100	$ 50,100
Operating Lease, Liability	$ 65,199	$ 65,199	$ 54,300	$ 54,300
Operating Lease, Weighted Average Remaining Lease Term	4 years 8 months 12 days	4 years 8 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	5.00%	5.00%
Short-term Lease, Cost	$ 700	$ 2,200

Supplemental Cash Flow Informat

Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 29, 2019	Sep. 29, 2019
Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows	$ 4,946	$ 14,998
Right-of-use assets obtained in exchange for new lease obligations	$ 8,315	$ 23,727

Schedule of Operating Lease, Ma

Schedule of Operating Lease, Maturity (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Jan. 01, 2019	Feb. 28, 2016
2019	$ 5,520
2020	20,368
2021	16,045
2022	11,603
2023	6,135
Thereafter	13,285
Total lease payments	72,956
Less imputed interest	(7,757)
Total lease liabilities	65,199	$ 54,300	$ 54,300
2019	19,570
2020	18,293
2021	13,578
2022	9,693
2023	5,449
Thereafter	9,472
Total lease payments	$ 76,055

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, $ in Thousands, shares in Millions	Dec. 12, 2016USD ($)Customershares	Sep. 29, 2019USD ($)$ / shares	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)shares	Jun. 27, 2019USD ($)	Dec. 31, 2016USD ($)$ / shares
Debt Instrument
Repurchase of common stock		$ 368,782	$ 562,263
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Aggregate principal amount	$ 460,000	$ 460,000		$ 460,000
Debt instrument, interest rate, stated percentage	1.25%
Debt instrument, net proceeds after issuance costs	$ 450,800
Payment for net cost of convertible note hedges net of warrant proceeds	33,000
Repurchase of common stock	$ 50,100
Repurchase of stock, shares | shares	2
Senior notes maturity date	Dec. 15, 2023
Debt instrument, frequency of periodic payment	payable semiannually 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 price | $ / shares						$ 31.70
Shares that would be issued upon conversion | shares				14.5
Strike price per share of warrant | $ / shares		$ 39.78
Debt instrument, convertible, carrying amount of equity component		$ 100,800
Financing cost		$ 4,600				$ 7,200
Debt issuance costs, amortization period		7 years
Unamortized discount		$ 69,100
Debt Instrument, convertible, remaining discount amortization period		4 years 3 months 18 days
Value of notes converted		$ 832,900
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Conversion option one
Debt Instrument
Trading days measurement period | Customer	20
Consecutive trading days measurement period | Customer	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 | Customer	5
Consecutive trading days measurement period | Customer	5
Percentage of closing sale price of common stock and conversion rate product	98.00%
Revolving Credit Facility | Maximum
Debt Instrument
Credit facility, borrowing capacity					$ 350,000

Components of Convertible Senio

Components of Convertible Senior Notes (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018	Dec. 12, 2016
Debt Instrument
Net carrying amount of convertible debt	$ 390,942	$ 379,981
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Debt principal	460,000	460,000	$ 460,000
Unamortized discount	69,058	80,019
Net carrying amount of convertible debt	$ 390,942	$ 379,981

Interest Expense on Convertible

Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Debt Instrument
Contractual interest expense on the coupon	$ 1,438	$ 1,438	$ 4,313	$ 4,313
Amortization of the discount component and debt issue fees recognized as interest expense	3,699	3,520	10,961	10,431
Total interest expense on the convertible debt	$ 5,137	$ 4,958	$ 15,274	$ 14,744

Schedule of Prepayments and Oth

Schedule of Prepayments and Other Assets (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Prepaid And Other Current Assets [Line Items]
Contract manufacturer and supplier prepayments	$ 136,470	$ 131,642
Prepaid taxes	9,754	9,646
Prepaid maintenance and other services	8,310	8,487
Other prepayments	17,180	12,744
Total prepayments	$ 171,714	$ 162,519

Deferred Revenue and Customer_3

Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Dec. 31, 2017
Deferred Revenue Arrangement
Maintenance and training	$ 61,048		$ 58,362
Extended warranty	29,937	$ 28,716	27,422	$ 27,617	$ 25,971	$ 24,438
Customer advances, undelivered performance obligations and other	47,543		24,677
Total deferred revenue and customer advances	$ 138,528		$ 110,461

Warranty Accrual Included in Ot

Warranty Accrual Included in Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 8,133	$ 7,136	$ 7,909	$ 8,200
Acquisition			14	41
Accruals for warranties issued during the period	3,508	2,760	10,008	9,171
Accruals related to pre-existing warranties	1,132	282	3,156	109
Settlements made during the period	(4,265)	(2,675)	(12,579)	(10,018)
Balance at end of period	$ 8,508	$ 7,503	$ 8,508	$ 7,503

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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 28,716	$ 25,971	$ 27,422	$ 24,438
Deferral of new extended warranty revenue	5,666	7,232	16,962	19,072
Recognition of extended warranty deferred revenue	(4,445)	(5,586)	(14,447)	(15,893)
Balance at end of period	$ 29,937	$ 27,617	$ 29,937	$ 27,617

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Jul. 17, 2019	Jan. 31, 2019	Jan. 31, 2018	Sep. 29, 2019	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Minimum age of retirement to be eligible for PRSUs					60 years
Estimated annual dividend amount per share					$ 0.36	$ 0.36
Stock Based Compensation Relating To Retirement Agreement				$ 2.1	$ 2.1
CEO Gregory Beecher [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Date Of Retirement	Jul. 17, 2019
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 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					$ 51.51	$ 54.85
Stock price		$ 37.95					$ 47.70
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	$ 0.36
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					$ 36.88	$ 46.62
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					0.7	0.6
Weighted average grant date fair value of restricted stock units granted					$ 36.85
Weighted average grant date fair value of restricted stock units granted						$ 46.25
Service-Based Restricted Stock Units | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted						0.1
Weighted average grant date fair value of restricted stock units granted						$ 12.17
Service-Based Restricted Stock Units | Non Employee Directors
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					$ 48.03	$ 35.81
Service-Based Restricted Stock Units | CEO Gregory Beecher [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Description Of Vesting Agreement	unvested time-based restricted stock units and stock options granted prior to 2019 were modified to allow continued vesting; unvested time-based restricted stock units and stock options granted in 2019 were modified to allow continued vesting through January 31, 2023 (the “Non-Competition Period”) in a pro-rated amount based on the number of days that Mr. Beecher was employed during 2019
Service Based Stock Options | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average grant date fair value of restricted stock units granted					$ 10.61
Number options granted during the period					0.1
Performance Shares | CEO Gregory Beecher [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Description Of Vesting Agreement	unvested, performance-based restricted stock units awarded in 2019 will vest on the date the amount of shares underlying the performance-based restricted stock units are determined in a pro-rated amount of shares based on the number of days that Mr. Beecher was employed during 2019

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. 29, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Risk-free interest rate	2.60%	2.20%
Expected historical volatility	31.90%	26.80%
Dividend yield	1.00%	0.80%
New York Stock Exchange Composite Index
Share-based Compensation Arrangement by Share-based Payment Award
Expected historical volatility	11.90%	12.40%

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. 29, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	5 years	5 years
Risk-free interest rate	2.50%	2.40%
Volatility-historical	30.10%	26.40%
Dividend yield	1.00%	0.80%

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,479,412	$ 1,739,940	$ 1,522,354	$ 1,953,646
Other comprehensive (loss) income	(16,630)	7,029	(11,181)	(12,896)
Less: reclassification adjustment for (gains) losses included in net income, net of tax	(345)	(57)	(442)	1,411
Balance	1,482,635	1,667,760	1,482,635	1,667,760
ASU 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: reclassification adjustment for (gains) losses included in net income, net of tax				(3,125)
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(12,523)	15,919
Other comprehensive loss before reclassifications, net of tax			(17,019)	(11,568)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax
Other comprehensive (loss) income			(17,019)	(11,568)
Balance	(29,542)	4,351	(29,542)	4,351
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(1,845)	1,362
Other comprehensive loss before reclassifications, net of tax			6,391	(2,555)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax			(442)	1,411
Other comprehensive (loss) income			5,949	(1,144)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax				691
Less: reclassification adjustment for (gains) losses included in net income, net of tax				(3,125)
Balance	4,104	(2,216)	4,104	(2,216)
Amortization of Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			1,328	1,495
Other comprehensive loss before reclassifications, net of tax
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(37)	(61)	(111)	(184)
Other comprehensive (loss) income			(111)	(184)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax				78
Balance	1,217	1,389	1,217	1,389
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(7,591)	(3,504)	(13,040)	18,776
Other comprehensive loss before reclassifications, net of tax			(10,628)	(14,123)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(382)	(118)	(553)	(769)
Other comprehensive (loss) income	(16,630)	7,028	(11,181)	(12,896)
Reclassification of tax effects resulting from the Tax Reform Act, net of tax				769
Balance	$ (24,221)	$ 3,524	$ (24,221)	$ 3,524

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss), tax	$ (110)	$ (35)	$ (157)	$ (59)
Reclassification of unrealized gains on equity securities, net of tax	(99)	(17)	(125)	(6)
Foreign currency translation adjustments, tax	0	0	0	0	$ 0	$ 0
Unrealized (losses) gains on marketable securities, tax	1,116	(590)	1,116	(590)	(521)	1,815
Retirement plans prior service benefit, tax	(1,113)	(1,063)	(1,113)	(1,063)	$ (1,081)	$ (932)
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
Reclassification of unrealized gains on equity securities, net of tax				0
Unrealized (Losses) Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax			1,762	(806)
Amounts reclassified from accumulated other comprehensive income (loss), tax	(99)	(17)	(125)	(6)
Other comprehensive income (loss), tax			1,637	(812)
Reclassification of income tax effects from the Tax Reform Act, net of tax				(691)
Reclassification of unrealized gains on equity securities, net of tax				(902)
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	$ (11)	$ (18)	(32)	(53)
Other comprehensive income (loss), tax			$ (32)	(53)
Reclassification of income tax effects from the Tax Reform Act, net of tax				(78)
Reclassification of unrealized gains on equity securities, net of tax				$ 0

Reclassifications Out of Accumu

Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)	$ 345	$ 57	$ 442	$ (1,411)
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	37	61	111	184
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	$ 382	$ 118	$ 553	$ 769

Reclassifications Out of Accu_2

Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 110	$ 35	$ 157	$ 59
Unrealized (Losses) Gains on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	99	17	125	6
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 11	$ 18	$ 32	$ 53

Goodwill and Acquired Intangi_3

Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Line Items]
Acquired intangible assets amortization	$ 9,647	$ 11,142	$ 30,363	$ 28,633

Changes in Carrying Amount of G

Changes in Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Sep. 29, 2019
Goodwill [Line Items]
Goodwill acquisition	$ 1,428
Foreign currency translation adjustment	(12,561)
Goodwill	1,144,416	$ 1,133,283
Accumulated impairment losses	(762,566)	(762,566)
Goodwill	381,850	370,717
Industrial Automation
Goodwill [Line Items]
Foreign currency translation adjustment	(12,572)
Goodwill	363,358	350,786
Accumulated impairment losses	0	0
Goodwill	363,358	350,786
Wireless Test
Goodwill [Line Items]
Goodwill	361,819	361,819
Accumulated impairment losses	(353,843)	(353,843)
Goodwill	7,976	7,976
Semiconductor Test
Goodwill [Line Items]
Goodwill acquisition	1,428
Foreign currency translation adjustment	11
Goodwill	260,540	261,979
Accumulated impairment losses	(260,540)	(260,540)
Goodwill		1,439
System Test
Goodwill [Line Items]
Goodwill	158,699	158,699
Accumulated impairment losses	(148,183)	(148,183)
Goodwill	$ 10,516	$ 10,516

Schedule of Amortizable Intangi

Schedule of Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 29, 2019		Dec. 31, 2018
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 502,181	[1]	$ 498,231
Accumulated Amortization	(397,225)	[1]	(367,531)
Foreign Currency Translation Adjustment	(8,383)		(5,218)
Net Carrying Amount	96,573		125,482
Developed technology
Finite-Lived Intangible Assets
Gross Carrying Amount	337,198	[1]	336,308
Accumulated Amortization	(272,317)	[1]	(252,080)
Foreign Currency Translation Adjustment	(6,461)		(4,079)
Net Carrying Amount	58,420		80,149
Customer Relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	100,313	[1]	97,153
Accumulated Amortization	(89,540)	[1]	(83,448)
Foreign Currency Translation Adjustment	(562)		(340)
Net Carrying Amount	10,211		13,365
Trademarks and tradenames
Finite-Lived Intangible Assets
Gross Carrying Amount	64,670	[1]	64,420
Accumulated Amortization	(35,368)	[1]	(31,653)
Foreign Currency Translation Adjustment	(1,360)		(799)
Net Carrying Amount	$ 27,942		31,968
Non-compete Agreements
Finite-Lived Intangible Assets
Gross Carrying Amount			320
Accumulated Amortization			(320)
Backlog
Finite-Lived Intangible Assets
Gross Carrying Amount			30
Accumulated Amortization			$ (30)
[1]	$0.7 million of amortizable intangible assets became fully amortized and have been eliminated from the gross carrying amount and accumulated amortization.

Schedule of Amortizable Intan_2

Schedule of Amortizable Intangible Assets (Parenthetical) (Detail) $ in Millions	9 Months Ended
	Sep. 29, 2019USD ($)
Intangible Assets [Member]
Finite-Lived Intangible Assets
Impairment of intangible assets	$ 0.7
Lemsys [Member]
Finite-Lived Intangible Assets
Intangible assets acquired	$ 4.6

Schedule of Estimated Intangibl

Schedule of Estimated Intangible Asset Amortization Expense (Detail) $ in Thousands	Sep. 29, 2019USD ($)
Finite-Lived Intangible Assets
2019 (remainder)	$ 8,694
2020	24,232
2021	14,340
2022	13,447
2023	12,976
Thereafter	$ 22,884

Computation of Basic and Dilute

Computation of Basic and Diluted Net (Loss) Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 135,860	$ 119,981	$ 342,395	$ 307,991
Weighted average common shares-basic		169,641	185,744	171,471	190,576
Incremental shares from assumed conversion of convertible notes	[1]	5,800	3,025	4,117	3,356
Convertible note hedge warrant shares	[2]	3,580	108	1,786	646
Employee stock purchase plan		5	22	13	26
Dilutive potential common shares		10,853	4,761	7,214	5,724
Weighted average common shares-diluted		180,494	190,505	178,685	196,300
Net income per common share-basic		$ 0.80	$ 0.65	$ 2	$ 1.62
Net income per common share-diluted		$ 0.75	$ 0.63	$ 1.92	$ 1.57
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,313	1,331	1,112	1,406
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		155	275	186	290
[1]	Incremental shares from assumed conversion of the convertible notes were calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.70, 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 note hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.78, 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 (Loss) Income Per Common Share (Parenthetical) (Detail) shares in Millions	9 Months Ended
	Sep. 29, 2019$ / sharesshares
Convertible Notes
Net Income Loss Per Common Share
Initial debt conversion price | $ / shares	$ 31.70
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	$ 39.78
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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Employee Stock Option [Member]
Net Income Loss Per Common Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.1		0.1
Restricted Stock Units (RSUs) [Member]
Net Income Loss Per Common Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0.5	0.2	0.5

Restructuring and Other - Addit

Restructuring and Other - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Restructuring Cost and Reserve
Contingent consideration adjustment	$ 7,800	$ 800	$ (16,460)	$ (9,236)
Acquisition related costs	500	800	2,300	4,100
Wireless Test
Restructuring Cost and Reserve
Impairment charges fixed assets	300		300
Semiconductor Test
Restructuring Cost and Reserve
Severance benefit and charges	$ 500	$ 1,700		$ 7,900
Semiconductor Test, Industrial Automation and Corporate
Restructuring Cost and Reserve
Severance benefit and charges			$ 2,100

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 29, 2019USD ($)
United States Plans
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans	$ 2.1
U.S. Supplemental Executive Defined Benefit Pension Plan
Defined Benefit Plan Disclosure
Contribution to defined benefit pension plans	$ 0.6

Schedule of Net Periodic Pensio

Schedule of Net Periodic Pension and Postretirement (income) Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure
Net actuarial (gain) loss			$ 448	$ 196
UNITED STATES
Defined Benefit Plan Disclosure
Service cost	$ 402	$ 538	1,206	1,657
Interest cost	1,797	1,750	5,392	7,188
Expected return on plan assets	(1,510)	(1,551)	(4,531)	(7,484)
Amortization of prior service cost		14		43
Net actuarial (gain) loss			252	(189)
Settlement loss		267		345
Total net periodic pension cost	689	1,018	2,319	1,560
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Service cost	183	203	550	609
Interest cost	168	177	505	532
Expected return on plan assets	(7)	(5)	(21)	(15)
Total net periodic pension cost	344	375	1,034	1,126
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Service cost	10	10	31	29
Interest cost	87	49	260	147
Amortization of prior service cost	(48)	(93)	(143)	(280)
Net actuarial (gain) loss			196	40
Special termination benefits		601		3,419
Total net periodic pension cost	$ 49	$ 567	$ 344	$ 3,355

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Sep. 29, 2019USD ($)
Purchase Commitment, Excluding Long-term Commitment
Aggregate purchase commitments	$ 360.3
Purchase commitments less than one year	$ 354.2

Schedule of Reconciliation of E

Schedule of Reconciliation of Effective Tax Rate (Detail)	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Income Tax Disclosure [Line Items]
US statutory federal tax rate	21.00%	21.00%	21.00%	21.00%
Discrete expense related to U.S. transition tax			3.90%	0.00%
Foreign taxes	(5.10%)	(4.40%)	(4.90%)	(3.70%)
International provisions of the U.S. Tax Cuts and Jobs Act of 2017	(2.80%)	(1.40%)	(0.60%)	(1.40%)
Tax credits	(1.80%)	(1.90%)	(2.20%)	(2.10%)
Discrete benefit related to equity compensation	(0.70%)	(0.10%)	(1.50%)	(2.20%)
Discrete benefit related to release of reserves for uncertain tax positions		(0.10%)	(6.90%)
Other, net	(0.10%)	1.70%	0.40%	2.00%
Effective tax rate	10.50%	14.80%	9.20%	13.60%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Taxes [Line Items]
Tax savings due to the tax holiday	$ 12	$ 8.9
Tax savings due to the tax holiday, per share	$ 0.07	$ 0.05
Reduction in un recognized tax benefits	$ 22.4
Accrued interest and penalties	0.5		$ 0.3
Interest and penalties related to income tax, expense (benefit)	0.2	$ 0.1
Uncertain tax positions	13.6		$ 43.4
Net decrease in uncertain tax positions	29.8
Minimum [Member]
Income Taxes [Line Items]
Potential tax reserve	5
Maximum [Member]
Income Taxes [Line Items]
Potential tax reserve	11
Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Net decrease in uncertain tax positions	$ 7.2

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 29, 2019Segment
Segment Reporting Information [Line Items]
Number of Operating Segments	4

Schedule of Segment Information

Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 29, 2019		Sep. 30, 2018		Sep. 29, 2019		Sep. 30, 2018		Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 582,038		$ 566,848		$ 1,640,315		$ 1,581,244
Income (loss) before income taxes	[1],[2]	151,733		140,844		376,889		356,675
Total assets		2,698,791	[3]	2,882,487	[3]	2,698,791	[3]	2,882,487	[3]	$ 2,706,606
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		397,737		417,297		1,113,489		1,150,712
Income (loss) before income taxes	[1],[2]	116,633		126,638		291,037		305,876
Total assets	[3]	757,422		709,616		757,422		709,616
System Test
Segment Reporting Information [Line Items]
Revenues		73,305		49,606		204,934		162,308
Income (loss) before income taxes	[1],[2]	24,381		9,056		63,254		35,296
Total assets	[3]	126,452		83,160		126,452		83,160
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		68,892		65,913		209,753		176,803
Income (loss) before income taxes	[1],[2]	(1,645)		940		(10,670)		(1,198)
Total assets	[3]	580,635		617,741		580,635		617,741
Wireless Test
Segment Reporting Information [Line Items]
Revenues		42,264		34,304		112,541		92,023
Income (loss) before income taxes	[1],[2]	11,182		7,843		25,740		18,615
Total assets	[3]	94,789		79,986		94,789		79,986
Corporate And Others [Member]
Segment Reporting Information [Line Items]
Revenues		(160)		(272)		(402)		(602)
Income (loss) before income taxes	[1],[2]	1,182		(3,633)		7,528		(1,914)
Total assets	[3]	$ 1,139,493		$ 1,391,984		$ 1,139,493		$ 1,391,984
[1]	Included in Corporate and Other are: contingent consideration adjustments, severance charges, interest income, interest expense, net foreign exchange gains (losses), intercompany eliminations, acquisition related charges, and pension and postretirement plans actuarial losses.
[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. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Acquisition related costs	$ 500	$ 800	$ 2,300	$ 4,100
Restructuring and other-employee severance	(6,500)	1,710	(11,792)	3,785
Contingent consideration adjustment	7,800	800	(16,460)	(9,236)
Universal Robots (UR)
Segment Reporting Information [Line Items]
Contingent consideration adjustment		24,600
Semiconductor Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge	1,867	2,071	5,319	5,851
Semiconductor Test | Severance And Benefits
Segment Reporting Information [Line Items]
Restructuring and other-employee severance		1,716	1,009	7,657
System Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge			1,129	812
Industrial Automation
Segment Reporting Information [Line Items]
Acquisition related costs		811	1,330	811
Cost of revenues-inventory charge			508	680
Industrial Automation | Severance And Benefits
Segment Reporting Information [Line Items]
Restructuring and other-employee severance			604
Wireless Test
Segment Reporting Information [Line Items]
Cost of revenues-inventory charge	724	716	1,892	2,179
Corporate And Eliminations
Segment Reporting Information [Line Items]
Selling and administrative – equity modification charge	2,108		2,108
Corporate And Eliminations | Restructuring and other
Segment Reporting Information [Line Items]
Acquisition related costs	816		928	3,318
Corporate And Eliminations | Universal Robots (UR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment		$ (768)		$ (9,236)
Corporate And Eliminations | Mobile Industrial Robots (MiR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment	$ (7,759)		$ (16,427)

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018	Dec. 31, 2019	Jan. 31, 2019	Jan. 31, 2018
Cumulative repurchases, value	$ 124,763	$ 201,472	$ 365,386	$ 568,660
Common stock average price			$ 41.93	$ 40.62
Dividends Payable, Amount Per Share						$ 0.09	$ 0.09
Dividend payment	15,300	16,600	$ 46,269	$ 51,320
Common Stock [Member]
Cumulative repurchases, value	$ 290	$ 626	$ 1,099	$ 1,730
Cumulative repurchases, shares	(2,323)	(5,005)	(8,794)	(13,843)
Share Repurchase Program [Member]
Stock repurchase program, authorized amount	$ 30,400		$ 30,400
Cumulative repurchases, value			$ 1,200,000
Common stock average price			$ 39.18
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	1,500,000		1,500,000
Maximum [Member]
Stock repurchase program, authorized amount							$ 1,500,000
Forecast [Member]
Cumulative repurchases, value					$ 500,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Oct. 18, 2019USD ($)	Dec. 31, 2018USD ($)
Subsequent Event [Line Items]
Business acquisiton consideration through earnouts		$ 30.8
Industrial Automation | Subsequent Event | Autoguide LLC [Member]
Subsequent Event [Line Items]
Business acquisition percentage of equity	100.00%
Business acquisition,cash consideration	$ 58
Business acquisiton consideration through earnouts	$ 107
Quantity of material to be transported	4,500

Accounting Policies - Additiona

Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Jan. 01, 2019	Feb. 28, 2016
Summary Of Significant Accounting Policies [Line Items]
Operating Lease, Liability	$ 65,199	$ 54,300	$ 54,300
Operating Lease, Right-of-Use Asset	$ 57,595	$ 50,100	$ 50,100