Teradyne (TER) 10-Q 5 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Oct. 03, 2021	Nov. 01, 2021
Cover [Abstract]
Amendment Flag	false
Document Type	10-Q
Document Fiscal Year Focus	2021
Entity Central Index Key	0000097210
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Document Period End Date	Oct. 3, 2021
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		163,004,340

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Oct. 03, 2021		Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 1,079,454		$ 914,121
Marketable securities	233,397		522,280
Accounts receivable, less allowance for credit losses of $1,913 and $2,034 at October 3, 2021 and December 31, 2020, respectively	597,124		497,506
Inventories, net	224,242		222,189
Prepayments and other current assets	386,967		259,338
Total current assets	2,521,184		2,415,434
Property, plant and equipment, net	390,545		394,800
Operating lease right-of-use assets, net	61,608		54,569
Marketable securities	136,664		117,980
Deferred tax assets	96,808		87,913
Retirement plans assets	16,958		17,468
Other assets	23,340		9,384
Acquired intangible assets, net	81,677		100,939
Goodwill	433,398		453,859
Total assets	3,762,182	[1],[2]	3,652,346
Current liabilities:
Accounts payable	154,912		133,663
Accrued employees' compensation and withholdings	196,928		220,321
Deferred revenue and customer advances	140,380		134,662
Other accrued liabilities	135,492		77,581
Operating lease liabilities	20,601		20,573
Income taxes payable	73,077		80,728
Current debt	32,219		33,343
Total current liabilities	753,609		700,871
Retirement plans liabilities	153,249		151,140
Long-term deferred revenue and customer advances	60,022		58,359
Long-term contingent consideration	0		7,227
Long-term other accrued liabilities	19,704		19,352
Deferred tax liabilities	6,907		10,821
Long-term operating lease liabilities	48,492		42,073
Long-term incomes taxes payable	67,041		74,930
Debt	112,784		376,768
Total liabilities	1,221,808		1,441,541
Commitments and Contingencies
Mezzanine equity:
Convertible common shares	2,881		3,787
SHAREHOLDERS' EQUITY
Common stock, $0.125 par value, 1,000,000 shares authorized; 163,728 and 166,123 shares issued and outstanding at October 3, 2021 and December 31, 2020, respectively	20,466		20,765
Additional paid-in capital	1,800,373		1,765,323
Accumulated other comprehensive income	4,217		33,516
Retained earnings	712,437		387,414
Total shareholders' equity	2,537,493		2,207,018
Total liabilities and shareholders' equity	$ 3,762,182		$ 3,652,346
[1]	The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods.
[2]	Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Accounts receivable, less allowance for credit losses	$ 1,913	$ 2,034
Common stock, par value	$ 0.125	$ 0.125
Common stock, shares authorized	1,000,000	1,000,000
Common stock, shares issued	163,728	166,123
Common stock, shares outstanding	163,728	166,123

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended				9 Months Ended
	Oct. 03, 2021		Sep. 27, 2020		Oct. 03, 2021		Sep. 27, 2020
Revenues:
Total revenues	$ 950,501	[1]	$ 819,484	[1]	$ 2,817,835	[2],[3]	$ 2,362,500	[2]
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	379,500		360,556		1,138,227		1,026,549
Gross profit	571,001		458,928		1,679,608		1,335,951
Operating expenses:
Selling and administrative	134,829		115,840		404,812		340,488
Engineering and development	107,220		94,909		317,644		274,170
Acquired intangible assets amortization	5,355		6,219		16,293		25,052
Restructuring and other	1,197		(27,701)		(3,426)		1,915
Total operating expenses	248,601		189,267		735,323		641,625
Income from operations	322,400		269,661		944,285		694,326
Non-operating (income) expense:
Interest income	(626)		(1,071)		(2,066)		(5,189)
Interest expense	3,785		6,237		15,354		17,831
Other (income) expense, net	21,486		764		25,223		3,595
Income before income taxes	297,755		263,731		905,774		678,089
Income tax provision	41,037		41,013		115,225		90,274
Net income	$ 256,718		$ 222,718		$ 790,549		$ 587,815
Net income per common share:
Basic	$ 1.56		$ 1.34		$ 4.77		$ 3.54
Diluted	$ 1.41		$ 1.21		$ 4.26		$ 3.23
Weighted average common shares—basic	164,583		166,014		165,690		166,131
Weighted average common shares—diluted	181,987		184,338		185,492		181,777
Product [Member]
Revenues:
Total revenues	$ 825,448		$ 697,745		$ 2,437,901		$ 2,043,281
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	333,229		300,174		989,859		882,902
Service [Member]
Revenues:
Total revenues	125,053		121,739		379,934		319,219
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 46,271		$ 60,382		$ 148,368		$ 143,647
[1]	Includes $3.8 million and $1.7 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside Accounting Standards Codification (“ASC”) 606 “Revenue from Contracts with Customers.
[2]	Includes $11.1 million and $6.1 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside ASC 606 “Revenue from Contracts with Customers.
[3]	The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Net income	$ 256,718	$ 222,718	$ 790,549	$ 587,815
Other comprehensive income, net of tax:
Foreign currency translation adjustment, net of tax of $0, $0, $0, $0, respectively	(10,698)	17,104	(26,672)	24,131
Available-for-sale marketable securities:
Unrealized (losses) gains on marketable securities arising during period, net of tax of $(44), $139, $(516), and $1,410, respectively	(176)	335	(1,952)	5,165
Less: Reclassification adjustment for gains included in net income, net of tax of $(65), $(194), $(186), $(615), respectively	(229)	(689)	(670)	(2,188)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	(405)	(354)	(2,622)	2,977
Defined benefit post-retirement plan:
Amortization of prior service credit, net of tax of $0, $0, $(2), $(1), respectively	(2)	(2)	(5)	(6)
Other comprehensive (loss) income	(11,105)	16,748	(29,299)	27,102
Comprehensive income	$ 245,613	$ 239,466	$ 761,250	$ 614,917

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Foreign currency translation adjustment, net of tax	$ 0	$ 0	$ 0	$ 0
Unrealized (losses) gains on marketable securities arising during period	(44)	139	(516)	1,410
Reclassification adjustment for gains included in net income	(65)	(194)	(186)	(615)
Amortization of prior service credit, net of tax	$ 0	$ 0	$ (2)	$ (1)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE COMMON SHARES AND SHAREHOLDERS'' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Convertible Common Shares	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2019	$ 1,480,158		$ 20,801	$ 1,720,129	$ (18,854)	$ (241,918)
Balance, Shares at Dec. 31, 2019			166,410
Net issuance of common stock under stock-based plans	3,163		$ 144	3,019
Net issuance of common stock under stock-based plans (in shares)			1,150
Stock-based compensation expense	33,683			33,683
Repurchase of common stock	$ (88,465)		$ (190)			(88,275)
Repurchase of common stock (in shares)	1,500		(1,517)
Cash dividends	$ (49,912)					(49,912)
Net income	587,815					587,815
Other comprehensive income (loss)	27,102				27,102
Balance at Sep. 27, 2020	1,993,544		$ 20,755	1,756,831	8,248	207,710
Balance, Shares at Sep. 27, 2020			166,043
Balance at Jun. 28, 2020	1,744,551		$ 20,725	1,730,716	(8,500)	1,610
Balance, Shares at Jun. 28, 2020			165,806
Net issuance of common stock under stock-based plans	13,545		$ 30	13,515
Net issuance of common stock under stock-based plans (in shares)			237
Stock-based compensation expense	12,600			12,600
Cash dividends	(16,618)					(16,618)
Net income	222,718					222,718
Other comprehensive income (loss)	16,748				16,748
Balance at Sep. 27, 2020	1,993,544		$ 20,755	1,756,831	8,248	207,710
Balance, Shares at Sep. 27, 2020			166,043
Balance at Dec. 31, 2020	2,207,018		$ 20,765	1,765,323	33,516	387,414
Balance, Shares at Dec. 31, 2020		3,787	166,123
Net issuance of common stock under stock-based plans	64		$ 112	(48)
Net issuance of common stock under stock-based plans (in shares)			893
Stock-based compensation expense	35,915			35,915
Repurchase of common stock	$ (416,180)		$ (411)			(415,769)
Repurchase of common stock (in shares)	3,300		(3,288)
Cash dividends	$ (49,757)					(49,757)
Settlements of convertible notes	841,202		$ 897	840,305
Settlement of convertible debt (in shares)			7,178
Exercise of convertible notes hedge call options	(842,925)		$ (897)	(842,028)
Exercise of convertible notes hedge call options (in shares)			(7,178)
Convertible common shares	906			906
Convertible common shares (in shares)		(906)
Net income	790,549					790,549
Other comprehensive income (loss)	(29,299)				(29,299)
Balance at Oct. 03, 2021	2,537,493		$ 20,466	1,800,373	4,217	712,437
Balance, Shares at Oct. 03, 2021		2,881	163,728
Balance at Jul. 04, 2021	2,493,256		$ 20,680	1,772,302	15,322	684,952
Balance, Shares at Jul. 04, 2021		21,386	165,444
Net issuance of common stock under stock-based plans	(258)		$ 1	(259)
Net issuance of common stock under stock-based plans (in shares)			8
Stock-based compensation expense	10,042			10,042
Repurchase of common stock	(212,996)		$ (215)			(212,781)
Repurchase of common stock (in shares)			(1,724)
Cash dividends	(16,452)					(16,452)
Settlements of convertible notes	637,497		$ 699	636,798
Settlement of convertible debt (in shares)			5,589
Exercise of convertible notes hedge call options	(637,714)		$ (699)	(637,015)
Exercise of convertible notes hedge call options (in shares)			(5,589)
Convertible common shares	18,505			18,505
Convertible common shares (in shares)		(18,505)
Net income	256,718					256,718
Other comprehensive income (loss)	(11,105)				(11,105)
Balance at Oct. 03, 2021	$ 2,537,493		$ 20,466	$ 1,800,373	$ 4,217	$ 712,437
Balance, Shares at Oct. 03, 2021		2,881	163,728

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE COMMON SHARES AND SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Common Stock, Dividends, Per Share, Cash Paid	$ 0.10	$ 0.10	$ 0.30	$ 0.30

CONDENSED CONSOLIDATED STATEM_6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020
Cash flows from operating activities:
Net income	$ 790,549	$ 587,815
Adjustments to reconcile net income from operations to net cash provided by operating activities:
Depreciation	67,866	58,111
Stock-based compensation	34,649	33,028
Amortization	27,626	36,577
Loss on convertible debt conversion	25,397
Provision for excess and obsolete inventory	11,775	13,116
Deferred taxes	(10,732)	(4,547)
Contingent consideration adjustment	(7,227)	(7,967)
Gains on investments	(4,750)	(3,515)
Retirement plan actuarial (gains) losses	(627)	2,589
Other	243	750
Changes in operating assets and liabilities, net of businesses acquired:
Accounts receivable	(103,299)	(222,015)
Inventories	21,943	16,998
Prepayments and other assets	(138,564)	(40,751)
Accounts payable and other liabilities	65,064	81,557
Deferred revenue and customer advances	8,699	36,589
Retirement plans contributions	(4,123)	(3,884)
Income taxes	(17,406)	24,060
Net cash provided by operating activities	767,083	608,511
Cash flows from investing activities:
Purchases of property, plant and equipment	(103,162)	(146,872)
Purchases of marketable securities	(509,470)	(488,428)
Proceeds from maturities of marketable securities	571,277	309,407
Proceeds from sales of marketable securities	209,437	32,611
Purchase of investment and acquisition of businesses	(12,000)	149
Proceeds from life insurance		546
Net cash provided by (used for) investing activities	156,082	(292,587)
Cash flows from financing activities:
Issuance of common stock under stock purchase and stock option plans	32,590	26,528
Repurchase of common stock	(406,180)	(88,465)
Payments of convertible debt principal	(301,997)
Dividend payments	(49,711)	(49,870)
Payments related to net settlement of employee stock compensation awards	(32,045)	(22,735)
Payments of contingent consideration		(8,852)
Net cash used for financing activities	(757,343)	(143,394)
Effects of exchange rate changes on cash and cash equivalents	(489)	(1,274)
Increase in cash and cash equivalents	165,333	171,256
Cash and cash equivalents at beginning of period	914,121	773,924
Cash and cash equivalents at end of period	1,079,454	945,180
Non-cash investing activities:
Capital expenditures incurred but not yet paid	$ 2,286	$ 3,119

The Company

The Company	9 Months Ended
	Oct. 03, 2021
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 many industries including 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, logistics and light industrial customers to improve quality, increase manufacturing and material handling efficiency and decrease manufacturing and logistics costs. Teradyne’s automatic test equipment and industrial automation products and services include: • semiconductor test (“Semiconductor Test”) systems; • storage and system level test (“Storage Test”) systems, defense/aerospace (“Defense/Aerospace”) test instrumentation and systems, and circuit-board test and inspection (“Production Board Test”) systems (collectively these products represent “System Test”); • wireless test (“Wireless Test”) systems; and • industrial automation (“Industrial Automation”) products.

Accounting Policies

Accounting Policies	9 Months Ended
	Oct. 03, 2021
Accounting Policies	B. ACCOUNTING POLICIES Basis of Presentation The consolidated interim financial statements include th e 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 of assets, liabilities, revenues and expenses, and related disclosures of contingent liabilities. On an on-going COVID-19 10-Q.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	9 Months Ended
	Oct. 03, 2021
Recently Issued Accounting Pronouncements	C. RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS In August 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-06 if-converted On November 4 2020-06, if-converted

Investment In Other Company

Investment In Other Company	9 Months Ended
	Oct. 03, 2021
Equity Method Investments and Joint Ventures [Abstract]
Investment In Other Company	D. INVESTMENT IN OTHER COMPANY On June

Revenue

Revenue	9 Months Ended
	Oct. 03, 2021
Revenue from Contract with Customer [Abstract]
Revenue	E. REVENUE Disaggregation of Revenue The following table provides information about disaggregated revenue by timing of revenue recognition, primary geographical market, and major product lines. Semiconductor Test Industrial Automation System on-a-Chip Memory System Test Universal Mobile AutoGuide Wireless Test Corporate and Other Total (in thousands) For the Three Months Ended October 3, 2021 (1) Timing of Revenue Recognition Point in Time $ 508,747 $ 105,454 $ 88,155 $ 76,008 $ 12,351 $ 226 $ 65,409 $ (63 ) $ 856,287 Over Time 66,270 7,761 14,450 1,742 607 80 3,304 — 94,214 Total $ 575,017 $ 113,215 $ 102,605 $ 77,750 $ 12,958 $ 306 $ 68,713 $ (63 ) $ 950,501 Geographical Market Asia Pacific $ 519,886 $ 110,362 $ 62,757 $ 19,654 $ 2,788 $ — $ 54,344 $ — $ 769,791 Americas 29,119 2,281 34,560 23,429 5,015 306 11,352 (63 ) 105,999 Europe, Middle East and Africa 26,012 572 5,288 34,667 5,155 — 3,017 — 74,711 Total $ 575,017 $ 113,215 $ 102,605 $ 77,750 $ 12,958 $ 306 $ 68,713 $ (63 ) $ 950,501 For the Three Months Ended September 27, 2020 (1) Timing of Revenue Recognition Point in Time $ 393,717 $ 137,929 $ 101,045 $ 51,523 $ 10,175 $ 4,076 $ 37,901 $ (41 ) $ 736,325 Over Time 55,988 4,507 17,124 1,686 59 1,192 2,603 — 83,159 Total $ 449,705 $ 142,436 $ 118,169 $ 53,209 $ 10,234 $ 5,268 $ 40,504 $ (41 ) $ 819,484 Geographical Market Asia Pacific $ 420,821 $ 137,286 $ 78,534 $ 14,471 $ 1,566 $ — $ 33,865 $ — $ 686,543 Americas 17,678 3,730 35,140 16,527 3,981 5,268 5,211 (41 ) 87,494 Europe, Middle East and Africa 11,206 1,420 4,495 22,211 4,687 — 1,428 — 45,447 Total $ 449,705 $ 142,436 $ 118,169 $ 53,209 $ 10,234 $ 5,268 $ 40,504 $ (41 ) $ 819,484 For the Nine Months Ended October 3, 2021 (2) Timing of Revenue Recognition Point in Time $ 1,548,895 $ 291,578 $ 295,666 $ 214,427 $ 41,506 $ 106 $ 154,908 $ (352 ) $ 2,546,734 Over Time 188,022 21,776 44,595 5,001 1,483 628 9,596 — 271,101 Total $ 1,736,917 $ 313,354 $ 340,261 $ 219,428 $ 42,989 $ 734 $ 164,504 $ (352 ) $ 2,817,835 Geographical Market Asia Pacific $ 1,618,117 $ 301,562 $ 223,507 $ 55,531 $ 8,674 $ — $ 133,678 $ — $ 2,341,069 Americas 71,562 9,373 98,475 66,390 17,065 734 24,228 (352 ) 287,475 Europe, Middle East and Africa 47,238 2,419 18,279 97,507 17,250 — 6,598 — 189,291 Total $ 1,736,917 $ 313,354 $ 340,261 $ 219,428 $ 42,989 $ 734 $ 164,504 $ (352 ) $ 2,817,835 For the Nine Months Ended September 27, 2020 (2) Timing of Revenue Recognition Point in Time $ 1,261,468 $ 298,150 $ 259,498 $ 140,829 $ 30,468 $ 8,608 $ 125,304 $ (294 ) $ 2,124,031 Over Time 162,159 14,000 46,553 5,628 176 2,083 7,870 — 238,469 Total $ 1,423,627 $ 312,150 $ 306,051 $ 146,457 $ 30,644 $ 10,691 $ 133,174 $ (294 ) $ 2,362,500 Geographical Market Asia Pacific $ 1,330,463 $ 296,679 $ 197,208 $ 39,665 $ 4,391 $ — $ 113,576 $ — $ 1,981,982 Americas 51,315 11,481 91,924 42,634 9,836 10,691 15,253 (294 ) 232,840 Europe, Middle East and Africa 41,849 3,990 16,919 64,158 16,417 — 4,345 — 147,678 Total $ 1,423,627 $ 312,150 $ 306,051 $ 146,457 $ 30,644 $ 10,691 $ 133,174 $ (294 ) $ 2,362,500 (1) Includes $3.8 million and $1.7 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside Accounting Standards Codification (“ASC”) 606 “Revenue from Contracts with Customers.” (2) Includes $11.1 million and $6.1 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside ASC 606 “ Revenue from Contracts with Customers Contract Balances During the three and nine months ended October 3, 2021, Teradyne recognized $32.9 million and $82.5 million, respectively, that was previously included within the deferred revenue and customer advances balances at the beginning of the period. During the three and nine months ended September 27, 2020, Teradyne recognized $17.6 million and $78.2 million, respectively, that was previously included within the deferred revenue and customer advances balances at the beginning of the period. This revenue primarily relates to undelivered hardware, extended warranties, training, application support, and post contract support. Each of these represents a distinct performance obligation. As of October 3, 2021, Teradyne has $1,293.0 million of unsatisfied performance obligations. Teradyne expects to recognize 94% of the remaining performance obligations in the next 12 months, 5% in 1-3 Accounts Receivable Teradyne sells certain trade accounts receivables on a non-recourse

Inventories

Inventories	9 Months Ended
	Oct. 03, 2021
Inventories	F. INVENTORIES Inventories, net consisted of th e October 3, 2021 December 31, 2020 (in thousands) Raw material $ 131,807 $ 114,133 Work-in-process 34,911 25,408 Finished goods 57,524 82,648 $ 224,242 $ 222,189 Inventory reserves at October 3, 2021 and December 31, 2020 were $112.5 million and $110.6 million, respectively.

Financial Instruments

Financial Instruments	9 Months Ended
	Oct. 03, 2021
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 October 3, 2021 and September 27, 2020, 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 October 3, 2021 were $0.5 million and $2.6 million, respectively. Realized gains recorded in the three and nine months ended September 27, 2020 were $1.1 million and $4.1 million, respectively. No realized losses were recorded in the three and nine months ended October 3, 2021. Realized losses recorded in the three and nine months ended September 27, 2020 were $0.1 million and $0.3 million, respectively. Realized gains and losses are included in other (income) expense, net. Unrealized gains on equity securities recorded in the nine months ended October 3, 2021 were $3.3 million. Unrealized losses on equity securities recorded in the three and nine months ended October 3, 2021 were $0.4 million and $1.1 million, respectively. Unrealized gains on equity securities recorded in the three and nine months ended September 27, 2020 were $2.0 million and $5.7 million, respectively. Unrealized losses on equity securities recorded in the nine months ended September 27, 2020 were $6.0 million. Unrealized gains and losses on equity securities are included in other (income) expense, net. Unrealized gains and losses on available-for-sale The cost of securities sold is based on average cost. 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 October 3, 2021 and December 31, 2020. October 3, 2021 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 $ 577,752 $ — $ — $ 577,752 Cash equivalents 176,703 324,999 — 501,702 Available-for-sale Commercial paper — 179,629 — 179,629 U.S. Treasury securities — 80,519 — 80,519 Corporate debt securities — 58,648 — 58,648 Debt mutual funds 8,937 — — 8,937 U.S. government agency securities — 4,616 — 4,616 Certificates of deposit and time deposits — 1,346 — 1,346 Non-U.S. — 590 — 590 Equity securities: Mutual funds 35,776 — — 35,776 $ 799,168 $ 650,347 $ — $ 1,449,515 Derivative assets — 93 — 93 Total $ 799,168 $ 650,440 $ — $ 1,449,608 Liabilities Derivative liabilities — 433 — 433 Total $ — $ 433 $ — $ 433 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 754,455 $ 324,999 $ — $ 1,079,454 Marketable securities — 233,397 — 233,397 Long-term marketable securities 44,713 91,951 — 136,664 Prepayments and other current assets — 93 — 93 Total $ 799,168 $ 650,440 $ — $ 1,449,608 Liabilities Other current liabilities $ — $ 433 $ — $ 433 Total $ — $ 433 $ — $ 433 December 31, 2020 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 $ 443,166 $ — $ — $ 443,166 Cash equivalents 347,768 123,187 — 470,955 Available-for-sale — U.S. Treasury securities — 258,304 — 258,304 Commercial paper — 254,413 — 254,413 Corporate debt securities — 83,615 — 83,615 Debt mutual funds 8,565 — — 8,565 U.S. government agency securities — 4,339 — 4,339 Certificates of deposit and time deposits — 979 — 979 Non-U.S. — 625 — 625 Equity securities: Equity mutual funds 29,420 — — 29,420 $ 828,919 $ 725,462 $ — $ 1,554,381 Derivative assets — 95 — 95 Total $ 828,919 $ 725,557 $ — $ 1,554,476 Liabilities Contingent consideration $ — $ — $ 7,227 $ 7,227 Derivative liabilities — 504 — 504 Total $ — $ 504 $ 7,227 $ 7,731 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 790,934 $ 123,187 $ — $ 914,121 Marketable securities — 522,280 — 522,280 Long-term marketable securities 37,985 79,995 — 117,980 Prepayments and other current assets — 95 — 95 Total $ 828,919 $ 725,557 $ — $ 1,554,476 Liabilities Other accrued liabilities $ — $ 504 $ — $ 504 Long-term contingent consideration — — 7,227 7,227 Total $ — $ 504 $ 7,227 $ 7,731 Changes in the fair value of Level 3 contingent consideration for the three and nine months ended October 3, 2021 and September 27, 2020 were as follows: For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ — $ 49,737 $ 7,227 $ 39,705 Fair value adjustment (a)(b)(c) — (27,206 ) (7,227 ) (7,967 ) Foreign currency impact — — — (355 ) Payments (d) — — — (8,852 ) Balance at end of period $ — $ 22,531 $ — $ 22,531 (a) In the nine months ended October 3, 2021, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide was reduced to zero, which resulted in a benefit of $7.2 million, primarily due to a decrease in forecasted revenues and earnings before interest and taxes. As of October 3, 2021, the maximum amount of contingent consideration that could be paid in connection with the acquisition of AutoGuide is $100.2 million. The remaining earn-out non-compliance earn-out (b) In the three and nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide decreased by $27.2 million and $4.4 million, respectively, due to lower forecasted revenues and earnings before interest and taxes. (c) In the nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of Mobile Industrial Robots (“MiR”) decreased by $3.5 million due to lower forecasted results. (d) In the nine months ended September 27, 2020, Teradyne paid $8.9 million of contingent consideration for the earn-out The carrying amounts and fair values of Teradyne’s financial instruments at October 3, 2021 and December 31, 2020 were as follows: October 3, 2021 December 31, 2020 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 1,079,454 $ 1,079,454 $ 914,121 $ 914,121 Marketable securities 370,061 370,061 640,260 640,260 Derivative assets 93 93 95 95 Liabilities Contingent consideration — — 7,227 7,227 Derivative liabilities 433 433 504 504 Convertible debt (1) 145,003 546,464 410,111 1,739,553 (1) The carrying value represents the bifurcated debt component only, while the level 2 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 October 3, 2021 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Commercial paper $ 179,624 $ 5 $ — $ 179,629 $ 20,799 U.S. Treasury securities 80,370 636 (487 ) 80,519 17,336 Corporate debt securities 53,329 5,421 (102 ) 58,648 22,010 Debt mutual funds 8,872 65 — 8,937 — U.S. government agency securities 4,610 11 (5 ) 4,616 3,302 Certificates of deposit and time deposits 1,346 — — 1,346 — Non-U.S. 590 — — 590 — $ 328,741 $ 6,138 $ (594 ) $ 334,285 $ 63,447 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 233,327 $ 92 $ (22 ) $ 233,397 $ 28,773 Long-term marketable securities 95,414 6,046 (572 ) 100,888 34,674 $ 328,741 $ 6,138 $ (594 ) $ 334,285 $ 63,447 The following table summarizes the composition of available-for-sale December 31, 2020 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 $ 257,132 $ 1,330 $ (158 ) $ 258,304 $ 17,243 Commercial paper 254,404 10 (1 ) 254,413 12,173 Corporate debt securities 76,129 7,539 (53 ) 83,615 39,896 Debt mutual funds 8,413 152 — 8,565 — U.S. government agency securities 4,294 46 (1 ) 4,339 1,106 Certificates of deposit and time deposits 979 — — 979 — Non-U.S. 625 — — 625 — $ 601,976 $ 9,077 $ (213 ) $ 610,840 $ 70,418 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 522,228 $ 92 $ (40 ) $ 522,280 $ 61,806 Long-term marketable securities 79,748 8,985 (173 ) 88,560 8,612 $ 601,976 $ 9,077 $ (213 ) $ 610,840 $ 70,418 As of October 3, 2021 and December 31, 2020, the fair market value of investments with unrealized losses less than one year totaled $57.3 million and $70.4 million, respectively. As of October 3, 2021, the fair market value of investments with unrealized losses for greater than one year totaled $6.2 million. 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 October 3, 2021 and December 31, 2020 were not other than temporary. The contractual maturities of investments in available-for-sale October 3, 2021 Cost Fair Market Value (in thousands) Due within one year $ 233,327 $ 233,397 Due after 1 year through 5 years 46,460 46,744 Due after 5 years through 10 years 6,120 6,586 Due after 10 years 33,962 38,621 Total $ 319,869 $ 325,348 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 October 3, 2021 and December 31, 2020 was $181.8 million and $152.9 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 October 3, 2021 and December 31, 2020: Balance Sheet Location October 3, December 31, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Prepayments $ 93 $ 95 Foreign exchange contracts Other current liabilities (433 ) (504 ) Total derivatives $ (340 ) $ (409 ) The following table summarizes the effect of derivative instruments recognized in the statement of operations for the three and nine months ended October 3, 2021 and September 27, 2020: Location of Losses (Gains) Recognized in Statement of Operations For the Three Months Ended For the Nine Months Ended October 3, 2021 September 27, 2020 October 3, 2021 September 27, 2020 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 2,288 $ (551 ) $ 5,937 $ 3,930 (1) The table does not reflect the corresponding gains and losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies. (2) For the three and nine months ended October 3, 2021, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.0 million and $1.3 million, respectively. (3) For the three months ended September 27, 2020, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.2 million. For the nine months ended September 27, 2020, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $0.4 million. See Note H: “Debt” regarding derivatives related to the convertible senior notes.

Debt

Debt	9 Months Ended
	Oct. 03, 2021
Debt	H. 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 nine 4 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 $31.53. The Note Hedge Transactions cover, subject to customary anti-dilution adjustments, approximately 8.7 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: October 3, 2021 December 31, (in thousands) Debt principal $ 157,972 $ 459,971 Unamortized discount 12,969 49,860 Net Carrying amount of convertible debt $ 145,003 $ 410,111 Reported as follows: October 3, 2021 December 31, (in thousands) Current debt $ 32,219 $ 33,343 Long-term debt 112,784 376,768 Net carrying amount of convertible debt $ 145,003 $ 410,111 For the Three Months Ended For the Nine Months Ended October 3, 2021 September 27, 2020 October 3, 2021 September 27, 2020 (in thousands) Contractual interest expense on the coupon $ 355 $ 1,438 $ 2,666 $ 4,313 Amortization of the discount component and debt issue fees recognized as interest expense 2,424 3,887 9,771 11,518 Total interest expense on the convertible debt $ 2,779 $ 5,325 $ 12,437 $ 15,831 As of October 3, 2021, the remaining unamortized discount was $13.0 million, which will be amortized over 2.3 years using the effective interest rate method. The carrying amount of the equity component was $100.8 million. As of October 3, 2021, the conversion price was approximately $31.53 per share and the if-converted During the three and nine months ended October 3, 2021, certain debt holders elected to convert $235.2 million and $302.0 million, respectively, of debt principal. The conversions in the three and nine months ended October 3, 2021 resulted in a loss of $20.2 million and $25.4 million, respectively, recorded to other (income) expense, net in the consolidated statement of operations. The conversion of the debt was settled in cash for principal amount and in shares for the excess of conversion value over principal amount. The 7.2 million shares issued to the debt holders were received from exercising the convertible notes hedge call options. Additional conversions of approximately $41.0 million of debt principal will occur in the fourth quarter of 2021. The liability component is included in current debt and the equity component is included in convertible common shares. Revolving Credit Facility On May 1, 2020, Teradyne entered into a credit agreement (the “Credit Agreement”) with Truist Bank, as administrative agent and collateral agent, and the lenders party thereto. The Credit Agreement provides for a three-year, senior secured revolving credit facility of $400.0 million (the “Credit Facility”). The Credit Agreement further provides that, subject to customary conditions, Teradyne may seek to obtain from existing or new lenders incremental commitments under the Credit Facility in an aggregate principal amount not to exceed $150.0 million. Proceeds from the Credit Facility may be used for general corporate purposes and working capital. Teradyne incurred $3.5 million in costs related to the revolving credit facility. These costs are being amortized over the three-year term of the revolving credit facility and are included in interest expense in the statement of operations. As of November 5, 2021, Teradyne has not borrowed any funds under the Credit Facility. The interest rates applicable to loans under the Credit Facility are, at Teradyne’s option, equal to either a base rate plus a margin ranging from 0.50% to 1.25% per annum or LIBOR, a minimum of 0.75%, plus a margin ranging from 1.50% to 2.25% per annum, based on the consolidated leverage ratio of Teradyne. In addition, Teradyne will pay a commitment fee on the unused portion of the commitments under the Credit Facility ranging from 0.25% to 0.40% per annum, based on the then applicable consolidated leverage ratio. Teradyne is not required to repay any loans under the Credit Facility prior to maturity, subject to certain customary exceptions. Teradyne is permitted to prepay all or any portion of the loans under the Credit Facility prior to maturity without premium or penalty, other than customary LIBOR breakage costs. The Credit Agreement contains customary events of default, representations, warranties and affirmative and negative covenants that, among other things, limit Teradyne’s ability to sell assets, grant liens on assets, incur other secured indebtedness and make certain investments and restricted payments, all subject to exceptions set forth in the Credit Agreement. The Credit Agreement also requires Teradyne to satisfy two financial ratios measured as of the end of each fiscal quarter: a consolidated leverage ratio and an interest coverage ratio. The Credit Facility is guaranteed by certain of Teradyne’s domestic subsidiaries and collateralized by assets of Teradyne and such subsidiaries, including a pledge of 65% of the capital stock of certain foreign subsidiaries. As of November 5, 2021, Teradyne was in compliance with all covenants.

Prepayments

Prepayments	9 Months Ended
	Oct. 03, 2021
Prepayments [Abstract]
Prepayments	I. PREPAYMENTS Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: October 3, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 334,660 $ 212,286 Prepaid maintenance and other services 13,574 13,116 Prepaid taxes 13,822 9,361 Other prepayments 12,093 15,329 Total prepayments $ 374,149 $ 250,092

Deferred Revenue and Customer A

Deferred Revenue and Customer Advances	9 Months Ended
	Oct. 03, 2021
Deferred Revenue and Customer Advances	J. 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: October 3, December 31, (in thousands) Maintenance, service and training $ 83,046 $ 77,654 Extended warranty 67,482 51,929 Customer advances, undelivered elements and other 49,874 63,438 Total deferred revenue and customer advances $ 200,402 $ 193,021

Product Warranty

Product Warranty	9 Months Ended
	Oct. 03, 2021
Product Warranties Disclosures [Abstract]
Product Warranty	K. PRODUCT WARRANTY Teradyne generally provides a one-year For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ 25,676 $ 13,016 $ 16,633 $ 8,996 Accruals for warranties issued during the period 6,641 8,255 28,719 19,522 Accruals related to pre-existing (963 ) 158 (3,966 ) 1,569 Settlements made during the period (5,233 ) (6,272 ) (15,265 ) (14,930 ) Balance at end of period $ 26,121 $ 15,157 $ 26,121 $ 15,157 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. For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ 63,525 $ 40,178 $ 51,929 $ 30,677 Deferral of new extended warranty revenue 12,728 13,674 36,533 32,724 Recognition of extended warranty deferred revenue (8,771 ) (5,149 ) (20,980 ) (14,698 ) Balance at end of period $ 67,482 $ 48,703 $ 67,482 $ 48,703

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Oct. 03, 2021
Stock-Based Compensation	L. STOCK-BASED COMPENSATION Under Teradyne’s stock compensation plans, Teradyne grants service-based restricted stock units, performance-based restricted stock units and stock options, and employees are eligible to purchase Teradyne’s common stock through its Employee Stock Purchase Plan (“ESPP”). Service-based restricted stock unit awards granted to employees vest in equal annual installments over four years. Restricted stock unit awards granted to non-employee one-year Performance-based restricted stock units (“PRSUs”) granted to Teradyne’s executive officers may have a performance metric based on relative total shareholder return (“TSR”). Teradyne’s three-year TSR performance is measured against the New York Stock Exchange (“NYSE”) Composite Index. The final number of TSR PRSUs that vest will vary based upon the level of performance achieved from 0% to 200% of the target shares. The TSR PRSUs will vest upon the three-year anniversary of the grant date. The TSR PRSUs are valued using a Monte Carlo simulation model. The number of units expected to be earned, based upon the achievement of the TSR market condition, is factored into the grant date Monte Carlo valuation. Compensation expense is recognized on a straight-line basis over the shorter of the three-year service period or the period from the grant to the date described in the retirement provisions below. Compensation expense for executive officers meeting the retirement provisions prior to the grant date is recognized during the year following 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. PRSUs granted to Teradyne’s executive officers may also have a performance metric based on three-year cumulative non-GAAP Non-GAAP non-cash non-recurring 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 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. During the nine months ended October 3, 2021 and September 27, 2020, Teradyne granted 0.3 million and 0.4 million of service-based restricted stock unit awards to employees at a weighted average grant date fair value of $113.76 and $70.76, respectively, and 0.1 million of service-based restricted stock unit awards to non-employee During the nine months ended October 3, 2021 and September 27, 2020, Teradyne granted 0.1 million of PBIT PRSUs with a grant date fair value of $113.65 and $70.94, respectively. During the nine months ended October 3, 2021 and September 27, 2020, Teradyne granted 0.1 million of TSR PRSUs, with a grant date fair value of $125.02 and $89.93, respectively. The fair value was estimated using the Monte Carlo simulation model with the following assumptions: For the Nine Months Ended October 3, September 27, Risk-free interest rate 0.2% 1.5% Teradyne volatility-historical 43.9% 34.9% NYSE Composite Index volatility-historical 22.9% 11.4% Dividend yield 0.4% 0.6% Expected volatility was based on the historical volatility of Teradyne’s stock and the NYSE Composite Index over the most recent three-year period. The risk-free interest rate was determined using the U.S. Treasury yield curve in effect at the time of grant. Dividend yield was based upon an estimated annual dividend amount of $0.40 per share divided by Teradyne’s stock price on the grant date of $113.48 for the 2021 grant and an estimated annual dividend amount of $0.40 per share divided by Teradyne’s stock price on the grant date of $72.10 for the 2020 grant. During the nine months ended October 3, 2021 and September 27, 2020, Teradyne granted 0.1 million of service-based stock options to executive officers at a weighted average grant date fair value of $36.60 and $20.67, respectively. The fair value of stock options was estimated using the Black-Scholes option-pricing model with the following assumptions: For the Nine Months Ended October 3, September 27, Expected life (years) 5.0 5.0 Risk-free interest rate 0.4% 1.6% Volatility-historical 37.8% 31.6% Dividend yield 0.4% 0.6% 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 $0.40 per share divided by Teradyne’s stock price on the grant date of $113.48 for the 2021 grant and an estimated annual dividend amount of $0.40 per share divided by Teradyne’s stock price on the grant date of $72.10 for the 2020 grant.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Oct. 03, 2021
Accumulated Other Comprehensive Income	M. ACCUMULATED OTHER COMPREHENSIVE INCOME Changes in accumulated other comprehensive income, which are presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains (Losses) on Marketable Securities Retirement Plans Service Credit Total (in thousands) Nine Months Ended October 3, 2021 Balance at December 31, 2020, net of tax of $0, $1,910, $(1,126), respectively $ 25,389 $ 6,954 $ 1,173 $ 33,516 Other comprehensive loss before reclassifications, net of tax of $0, $(516), $0, respectively (26,672 ) (1,952 ) — (28,624 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(186), $(2), respectively — (670 ) (5 ) (675 ) Net current period other comprehensive loss, net of tax of $0 , $(702), $ (26,672 ) (2,622 ) (5 ) (29,299 ) Balance at October 3, 2021, net of tax of $0, $1,208, $(1,128), respectively $ (1,283 ) $ 4,332 $ 1,168 $ 4,217 Nine Months Ended September 27, 2020 Balance at December 31, 2019, net of tax of $0, $946, $(1,124), respectively $ (23,514 ) $ 3,480 $ 1,180 $ (18,854 ) Other comprehensive income before reclassifications, net of tax of $0, $1,410, $0, respectively 24,131 5,165 — 29,296 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(615), $ (1 — (2,188 ) (6 ) (2,194 ) Net current period other comprehensive income (loss), net of tax of $0, $795, $(1), respectively 24,131 2,977 (6 ) 27,102 Balance at September 27, 2020, net of tax of $0, $1,741, $(1,125), respectively $ 617 $ 6,457 $ 1,174 $ 8,248 Reclassifications out of accumulated other comprehensive income to the statement of operations for the three and nine months ended October 3, 2021 and September 27, 2020 were as follows: Details about Accumulated Other Comprehensive Income Components For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations October 3, September 27, October 3, September 27, (in thousands) Available-for-sale Unrealized gains, net of tax of $65, $194, $186, $615, respectively $ 229 $ 689 $ 670 $ 2,188 Other (income) Defined benefit postretirement plan: Amortization of prior service credit, net of tax of $0, $0, $2, $1, respectively 2 2 5 6 (a) Total reclassifications, net of tax of $65, $194, $188, $616, respectively $ 231 $ 691 $ 675 $ 2,194 Net income (a) The amortization of prior service credit is included in the computation of net periodic postretirement benefit cost. See Note Q: “Retirement Plans.”

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	9 Months Ended
	Oct. 03, 2021
Goodwill and Intangible Assets	N. 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 October 3, 2021, were as follows: Industrial Automation System Wireless Semiconductor Total (in thousands) Balance at December 31, 2020 Goodwill $ 433,752 $ 158,699 $ 361,819 $ 262,155 $ 1,216,425 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 433,752 10,516 7,976 1,615 453,859 Foreign currency translation adjustment (20,373 ) — — (88 ) (20,461 ) Balance at October 3, 2021 Goodwill 413,379 158,699 361,819 262,067 1,195,964 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 413,379 $ 10,516 $ 7,976 $ 1,527 $ 433,398 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: Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount Balance at October 3, 2021 (in thousands) Developed technology $ 272,547 $ (220,147 ) $ (3,489 ) $ 48,911 Customer relationships 57,739 (48,351 ) 174 9,562 Tradenames and trademarks 70,120 (46,643 ) (273 ) 23,204 Total intangible assets $ 400,406 $ (315,141 ) $ (3,588 ) $ 81,677 Balance, December 31, 2020 Developed technology $ 272,547 $ (210,479 ) $ (1,610 ) $ 60,458 Customer relationships 66,239 (54,524 ) 305 12,020 Tradenames and trademarks 70,120 (42,344 ) 685 28,461 Total intangible assets $ 408,906 $ (307,347 ) $ (620 ) $ 100,939 Aggregate intangible asset amortization expense was $5.4 million and $16.3 million, respectively, for the three and nine months ended October 3, 2021 and $6.2 million and $25.1 million, respectively, for the three and nine months ended September 27, 2020. Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2021 (remainder) $ 5,199 2022 20,299 2023 19,815 2024 19,507 2025 11,645 Thereafter 5,212

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Oct. 03, 2021
Net Income per Common Share	O. 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 October 3, September 27, October 3, September 27, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 256,718 $ 222,718 $ 790,549 $ 587,815 Weighted average common shares-basic 164,583 166,014 165,690 166,131 Effect of dilutive potential common shares: Convertible note hedge warrant shares (1) 9,819 7,775 9,774 6,364 Incremental shares from assumed conversion of convertible notes (2) 6,464 9,156 8,784 8,029 Restricted stock units 1,035 1,237 1,147 1,104 Stock options 73 141 87 136 Employee stock purchase plan 13 15 10 13 Dilutive potential common shares 17,404 18,324 19,802 15,646 Weighted average common shares-diluted 181,987 184,338 185,492 181,777 Net income per common share-basic $ 1.56 $ 1.34 $ 4.77 $ 3.54 Net income per common share-diluted $ 1.41 $ 1.21 $ 4.26 $ 3.23 (1) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.56 and $39.58, multiplied by million shares and 14.6 million shares for the three and nine months ended October 3, 2021, respectively. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period. (2) 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 $31.53 and $31.54, multiplied by million shares and 11.7 million shares, for the three and nine months ended October 3, 2021, respectively. 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. The computation of diluted net income per common share for the three and nine months ended October 3, 2021 excludes the effect of the potential vesting of 0.1 million and 0.1 million, respectively, 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 27, 2020 excludes the effect of the potential vesting of 0.1 million and 0.2 million, respectively, of restricted stock units because the effect would have been anti-dilutive.

Restructuring and Other

Restructuring and Other	9 Months Ended
	Oct. 03, 2021
Restructuring and Related Activities [Abstract]
Restructuring and Other	P. RESTRUCTURING AND OTHER During the three months ended October 3, 2021, Teradyne recorded $0.6 million of severance charges primarily in Industrial Automation, $0.3 million of acquisition related compensation expenses and $0.3 million for other expenses. During the three months ended September 27, 2020, Teradyne recorded a $27.2 million gain for the decrease in the fair value of the AutoGuide contingent consideration liability, a $1.1 million gain for the decrease in acquisition related compensation liability, partially offset by $0.5 million recorded for employee severance charges primarily in Industrial Automation. During the nine months ended October 3, 2021, Teradyne recorded a gain of $7.2 million for the decrease in the fair value of the AutoGuide contingent consideration liability, partially offset by a charge of $1.7 million for an increase in environmental and legal liabilities, $1.2 million of severance charges primarily in Industrial Automation, $0.6 million for other expenses and $0.3 million of acquisition related compensation expenses. During the nine months ended September 27, 2020, Teradyne recorded a $4.0 million contract termination settlement charge, $3.4 million of acquisition related compensation and expenses, $1.2 million of severance charges primarily in Industrial Automation, and $1.2 million of other expenses, partially offset by a $4.4 million gain for the decrease in the fair value of the AutoGuide contingent consideration liabilities, and a $3.5 million gain for the decrease in the fair value of the MiR contingent consideration liability.

Retirement Plans

Retirement Plans	9 Months Ended
	Oct. 03, 2021
Retirement Plans	Q. 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 October 3, 2021, and September 27, 2020, Teradyne contributed $2.5 million and $2.2 million, respectively, to the U.S. supplemental executive defined benefit pension plan and $0.8 million and $0.7 million, respectively, to certain qualified pension plans for non-U.S. For the three and nine months ended October 3, 2021 and September 27, 2020, Teradyne’s net periodic pension cost was comprised of the following components: For the Three Months Ended October 3, 2021 September 27, 2020 United States Foreign United States Foreign (in thousands) Service cost $ 452 $ 240 $ 417 $ 216 Interest cost 1,098 86 1,460 123 Expected return on plan assets (936 ) (17 ) (1,170 ) (16 ) Net actuarial loss — — 2,238 — Settlement loss — — 450 — Total net periodic pension cost $ 614 $ 309 $ 3,395 $ 323 For the Nine Months Ended October 3, 2021 September 27, 2020 United States Foreign United States Foreign (in thousands) Service cost $ 1,357 $ 720 $ 1,283 $ 648 Interest cost 3,295 257 4,505 369 Expected return on plan assets (2,809 ) (50 ) (3,634 ) (47 ) Net actuarial (gain) loss (400 ) — 2,418 — Settlement loss — — 450 — Total net periodic pension cost $ 1,443 $ 927 $ 5,022 $ 970 The net periodic pension cost components other than service cost were recorded in other (income) expense, net in the statement of operations. 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 October 3, 2021 and September 27, 2020, Teradyne’s net periodic postretirement benefit cost (credit) was comprised of the following components: For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Service cost $ 16 $ 14 $ 48 $ 43 Interest cost 43 60 128 180 Amortization of prior service credit (2 ) (2 ) (7 ) (7 ) Net actuarial gain — — (228 ) (279 ) Total net periodic postretirement benefit cost (credit) $ 57 $ 72 $ (59 ) $ (63 ) The net periodic postretirement benefit cost (credit) components other than service cost were recorded in other (income) expense, net in the statement of operations.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Oct. 03, 2021
Commitments and Contingencies	R. COMMITMENTS AND CONTINGENCIES Purchase Commitments As of October 3, 2021, Teradyne had entered into purchase commitments for certain components and materials. The purchase commitments covered by the agreements aggregate to approximately $811.9 million, of which $777.8 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 such as, but not limited to, patent, employment, commercial and environmental matters. Teradyne believes that it has meritorious defenses against all pending claims and intends to vigorously contest them. While it is not possible to predict or determine the outcomes of any pending claims or to provide possible ranges of losses that may arise, Teradyne believes the potential losses associated with all of these actions are unlikely to have a material adverse effect on its business, financial position or results of operations. On March 8, 2021, Industrial Automation LLC submitted a demand for arbitration against Teradyne and AutoGuide in Wilmington, Delaware alleging that Teradyne and AutoGuide breached certain provisions of the Membership Interests Purchase Agreement (the “Purchase Agreement”), dated as of October 18, 2019, among Industrial Automation LLC, Teradyne and AutoGuide. The arbitration demand seeks full acceleration of the maximum earnout amount payable under the Purchase Agreement, or $106.9 million, for the alleged breach of the earnout provisions of the Purchase Agreement. On March 26, 2021, Teradyne and AutoGuide filed an answer denying that Teradyne and AutoGuide breached any provisions of the Purchase Agreement. The arbitration hearing is scheduled for March 21, 2022. While it is not possible at this stage to predict the outcome of the arbitration, Teradyne and AutoGuide intend to vigorously defend against the Industrial Automation LLC claims.

Income Taxes

Income Taxes	9 Months Ended
	Oct. 03, 2021
Income Taxes	S. 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 Ended For the Nine Months Ended October 3, September 27, October 3, September 27, U.S. statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % Foreign taxes (4.4 ) (6.9 ) (4.4 ) (5.8 ) Tax credits (1.9 ) (1.6 ) (1.4 ) (1.6 ) International provisions of the U.S. Tax Cuts and Jobs Act of 2017 (1.5 ) 3.0 (1.6 ) 0.5 Discrete benefit related to equity compensation (0.1 ) (0.4 ) (1.6 ) (1.4 ) Other, net 0.7 0.5 0.7 0.6 Effective tax rate 13.8 % 15.6 % 12.7 % 13.3 % 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 October 3, 2021, 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 October 3, 2021, and December 31, 2020, Teradyne had $16.8 million and $17.9 million, respectively, of reserves for uncertain tax positions. The $1.1 million net decrease in reserves for uncertain tax positions is primarily related to U.S. state research and development credits generated in prior years, as well as U.S. federal research and development credits generated in the current year. As of October 3, 2021, Teradyne estimates that it is reasonably possible that the balance of unrecognized tax benefits may decrease approximately $1.6 million in the next twelve months because of a lapse of statutes of limitation. The estimated decrease relates to loss carryforwards, research credits and U.S. manufacturing activities deductions. Teradyne recognizes interest and penalties related to income tax matters in income tax expense. As of October 3, 2021, and December 31, 2020, $1.5 million and $1.2 million, respectively, of interest and penalties were accrued for uncertain tax positions. For the nine months ended October 3, 2021 and September 27, 2020, expense of $0.3 million and $0.0 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 October 3, 2021 was $23.9 million, or $0.13 per diluted share. The tax savings due to the tax holiday for the nine months ended September 27, 2020 was $24.9 million, or $0.14 per diluted share. In November 2020, Teradyne entered into an agreement with the Singapore Economic Development Board which extended its Singapore tax holiday under substantially similar terms to the agreement which expired on December 31, 2020. The new tax holiday is scheduled to expire on December 31, 2025.

Segment Information

Segment Information	9 Months Ended
	Oct. 03, 2021
Segment Reporting [Abstract]
Segment Information	T. SEGMENT INFORMATION Teradyne has four reportable segments (Semiconductor Test, System Test, Industrial Automation and Wireless Test). Each of the reportable segments is also an individual operating segment. 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 and system level 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. Each operating segment has a segment manager who is directly accountable to and maintains regular contact with Teradyne’s chief operating decision maker (Teradyne’s chief executive officer) to discuss operating activities, financial results, forecasts, and plans for the segment. 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 th e Semiconductor Test System Test Industrial Automation Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended October 3, 2021 Revenues $ 688,232 $ 102,605 $ 91,014 $ 68,713 $ (63 ) $ 950,501 Income (loss) before income taxes (1)(2) 265,017 31,773 (4,226 ) 31,726 (26,535 ) 297,755 Total assets (3) 1,251,549 147,970 696,792 119,568 1,546,303 3,762,182 Three Months Ended September 27, 2020 Revenues $ 592,141 $ 118,169 $ 68,711 $ 40,504 $ (41 ) $ 819,484 Income (loss) before income taxes (1)(2) 189,116 47,368 (5,302 ) 10,938 21,611 263,731 Total assets (3) 1,069,830 155,642 667,132 108,671 1,435,237 3,436,512 Nine Months Ended October 3, 2021 (4) Revenues $ 2,050,271 $ 340,261 $ 263,151 $ 164,504 $ (352 ) $ 2,817,835 Income (loss) before income taxes (1)(2) 778,687 116,788 (14,586 ) 63,810 (38,925 ) 905,774 Total assets (3) 1,251,549 147,970 696,792 119,568 1,546,303 3,762,182 Nine Months Ended September 27, 2020 Revenues $ 1,735,777 $ 306,051 $ 187,792 $ 133,174 $ (294 ) $ 2,362,500 Income (loss) before income taxes (1)(2) 571,719 114,968 (32,041 ) 35,640 (12,197 ) 678,089 Total assets (3) 1,069,830 155,642 667,132 108,671 1,435,237 3,436,512 (1) Included in Corporate and Other are: contingent consideration adjustments, loss on convertible debt conversions, interest income, interest expense, net foreign exchange gains (losses), pension, intercompany eliminations and acquisition related: (a) charges; (b) legal fees; (c) compensation. (2) Included in income (loss) before taxes are charges and credits related to restructuring and other, loss on convertible debt conversions and inventory charges. (3) Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets. (4) The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods. 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 October 3, September 27, October 3, September 27, (in thousands) Semiconductor Test: Cost of revenues—inventory charge $ 3,725 $ 1,131 $ 4,959 $ 7,956 Restructuring and other—Contract termination settlement charge — — — 4,000 Industrial Automation: Cost of revenues—inventory charge $ 3,656 $ — $ 4,941 $ 505 Restructuring and other—employee severance 476 — 965 664 Restructuring and other—acquisition related expenses and compensation — — 825 790 Wireless: Cost of revenues—inventory charge $ 679 $ 1,802 $ 1,351 $ 3,957 System Test: Cost of revenues—inventory charge $ — $ — $ 524 $ 698 Corporate and Other: Other (income) expense, net—loss on convertible debt conversion $ 20,153 $ — $ 25,397 $ — Restructuring and other—other — — 1,846 — Restructuring and other—AutoGuide contingent consideration adjustment — (27,206 ) (7,227 ) (4,421 ) Restructuring and other—acquisition related expenses and compensation — (1,086 ) (513 ) 2,629 Restructuring and other—MiR contingent consideration adjustment — — — (3,546 )

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Oct. 03, 2021
Equity [Abstract]
Shareholders' Equity	U. SHAREHOLDERS’ EQUITY Stock Repurchase Program In January 2021, Teradyne’s Board of Directors cancelled the January 2020 repurchase program and approved a new repurchase program for up to $2.0 billion of common stock. Teradyne intends to repurchase a minimum of $600 million in 2021. During the nine months ended October 3, 2021, Teradyne repurchased 3.3 million shares of common stock for $406.2 million at an average price of $123.53 per share. During the nine months ended September 27, 2020, Teradyne repurchased 1.5 million shares of common stock for $88.5 million at an average price of $58.33 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 2021, May 2021 and August 2021, Teradyne’s Board of Directors declared a quarterly cash dividend of $0.10 per share. Dividend payments for the three and nine months ended October 3, 2021 were $16.4 million and $49.7 million, respectively. In January 2020, May 2020 and August 2020, Teradyne’s Board of Directors declared a quarterly cash dividend of $0.10 per share. Dividend payments for the three and nine months ended September 27, 2020 were $16.6 million and $49.9 million, respectively. While Teradyne declared a quarterly cash dividend and authorized a share repurchase program, it may reduce or eliminate the cash dividend or share repurchase program in the future. Future cash dividends and stock repurchases are subject to the discretion of Teradyne’s Board of Directors, which will consider, among other things, Teradyne’s earnings, capital requirements and financial condition.

Accounting Policies (Policies)

Accounting Policies (Policies)	9 Months Ended
	Oct. 03, 2021
Basis of Presentation	Basis of Presentation The consolidated interim financial statements include th e 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 of assets, liabilities, revenues and expenses, and related disclosures of contingent liabilities. On an on-going COVID-19 10-Q.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Oct. 03, 2021
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 timing of revenue recognition, primary geographical market, and major product lines. Semiconductor Test Industrial Automation System on-a-Chip Memory System Test Universal Mobile AutoGuide Wireless Test Corporate and Other Total (in thousands) For the Three Months Ended October 3, 2021 (1) Timing of Revenue Recognition Point in Time $ 508,747 $ 105,454 $ 88,155 $ 76,008 $ 12,351 $ 226 $ 65,409 $ (63 ) $ 856,287 Over Time 66,270 7,761 14,450 1,742 607 80 3,304 — 94,214 Total $ 575,017 $ 113,215 $ 102,605 $ 77,750 $ 12,958 $ 306 $ 68,713 $ (63 ) $ 950,501 Geographical Market Asia Pacific $ 519,886 $ 110,362 $ 62,757 $ 19,654 $ 2,788 $ — $ 54,344 $ — $ 769,791 Americas 29,119 2,281 34,560 23,429 5,015 306 11,352 (63 ) 105,999 Europe, Middle East and Africa 26,012 572 5,288 34,667 5,155 — 3,017 — 74,711 Total $ 575,017 $ 113,215 $ 102,605 $ 77,750 $ 12,958 $ 306 $ 68,713 $ (63 ) $ 950,501 For the Three Months Ended September 27, 2020 (1) Timing of Revenue Recognition Point in Time $ 393,717 $ 137,929 $ 101,045 $ 51,523 $ 10,175 $ 4,076 $ 37,901 $ (41 ) $ 736,325 Over Time 55,988 4,507 17,124 1,686 59 1,192 2,603 — 83,159 Total $ 449,705 $ 142,436 $ 118,169 $ 53,209 $ 10,234 $ 5,268 $ 40,504 $ (41 ) $ 819,484 Geographical Market Asia Pacific $ 420,821 $ 137,286 $ 78,534 $ 14,471 $ 1,566 $ — $ 33,865 $ — $ 686,543 Americas 17,678 3,730 35,140 16,527 3,981 5,268 5,211 (41 ) 87,494 Europe, Middle East and Africa 11,206 1,420 4,495 22,211 4,687 — 1,428 — 45,447 Total $ 449,705 $ 142,436 $ 118,169 $ 53,209 $ 10,234 $ 5,268 $ 40,504 $ (41 ) $ 819,484 For the Nine Months Ended October 3, 2021 (2) Timing of Revenue Recognition Point in Time $ 1,548,895 $ 291,578 $ 295,666 $ 214,427 $ 41,506 $ 106 $ 154,908 $ (352 ) $ 2,546,734 Over Time 188,022 21,776 44,595 5,001 1,483 628 9,596 — 271,101 Total $ 1,736,917 $ 313,354 $ 340,261 $ 219,428 $ 42,989 $ 734 $ 164,504 $ (352 ) $ 2,817,835 Geographical Market Asia Pacific $ 1,618,117 $ 301,562 $ 223,507 $ 55,531 $ 8,674 $ — $ 133,678 $ — $ 2,341,069 Americas 71,562 9,373 98,475 66,390 17,065 734 24,228 (352 ) 287,475 Europe, Middle East and Africa 47,238 2,419 18,279 97,507 17,250 — 6,598 — 189,291 Total $ 1,736,917 $ 313,354 $ 340,261 $ 219,428 $ 42,989 $ 734 $ 164,504 $ (352 ) $ 2,817,835 For the Nine Months Ended September 27, 2020 (2) Timing of Revenue Recognition Point in Time $ 1,261,468 $ 298,150 $ 259,498 $ 140,829 $ 30,468 $ 8,608 $ 125,304 $ (294 ) $ 2,124,031 Over Time 162,159 14,000 46,553 5,628 176 2,083 7,870 — 238,469 Total $ 1,423,627 $ 312,150 $ 306,051 $ 146,457 $ 30,644 $ 10,691 $ 133,174 $ (294 ) $ 2,362,500 Geographical Market Asia Pacific $ 1,330,463 $ 296,679 $ 197,208 $ 39,665 $ 4,391 $ — $ 113,576 $ — $ 1,981,982 Americas 51,315 11,481 91,924 42,634 9,836 10,691 15,253 (294 ) 232,840 Europe, Middle East and Africa 41,849 3,990 16,919 64,158 16,417 — 4,345 — 147,678 Total $ 1,423,627 $ 312,150 $ 306,051 $ 146,457 $ 30,644 $ 10,691 $ 133,174 $ (294 ) $ 2,362,500 (1) Includes $3.8 million and $1.7 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside Accounting Standards Codification (“ASC”) 606 “Revenue from Contracts with Customers.” (2) Includes $11.1 million and $6.1 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside ASC 606 “ Revenue from Contracts with Customers

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Oct. 03, 2021
Composition of Inventories, Net	Inventories, net consisted of th e October 3, 2021 December 31, 2020 (in thousands) Raw material $ 131,807 $ 114,133 Work-in-process 34,911 25,408 Finished goods 57,524 82,648 $ 224,242 $ 222,189

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Oct. 03, 2021
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 October 3, 2021 and December 31, 2020. October 3, 2021 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 $ 577,752 $ — $ — $ 577,752 Cash equivalents 176,703 324,999 — 501,702 Available-for-sale Commercial paper — 179,629 — 179,629 U.S. Treasury securities — 80,519 — 80,519 Corporate debt securities — 58,648 — 58,648 Debt mutual funds 8,937 — — 8,937 U.S. government agency securities — 4,616 — 4,616 Certificates of deposit and time deposits — 1,346 — 1,346 Non-U.S. — 590 — 590 Equity securities: Mutual funds 35,776 — — 35,776 $ 799,168 $ 650,347 $ — $ 1,449,515 Derivative assets — 93 — 93 Total $ 799,168 $ 650,440 $ — $ 1,449,608 Liabilities Derivative liabilities — 433 — 433 Total $ — $ 433 $ — $ 433 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 754,455 $ 324,999 $ — $ 1,079,454 Marketable securities — 233,397 — 233,397 Long-term marketable securities 44,713 91,951 — 136,664 Prepayments and other current assets — 93 — 93 Total $ 799,168 $ 650,440 $ — $ 1,449,608 Liabilities Other current liabilities $ — $ 433 $ — $ 433 Total $ — $ 433 $ — $ 433 December 31, 2020 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 $ 443,166 $ — $ — $ 443,166 Cash equivalents 347,768 123,187 — 470,955 Available-for-sale — U.S. Treasury securities — 258,304 — 258,304 Commercial paper — 254,413 — 254,413 Corporate debt securities — 83,615 — 83,615 Debt mutual funds 8,565 — — 8,565 U.S. government agency securities — 4,339 — 4,339 Certificates of deposit and time deposits — 979 — 979 Non-U.S. — 625 — 625 Equity securities: Equity mutual funds 29,420 — — 29,420 $ 828,919 $ 725,462 $ — $ 1,554,381 Derivative assets — 95 — 95 Total $ 828,919 $ 725,557 $ — $ 1,554,476 Liabilities Contingent consideration $ — $ — $ 7,227 $ 7,227 Derivative liabilities — 504 — 504 Total $ — $ 504 $ 7,227 $ 7,731 Reported as follows: (Level 1) (Level 2) (Level 3) Total (in thousands) Assets Cash and cash equivalents $ 790,934 $ 123,187 $ — $ 914,121 Marketable securities — 522,280 — 522,280 Long-term marketable securities 37,985 79,995 — 117,980 Prepayments and other current assets — 95 — 95 Total $ 828,919 $ 725,557 $ — $ 1,554,476 Liabilities Other accrued liabilities $ — $ 504 $ — $ 504 Long-term contingent consideration — — 7,227 7,227 Total $ — $ 504 $ 7,227 $ 7,731
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 October 3, 2021 and September 27, 2020 were as follows: For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ — $ 49,737 $ 7,227 $ 39,705 Fair value adjustment (a)(b)(c) — (27,206 ) (7,227 ) (7,967 ) Foreign currency impact — — — (355 ) Payments (d) — — — (8,852 ) Balance at end of period $ — $ 22,531 $ — $ 22,531 (a) In the nine months ended October 3, 2021, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide was reduced to zero, which resulted in a benefit of $7.2 million, primarily due to a decrease in forecasted revenues and earnings before interest and taxes. As of October 3, 2021, the maximum amount of contingent consideration that could be paid in connection with the acquisition of AutoGuide is $100.2 million. The remaining earn-out non-compliance earn-out (b) In the three and nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide decreased by $27.2 million and $4.4 million, respectively, due to lower forecasted revenues and earnings before interest and taxes. (c) In the nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of Mobile Industrial Robots (“MiR”) decreased by $3.5 million due to lower forecasted results. (d) In the nine months ended September 27, 2020, Teradyne paid $8.9 million of contingent consideration for the earn-out
Schedule of Carrying Amounts and Fair Values of Financial Instruments	The carrying amounts and fair values of Teradyne’s financial instruments at October 3, 2021 and December 31, 2020 were as follows: October 3, 2021 December 31, 2020 Carrying Value Fair Value Carrying Value Fair Value (in thousands) Assets Cash and cash equivalents $ 1,079,454 $ 1,079,454 $ 914,121 $ 914,121 Marketable securities 370,061 370,061 640,260 640,260 Derivative assets 93 93 95 95 Liabilities Contingent consideration — — 7,227 7,227 Derivative liabilities 433 433 504 504 Convertible debt (1) 145,003 546,464 410,111 1,739,553 (1) The carrying value represents the bifurcated debt component only, while the level 2 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 October 3, 2021 Available-for-Sale Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Commercial paper $ 179,624 $ 5 $ — $ 179,629 $ 20,799 U.S. Treasury securities 80,370 636 (487 ) 80,519 17,336 Corporate debt securities 53,329 5,421 (102 ) 58,648 22,010 Debt mutual funds 8,872 65 — 8,937 — U.S. government agency securities 4,610 11 (5 ) 4,616 3,302 Certificates of deposit and time deposits 1,346 — — 1,346 — Non-U.S. 590 — — 590 — $ 328,741 $ 6,138 $ (594 ) $ 334,285 $ 63,447 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 233,327 $ 92 $ (22 ) $ 233,397 $ 28,773 Long-term marketable securities 95,414 6,046 (572 ) 100,888 34,674 $ 328,741 $ 6,138 $ (594 ) $ 334,285 $ 63,447 The following table summarizes the composition of available-for-sale December 31, 2020 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 $ 257,132 $ 1,330 $ (158 ) $ 258,304 $ 17,243 Commercial paper 254,404 10 (1 ) 254,413 12,173 Corporate debt securities 76,129 7,539 (53 ) 83,615 39,896 Debt mutual funds 8,413 152 — 8,565 — U.S. government agency securities 4,294 46 (1 ) 4,339 1,106 Certificates of deposit and time deposits 979 — — 979 — Non-U.S. 625 — — 625 — $ 601,976 $ 9,077 $ (213 ) $ 610,840 $ 70,418 Reported as follows: Cost Unrealized Gain Unrealized (Loss) Fair Market Value Fair Market Value of Investments with Unrealized Losses (in thousands) Marketable securities $ 522,228 $ 92 $ (40 ) $ 522,280 $ 61,806 Long-term marketable securities 79,748 8,985 (173 ) 88,560 8,612 $ 601,976 $ 9,077 $ (213 ) $ 610,840 $ 70,418
Contractual Maturities of Investments Held	The contractual maturities of investments in available-for-sale October 3, 2021 Cost Fair Market Value (in thousands) Due within one year $ 233,327 $ 233,397 Due after 1 year through 5 years 46,460 46,744 Due after 5 years through 10 years 6,120 6,586 Due after 10 years 33,962 38,621 Total $ 319,869 $ 325,348
Schedule of Derivative Instruments in Statement of Financial Position at Fair Value	The following table summarizes the fair value of derivative instruments as of October 3, 2021 and December 31, 2020: Balance Sheet Location October 3, December 31, (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Prepayments $ 93 $ 95 Foreign exchange contracts Other current liabilities (433 ) (504 ) Total derivatives $ (340 ) $ (409 )
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 October 3, 2021 and September 27, 2020: Location of Losses (Gains) Recognized in Statement of Operations For the Three Months Ended For the Nine Months Ended October 3, 2021 September 27, 2020 October 3, 2021 September 27, 2020 (in thousands) Derivatives not designated as hedging instruments: Foreign exchange contracts Other (income) expense, net $ 2,288 $ (551 ) $ 5,937 $ 3,930 (1) The table does not reflect the corresponding gains and losses from the remeasurement of the monetary assets and liabilities denominated in foreign currencies. (2) For the three and nine months ended October 3, 2021, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.0 million and $1.3 million, respectively. (3) For the three months ended September 27, 2020, net losses from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $1.2 million. For the nine months ended September 27, 2020, net gains from the remeasurement of monetary assets and liabilities denominated in foreign currencies were $0.4 million.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Oct. 03, 2021
Components of Convertible Senior Notes	The below tables represent the key components of Teradyne’s convertible senior notes: October 3, 2021 December 31, (in thousands) Debt principal $ 157,972 $ 459,971 Unamortized discount 12,969 49,860 Net Carrying amount of convertible debt $ 145,003 $ 410,111 Reported as follows: October 3, 2021 December 31, (in thousands) Current debt $ 32,219 $ 33,343 Long-term debt 112,784 376,768 Net carrying amount of convertible debt $ 145,003 $ 410,111 For the Three Months Ended For the Nine Months Ended October 3, 2021 September 27, 2020 October 3, 2021 September 27, 2020 (in thousands) Contractual interest expense on the coupon $ 355 $ 1,438 $ 2,666 $ 4,313 Amortization of the discount component and debt issue fees recognized as interest expense 2,424 3,887 9,771 11,518 Total interest expense on the convertible debt $ 2,779 $ 5,325 $ 12,437 $ 15,831

Prepayments (Tables)

Prepayments (Tables)	9 Months Ended
	Oct. 03, 2021
Prepayments [Abstract]
Schedule of Prepayments and other assets	Prepayments consist of the following and are included in prepayments and other assets on the balance sheet: October 3, December 31, (in thousands) Contract manufacturer and supplier prepayments $ 334,660 $ 212,286 Prepaid maintenance and other services 13,574 13,116 Prepaid taxes 13,822 9,361 Other prepayments 12,093 15,329 Total prepayments $ 374,149 $ 250,092

Deferred Revenue and Customer_2

Deferred Revenue and Customer Advances (Tables)	9 Months Ended
	Oct. 03, 2021
Revenue Recognition and Deferred Revenue [Abstract]
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: October 3, December 31, (in thousands) Maintenance, service and training $ 83,046 $ 77,654 Extended warranty 67,482 51,929 Customer advances, undelivered elements and other 49,874 63,438 Total deferred revenue and customer advances $ 200,402 $ 193,021

Product Warranty (Tables)

Product Warranty (Tables)	9 Months Ended
	Oct. 03, 2021
Other Accrued Liabilities	Related costs are charged to the warranty accrual as incurred. The balance below is included in other accrued liabilities. For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ 25,676 $ 13,016 $ 16,633 $ 8,996 Accruals for warranties issued during the period 6,641 8,255 28,719 19,522 Accruals related to pre-existing (963 ) 158 (3,966 ) 1,569 Settlements made during the period (5,233 ) (6,272 ) (15,265 ) (14,930 ) Balance at end of period $ 26,121 $ 15,157 $ 26,121 $ 15,157
Extended Product Warranty of Short and Long-Term Deferred Revenue and Customer Advances	Related costs are expensed as incurred. The balance below is included in short and long-term deferred revenue and customer advances. For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Balance at beginning of period $ 63,525 $ 40,178 $ 51,929 $ 30,677 Deferral of new extended warranty revenue 12,728 13,674 36,533 32,724 Recognition of extended warranty deferred revenue (8,771 ) (5,149 ) (20,980 ) (14,698 ) Balance at end of period $ 67,482 $ 48,703 $ 67,482 $ 48,703

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Oct. 03, 2021
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 October 3, September 27, Risk-free interest rate 0.2% 1.5% Teradyne volatility-historical 43.9% 34.9% NYSE Composite Index volatility-historical 22.9% 11.4% Dividend yield 0.4% 0.6%
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 October 3, September 27, Expected life (years) 5.0 5.0 Risk-free interest rate 0.4% 1.6% Volatility-historical 37.8% 31.6% Dividend yield 0.4% 0.6%

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Oct. 03, 2021
Changes in Accumulated Other Comprehensive Income	Changes in accumulated other comprehensive income, which are presented net of tax, consist of the following: Foreign Currency Translation Adjustment Unrealized Gains (Losses) on Marketable Securities Retirement Plans Service Credit Total (in thousands) Nine Months Ended October 3, 2021 Balance at December 31, 2020, net of tax of $0, $1,910, $(1,126), respectively $ 25,389 $ 6,954 $ 1,173 $ 33,516 Other comprehensive loss before reclassifications, net of tax of $0, $(516), $0, respectively (26,672 ) (1,952 ) — (28,624 ) Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(186), $(2), respectively — (670 ) (5 ) (675 ) Net current period other comprehensive loss, net of tax of $0 , $(702), $ (26,672 ) (2,622 ) (5 ) (29,299 ) Balance at October 3, 2021, net of tax of $0, $1,208, $(1,128), respectively $ (1,283 ) $ 4,332 $ 1,168 $ 4,217 Nine Months Ended September 27, 2020 Balance at December 31, 2019, net of tax of $0, $946, $(1,124), respectively $ (23,514 ) $ 3,480 $ 1,180 $ (18,854 ) Other comprehensive income before reclassifications, net of tax of $0, $1,410, $0, respectively 24,131 5,165 — 29,296 Amounts reclassified from accumulated other comprehensive income, net of tax of $0, $(615), $ (1 — (2,188 ) (6 ) (2,194 ) Net current period other comprehensive income (loss), net of tax of $0, $795, $(1), respectively 24,131 2,977 (6 ) 27,102 Balance at September 27, 2020, net of tax of $0, $1,741, $(1,125), respectively $ 617 $ 6,457 $ 1,174 $ 8,248
Reclassifications Out of Accumulated Other Comprehensive Income to Statements of Operations	Reclassifications out of accumulated other comprehensive income to the statement of operations for the three and nine months ended October 3, 2021 and September 27, 2020 were as follows: Details about Accumulated Other Comprehensive Income Components For the Three Months Ended For the Nine Months Ended Affected Line Item in the Statements of Operations October 3, September 27, October 3, September 27, (in thousands) Available-for-sale Unrealized gains, net of tax of $65, $194, $186, $615, respectively $ 229 $ 689 $ 670 $ 2,188 Other (income) Defined benefit postretirement plan: Amortization of prior service credit, net of tax of $0, $0, $2, $1, respectively 2 2 5 6 (a) Total reclassifications, net of tax of $65, $194, $188, $616, respectively $ 231 $ 691 $ 675 $ 2,194 Net income (a) The amortization of prior service credit is included in the computation of net periodic postretirement benefit cost. See Note Q: “Retirement Plans.”

Goodwill and Acquired Intangi_2

Goodwill and Acquired Intangible Assets (Tables)	9 Months Ended
	Oct. 03, 2021
Changes in Carrying Amount of Goodwill by Segment	The changes in the carrying amount of goodwill by reportable segments for the nine months ended October 3, 2021, were as follows: Industrial Automation System Wireless Semiconductor Total (in thousands) Balance at December 31, 2020 Goodwill $ 433,752 $ 158,699 $ 361,819 $ 262,155 $ 1,216,425 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) 433,752 10,516 7,976 1,615 453,859 Foreign currency translation adjustment (20,373 ) — — (88 ) (20,461 ) Balance at October 3, 2021 Goodwill 413,379 158,699 361,819 262,067 1,195,964 Accumulated impairment losses — (148,183 ) (353,843 ) (260,540 ) (762,566 ) $ 413,379 $ 10,516 $ 7,976 $ 1,527 $ 433,398
Schedule of Estimated Intangible Assets Amortization Expense	Estimated intangible asset amortization expense for each of the five succeeding fiscal years is as follows: Year Amortization Expense (in thousands) 2021 (remainder) $ 5,199 2022 20,299 2023 19,815 2024 19,507 2025 11,645 Thereafter 5,212
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: Gross Carrying Amount Accumulated Amortization Foreign Currency Net Carrying Amount Balance at October 3, 2021 (in thousands) Developed technology $ 272,547 $ (220,147 ) $ (3,489 ) $ 48,911 Customer relationships 57,739 (48,351 ) 174 9,562 Tradenames and trademarks 70,120 (46,643 ) (273 ) 23,204 Total intangible assets $ 400,406 $ (315,141 ) $ (3,588 ) $ 81,677 Balance, December 31, 2020 Developed technology $ 272,547 $ (210,479 ) $ (1,610 ) $ 60,458 Customer relationships 66,239 (54,524 ) 305 12,020 Tradenames and trademarks 70,120 (42,344 ) 685 28,461 Total intangible assets $ 408,906 $ (307,347 ) $ (620 ) $ 100,939

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Oct. 03, 2021
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 October 3, September 27, October 3, September 27, (in thousands, except per share amounts) Net income for basic and diluted net income per share $ 256,718 $ 222,718 $ 790,549 $ 587,815 Weighted average common shares-basic 164,583 166,014 165,690 166,131 Effect of dilutive potential common shares: Convertible note hedge warrant shares (1) 9,819 7,775 9,774 6,364 Incremental shares from assumed conversion of convertible notes (2) 6,464 9,156 8,784 8,029 Restricted stock units 1,035 1,237 1,147 1,104 Stock options 73 141 87 136 Employee stock purchase plan 13 15 10 13 Dilutive potential common shares 17,404 18,324 19,802 15,646 Weighted average common shares-diluted 181,987 184,338 185,492 181,777 Net income per common share-basic $ 1.56 $ 1.34 $ 4.77 $ 3.54 Net income per common share-diluted $ 1.41 $ 1.21 $ 4.26 $ 3.23 (1) Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.56 and $39.58, multiplied by million shares and 14.6 million shares for the three and nine months ended October 3, 2021, respectively. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period. (2) 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 $31.53 and $31.54, multiplied by million shares and 11.7 million shares, for the three and nine months ended October 3, 2021, respectively. 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.

Retirement Plans (Tables)

Retirement Plans (Tables)	9 Months Ended
	Oct. 03, 2021
Defined Benefit Pension Plans
Net Periodic Pension and Postretirement Benefit Costs	For the three and nine months ended October 3, 2021 and September 27, 2020, Teradyne’s net periodic pension cost was comprised of the following components: For the Three Months Ended October 3, 2021 September 27, 2020 United States Foreign United States Foreign (in thousands) Service cost $ 452 $ 240 $ 417 $ 216 Interest cost 1,098 86 1,460 123 Expected return on plan assets (936 ) (17 ) (1,170 ) (16 ) Net actuarial loss — — 2,238 — Settlement loss — — 450 — Total net periodic pension cost $ 614 $ 309 $ 3,395 $ 323 For the Nine Months Ended October 3, 2021 September 27, 2020 United States Foreign United States Foreign (in thousands) Service cost $ 1,357 $ 720 $ 1,283 $ 648 Interest cost 3,295 257 4,505 369 Expected return on plan assets (2,809 ) (50 ) (3,634 ) (47 ) Net actuarial (gain) loss (400 ) — 2,418 — Settlement loss — — 450 — Total net periodic pension cost $ 1,443 $ 927 $ 5,022 $ 970
Postretirement Benefit Plans
Net Periodic Pension and Postretirement Benefit Costs	For the three and nine months ended October 3, 2021 and September 27, 2020, Teradyne’s net periodic postretirement benefit cost (credit) was comprised of the following components: For the Three Months Ended For the Nine Months Ended October 3, September 27, October 3, September 27, (in thousands) Service cost $ 16 $ 14 $ 48 $ 43 Interest cost 43 60 128 180 Amortization of prior service credit (2 ) (2 ) (7 ) (7 ) Net actuarial gain — — (228 ) (279 ) Total net periodic postretirement benefit cost (credit) $ 57 $ 72 $ (59 ) $ (63 )

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Oct. 03, 2021
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 Ended For the Nine Months Ended October 3, September 27, October 3, September 27, U.S. statutory federal tax rate 21.0 % 21.0 % 21.0 % 21.0 % Foreign taxes (4.4 ) (6.9 ) (4.4 ) (5.8 ) Tax credits (1.9 ) (1.6 ) (1.4 ) (1.6 ) International provisions of the U.S. Tax Cuts and Jobs Act of 2017 (1.5 ) 3.0 (1.6 ) 0.5 Discrete benefit related to equity compensation (0.1 ) (0.4 ) (1.6 ) (1.4 ) Other, net 0.7 0.5 0.7 0.6 Effective tax rate 13.8 % 15.6 % 12.7 % 13.3 %

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Oct. 03, 2021
Segment Information	Segment information for th e Semiconductor Test System Test Industrial Automation Wireless Test Corporate and Other Consolidated (in thousands) Three Months Ended October 3, 2021 Revenues $ 688,232 $ 102,605 $ 91,014 $ 68,713 $ (63 ) $ 950,501 Income (loss) before income taxes (1)(2) 265,017 31,773 (4,226 ) 31,726 (26,535 ) 297,755 Total assets (3) 1,251,549 147,970 696,792 119,568 1,546,303 3,762,182 Three Months Ended September 27, 2020 Revenues $ 592,141 $ 118,169 $ 68,711 $ 40,504 $ (41 ) $ 819,484 Income (loss) before income taxes (1)(2) 189,116 47,368 (5,302 ) 10,938 21,611 263,731 Total assets (3) 1,069,830 155,642 667,132 108,671 1,435,237 3,436,512 Nine Months Ended October 3, 2021 (4) Revenues $ 2,050,271 $ 340,261 $ 263,151 $ 164,504 $ (352 ) $ 2,817,835 Income (loss) before income taxes (1)(2) 778,687 116,788 (14,586 ) 63,810 (38,925 ) 905,774 Total assets (3) 1,251,549 147,970 696,792 119,568 1,546,303 3,762,182 Nine Months Ended September 27, 2020 Revenues $ 1,735,777 $ 306,051 $ 187,792 $ 133,174 $ (294 ) $ 2,362,500 Income (loss) before income taxes (1)(2) 571,719 114,968 (32,041 ) 35,640 (12,197 ) 678,089 Total assets (3) 1,069,830 155,642 667,132 108,671 1,435,237 3,436,512 (1) Included in Corporate and Other are: contingent consideration adjustments, loss on convertible debt conversions, interest income, interest expense, net foreign exchange gains (losses), pension, intercompany eliminations and acquisition related: (a) charges; (b) legal fees; (c) compensation. (2) Included in income (loss) before taxes are charges and credits related to restructuring and other, loss on convertible debt conversions and inventory charges. (3) Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets. (4) The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods.
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 October 3, September 27, October 3, September 27, (in thousands) Semiconductor Test: Cost of revenues—inventory charge $ 3,725 $ 1,131 $ 4,959 $ 7,956 Restructuring and other—Contract termination settlement charge — — — 4,000 Industrial Automation: Cost of revenues—inventory charge $ 3,656 $ — $ 4,941 $ 505 Restructuring and other—employee severance 476 — 965 664 Restructuring and other—acquisition related expenses and compensation — — 825 790 Wireless: Cost of revenues—inventory charge $ 679 $ 1,802 $ 1,351 $ 3,957 System Test: Cost of revenues—inventory charge $ — $ — $ 524 $ 698 Corporate and Other: Other (income) expense, net—loss on convertible debt conversion $ 20,153 $ — $ 25,397 $ — Restructuring and other—other — — 1,846 — Restructuring and other—AutoGuide contingent consideration adjustment — (27,206 ) (7,227 ) (4,421 ) Restructuring and other—acquisition related expenses and compensation — (1,086 ) (513 ) 2,629 Restructuring and other—MiR contingent consideration adjustment — — — (3,546 )

Recently Issued Accounting Pr_2

Recently Issued Accounting Pronouncements - Additional Information (Detail)	Nov. 04, 2021	Dec. 12, 2016
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt instrument, interest rate, stated percentage	1.25%	1.25%

Investment In Other Company - A

Investment In Other Company - Additional Information (Details) - MachineMetrics, Inc [Member] - USD ($) $ in Millions	3 Months Ended
	Oct. 03, 2021	Jun. 01, 2021
Schedule of Equity Method Investments [Line Items]
Long-term Investments	$ 12	$ 12
Unrealized Gain (Loss) on Investments	$ 0

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Deferred Revenue And Customer Advances	$ 32.9	$ 17.6	$ 82.5	$ 78.2
Deferred Revenue and Trade Accounts Receivable	66.9	$ 16.5	81.7	$ 113.5
Revenue, Remaining Performance Obligation, Amount	$ 1,293		$ 1,293
Short-term Contract with Customer [Member]
Revenue, Remaining Performance Obligation, Percentage	94.00%		94.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period			12 months
Long-term Contract with Customer [Member]
Revenue, Remaining Performance Obligation, Percentage	5.00%		5.00%
Long-term Contract with Customer [Member] | Revenue Remaining Performance Obligation Percentage Two [Member]
Revenue, Remaining Performance Obligation, Percentage	1.00%		1.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Period			3 years
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

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
	Oct. 03, 2021		Sep. 27, 2020		Oct. 03, 2021		Sep. 27, 2020
Disaggregation of Revenue [Line Items]
Total	$ 950,501	[1]	$ 819,484	[1]	$ 2,817,835	[2],[3]	$ 2,362,500	[2]
Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	688,232		592,141		2,050,271	[3]	1,735,777
System Test
Disaggregation of Revenue [Line Items]
Total	102,605	[1]	118,169	[1]	340,261	[2],[3]	306,051	[2]
Industrial Automation
Disaggregation of Revenue [Line Items]
Total	91,014		68,711		263,151	[3]	187,792
Wireless Test
Disaggregation of Revenue [Line Items]
Total	68,713	[1]	40,504	[1]	164,504	[2],[3]	133,174	[2]
Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(63)	[1]	(41)	[1]	(352)	[2]	(294)	[2]
Point in Time
Disaggregation of Revenue [Line Items]
Total	856,287	[1]	736,325	[1]	2,546,734	[2]	2,124,031	[2]
Point in Time | System Test
Disaggregation of Revenue [Line Items]
Total	88,155	[1]	101,045	[1]	295,666	[2]	259,498	[2]
Point in Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	65,409	[1]	37,901	[1]	154,908	[2]	125,304	[2]
Point in Time | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(63)	[1]	(41)	[1]	(352)	[2]	(294)	[2]
Over Time
Disaggregation of Revenue [Line Items]
Total	94,214	[1]	83,159	[1]	271,101	[2]	238,469	[2]
Over Time | System Test
Disaggregation of Revenue [Line Items]
Total	14,450	[1]	17,124	[1]	44,595	[2]	46,553	[2]
Over Time | Wireless Test
Disaggregation of Revenue [Line Items]
Total	3,304	[1]	2,603	[1]	9,596	[2]	7,870	[2]
Americas
Disaggregation of Revenue [Line Items]
Total	105,999	[1]	87,494	[1]	287,475	[2]	232,840	[2]
Americas | System Test
Disaggregation of Revenue [Line Items]
Total	34,560	[1]	35,140	[1]	98,475	[2]	91,924	[2]
Americas | Wireless Test
Disaggregation of Revenue [Line Items]
Total	11,352	[1]	5,211	[1]	24,228	[2]	15,253	[2]
Americas | Corporate and Other
Disaggregation of Revenue [Line Items]
Total	(63)	[1]	(41)	[1]	(352)	[2]	(294)	[2]
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total	74,711	[1]	45,447	[1]	189,291	[2]	147,678	[2]
Europe, Middle East and Africa | System Test
Disaggregation of Revenue [Line Items]
Total	5,288	[1]	4,495	[1]	18,279	[2]	16,919	[2]
Europe, Middle East and Africa | Wireless Test
Disaggregation of Revenue [Line Items]
Total	3,017	[1]	1,428	[1]	6,598	[2]	4,345	[2]
Asia Pacific
Disaggregation of Revenue [Line Items]
Total	769,791	[1]	686,543	[1]	2,341,069	[2]	1,981,982	[2]
Asia Pacific | System Test
Disaggregation of Revenue [Line Items]
Total	62,757	[1]	78,534	[1]	223,507	[2]	197,208	[2]
Asia Pacific | Wireless Test
Disaggregation of Revenue [Line Items]
Total	54,344	[1]	33,865	[1]	133,678	[2]	113,576	[2]
SOC | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	575,017	[1]	449,705	[1]	1,736,917	[2]	1,423,627	[2]
SOC | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	508,747	[1]	393,717	[1]	1,548,895	[2]	1,261,468	[2]
SOC | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	66,270	[1]	55,988	[1]	188,022	[2]	162,159	[2]
SOC | Americas | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	29,119	[1]	17,678	[1]	71,562	[2]	51,315	[2]
SOC | Europe, Middle East and Africa | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	26,012	[1]	11,206	[1]	47,238	[2]	41,849	[2]
SOC | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	519,886	[1]	420,821	[1]	1,618,117	[2]	1,330,463	[2]
Memory | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	113,215	[1]	142,436	[1]	313,354	[2]	312,150	[2]
Memory | Point in Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	105,454	[1]	137,929	[1]	291,578	[2]	298,150	[2]
Memory | Over Time | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	7,761	[1]	4,507	[1]	21,776	[2]	14,000	[2]
Memory | Americas | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	2,281	[1]	3,730	[1]	9,373	[2]	11,481	[2]
Memory | Europe, Middle East and Africa | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	572	[1]	1,420	[1]	2,419	[2]	3,990	[2]
Memory | Asia Pacific | Semiconductor Test
Disaggregation of Revenue [Line Items]
Total	110,362	[1]	137,286	[1]	301,562	[2]	296,679	[2]
Universal Robots (UR) | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	77,750	[1]	53,209	[1]	219,428	[2]	146,457	[2]
Universal Robots (UR) | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	76,008	[1]	51,523	[1]	214,427	[2]	140,829	[2]
Universal Robots (UR) | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	1,742	[1]	1,686	[1]	5,001	[2]	5,628	[2]
Universal Robots (UR) | Americas | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	23,429	[1]	16,527	[1]	66,390	[2]	42,634	[2]
Universal Robots (UR) | Europe, Middle East and Africa | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	34,667	[1]	22,211	[1]	97,507	[2]	64,158	[2]
Universal Robots (UR) | Asia Pacific | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	19,654	[1]	14,471	[1]	55,531	[2]	39,665	[2]
MiR | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	12,958	[1]	10,234	[1]	42,989	[2]	30,644	[2]
MiR | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	12,351	[1]	10,175	[1]	41,506	[2]	30,468	[2]
MiR | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	607	[1]	59	[1]	1,483	[2]	176	[2]
MiR | Americas | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	5,015	[1]	3,981	[1]	17,065	[2]	9,836	[2]
MiR | Europe, Middle East and Africa | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	5,155	[1]	4,687	[1]	17,250	[2]	16,417	[2]
MiR | Asia Pacific | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	2,788	[1]	1,566	[1]	8,674	[2]	4,391	[2]
Autoguide LLC [Member] | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	306	[1]	5,268	[1]	734	[2]	10,691	[2]
Autoguide LLC [Member] | Point in Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	226	[1]	4,076	[1]	106	[2]	8,608	[2]
Autoguide LLC [Member] | Over Time | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	80	[1]	1,192	[1]	628	[2]	2,083	[2]
Autoguide LLC [Member] | Americas | Industrial Automation
Disaggregation of Revenue [Line Items]
Total	$ 306	[1]	$ 5,268	[1]	$ 734	[2]	$ 10,691	[2]
[1]	Includes $3.8 million and $1.7 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside Accounting Standards Codification (“ASC”) 606 “Revenue from Contracts with Customers.
[2]	Includes $11.1 million and $6.1 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside ASC 606 “Revenue from Contracts with Customers.
[3]	The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods.

Disaggregated Revenue by Prim_2

Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing of Revenue Recognition (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Accounting Policies [Abstract]
Revenue on leases	$ 3.8	$ 1.7	$ 11.1	$ 6.1

Composition of Inventories, Net

Composition of Inventories, Net (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw material	$ 131,807	$ 114,133
Work-in-process	34,911	25,408
Finished goods	57,524	82,648
Inventories, net	$ 224,242	$ 222,189

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Oct. 03, 2021	Dec. 31, 2020
Inventory [Line Items]
Inventory reserves	$ 112.5	$ 110.6

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020	Dec. 31, 2020
Financial Instruments and Fair Value [Line Items]
Available-for-sale securities, realized gain	$ 0.5	$ 1.1	$ 2.6	$ 4.1
Available-for-sale securities, realized loss	0	0.1	0	0.3
Aggregate loss of investments with unrealized losses greater than one year	6.2		6.2
Fair market value of investments with unrealized losses less than one year	57.3		57.3		$ 70.4
Unrealized Gain (loss) on contracts	1	1.2	1.3	0.4
Equity securities unrealized gain		$ 2	3.3	5.7
Equity securities unrealized loss	0.4		1.1	$ 6
Debt Mutual Funds
Financial Instruments and Fair Value [Line Items]
Available for sale securities with out contractual maturity date	$ 8.9		8.9
Foreign Exchange Contracts
Financial Instruments and Fair Value [Line Items]
Unrealized Gain (loss) on contracts			$ 181.8		$ 152.9

Schedule of Fair Value of Finan

Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 334,285	$ 610,840
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	80,519	258,304
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	179,629	254,413
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	58,648	83,615
Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	1,346	979
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	4,616	4,339
Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	8,937	8,565
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	590	625
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,449,515	1,554,381
Derivative assets	93	95
Total	1,449,608	1,554,476
Contingent consideration		7,227
Derivative liabilities	433	504
Total	433	7,731
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	577,752	443,166
Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	501,702	470,955
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	80,519	258,304
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	179,629	254,413
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	58,648	83,615
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	1,346	979
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	4,616	4,339
Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	8,937	8,565
Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	590	625
Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	35,776	29,420
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	799,168	828,919
Total	799,168	828,919
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	577,752	443,166
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	176,703	347,768
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	8,937	8,565
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	35,776	29,420
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	650,347	725,462
Derivative assets	93	95
Total	650,440	725,557
Derivative liabilities	433	504
Total	433	504
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	324,999	123,187
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	80,519	258,304
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	179,629	254,413
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	58,648	83,615
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	1,346	979
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	4,616	4,339
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	$ 590	625
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration		7,227
Total		$ 7,227

Schedule of Reported Financial

Schedule of Reported Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	$ 1,449,608	$ 1,554,476
Liabilities	433	7,731
Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	433	504
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	1,079,454	914,121
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	233,397	522,280
Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	136,664	117,980
Prepayments and other current assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	93	95
Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities		7,227
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	799,168	828,919
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	754,455	790,934
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	44,713	37,985
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	650,440	725,557
Liabilities	433	504
Significant Other Observable Inputs (Level 2) | Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities	433	504
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	324,999	123,187
Significant Other Observable Inputs (Level 2) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	233,397	522,280
Significant Other Observable Inputs (Level 2) | Long-term marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	91,951	79,995
Significant Other Observable Inputs (Level 2) | Prepayments and other current assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets	$ 93	95
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities		7,227
Significant Unobservable Inputs (Level 3) | Long Term Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities		$ 7,227

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
		Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 0	$ 49,737	$ 7,227	$ 39,705
Fair value adjustment	[1],[2],[3]	0	(27,206)	(7,227)	(7,967)
Foreign currency impact		0	0	0	(355)
Payments	[4]				(8,852)
Balance at end of period		$ 0	$ 22,531	$ 0	$ 22,531
[1]	In the nine months ended October 3, 2021, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide was reduced to zero, which resulted in a benefit of $7.2 million, primarily due to a decrease in forecasted revenues and earnings before interest and taxes. As of October 3, 2021, the maximum amount of contingent consideration that could be paid in connection with the acquisition of AutoGuide is $100.2 million. The remaining earn-out periods end on December 31, 2021 and December 31, 2022. The sellers of AutoGuide have filed an arbitration claim against Teradyne related to allegations of non-compliance with its earn-out obligations. The ultimate amount of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide may be affected by the outcome of the arbitration (see Note R: “Commitments and Contingencies”).
[2]	In the nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of Mobile Industrial Robots (“MiR”) decreased by $3.5 million due to lower forecasted results.
[3]	In the three and nine months ended September 27, 2020, the fair value of contingent consideration for the earn-outs in connection with the acquisition of AutoGuide decreased by $27.2 million and $4.4 million, respectively, due to lower forecasted revenues and earnings before interest and taxes.
[4]	In the nine months ended September 27, 2020, Teradyne paid $8.9 million of contingent consideration for the earn-out in connection with the acquisition of MiR.

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. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			$ 8,852
Increase (decrease) in contingent consideration		$ (7,227)	(7,967)
Maximum amount of contingent consideration paid for acquisition			8,852
Avionics Interface Technologies, LLC
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration			8,900
Maximum amount of contingent consideration paid for acquisition			8,900
MiR
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration	$ 27,200	4,400
Maximum amount of contingent consideration paid for acquisition	$ 27,200	4,400
Autoguide LLC [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments of contingent consideration		100,200	3,500
Maximum amount of contingent consideration paid for acquisition		100,200	$ 3,500
Autoguide LLC [Member] | Dispute In Respect Of Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Increase (decrease) in contingent consideration		$ 7,200

Schedule of Carrying Amounts an

Schedule of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Oct. 03, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Marketable securities		$ 334,285	$ 610,840
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		1,079,454	914,121
Marketable securities		370,061	640,260
Derivative assets		93	95
Contingent consideration			7,227
Derivative liabilities		433	504
Convertible debt	[1]	145,003	410,111
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Cash and cash equivalents		1,079,454	914,121
Marketable securities		370,061	640,260
Derivative assets		93	95
Contingent consideration			7,227
Derivative liabilities		433	504
Convertible debt	[1]	$ 546,464	$ 1,739,553
[1]	The carrying value represents the bifurcated debt component only, while the level 2 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	Oct. 03, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 328,741	$ 601,976
Available-for-sale marketable securities, Unrealized Gain	6,138	9,077
Available-for-sale marketable securities, Unrealized (Loss)	(594)	(213)
Available-for-sale marketable securities, Fair Market Value	334,285	610,840
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	63,447	70,418
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	80,370	257,132
Available-for-sale marketable securities, Unrealized Gain	636	1,330
Available-for-sale marketable securities, Unrealized (Loss)	(487)	(158)
Available-for-sale marketable securities, Fair Market Value	80,519	258,304
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	17,336	17,243
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	179,624	254,404
Available-for-sale marketable securities, Unrealized Gain	5	10
Available-for-sale marketable securities, Unrealized (Loss)	0	(1)
Available-for-sale marketable securities, Fair Market Value	179,629	254,413
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	20,799	12,173
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	53,329	76,129
Available-for-sale marketable securities, Unrealized Gain	5,421	7,539
Available-for-sale marketable securities, Unrealized (Loss)	(102)	(53)
Available-for-sale marketable securities, Fair Market Value	58,648	83,615
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	22,010	39,896
Certificates of Deposit and Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	1,346	979
Available-for-sale marketable securities, Unrealized Gain	0
Available-for-sale marketable securities, Fair Market Value	1,346	979
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	4,610	4,294
Available-for-sale marketable securities, Unrealized Gain	11	46
Available-for-sale marketable securities, Unrealized (Loss)	(5)	(1)
Available-for-sale marketable securities, Fair Market Value	4,616	4,339
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	3,302	1,106
Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	8,872	8,413
Available-for-sale marketable securities, Unrealized Gain	65	152
Available-for-sale marketable securities, Fair Market Value	8,937	8,565
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	590	625
Available-for-sale marketable securities, Fair Market Value	$ 590	$ 625

Schedule of Reported Available

Schedule of Reported Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 328,741	$ 601,976
Available-for-sale marketable securities, Unrealized Gain	6,138	9,077
Available-for-sale marketable securities, Unrealized (Loss)	(594)	(213)
Available-for-sale marketable securities, Fair Market Value	334,285	610,840
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	63,447	70,418
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	233,327	522,228
Available-for-sale marketable securities, Unrealized Gain	92	92
Available-for-sale marketable securities, Unrealized (Loss)	(22)	(40)
Available-for-sale marketable securities, Fair Market Value	233,397	522,280
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	28,773	61,806
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	95,414	79,748
Available-for-sale marketable securities, Unrealized Gain	6,046	8,985
Available-for-sale marketable securities, Unrealized (Loss)	(572)	(173)
Available-for-sale marketable securities, Fair Market Value	100,888	88,560
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 34,674	$ 8,612

Contractual Maturities of Inves

Contractual Maturities of Investments in Debt Securities Held (Detail) $ in Thousands	Oct. 03, 2021USD ($)
Schedule of Available-for-sale Securities
Due within one year, cost	$ 233,327
Due after 1 year through 5 years, cost	46,460
Due after 5 years through 10 years, cost	6,120
Due after 10 years, cost	33,962
Total, cost	319,869
Due within one year, fair market value	233,397
Due after 1 year through 5 years, fair market value	46,744
Due after 5 years through 10 years, fair market value	6,586
Due after 10 years, fair maket value	38,621
Total, fair market value	$ 325,348

Schedule of Derivative Instrume

Schedule of Derivative Instruments in Statement of Financial Position at Fair Value (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	$ (340)	$ (409)
Not Designated as Hedging Instrument | Foreign currency forward contracts | Prepayments
Derivatives, Fair Value [Line Items]
Derivative assets	93	95
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ (433)	$ (504)

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
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses (Gains) on derivatives recognized in statements of operations	$ 2,288	$ (551)	$ 5,937	$ 3,930

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
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on foreign currency transactions	$ 1	$ 1.2	$ 1.3	$ 0.4

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, shares in Millions	Nov. 05, 2021USD ($)	May 01, 2020USD ($)	Dec. 12, 2016USD ($)Customer$ / sharesshares	Dec. 31, 2021USD ($)	Oct. 03, 2021USD ($)$ / shares	Oct. 03, 2021USD ($)$ / sharesshares	Sep. 27, 2020USD ($)shares	Dec. 31, 2020USD ($)	Nov. 04, 2021
Debt Instrument
Repurchase of common stock						$ 406,180,000	$ 88,465,000
Repurchase of stock, shares | shares						3.3	1.5
Line of Credit Facility, Maximum Borrowing Capacity		$ 400,000,000
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases		$ 150,000,000
Line of Credit Facility, Interest Rate Description		The interest rates applicable to loans under the Credit Facility are, at Teradyne’s option, equal to either a base rate plus a margin ranging from 0.50% to 1.25% per annum or LIBOR, a minimum of 0.75%, plus a margin ranging from 1.50% to 2.25% per annum, based on the consolidated leverage ratio of Teradyne. In addition, Teradyne will pay a commitment fee on the unused portion of the commitments under the Credit Facility ranging from 0.25% to 0.40% per annum, based on the then applicable consolidated leverage ratio.
Term of revolving credit facility		3 years
Convertible common shares					$ 235,200,000	$ 302,000,000
Other (income) expense [Member]
Debt Instrument
Gain loss on debt conversion					20,200,000	25,400,000
Convertible Common Shares [Member]
Debt Instrument
Shares Issued, Stock Options Exercised						7,200,000
Subsequent Event [Member] | Convertible Common Shares [Member]
Debt Instrument
Increase in debt principal, Additional conversion				$ 41,000,000
Collateral Pledged [Member]
Debt Instrument
Line of Credit Facility, Interest Rate Description		65
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Aggregate principal amount			$ 460,000,000		$ 157,972,000	157,972,000		$ 459,971,000
Debt instrument, interest rate, stated percentage			1.25%						1.25%
Debt instrument, net proceeds after issuance costs			$ 450,800,000
Payment for net cost of convertible note hedges net of warrant proceeds			33,000,000			$ 33,000,000
Repurchase of common stock			$ 50,100,000
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			$ 31.53		$ 31.53	$ 31.53
Shares that would be issued upon conversion | shares			14.6			8.7
Strike price per share of warrant | $ / shares						$ 39.56
Debt instrument, convertible, carrying amount of equity component					$ 100,800,000	$ 100,800,000	$ 100,800,000
Debt instrument, effective annual interest rate					5.00%	5.00%
Financing cost					$ 900,000	$ 900,000	$ 7,200,000
Debt issuance costs, amortization period							7 years
Unamortized discount					13,000,000	13,000,000
Debt Instrument, convertible, remaining discount amortization period								2 years 3 months 18 days
Value of notes converted						1,364,600,000
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 | Subsequent Event [Member]
Debt Instrument
Debt instrument conversion converted instrument amount	$ 343,000,000
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
Aggregate principal amount			$ 1,000
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
Debt Instrument
Revolving credit facility costs incurred					$ 3,500,000	$ 3,500,000

Components of Convertible Senio

Components of Convertible Senior Notes (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020	Dec. 12, 2016
Debt Instrument
Current debt	$ 32,219	$ 33,343
Long-term debt	112,784	376,768
Net carrying amount of convertible debt	145,003	410,111
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Debt principal	157,972	459,971	$ 460,000
Unamortized discount	12,969	49,860
Net carrying amount of convertible debt	$ 145,003	$ 410,111

Interest Expense on Convertible

Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Debt Instrument
Contractual interest expense on the coupon	$ 355	$ 1,438	$ 2,666	$ 4,313
Amortization of the discount component and debt issue fees recognized as interest expense	2,424	3,887	9,771	11,518
Total interest expense on the convertible debt	$ 2,779	$ 5,325	$ 12,437	$ 15,831

Prepayments (Detail)

Prepayments (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Dec. 31, 2020
Prepaid And Other Current Assets [Line Items]
Contract manufacturer and supplier prepayments	$ 334,660	$ 212,286
Prepaid maintenance and other services	13,574	13,116
Prepaid taxes	13,822	9,361
Other prepayments	12,093	15,329
Total prepayments	$ 374,149	$ 250,092

Deferred Revenue and Customer_3

Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	Oct. 03, 2021	Jul. 04, 2021	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Dec. 31, 2019
Deferred Revenue Arrangement
Maintenance, service and training	$ 83,046		$ 77,654
Extended warranty	67,482	$ 63,525	51,929	$ 48,703	$ 40,178	$ 30,677
Customer advances, undelivered elements and other	49,874		63,438
Total deferred revenue and customer advances	$ 200,402		$ 193,021

Product Warranty (Detail)

Product Warranty (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 25,676	$ 13,016	$ 16,633	$ 8,996
Accruals for warranties issued during the period	6,641	8,255	28,719	19,522
Accruals related to pre-existing warranties	(963)	158	(3,966)	1,569
Settlements made during the period	(5,233)	(6,272)	(15,265)	(14,930)
Balance at end of period	$ 26,121	$ 15,157	$ 26,121	$ 15,157

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
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Product Warranty Liability [Line Items]
Balance at beginning of period	$ 63,525	$ 40,178	$ 51,929	$ 30,677
Deferral of new extended warranty revenue	12,728	13,674	36,533	32,724
Recognition of extended warranty deferred revenue	(8,771)	(5,149)	(20,980)	(14,698)
Balance at end of period	$ 67,482	$ 48,703	$ 67,482	$ 48,703

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - $ / shares shares in Millions	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Stock price	$ 72.10	$ 113.48
Stock Options | Measurement Input, Expected Dividend Payment [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Estimated annual dividend amount per share	$ 0.40	$ 0.40
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
Percentage of awards vesting on the first anniversary of grant date	100.00%
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
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period	3 years	3 years
Minimum age of retirement to be eligible for PRSUs	60 years
Minimum years of service for retirement to be eligible for PRSUs	10 years
Restricted stock unit awards granted	0.1
Weighted average grant date fair value of restricted stock units granted	$ 125.02	$ 89.93
Stock price	0.40	72.10
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	$ 0.40	113.48
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	0.00%
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	200.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of common stock price paid	100.00%
PBIT Performance-Based Restricted Stock Units
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	$ 113.65	$ 70.94
Service-Based Restricted Stock Units | Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted	0.3	0.4
Weighted average grant date fair value of restricted stock units granted	$ 113.76	$ 70.76
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	$ 36.60	20.67
Service-Based Restricted Stock Units | Non Employee Directors
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	$ 127.77	$ 64.99

Schedule of Estimated Fair Valu

Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions (Detail)	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Expected historical volatility	37.80%	31.60%
New York Stock Exchange Composite Index
Share-based Compensation Arrangement by Share-based Payment Award
Expected historical volatility	22.90%	11.40%
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Risk-free interest rate	0.20%	1.50%
Expected historical volatility	43.90%	34.90%
Dividend yield	0.40%	0.60%

Schedule of Estimated Fair Va_2

Schedule of Estimated Fair Value of Stock Options Grant Using Black Scholes Option Pricing Model (Detail)	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Volatility-historical	37.80%	31.60%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Expected life (years)	5 years	5 years
Risk-free interest rate	0.40%	1.60%
Dividend yield	0.40%	0.60%

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		$ 2,493,256	$ 1,744,551	$ 2,207,018	$ 1,480,158
Other comprehensive (loss) income		(11,105)	16,748	(29,299)	27,102
Balance		2,537,493	1,993,544	2,537,493	1,993,544
Foreign Currency Translation Reclassification Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance				25,389	(23,514)
Other comprehensive (loss) income before reclassifications, net of tax				(26,672)	24,131
Amounts reclassified from accumulated other comprehensive income (loss), net of tax				0	0
Other comprehensive (loss) income				(26,672)	24,131
Balance		(1,283)	617	(1,283)	617
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance				6,954	3,480
Other comprehensive (loss) income before reclassifications, net of tax				(1,952)	5,165
Amounts reclassified from accumulated other comprehensive income (loss), net of tax				(670)	(2,188)
Other comprehensive (loss) income				(2,622)	2,977
Balance		4,332	6,457	4,332	6,457
Retirement Plans Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance				1,173	1,180
Other comprehensive (loss) income before reclassifications, net of tax				0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	[1]	(2)	(2)	(5)	(6)
Other comprehensive (loss) income				(5)	(6)
Balance		1,168	1,174	1,168	1,174
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		15,322	(8,500)	33,516	(18,854)
Other comprehensive (loss) income before reclassifications, net of tax				(28,624)	29,296
Amounts reclassified from accumulated other comprehensive income (loss), net of tax		(231)	(691)	(675)	(2,194)
Other comprehensive (loss) income		(11,105)	16,748	(29,299)	27,102
Balance		$ 4,217	$ 8,248	$ 4,217	$ 8,248
[1]	The amortization of prior service credit is included in the computation of net periodic postretirement benefit cost. See Note Q: “Retirement Plans.

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss), tax	$ (65)	$ (194)	$ (188)	$ (616)
Foreign currency translation adjustments, tax	0	0	0	0	$ 0	$ 0
Unrealized (losses) gains on marketable securities, tax	1,208	1,741	1,208	1,741	1,910	946
Retirement plans prior service benefit, tax	(1,128)	(1,125)	(1,128)	(1,125)	$ (1,126)	$ (1,124)
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
Unrealized (Losses) Gains on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, tax			(516)	1,410
Amounts reclassified from accumulated other comprehensive income (loss), tax	(65)	(194)	(186)	(615)
Other comprehensive income (loss), tax			(702)	795
Retirement Plans 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	$ 0	$ 0	(2)	(1)
Other comprehensive income (loss), tax			$ (2)	$ (1)

Reclassifications Out of Accumu

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)		$ 229	$ 689	$ 670	$ 2,188
Retirement Plans Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax	[1]	2	2	5	6
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax		$ 231	$ 691	$ 675	$ 2,194
[1]	The amortization of prior service credit is included in the computation of net periodic postretirement benefit cost. See Note Q: “Retirement Plans.

Reclassifications Out of Accu_2

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) to Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 65	$ 194	$ 188	$ 616
Unrealized (Losses) Gains on Marketable Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	65	194	186	615
Amortization of Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, tax	$ 0	$ 0	$ 2	$ 1

Goodwill and Acquired Intangi_3

Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Goodwill and Intangible Assets Disclosure [Line Items]
Acquired intangible assets amortization	$ 5,355	$ 6,219	$ 16,293	$ 25,052

Changes in Carrying Amount of G

Changes in Carrying Amount of Goodwill by Segment (Detail) - USD ($) $ in Thousands	9 Months Ended
	Oct. 03, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 1,195,964	$ 1,216,425
Accumulated impairment losses	(762,566)	(762,566)
Foreign currency translation adjustment	(20,461)
Goodwill	433,398	453,859
Industrial Automation
Goodwill [Line Items]
Goodwill	413,379	433,752
Accumulated impairment losses	0	0
Foreign currency translation adjustment	(20,373)
Goodwill	413,379	433,752
Wireless Test
Goodwill [Line Items]
Goodwill	361,819	361,819
Accumulated impairment losses	(353,843)	(353,843)
Foreign currency translation adjustment	0
Goodwill	7,976	7,976
Semiconductor Test
Goodwill [Line Items]
Goodwill	262,067	262,155
Accumulated impairment losses	(260,540)	(260,540)
Foreign currency translation adjustment	(88)
Goodwill	1,527	1,615
System Test
Goodwill [Line Items]
Goodwill	158,699	158,699
Accumulated impairment losses	(148,183)	(148,183)
Foreign currency translation adjustment	0
Goodwill	$ 10,516	$ 10,516

Schedule of Amortizable Intangi

Schedule of Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Oct. 03, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 400,406	$ 408,906
Accumulated Amortization	(315,141)	(307,347)
Foreign Currency Translation Adjustment	(3,588)	(620)
Net Carrying Amount	81,677	100,939
Developed technology
Finite-Lived Intangible Assets
Gross Carrying Amount	272,547	272,547
Accumulated Amortization	(220,147)	(210,479)
Foreign Currency Translation Adjustment	(3,489)	(1,610)
Net Carrying Amount	48,911	60,458
Customer Relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	57,739	66,239
Accumulated Amortization	(48,351)	(54,524)
Foreign Currency Translation Adjustment	174	305
Net Carrying Amount	9,562	12,020
Trademarks and tradenames
Finite-Lived Intangible Assets
Gross Carrying Amount	70,120	70,120
Accumulated Amortization	(46,643)	(42,344)
Foreign Currency Translation Adjustment	(273)	685
Net Carrying Amount	$ 23,204	$ 28,461

Schedule of Estimated Intangibl

Schedule of Estimated Intangible Asset Amortization Expense (Detail) $ in Thousands	Oct. 03, 2021USD ($)
Finite-Lived Intangible Assets
2021 (remainder)	$ 5,199
2022	20,299
2023	19,815
2024	19,507
2025	11,645
Thereafter	$ 5,212

Computation of Basic and Dilute

Computation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 256,718	$ 222,718	$ 790,549	$ 587,815
Weighted average common shares-basic		164,583	166,014	165,690	166,131
Convertible note hedge warrant shares	[1]	9,819	7,775	9,774	6,364
Incremental shares from assumed conversion of convertible notes	[2]	6,464	9,156	8,784	8,029
Employee stock purchase plan		13	15	10	13
Dilutive potential common shares		17,404	18,324	19,802	15,646
Weighted average common shares-diluted		181,987	184,338	185,492	181,777
Net income per common share-basic		$ 1.56	$ 1.34	$ 4.77	$ 3.54
Net income per common share-diluted		$ 1.41	$ 1.21	$ 4.26	$ 3.23
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,035	1,237	1,147	1,104
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		73	141	87	136
[1]	Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.56 and $39.58, multiplied by 14.6 million shares and 14.6 million shares for the three and nine months ended October 3, 2021, respectively. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.
[2]	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 $31.53 and $31.54, multiplied by 8.7 million shares and 11.7 million shares, for the three and nine months ended October 3, 2021, respectively. 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.

Computation of Basic and Dilu_2

Computation of Basic and Diluted Net Income Per Common Share (Parenthetical) (Detail) - $ / shares shares in Millions	3 Months Ended	9 Months Ended
	Oct. 03, 2021	Oct. 03, 2021
Convertible Notes
Net Income Loss Per Common Share
Debt instrument, convertible, stock price trigger	$ 31.53	$ 31.54
Shares that would be issued upon conversion	8.7	11.7
Convertible Notes Hedge Warrant
Net Income Loss Per Common Share
Debt instrument, convertible, stock price trigger	$ 39.56	$ 39.58
Shares that would be issued upon conversion	14.6	14.6

Net Income Per Common Share - A

Net Income Per Common Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Net Income Loss Per Common Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.1	0.1	0.1	0.2

Restructuring and Other - Addit

Restructuring and Other - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Restructuring Cost and Reserve
Severance benefit and charges	$ 600		$ 1,200
Contingent consideration adjustment			(7,227)	$ (7,967)
Restructuring and other	300		600
Increase Decrease in environmental and legal liabilities			1,700
Acquisition related costs	$ 300		300
MiR Contingent Consideration Liability [Member]
Restructuring Cost and Reserve
Contingent consideration adjustment				3,500
Semiconductor Test
Restructuring Cost and Reserve
Severance benefit and charges		$ 500		1,200
Gain for the decrease in acquisition related comepnsation liability		1,100
Acquisition related costs				3,400
Loss on Contract Termination				4,000
Semiconductor Test, Industrial Automation and Corporate
Restructuring Cost and Reserve
Restructuring and other				1,200
Semiconductor Test, Industrial Automation and Corporate | Mobile Industrial Robots (MiR)
Restructuring Cost and Reserve
Contingent consideration adjustment		$ 27,200	$ 7,200	$ 4,400

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) - United States Plans - Annuity Plan For Participants In The US Qualified Pension Plan [Member] - USD ($) $ in Millions	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020
Defined Benefit Plan Disclosure
Pension benefit obligation acturial gain loss	$ 2.5	$ 2.2
Defined benefit obligation increase decrease for remeasurement due to settlement	$ 0.8	$ 0.7

Schedule of Net Periodic Pensio

Schedule of Net Periodic Pension and Postretirement (income) Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Defined Benefit Plan Disclosure
Net actuarial loss (gain)			$ (627)	$ 2,589
UNITED STATES
Defined Benefit Plan Disclosure
Service cost	$ 452	$ 417	1,357	1,283
Interest cost	1,098	1,460	3,295	4,505
Expected return on plan assets	(936)	(1,170)	(2,809)	(3,634)
Net actuarial loss (gain)		2,238	(400)	2,418
Settlement loss		450		450
Total net periodic pension cost	614	3,395	1,443	5,022
Foreign Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure
Service cost	240	216	720	648
Interest cost	86	123	257	369
Expected return on plan assets	(17)	(16)	(50)	(47)
Total net periodic pension cost	309	323	927	970
Postretirement Benefit Plans
Defined Benefit Plan Disclosure
Service cost	16	14	48	43
Interest cost	43	60	128	180
Net actuarial loss (gain)	0	0	(228)	(279)
Amortization of prior service cost	(2)	(2)	(7)	(7)
Total net periodic pension cost	$ 57	$ 72	$ (59)	$ (63)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Oct. 18, 2019	Oct. 03, 2021
Purchase Commitment, Excluding Long-term Commitment
Aggregate purchase commitments		$ 811.9
Purchase commitments less than one year		$ 777.8
Legal claims, damage sought by party	$ 106.9

Schedule of Reconciliation of E

Schedule of Reconciliation of Effective Tax Rate (Detail)	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Income Tax Disclosure [Line Items]
US statutory federal tax rate	21.00%	21.00%	21.00%	21.00%
Foreign taxes	(4.40%)	(6.90%)	(4.40%)	(5.80%)
Tax credits	(1.90%)	(1.60%)	(1.40%)	(1.60%)
International provisions of the U.S. Tax Cuts and Jobs Act of 2017	(1.50%)	3.00%	(1.60%)	0.50%
Discrete benefit related to equity compensation	(0.10%)	(0.40%)	(1.60%)	(1.40%)
Other, net	0.70%	0.50%	0.70%	0.60%
Effective tax rate	13.80%	15.60%	12.70%	13.30%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Dec. 31, 2020
Income Taxes [Line Items]
Tax savings due to the tax holiday	$ 23.9	$ 24.9
Tax savings due to the tax holiday, per share	$ 0.13	$ 0.14
Accrued interest and penalties	$ 1.5		$ 1.2
Interest and penalties related to income tax, expense (benefit)	0.3	$ 0
Uncertain tax positions	16.8		$ 17.9
Net decrease in reserves for uncertain tax positions	(1.1)
Possible Lapse Of Statutes Of Limitations [Member]
Income Taxes [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 1.6

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Oct. 03, 2021Segment
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
		Oct. 03, 2021		Sep. 27, 2020		Oct. 03, 2021	[3]	Sep. 27, 2020		Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues		$ 950,501	[1]	$ 819,484	[1]	$ 2,817,835	[2]	$ 2,362,500	[2]
Income (loss) before income taxes	[4],[5]	297,755		263,731		905,774		678,089
Total assets		3,762,182	[3],[6]	3,436,512	[6]	3,762,182	[6]	3,436,512	[6]	$ 3,652,346
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		688,232		592,141		2,050,271		1,735,777
Income (loss) before income taxes	[4],[5]	265,017		189,116		778,687		571,719
Total assets	[6]	1,251,549	[3]	1,069,830		1,251,549		1,069,830
System Test
Segment Reporting Information [Line Items]
Revenues		102,605	[1]	118,169	[1]	340,261	[2]	306,051	[2]
Income (loss) before income taxes	[4],[5]	31,773		47,368		116,788		114,968
Total assets	[6]	147,970	[3]	155,642		147,970		155,642
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		91,014		68,711		263,151		187,792
Income (loss) before income taxes	[4],[5]	(4,226)		(5,302)		(14,586)		(32,041)
Total assets	[6]	696,792	[3]	667,132		696,792		667,132
Wireless Test
Segment Reporting Information [Line Items]
Revenues		68,713	[1]	40,504	[1]	164,504	[2]	133,174	[2]
Income (loss) before income taxes	[4],[5]	31,726		10,938		63,810		35,640
Total assets	[6]	119,568	[3]	108,671		119,568		108,671
Corporate And Others [Member]
Segment Reporting Information [Line Items]
Revenues		(63)		(41)		(352)		(294)
Income (loss) before income taxes	[4],[5]	(26,535)		21,611		(38,925)		(12,197)
Total assets	[6]	$ 1,546,303	[3]	$ 1,435,237		$ 1,546,303		$ 1,435,237
[1]	Includes $3.8 million and $1.7 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside Accounting Standards Codification (“ASC”) 606 “Revenue from Contracts with Customers.
[2]	Includes $11.1 million and $6.1 million in 2021 and 2020, respectively, for leases of Teradyne’s systems recognized outside ASC 606 “Revenue from Contracts with Customers.
[3]	The (loss) before income taxes for the nine months ended October 3, 2021 for Industrial Automation has been decreased and Corporate and Other has been increased to correctly eliminate a $10.1 million immaterial error in the three and six months ended July 4, 2021 related to intercompany charges. The error is not material to any historical periods.
[4]	Included in Corporate and Other are: contingent consideration adjustments, loss on convertible debt conversions, interest income, interest expense, net foreign exchange gains (losses), pension, intercompany eliminations and acquisition related: (a) charges; (b) legal fees; (c) compensation.
[5]	Included in income (loss) before taxes are charges and credits related to restructuring and other, loss on convertible debt conversions and inventory charges.
[6]	Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.

Schedule of Segment Informati_2

Schedule of Segment Information (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jul. 04, 2021	Jul. 04, 2021
Segment Reporting [Abstract]
Immaterial error correction amount	$ 10.1	$ 10.1

Schedule of Segment Reporting I

Schedule of Segment Reporting Information by Segment Charges (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Segment Reporting Information [Line Items]
Restructuring and other	$ 300		$ 600
Acquisition related costs	300		300
Restructuring and other—employee severance	1,197	$ (27,701)	(3,426)	$ 1,915
Other (income) expense, net - loss on convertible debt conversion	(21,486)	(764)	(25,223)	(3,595)
Contingent consideration adjustment			(7,227)	(7,967)
Semiconductor Test
Segment Reporting Information [Line Items]
Cost of revenues - inventory charge	3,725	1,131	4,959	7,956
Restructuring and other—Contract termination settlement charge				4,000
Acquisition related costs				3,400
Industrial Automation
Segment Reporting Information [Line Items]
Cost of revenues - inventory charge	3,656		4,941	505
Acquisition related costs			825	790
Restructuring and other—employee severance	476		965	664
System Test
Segment Reporting Information [Line Items]
Cost of revenues - inventory charge			524	698
Wireless Test
Segment Reporting Information [Line Items]
Cost of revenues - inventory charge	679	1,802	1,351	3,957
Corporate And Eliminations
Segment Reporting Information [Line Items]
Restructuring and other			1,846
Corporate And Eliminations | Restructuring and other
Segment Reporting Information [Line Items]
Acquisition related costs		(1,086)	(513)	2,629
Other (income) expense, net - loss on convertible debt conversion	$ 20,153		25,397
Corporate And Eliminations | Universal Robots (UR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment		$ (27,206)	$ (7,227)	(4,421)
Corporate And Eliminations | Mobile Industrial Robots (MiR) | Restructuring and other
Segment Reporting Information [Line Items]
Contingent consideration adjustment				$ (3,546)

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020	Jan. 31, 2021	Jan. 01, 2021	Jan. 31, 2020
Cumulative repurchases, shares			3.3	1.5
Common stock average price			$ 123.53	$ 58.33
Dividends Payable, Amount Per Share					$ 0.10		$ 0.10
Dividend payment	$ 16,400	$ 16,600	$ 49,711	$ 49,870
Treasury Stock, Value						$ 600,000
Treasury Stock, Shares						2,000
Share Repurchase Program [Member]
Cumulative repurchases, value			$ 406,200	$ 88,500