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.