Schedule of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended
		Apr. 04, 2021		Mar. 29, 2020		Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues	[1]	$ 781,606		$ 704,355
Income (loss) before income taxes	[2],[3]	223,993		197,069
Total assets		3,719,717	[4]	2,820,388	[4]	$ 3,652,346
Semiconductor Test
Segment Reporting Information [Line Items]
Revenues		528,063		484,489
Income (loss) before income taxes	[2],[3]	176,368		153,816
Total assets	[4]	1,243,358		921,108
System Test
Segment Reporting Information [Line Items]
Revenues	[1]	132,837		116,076
Income (loss) before income taxes	[2],[3]	51,061		48,407
Total assets	[4]	672,596		643,011
Industrial Automation
Segment Reporting Information [Line Items]
Revenues		79,951		60,305
Income (loss) before income taxes	[2],[3]	(12,967)		(15,335)
Total assets	[4]	179,195		137,056
Wireless Test
Segment Reporting Information [Line Items]
Revenues	[1]	40,898		43,485
Income (loss) before income taxes	[2],[3]	9,616		10,220
Total assets	[4]	104,367		106,400
Corporate And Others [Member]
Segment Reporting Information [Line Items]
Revenues		(143)
Income (loss) before income taxes	[2],[3]	(85)		(39)
Total assets	[4]	$ 1,520,201		$ 1,012,813

[1] Includes $3.1 million and $1.8 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] 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 charges, legal fees and compensation.

[3] Included in income (loss) before taxes are charges and credits related to restructuring and other, loss on convertible debt conversions and inventory charges.

[4] Total assets are attributable to each segment. Corporate assets consist of cash and cash equivalents, marketable securities and certain other assets.