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.