Computation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 29, 2020	Mar. 31, 2019
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 176,191	$ 109,138
Weighted average common shares-basic		166,589	173,532
Incremental shares from assumed conversion of convertible notes	[1]	7,333	2,186
Convertible note hedge warrant shares	[2]	5,492
Employee stock purchase plan		25	11
Dilutive potential common shares		14,147	3,440
Weighted average common shares-diluted		180,736	176,972
Net income per common share-basic		$ 1.06	$ 0.63
Net income per common share-diluted		$ 0.97	$ 0.62
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,163	1,021
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		134	222

[1] Incremental shares from assumed conversion of the convertible notes was calculated using the difference between the average Teradyne stock price for the period and the conversion price of $31.61, multiplied by 14.6 million shares. The result of this calculation, representing the total intrinsic value of the convertible debt, was divided by the average Teradyne stock price for the period.

[2] Convertible notes hedge warrant shares were calculated using the difference between the average Teradyne stock price for the period and the warrant price of $39.66, multiplied by 14.6 million shares. The result of this calculation, representing the total intrinsic value of the warrant, was divided by the average Teradyne stock price for the period.