Computation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 1,014,589	$ 784,147	$ 467,468
Weighted average common shares-basic		164,960	166,120	170,425
Convertible note hedge warrant shares	[1]	9,956	6,989	2,698
Incremental shares from assumed conversion of convertible notes	[2]	7,435	8,528	4,909
Employee stock purchase rights		8	10	13
Dilutive potential common shares		18,665	16,922	9,034
Weighted average common shares-diluted		183,625	183,042	179,459
Net income per common share-basic		$ 6.15	$ 4.72	$ 2.74
Net income per common share-diluted		$ 5.53	$ 4.28	$ 2.60
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,180	1,264	1,236
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		86	131	178

[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 $39.55, 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.

[2] Incremental shares from the 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 $31.52, multiplied by 4.4 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.