Computation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Apr. 01, 2018	Apr. 02, 2017
Net Income Loss Per Common Share
Net income for basic and diluted net income per share		$ 86,974	$ 85,221
Weighted average common shares-basic		195,255	200,005
Incremental shares from assumed conversion of convertible notes	[1]	4,398
Convertible note hedge warrant shares	[2]	1,830
Employee stock purchase plan		14	8
Dilutive potential common shares		8,229	1,931
Weighted average common shares-diluted		203,484	201,936
Net income per common share-basic		$ 0.45	$ 0.43
Net income per common share-diluted		$ 0.43	$ 0.42
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		1,666	1,533
Stock Options
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements		321	390

[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 $31.80, multiplied by 14.5 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 $39.91, multiplied by 14.5 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.