Computation of Basic and Diluted Net Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 28, 2014		Sep. 29, 2013		Sep. 28, 2014		Sep. 29, 2013
Net Income Loss Per Common Share
Net income for basic and diluted net income per share	$ 82,949		$ 69,459		$ 185,083		$ 142,604
Weighted average common shares-basic	207,381		191,307		198,367		190,521
Incremental shares from assumed conversion of convertible notes			23,257	[1]	6,684	[1]	23,303	[1]
Convertible note hedge warrant shares	8,885	[2]	18,678	[2]	16,744	[2]	18,742	[2]
Employee stock purchase rights	21		19		28		35
Dilutive potential common shares	10,952		44,521		25,428		44,644
Weighted average common shares-diluted	218,333		235,828		223,795		235,165
Net income per common share-basic	$ 0.40		$ 0.36		$ 0.93		$ 0.75
Net income per common share-diluted	$ 0.38		$ 0.29		$ 0.83		$ 0.61
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements	1,167		1,102		975		1,000
Stock Option
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements	879		1,465		997		1,564

[1] Incremental shares from conversion of the convertible notes for the nine months ended September 28, 2014 were calculated using the difference between the average Teradyne stock price from January 1, 2014 through March 12, 2014 and the conversion price of $5.4750, multiplied by 34.7 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 from January 1, 2014 to March 12, 2014 and adjusted for the number of days the convertible notes were outstanding. Incremental shares from assumed conversion of the convertible notes for the three and nine months ended September 29, 2013 were calculated using the difference between the average Teradyne stock price for the period the convertible notes were outstanding and the conversion price of $5.48, multiplied by the 34.7 million shares to be issued upon conversion. 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 note hedge warrant shares for the three and nine months ended September 28, 2014 are calculated using the difference between the average Teradyne stock price for the period the warrants were outstanding and the warrant price of $7.63 and $7.64, respectively, multiplied by the weighted average warrant shares outstanding. The result of this calculation, representing the total intrinsic value of the warrant, is divided by the average Teradyne stock price for the period the warrants were outstanding. Convertible note hedge warrant shares for the three and nine months ended September 29, 2013 are calculated using the difference between the average Teradyne stock price for the period and the warrant price of $7.67, multiplied by the 34.7 million shares that would be issued upon conversion. The result of this calculation, representing the total intrinsic value of the warrant, is divided by the average Teradyne stock price for the period.