Net Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 29, 2013		Sep. 30, 2012		Sep. 29, 2013		Sep. 30, 2012
Net Income Loss Per Common Share
Net income for basic and diluted net income per share	$ 69,459		$ 88,641		$ 142,604		$ 233,592
Weighted average common shares-basic	191,307		187,364		190,521		186,592
Incremental shares from assumed conversion of convertible notes	23,257	[1]	21,890	[1]	23,303	[1]	22,397	[1]
Convertible note hedge warrant shares	18,678	[2]	16,765	[2]	18,742	[2]	17,474	[2]
Restricted stock units	1,102		1,423		1,000		1,413
Stock options	1,465		1,735		1,564		2,075
Employee stock purchase rights	19		33		35		52
Dilutive potential common shares	44,521		41,846		44,644		43,411
Weighted average common shares-diluted	235,828		229,210		235,165		230,003
Net income per common share-basic	$ 0.36		$ 0.47		$ 0.75		$ 1.25
Net income per common share-diluted	$ 0.29		$ 0.39		$ 0.61		$ 1.02

[1] Incremental shares from assumed conversion of the convertible notes for the three and nine months ended September 29, 2013 and September 30, 2012 are calculated using the difference between the average Teradyne stock price for the period and the conversion price of $5.48, 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 convertible debt, is divided by the average Teradyne stock price for the period.

[2] Convertible note hedge warrant shares for the three and nine months ended September 29, 2013 and September 30, 2012 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.