Computation of Basic and Diluted Net Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 29, 2014		Jun. 30, 2013		Jun. 29, 2014		Jun. 30, 2013
Net Income Loss Per Common Share
Net income for basic and diluted net income per share	$ 101,205		$ 66,556		$ 102,134		$ 73,145
Weighted average common shares-basic	194,408		190,569		193,860		190,128
Incremental shares from assumed conversion of convertible notes			23,266	[1]	10,026	[1]	23,326	[1]
Convertible note hedge warrant shares	20,406	[2]	18,689	[2]	20,674	[2]	18,774	[2]
Employee stock purchase rights	43		59		32		43
Dilutive potential common shares	22,160		44,340		32,666		44,705
Weighted average common shares-diluted	216,568		234,909		226,526		234,833
Net income per common share-basic	$ 0.52		$ 0.35		$ 0.53		$ 0.38
Net income per common share-diluted	$ 0.47		$ 0.28		$ 0.45		$ 0.31
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements	705		772		878		947
Stock Option
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements	1,006		1,554		1,056		1,615

[1] Incremental shares from conversion of the convertible notes for the six months ended June 29, 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 during the six months ended June 29, 2014. Incremental shares from assumed conversion of the convertible notes for the three and six months ended June 30, 2013 were calculated using the difference between the average Teradyne stock price for the period and the conversion price of $5.4750, 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 six months ended June 29, 2014 and June 30, 2013 are calculated using the difference between the average Teradyne stock price for the period and the warrant price of $7.6389, 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.