Computation of Basic and Diluted Net Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013		Sep. 29, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net Income Loss Per Common Share
Income from continuing operations													$ 164,947		$ 217,049		$ 343,957
Income from discontinued operations																	1,545
Gain on disposal of discontinued operations																	24,371
Net income for basic and diluted net income per share	$ 22,343	[1],[2]	$ 69,459	$ 66,556	$ 6,589	$ (16,543)	[3],[4]	$ 88,641	$ 111,387	[5]	$ 33,564	[6]	$ 164,947		$ 217,049		$ 369,873
Weighted average common shares-basic													190,772		186,878		184,683
Incremental shares from assumed conversion of convertible notes													23,341	[7]	22,367	[7]	21,504	[7]
Convertible note hedge warrant shares													18,795	[8]	17,433	[8]	16,224	[8]
Employee stock purchase rights													36		64		70
Dilutive potential common shares													44,827		43,368		42,137
Weighted average common shares-diluted													235,599		230,246		226,820
Net income per common share-basic, Continuing operations													$ 0.86		$ 1.16		$ 1.86
Net income per common share-basic, Discontinued operations																	$ 0.14
Net income per common share-basic, Total	$ 0.12	[1],[2]	$ 0.36	$ 0.35	$ 0.03	$ (0.09)	[3],[4]	$ 0.47	$ 0.60	[5]	$ 0.18	[6]	$ 0.86		$ 1.16		$ 2.00
Net income per common share-diluted, Continuing operations													$ 0.70		$ 0.94		$ 1.52
Net income per common share-diluted, Discontinued operations																	$ 0.11
Net income per common share-diluted, Total	$ 0.09	[1],[2]	$ 0.29	$ 0.28	$ 0.03	$ (0.09)	[3],[4]	$ 0.39	$ 0.49	[5]	$ 0.15	[6]	$ 0.70		$ 0.94		$ 1.63
Restricted Stock Units
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements													1,127		2,291		3,773
Stock Option
Net Income Loss Per Common Share
Incremental shares attributable to share based payment arrangements													1,528		1,213		566

[1] Interest expense and other includes a $34.2 million gain from the sale of an equity investment.

[2] In the fourth quarter ended December 31, 2013, pension and post retirement net actuarial gains increased gross profit and net income by $2.7 million and $9.1 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[3] In the fourth quarter ended December 31, 2012, we corrected prior period income tax provision (benefit) errors that resulted in a $0.2 million income tax provision. These errors were not individually or in aggregate material to the fourth quarter of 2012 or any prior period.

[4] In the fourth quarter ended December 31, 2012, pension and postretirement actuarial losses decreased gross profit and net income by $8.1 million and $18.3 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[5] Restructuring and other includes $0.3 million of severance charges related to headcount reductions of 10 people in Semiconductor Test and ($6.5) million fair value adjustment to decrease the LitePoint acquisition contingent consideration.

[6] Restructuring and other includes a ($1.8) million fair value adjustment to decrease the LitePoint acquisition contingent consideration.

[7] Incremental shares from assumed conversion of the convertible notes 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 will 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.

[8] Convertible notes hedge warrant shares 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 will be issued upon exercise. The result of this calculation, representing the total intrinsic value of the warrant, is divided by the average Teradyne stock price for the period. Teradyne's call option on its common stock (convertible note hedge transaction) is excluded from the calculation of diluted shares because the effect would be anti-dilutive. See Note H: "Debt" regarding convertible note hedge transaction.