Net Income Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net Income Loss Per Common Share
Income from continuing operations	$ (16,543)	[1],[2],[3]	$ 88,641	[4]	$ 111,387	[5]	$ 33,564	[6]	$ 129,071	[7],[8]	$ 56,706	[9]	$ 88,084	[10]	$ 70,096	[11]	$ 217,049		$ 343,957		$ 379,692
Income from discontinued operations															1,545	[11]			1,545		5,128
Gain on disposal of discontinued operations													(832)	[10]	25,203	[11]			24,371
Net income or basic net income per share																	217,049		369,873		384,820
Income impact of assumed conversion of convertible notes																					13,203	[12]
Net income for diluted net income per share																	$ 217,049		$ 369,873		$ 398,023
Weighted average common shares-basic																	186,878		184,683		179,924
Incremental shares from assumed conversion of convertible notes																	22,367	[13]	21,504	[13]	30,848	[13]
Convertible note hedge warrant shares																	17,433	[14]	16,224	[14]	10,492	[14]
Restricted stock units																	2,291		3,773		5,001
Stock options																	1,213		566		443
Employee stock purchase rights																	64		70		99
Dilutive potential common shares																	43,368		42,137		46,883
Weighted average commons shares-diluted																	230,246		226,820		226,807
Net income per common share-basic, Continuing operations	$ (0.09)	[1],[2],[3]	$ 0.47	[4]	$ 0.60	[5]	$ 0.18	[6]	$ 0.70	[7],[8]	$ 0.31	[9]	$ 0.48	[10]	$ 0.38	[11]	$ 1.16		$ 1.86		$ 2.11
Net income per common share-basic, Discontinued operations																			$ 0.14		$ 0.03
Net income per common share-basic, Total	$ (0.09)	[1],[2],[3]	$ 0.47	[4]	$ 0.60	[5]	$ 0.18	[6]	$ 0.70	[7],[8]	$ 0.31	[9]	$ 0.47	[10]	$ 0.52	[11]	$ 1.16		$ 2.00		$ 2.14
Net income per common share-diluted, Continuing operations	$ (0.09)	[1],[2],[3]	$ 0.39	[4]	$ 0.49	[5]	$ 0.15	[6]	$ 0.58	[7],[8]	$ 0.26	[9]	$ 0.38	[10]	$ 0.30	[11]	$ 0.94		$ 1.52		$ 1.73
Net income per common share-diluted, Discontinued operations																			$ 0.11		$ 0.02
Net income per common share-diluted, Total	$ (0.09)	[1],[2],[3]	$ 0.39	[4]	$ 0.49	[5]	$ 0.15	[6]	$ 0.58	[7],[8]	$ 0.26	[9]	$ 0.38	[10]	$ 0.42	[11]	$ 0.94		$ 1.63		$ 1.75

[1] Restructuring and other, net includes a ($0.4) million fair value adjustment to decrease LitePoint acquisition contingent consideration.

[2] 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.

[3] In the fourth quarter ended December 31, 2012, the change in recognizing pension and postretirement benefit plans expense, as a result of the mark-to-market adjustments, 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.

[4] Restructuring and other, net includes $0.7 million of severance charges related to the headcount reductions of 9 people, of which $0.5 million and 7 people were in Systems Test Group, $0.2 million and 2 people were in Wireless Test.

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

[7] Restructuring and other, net includes $0.5 million of charges related to pension settlement and $3.3 million to the acquisition of LitePoint.

[8] In the fourth quarter ended December 31, 2011, the change in recognizing pension and postretirement benefit plans expense, as a result of the mark-to-market adjustments, decreased gross profit and net income by $2.4 million and $6.1 million, respectively. See Note B: "Accounting Policies" for a discussion of our accounting policy.

[9] Restructuring and other, net includes $1.4 million of charges related to the acquisition of LitePoint.

[10] Restructuring and other, net includes $0.3 million of severance charges related to headcount reductions of approximately 2 people in Semiconductor Test and $0.7 million related to pension settlement charges.

[11] Restructuring and other, net includes $0.8 million of severance charges related to headcount reductions of approximately 5 people in Semiconductor Test and $(0.4) million credit related to early exit of previously impaired leased facilities in Westford and North Reading, Massachusetts.

[12] Income impact of convertible notes for 2010 represents interest expense that would have not been recorded if the notes converted at the beginning of the period.

[13] Incremental shares from assumed conversion of the convertible notes for 2012 and 2011 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. For 2010, incremental shares from assumed conversion of the convertible notes represent the 34.7 million of shares that will be issued upon conversion.

[14] Convertible notes hedge warrant shares for 2012, 2011 and 2010 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 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. 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 I: "Debt" regarding convertible note hedge transaction.