Debt - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended					1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended
	Mar. 31, 2009 Y	Mar. 30, 2012	Sep. 30, 2012	Dec. 31, 2012 M D	Dec. 31, 2011	Apr. 30, 2009	Apr. 06, 2009	Mar. 31, 2009 4.50% Convertible Senior Notes Due March 15, 2014	Apr. 30, 2009 Convertible Senior Notes	Dec. 31, 2012 Convertible Senior Notes	Apr. 30, 2009 4.50% Convertible Senior Notes	Mar. 31, 2009 4.50% Convertible Senior Notes	Dec. 31, 2012 4.50% Convertible Senior Notes	Dec. 31, 2010 Convertible Notes Hedge Warrant	Dec. 31, 2012 Convertible Notes Hedge Warrant	Dec. 31, 2011 Convertible Notes Hedge Warrant	Mar. 31, 2009 Convertible Notes Hedge Warrant	Dec. 31, 2012 Current Debt	Dec. 31, 2012 Long-term Debt
Debt Instrument
Borrowings from local bank	$ 10,000,000
Term of loan, years	5
Debt instrument, interest rate, stated percentage	0.80%							4.50%
Loan collateralized by real estate mortgage	6,000,000
Loan collateralized by real estate mortgage net book value				12,300,000
Unsecured loan	4,000,000
Semiannual principal payments of loan		1,000,000	1,000,000
Outstanding loan principal amount																		2,300,000	1,200,000
Aggregate principal amount				190,000,000	190,000,000	190,000,000	190,000,000	175,000,000		190,000,000
Additional aggregate principal amount									15,000,000				1,000
Senior notes maturity date											March 15, 2014
Initial conversion rate in number of shares													182.65
Initial debt conversion price				$ 5.48								$ 5.48		$ 7.67	$ 7.67	$ 7.67	$ 7.67
Debt conversion premium percentage												25.00%
Last reported sale price per share of debt												$ 4.38
Initial conversion rate				The Notes may be converted, under certain circumstances and during certain periods, at an initial conversion rate of approximately 182.65 shares of Teradyne's common stock per $1,000 principal amount of Notes, which is equivalent to an initial conversion price of approximately $5.48, a 25% conversion premium based on the last reported sale price of $4.38 per share of Teradyne's common stock on March 31, 2009.
Number of business days as measurement period for conversion of notes				5
Number of trading days as measurement period for conversion of notes				5
Conversion period before expiration, period, months				3
Maximum price per Note for each day of that measurement period				98.00%
Conversion of common stock for trading days, number of days				20
Consecutive trading days				30
Percent of increase in conversion price				130.00%
Percentage of principal amount				100.00%
Percentage of acquisition of total voting shares				50.00%
Antidilution adjustments, shares				34,703,196										34,700,000
Convertible note hedges				64,600,000
Strike price per share of warrant	$ 7.67
Percentage of warrant price in excess of closing price of common stock	75.00%
Proceeds from warrants	43,000,000
Warrants conversion premium percentage	75.00%
Financing transaction							163,000,000
Carrying amount of equity component				63,400,000
Effective annual interest rate on notes				14.50%
Term of amortization, years										Five
Debt issuance costs, amortized to interest expense										4,100,000
Debt issuance costs										1,000,000
Unamortized discount				20,104,000	33,902,000					20,100,000
Amortization period of unamortized discount, years				1 year 3 months
Debt instrument conversion price				$ 5.48
If-converted value of notes				$ 586,100,000