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Debt - Additional Information (Detail) (USD $)
 1 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 1 Months Ended 3 Months Ended
Mar. 31, 2009
Y
Mar. 31, 2013
Mar. 30, 2012
Sep. 30, 2012
Dec. 31, 2012
Mar. 31, 2013
Convertible Notes Hedge Warrant
Apr. 01, 2012
Convertible Notes Hedge Warrant
Mar. 31, 2009
Convertible Notes Hedge Warrant
Mar. 31, 2013
Convertible Senior Notes
Apr. 30, 2009
4.50% Convertible Senior Notes Due March 15, 2014
Mar. 31, 2009
4.50% Convertible Senior Notes Due March 15, 2014
Mar. 31, 2013
4.50% Convertible Senior Notes Due March 15, 2014
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                      
Unsecured loan 4,000,000                      
Semiannual principal payments of loan     1,000,000 1,000,000                
Outstanding loan principal amount   3,200,000                    
Aggregate principal amount   189,998,000     190,000,000         190,000,000    
Senior notes maturity date                   March 15, 2014    
Initial conversion rate in number of shares                       182.65
Additional aggregate principal amount                       1,000
Initial debt conversion price   $ 5.48       $ 7.67 $ 7.67 $ 7.67     $ 5.48  
Debt conversion premium percentage                     25.00%  
Last reported sale price per share of debt                     $ 4.38  
Initial conversion rate   The Notes may be converted, at the option of the holder, 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.                    
Antidilution adjustments, shares   34,703,196       34,700,000 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%                      
Unamortized discount   16,350,000     20,104,000       16,400,000      
Amortization period of unamortized discount, months   12 months                    
Carrying amount of equity component   63,400,000                    
Debt instrument conversion price   $ 5.48                    
If-converted value of notes   $ 562,900,000