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Valuation and Qualifying Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Allowance for Doubtful Accounts      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period $ 2,491 $ 2,912 $ 4,118
Additions Charged to Cost and Expenses   55 69
Deductions 84 476 1,275 [1]
Balance at End of Period 2,407 2,491 2,912
Inventory Reserve      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 111,252 115,857 141,838
Additions Charged to Cost and Expenses 21,332 22,193 16,592
Other 1,680 7,064 2,568
Deductions 14,888 33,862 45,141
Balance at End of Period 119,376 111,252 115,857
Valuation Allowance of Deferred Tax Assets      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 41,737 40,386 55,446
Additions Charged to Cost and Expenses 1,322 1,380 4,546
Deductions 20 29 19,606
Balance at End of Period $ 43,039 $ 41,737 $ 40,386
[1] Based upon an improvement in the aging of accounts receivables in 2013, Teradyne reduced its allowance for doubtful accounts by approximately $1 million.