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Stock-Based Compensation (Tables) | 3 Months Ended
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Mar. 31, 2019
Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions | The fair value was estimated using the Monte Carlo simulation model with the following assumptions:
|  | For the Three Months Ended |
|  | March 31, |  |  | April 1, |
|  | 2019 |  |  | 2018 |
Risk-free interest rate |  |  | 2.6 | % |  |  | 2.2 | %
Teradyne volatility-historical |  |  | 31.8 | % |  |  | 26.8 | %
NYSE Composite Index volatility-historical |  |  | 12.0 | % |  |  | 12.4 | %
Dividend yield |  |  | 1.0 | % |  |  | 0.8 | %
Fair Value of Stock Options Using Assumptions | The fair value of stock options was estimated using the Black-Scholes option-pricing model with the following assumptions:
|  | For the Three Months Ended |
|  | March 31, |  |  | April 1, |
|  | 2019 |  |  | 2018 |
Expected life (years) |  |  | 5.0 |  |  |  | 5.0 |
Risk-free interest rate |  |  | 2.6 | % |  |  | 2.4 | %
Volatility-historical |  |  | 30.1 | % |  |  | 26.4 | %
Dividend yield |  |  | 1.0 | % |  |  | 0.8 | %

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- Definition Schedule Of Share Based Payment Award Total Shareholder Return Plan Valuation Assumptions [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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