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Income Taxes - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2017 | Oct. 01, 2017 | [3] | Jul. 02, 2017 | [2],[4] | Apr. 02, 2017 | [5] | Dec. 31, 2016 | Oct. 02, 2016 | [7],[8] | Jul. 03, 2016 | [7],[9] | Apr. 03, 2016 | [7],[10] | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total (benefit) provision for income taxes | $ 204,007,000 | [1],[2] | $ 24,017,000 | $ 31,901,000 | $ 6,795,000 | $ (7,461,000) | [6],[7] | $ (4,113,000) | $ (7,271,000) | $ 7,206,000 |  | $ 266,720,000 | $ (11,639,000) | $ 46,647,000 |
Effective tax rate |  |  |  |  |  |  |  |  |  |  |  | 50.90% | 21.10% | 18.40% |
Corporate tax rate |  |  |  |  |  |  |  |  |  |  |  | 35.00% | 35.00% | 35.00% |
Provisional amount of additional income tax expense | 186,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Transition tax on mandatory deemed repatriation of foreign earnings |  |  |  |  |  |  |  |  |  |  |  | $ 161,000,000 |  |  |
Expense related to remeasurement of deferred tax assets and liabilities |  |  |  |  |  |  |  |  |  |  |  | 33,600,000 |  |  |
Benefit associated with impact of correlative adjustments on tax positions |  |  |  |  |  |  |  |  |  |  |  | 10,300,000 |  |  |
Tax savings due to the tax holiday |  |  |  |  |  |  |  |  |  |  |  | $ 24,800,000 | $ 17,000,000 | $ 11,500,000 |
Tax savings due to the tax holiday, per share |  |  |  |  |  |  |  |  |  |  |  | $ 0.12 | $ 0.08 | $ 0.05 |
Tax holiday expiration date |  |  |  |  |  |  |  |  |  |  |  | December 31, 2020 |  |  |
Valuation allowance amount decrease/increase |  |  |  |  |  |  |  |  |  |  |  | $ 15,600,000 |  |  |
Valuation allowance resulted from effect of reduction in U.S. Federal corporate tax rate |  |  |  |  |  |  |  |  |  |  |  | 11,300,000 |  |  |
Valuation allowance includes net deferred tax assets | 63,919,000 |  |  |  |  | 48,369,000 |  |  |  |  |  | 63,919,000 | $ 48,369,000 |  |
Tax credit carryforwards, approximately | 123,500,000 |  |  |  |  |  |  |  |  |  |  | 123,500,000 |  |  |
Tax credits carryforwards | 76,083,000 |  |  |  |  | 57,313,000 |  |  |  |  |  | 76,083,000 | 57,313,000 |  |
Unrecognized tax benefits | 36,263,000 |  |  |  |  | 38,958,000 |  |  |  |  |  | 36,263,000 | 38,958,000 | $ 36,792,000 | $ 30,418,000
Unrecognized tax benefits, if recognized would impact effective tax rate | 24,800,000 |  |  |  |  |  |  |  |  |  |  | 24,800,000 |  |  |
Unrecognized tax benefits, if recognized would impact deferred taxes | 11,500,000 |  |  |  |  |  |  |  |  |  |  | 11,500,000 |  |  |
Accrued interest and penalties | 300,000 |  |  |  |  | $ 400,000 |  |  |  |  |  | 300,000 | 400,000 |  |
Interest and penalties related to income tax |  |  |  |  |  |  |  |  |  |  |  | 100,000 | $ 100,000 | $ 200,000 |
Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate tax rate |  |  |  |  |  |  |  |  |  |  | 21.00% |  |  |  |
Do Not Expire |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alternative minimum tax credits carryforwards | 6,600,000 |  |  |  |  |  |  |  |  |  |  | 6,600,000 |  |  |
United States |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carryforwards, business | 28,300,000 |  |  |  |  |  |  |  |  |  |  | $ 28,300,000 |  |  |
United States | Earliest Tax Year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carryforward, expiration date |  |  |  |  |  |  |  |  |  |  |  | 2018 |  |  |
United States | Latest Tax Year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carryforward, expiration date |  |  |  |  |  |  |  |  |  |  |  | 2037 |  |  |
State and Local Jurisdiction |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carryforwards | 88,600,000 |  |  |  |  |  |  |  |  |  |  | $ 88,600,000 |  |  |
State and Local Jurisdiction | Earliest Tax Year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carryforward, expiration date |  |  |  |  |  |  |  |  |  |  |  | 2018 |  |  |
State and Local Jurisdiction | Latest Tax Year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credit carryforward, expiration date |  |  |  |  |  |  |  |  |  |  |  | 2037 |  |  |
State and Local Jurisdiction | Do Not Expire |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tax credits carryforwards | $ 51,400,000 |  |  |  |  |  |  |  |  |  |  | $ 51,400,000 |  |  |
[1] | Restructuring and other includes a $6.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, $1.8 million of employee severance charges, and $1.1 million of charges for impairment of fixed assets.
[2] | Teradyne recorded pension and post retirement net actuarial gains of $2.5 million and $3.8 million for the second and fourth quarter in 2017, respectively. See Note B: "Accounting Policies" for a discussion of Teradyne's accounting policy.
[3] | Restructuring and other includes $5.1 million of property insurance recovery related to the Japan earthquake, a $0.4 million credit related to previously impaired lease termination of a Wireless Test facility in Sunnyvale, CA, and a $0.3 million credit for the decrease in the fair value of the Universal Robots contingent consideration liability, partially offset by $0.8 million of Japan earthquake related expenses and $0.6 million of employee severance charges.
[4] | Restructuring and other includes a $1.5 million charge for a fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.8 million of employee severance charges.
[5] | Restructuring and other includes a $1.3 million charge for a lease impairment of a Wireless Test facility in Sunnyvale, CA, a $0.6 million fair value adjustment to increase the Universal Robots acquisition contingent consideration, and $0.6 million of employee severance charges.
[6] | Restructuring and other includes a $5.4 million fair value adjustment to increase the Universal Robots acquisition contingent consideration.
[7] | Teradyne recorded pension and post retirement net actuarial (gains) losses of $(1.2) million, $(0.7) million, $0.7 million and $(2.0) million for the first, second, third, and fourth quarter in 2016, respectively. See Note B: "Accounting Policies" for a discussion of Teradyne's accounting policy.
[8] | Restructuring and other includes an $8.0 million fair value adjustment to increase the Universal Robots acquisition contingent consideration.
[9] | Restructuring and other includes $4.2 million for an impairment of fixed assets, $0.9 million for expenses related to an earthquake in Kumamoto, Japan, and a $1.4 million fair value adjustment to increase contingent consideration liability, of which $0.8 million was related to Universal Robots and $0.6 million was related to AIT, partially offset by $5.1 million of property insurance recovery related to the Japan earthquake.
[10] | Restructuring and other includes a $1.2 million fair value adjustment to increase the Universal Robots acquisition contingent consideration.

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