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Note 2 - Acquisitions and Dispositions (Details Textual) $ / shares in Units, $ in Thousands |  |  |  |  |  |  |  |  | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 17, 2018 USD ($) $ / shares | Jul. 07, 2017 USD ($) | Mar. 01, 2017 USD ($) | Feb. 28, 2017 USD ($) | Aug. 29, 2016 USD ($) | Apr. 04, 2016 USD ($) | Mar. 25, 2016 USD ($) | Oct. 01, 2015 USD ($) | Jan. 17, 2018 USD ($) $ / shares | Dec. 30, 2017 USD ($) $ / shares | Dec. 31, 2016 USD ($) $ / shares | Jan. 02, 2016 USD ($) | Dec. 31, 2015 USD ($)
Common Stock, Par or Stated Value Per Share | $ / shares |  |  |  |  |  |  |  |  |  | $ 0.01 |  | $ 0.01 |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill, Acquired During Period |  |  |  |  |  |  |  |  |  | $ 36,716 | [1] | $ 232,934 | [2] |  |
Gain (Loss) on Disposition of Business |  |  |  |  |  |  |  |  |  |  |  | (1,391) |  |  |
Marine Product Line [Member} |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Disposition of Business |  |  |  |  |  |  |  |  |  |  |  | 1,400 |  |  |
Electronics [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill, Acquired During Period |  |  |  |  |  |  | $ 103,800 |  |  | 36,716 | [1] | 162,172 | [2] |  |
Automotive [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill, Acquired During Period |  |  |  |  |  |  | 61,300 |  |  |  | [1] | 70,762 | [2] |  |
Trademarks and Trade Names [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |
Trademarks and Trade Names [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  | 20 years |  |  |  |  |
Monolith [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Method Investments |  |  |  |  |  |  |  |  |  |  |  | 3,500 |  |  | $ 3,500
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12.00%
U.S. Sensor [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Businesses, Gross |  | $ 24,340 |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables |  | 1,500 |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory |  | $ 1,600 |  |  |  |  |  |  |  |  |  |  |  |  |
Monolith [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  | $ 15,000 |  |  |  |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables |  |  |  | $ 700 |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  |  |  | 62.00% |  |  |  |  |  |  |  |  |  |  |
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low |  |  |  | $ 1,000 |  |  |  |  |  |  |  |  |  |  |
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High |  |  |  | 10,000 |  |  |  |  |  |  |  |  |  |  |
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value |  |  | $ 3,500 | $ 3,500 |  |  |  |  |  |  |  |  |  |  |
ON Portfolio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Businesses, Gross |  |  |  |  | $ 104,000 |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  |  | 104,000 |  |  |  |  |  |  |  |  |  |
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory |  |  |  |  | 700 |  |  |  |  |  |  |  |  |  |
Business Acquisition, Goodwill, Expected Tax Deductible Amount |  |  |  |  | $ 7,300 |  |  |  |  |  |  |  |  |  |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  |  |  |  |  |  |  |  |  | 21,800 |  |  |
ON Portfolio [Member] | Customer Relationships [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  | 13 years 182 days |  |  |  |  |  |  |  |  |  |
ON Portfolio [Member] | Patented and Unpatented Technologies [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  | 6 years |  |  |  |  |  |  |  |  |  |
ON Portfolio [Member] | Patented and Unpatented Technologies [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  | 8 years 182 days |  |  |  |  |  |  |  |  |  |
ON Portfolio [Member] | Noncompete Agreements [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |
Menber's S.p.A. [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  |  |  | $ 19,200 |  |  |  |  |  |  |  |  |
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory |  |  |  |  |  | $ 200 |  |  |  |  |  |  |  |  |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  |  |  |  |  |  |  |  |  | 17,300 |  |  |
Menber's S.p.A. [Member] | Customer Relationships [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |
Menber's S.p.A. [Member] | Patented and Unpatented Technologies [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |
Menber's S.p.A. [Member] | Trademarks and Trade Names [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |
PolySwitch [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  |  |  |  | 348,292 |  |  |  |  |  |  |  |
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory |  |  |  |  |  |  | $ 6,900 |  |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |
Business Acquisition, Goodwill, Expected Tax Deductible Amount |  |  |  |  |  |  | $ 64,900 |  |  |  |  |  |  |  |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  |  |  |  |  |  |  |  |  | $ 126,500 |  |  |
PolySwitch [Member] | Customer Relationships [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |
PolySwitch [Member] | Patented and Unpatented Technologies [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |
Sigmar [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Businesses, Gross |  |  |  |  |  |  |  | $ 5,558 |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  |  |  |  |  | $ 6,459 |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High |  |  |  |  |  |  |  | $ 900 |  |  |  |  |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Price | $ / shares | $ 207.50 |  |  |  |  |  |  |  | $ 207.50 |  |  |  |  |  |
Subsequent Event [Member] | IXYS Corporation [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Share Price | $ / shares | $ 23 |  |  |  |  |  |  |  | $ 23 |  |  |  |  |  |
Business Acquisition, Share Exchange Ratio | 0.1265 |  |  |  |  |  |  |  | 0.1265 |  |  |  |  |  |
Business Combination, Consideration Transferred, Excluding Value of Stock Options Converted |  |  |  |  |  |  |  |  | $ 814,800 |  |  |  |  |  |
Payments to Acquire Businesses, Gross | $ 380,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable | 434,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Value of Stock Options Converted to Company’s Stock Options | 41,700 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred | $ 856,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
IXYS Corporation [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Customers | 3,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ / shares | $ 0.01 |  |  |  |  |  |  |  | $ 0.01 |  |  |  |  |  |
[1] | The 2017 additions resulted from the acquisitions of U.S. Sensor and Monolith.
[2] | The 2016 additions resulted primarily from the acquisitions of PolySwitch, ON and Menber's.

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