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Note 2 - Acquisitions (Details Textual) $ / shares in Units, $ in Thousands |  |  |  |  | 1 Months Ended | 2 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 17, 2018 USD ($) $ / shares | Jul. 07, 2017 USD ($) | Mar. 01, 2017 USD ($) | Feb. 28, 2017 USD ($) | Apr. 30, 2018 USD ($) | Mar. 31, 2018 USD ($) $ / shares | Mar. 31, 2018 USD ($) $ / shares | Apr. 01, 2017 USD ($) | Dec. 30, 2017 $ / shares | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Common Stock, Par or Stated Value Per Share | $ / shares |  |  |  |  |  | $ 0.01 | $ 0.01 |  | $ 0.01 |  |
Share Price | $ / shares | $ 207.50 |  |  |  |  |  |  |  |  |  |
Inventory Charge Related to Step-up in Cost Basis |  |  |  |  |  |  | $ 17,896 |  |  |  |
Payments to Acquire Businesses, Net of Cash Acquired, Total |  |  |  |  |  |  | $ 306,487 | $ 14,172 |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  |  |  |  |  |
Inventory, Amortization Period |  |  |  |  |  |  | 150 days |  |  |  |
Order or Production Backlog [Member] |  |  |  |  |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  |  | 1 year |  |  |  |
Monolith [Member] |  |  |  |  |  |  |  |  |  |  |
Cost Method Investments |  |  |  |  |  |  |  |  |  | $ 3,500 | $ 3,500
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners |  |  |  |  |  |  |  |  |  |  | 12.00%
IXYS Corporation [Member] |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Share Price | $ / shares | $ 23 |  |  |  |  |  |  |  |  |  |
Business Acquisition, Share Exchange Ratio | 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 | 434,192 |  |  |  |  |  |  |  |  |  |
Business Combination, Value of Stock Options Converted to Company’s Stock Options | 41,700 |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Total | 856,500 |  |  |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables | 49,100 |  |  |  |  |  |  |  |  |  |
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual |  |  |  |  |  | $ 86,300 |  |  |  |  |
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual |  |  |  |  |  | $ (17,800) |  |  |  |  |
Business Combination, Step Up of Inventory at Acquisition Date | 36,900 |  |  |  |  |  |  |  |  |  |
Inventory Charge Related to Step-up in Cost Basis |  |  |  |  |  |  | $ 17,900 |  |  |  |
Business Combination, Acquisition Related Costs |  |  |  |  |  |  | 38,600 |  |  |  |
Payments to Acquire Businesses, Net of Cash Acquired, Total | 302,865 |  |  |  |  |  |  |  |  |  |
IXYS Corporation [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |  |  |  |  |  |  |  |
Business Combination, Acquisition Related Costs |  |  |  |  |  |  | 10,200 |  |  |  |
IXYS Corporation [Member] | Employee Stock Option [Member] |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense, Total | $ 4,500 |  |  |  |  |  | $ 5,900 |  |  |  |
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, Total |  |  |  | $ 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 |  |  |  | $ 500 |  |  |  |  |  |  |
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High |  |  |  | 5,000 |  |  |  |  |  |  |
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value |  |  | $ 3,500 | 3,500 |  |  |  |  |  |  |
Payments to Acquire Businesses, Net of Cash Acquired, Total |  |  | 14,172 | 14,200 |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Commitment to Purchase Noncontrolling Interest |  |  | 9,000 | 9,000 |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination, Total |  |  | $ 26,672 | $ 26,700 |  |  |  |  |  |  |
Monolith [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Total |  |  |  |  | $ 5,000 |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  |  |  |  | 19.00% |  |  |  |  |  |
Business Combination, Step Acquisition, Remaining Interest Percentage |  |  |  |  | 19.00% |  |  |  |  |  |
IXYS Corporation [Member] |  |  |  |  |  |  |  |  |  |  |
Number of Customers | 3,500 |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ / shares | $ 0.01 |  |  |  |  |  |  |  |  |  |

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- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer, but excluding the value of stock options converted. + References No definition available. + Details
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- Definition This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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- Definition This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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- Definition This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to inventory acquired in connection with a business combination for which the initial accounting was incomplete. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 4A -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=SL65897772-128472 + Details
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