3.8.0.1 html 165 248 1 true 42 0 false 5 false false R1.htm 000 - Document - Document And Entity Information Sheet http://www.cohu.com/20170930/role/statement-document-and-entity-information Document And Entity Information Cover 1 false false R2.htm 001 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited) Sheet http://www.cohu.com/20170930/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited Condensed Consolidated Balance Sheets (Current Period Unaudited) Statements 2 false false R3.htm 002 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) Sheet http://www.cohu.com/20170930/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited-parentheticals Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) Statements 3 false false R4.htm 003 - Statement - Condensed Consolidated Statements of Income (Unaudited) Sheet http://www.cohu.com/20170930/role/statement-condensed-consolidated-statements-of-income-unaudited Condensed Consolidated Statements of Income (Unaudited) Statements 4 false false R5.htm 004 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited) Sheet http://www.cohu.com/20170930/role/statement-condensed-consolidated-statements-of-comprehensive-income-unaudited Condensed Consolidated Statements of Comprehensive Income (Unaudited) Statements 5 false false R6.htm 005 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) Sheet http://www.cohu.com/20170930/role/statement-condensed-consolidated-statements-of-cash-flows-unaudited Condensed Consolidated Statements of Cash Flows (Unaudited) Statements 6 false false R7.htm 006 - Disclosure - Note 1 - Summary of Significant Accounting Policies Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies Note 1 - Summary of Significant Accounting Policies Notes 7 false false R8.htm 007 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets Notes 8 false false R9.htm 008 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value Note 3 - Financial Instruments Measured at Fair Value Notes 9 false false R10.htm 009 - Disclosure - Note 4 - Employee Stock Benefit Plans Sheet http://www.cohu.com/20170930/role/statement-note-4-employee-stock-benefit-plans Note 4 - Employee Stock Benefit Plans Notes 10 false false R11.htm 010 - Disclosure - Note 5 - Income Taxes Sheet http://www.cohu.com/20170930/role/statement-note-5-income-taxes Note 5 - Income Taxes Notes 11 false false R12.htm 011 - Disclosure - Note 6 - Discontinued Operations Sheet http://www.cohu.com/20170930/role/statement-note-6-discontinued-operations Note 6 - Discontinued Operations Notes 12 false false R13.htm 012 - Document - Note 7 - Contingencies Sheet http://www.cohu.com/20170930/role/statement-note-7-contingencies Note 7 - Contingencies Uncategorized 13 false false R14.htm 013 - Disclosure - Note 8 - Guarantees and Other Obligations Sheet http://www.cohu.com/20170930/role/statement-note-8-guarantees-and-other-obligations Note 8 - Guarantees and Other Obligations Uncategorized 14 false false R15.htm 014 - Disclosure - Significant Accounting Policies (Policies) Sheet http://www.cohu.com/20170930/role/statement-significant-accounting-policies-policies Significant Accounting Policies (Policies) Uncategorized 15 false false R16.htm 015 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Tables) Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies-tables Note 1 - Summary of Significant Accounting Policies (Tables) Uncategorized 16 false false R17.htm 016 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets (Tables) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-tables Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets (Tables) Uncategorized 17 false false R18.htm 017 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value (Tables) Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value-tables Note 3 - Financial Instruments Measured at Fair Value (Tables) Uncategorized 18 false false R19.htm 018 - Disclosure - Note 6 - Discontinued Operations (Tables) Sheet http://www.cohu.com/20170930/role/statement-note-6-discontinued-operations-tables Note 6 - Discontinued Operations (Tables) Uncategorized 19 false false R20.htm 019 - Disclosure - Note 8 - Guarantees and Other Obligations (Tables) Sheet http://www.cohu.com/20170930/role/statement-note-8-guarantees-and-other-obligations-tables Note 8 - Guarantees and Other Obligations (Tables) Uncategorized 20 false false R21.htm 020 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies-details-textual Note 1 - Summary of Significant Accounting Policies (Details Textual) Uncategorized 21 false false R22.htm 021 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation (Details) Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies-reported-sharebased-compensation-details Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation (Details) Uncategorized 22 false false R23.htm 022 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Computation of Basic and Diluted Income (Loss) Per Share (Details) Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies-computation-of-basic-and-diluted-income-loss-per-share-details Note 1 - Summary of Significant Accounting Policies - Computation of Basic and Diluted Income (Loss) Per Share (Details) Uncategorized 23 false false R24.htm 023 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Customer Concentration (Details) Sheet http://www.cohu.com/20170930/role/statement-note-1-summary-of-significant-accounting-policies-customer-concentration-details Note 1 - Summary of Significant Accounting Policies - Customer Concentration (Details) Uncategorized 24 false false R25.htm 024 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-details-textual Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets (Details Textual) Uncategorized 25 false false R26.htm 025 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Total Purchase Price (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-total-purchase-price-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Total Purchase Price (Details) Uncategorized 26 false false R27.htm 026 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Fair Value of Contingent Consideration (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-fair-value-of-contingent-consideration-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Fair Value of Contingent Consideration (Details) Uncategorized 27 false false R28.htm 027 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Purchase Price Allocation (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-purchase-price-allocation-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Purchase Price Allocation (Details) Uncategorized 28 false false R29.htm 028 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Preliminary Allocation of Intangible Assets (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-preliminary-allocation-of-intangible-assets-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Preliminary Allocation of Intangible Assets (Details) Uncategorized 29 false false R30.htm 029 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-changes-in-carrying-value-of-goodwill-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details) Uncategorized 30 false false R31.htm 030 - Disclosure - Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Purchased Intangible Assets, Subject to Amortization (Details) Sheet http://www.cohu.com/20170930/role/statement-note-2-business-acquisitions-goodwill-and-other-purchased-intangible-assets-purchased-intangible-assets-subject-to-amortization-details Note 2 - Business Acquisitions, Goodwill and Other Purchased Intangible Assets - Purchased Intangible Assets, Subject to Amortization (Details) Uncategorized 31 false false R32.htm 031 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value-details-textual Note 3 - Financial Instruments Measured at Fair Value (Details Textual) Uncategorized 32 false false R33.htm 032 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value-shortterm-investments-by-security-type-details Note 3 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) Uncategorized 33 false false R34.htm 033 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details) Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value-effective-maturities-of-shortterm-investments-details Note 3 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details) Uncategorized 34 false false R35.htm 034 - Disclosure - Note 3 - Financial Instruments Measured at Fair Value - Assets Measured at Fair Value on Recurring Basis (Details) Sheet http://www.cohu.com/20170930/role/statement-note-3-financial-instruments-measured-at-fair-value-assets-measured-at-fair-value-on-recurring-basis-details Note 3 - Financial Instruments Measured at Fair Value - Assets Measured at Fair Value on Recurring Basis (Details) Uncategorized 35 false false R36.htm 035 - Disclosure - Note 4 - Employee Stock Benefit Plans (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-4-employee-stock-benefit-plans-details-textual Note 4 - Employee Stock Benefit Plans (Details Textual) Uncategorized 36 false false R37.htm 036 - Disclosure - Note 5 - Income Taxes (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-5-income-taxes-details-textual Note 5 - Income Taxes (Details Textual) Uncategorized 37 false false R38.htm 037 - Disclosure - Note 6 - Discontinued Operations (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-6-discontinued-operations-details-textual Note 6 - Discontinued Operations (Details Textual) Uncategorized 38 false false R39.htm 038 - Disclosure - Note 6 - Discontinued Operations - Summary of Operating Results (Details) Sheet http://www.cohu.com/20170930/role/statement-note-6-discontinued-operations-summary-of-operating-results-details Note 6 - Discontinued Operations - Summary of Operating Results (Details) Uncategorized 39 false false R40.htm 039 - Disclosure - Note 8 - Guarantees and Other Obligations (Details Textual) Sheet http://www.cohu.com/20170930/role/statement-note-8-guarantees-and-other-obligations-details-textual Note 8 - Guarantees and Other Obligations (Details Textual) Uncategorized 40 false false R41.htm 040 - Disclosure - Note 8 - Guarantees and Other Obligations - Changes in Accrued Warranty (Details) Sheet http://www.cohu.com/20170930/role/statement-note-8-guarantees-and-other-obligations-changes-in-accrued-warranty-details Note 8 - Guarantees and Other Obligations - Changes in Accrued Warranty (Details) Uncategorized 41 false false All Reports Book All Reports cohu-20170930.xml cohu-20170930.xsd cohu-20170930_cal.xml cohu-20170930_def.xml cohu-20170930_lab.xml cohu-20170930_pre.xml http://fasb.org/us-gaap/2017-01-31 http://xbrl.sec.gov/dei/2014-01-31 true true