Document And Entity Information
Deferred rent
Note To Financial Statement Details Textual
Note 2 - Net Income Per Share
Note 3 - Cash, Cash Equivalents and Investments
Note 4 - Stock Based Compensation
Tax withholding related to vesting of restricted stock grants
Note 6 - Inventories
Note 7 - Major Customer Concentration
us-gaap_HeldToMaturitySecurities
Total
Note 2 - Net Income Per Share - Net Income Per Common Share (Details)
Financing Receivables [Text Block]
Note 3 - Cash, Cash Equivalents and Investments - CD Maturity Dates (Details)
Operating expenses
Note 4 - Stock-based Compensation - Stock Option Activity (Details)
Note 4 - Stock-based Compensation - Restricted Stock Transactions (Details)
Note 6 - Inventories - Components of Inventory (Details)
Note 7 - Major Customer Concentrations - Customers Comprising 10% or More of Net Sales (Details)
Notes To Financial Statements
Notes To Financial Statements [Abstract]
us-gaap_PaymentsForRepurchaseOfCommonStock
Repurchases of common stock
Proceeds from issuance of common stock upon exercise of stock options
Proceeds from Stock Options Exercised
Cash flows from investing activities
Proceeds from issuance of common stock under employee stock purchase plan
Equity Component [Domain]
Equity Components [Axis]
Accounts payable, accrued expenses and deferred rent
Preferred stock, shares outstanding (in shares)
Cash and Cash Equivalents Disclosure [Text Block]
Common stock, shares outstanding (in shares)
Diluted (in shares)
Weighted average dilutive common shares outstanding (in shares)
Dilutive potential common shares (in shares)
Deferred Tax Assets Related to Operating Loss Carryforwards [Member]
Represents the information pertaining to the deferred tax assets related to operating loss carryforwards.
Basis of Accounting [Text Block]
Diluted (in dollars per share)
Net sales
Cash and cash equivalents
Cash and cash equivalents, beginning of period
Cash and cash equivalents, end of period
Basic (in shares)
Weighted average common shares (in shares)
Basic (in dollars per share)
Selling, General and Administrative Expenses [Member]
Scenario, Unspecified [Domain]
Scenario [Axis]
State and Local Jurisdiction [Member]
Income Tax Authority [Domain]
Income Tax Authority [Axis]
Cost of Sales [Member]
us-gaap_ConcentrationRiskPercentage1
Concentration Risk, Percentage
Income Statement Location [Domain]
Income Statement Location [Axis]
Maximum [Member]
Customer Concentration Risk [Member]
Range [Domain]
Minimum [Member]
Customer [Axis]
Concentration Risk Type [Domain]
Range [Axis]
Customer [Domain]
us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits
Accounting Policies [Abstract]
Statement of Financial Position [Abstract]
Relationship to Entity [Domain]
Concentration Risk Type [Axis]
Title of Individual [Axis]
Employee and Non-Employee Directors [Member]
Represents key employees and non-employee directors.
Stock Compensation Plan 2007 [Member]
Name of the Company's equity-based compensation arrangement plan.
Sales Revenue, Net [Member]
Statement of Cash Flows [Abstract]
Accounts Receivable [Member]
Employees [Member]
Represents information about the Company's employees.
Weighted average shares outstanding:
The weighted average shares outstanding.
us-gaap_AllocatedShareBasedCompensationExpense
Allocated Share-based Compensation Expense
Concentration Risk Benchmark [Domain]
Concentration Risk Benchmark [Axis]
us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Stock Issued During Period, Shares, Employee Stock Purchase Plans
us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period
Exercised (in shares)
clfd_NumberOfPatentsGranted
Number of Patents Granted
Represents the number of patents granted in the United States.
Investments Classified by Contractual Maturity Date [Table Text Block]
1-5 years
Non-cash financing activities
Less than one year
us-gaap_IncreaseDecreaseInAccountsReceivable
Accounts receivable
Cashless exercise of stock options
The issuance of common stock funded through shares sold to the company.
us-gaap_LiabilitiesNoncurrent
Total other liabilities
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross
us-gaap_OperatingLossCarryforwardsValuationAllowance
Operating Loss Carryforwards, Valuation Allowance
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Income before income taxes
us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount
us-gaap_LiabilitiesAndStockholdersEquity
Total Liabilities and Shareholders’ Equity
Income tax (benefit) expense
Income Tax Expense (Benefit)
us-gaap_EffectiveIncomeTaxRateContinuingOperations
Effective Income Tax Rate Reconciliation, Percent
Valuation Allowance by Deferred Tax Asset [Axis]
Retained earnings
Deferred Tax Asset [Domain]
us-gaap_PolicyTextBlockAbstract
Accounting Policies
us-gaap_IncreaseDecreaseInInventories
Inventories
us-gaap_IncreaseDecreaseInOtherCurrentAssets
Other assets
Statement [Table]
Income Statement [Abstract]
Cash flows from financing activities
Patents [Member]
Class of Stock [Axis]
Award Type [Axis]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Employee Stock Purchase Plan [Member]
The employee stock purchase plan.
clfd_HeldtomaturitySecuritiesInvestmentTerm
Held-to-maturity Securities, Investment Term
Represents information about the Company's investment term in money market accounts and bank certificates of deposit.
Equity Award [Domain]
Finite-Lived Intangible Assets, Major Class Name [Domain]
Finite-Lived Intangible Assets by Major Class [Axis]
clfd_SharebasedCompensationArrangementBySharebasedPaymentAwardMarketPricePercentageOfferingDate
Share-based Compensation Arrangement by Share-based Payment Award, Market Price Percentage, Offering Date
Percentage of market price of one share of common stock on offering date that participants pay for shares.
clfd_AssetsNoncurrentExcludingPropertyPlantAndEquipment
Total other assets
Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer excluding property, plant and equipment.
clfd_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePrice
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price
Represents information about the purchase price of each share under the employee stock purchase plan.
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
Other Assets
us-gaap_LiabilitiesCurrent
Total current liabilities
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]
Changes in operating assets and liabilities:
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]
Share-based Compensation, Stock Options, Activity [Table Text Block]
Deferred taxes
Interest income
us-gaap_OperatingIncomeLoss
Income from operations
Schedule of Inventory, Current [Table Text Block]
Cost of sales
Inventory Disclosure [Text Block]
Deferred taxes
us-gaap_DeferredIncomeTaxExpenseBenefit
us-gaap_GrossProfit
Gross profit
Amendment Flag
Common stock, authorized 50,000,000, $.01 par value; 13,824,191 and 13,812,821, shares issued and outstanding at December 31, 2017 and September 30, 2017
Forfeited (in dollars per share)
Common stock, shares authorized (in shares)
Vested (in dollars per share)
Proceeds from maturities of investments
Common stock, shares issued (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Balance, weighted-average grant date fair value (in dollars per share)
Balance, weighted-average grant date fair value (in dollars per share)
Other
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Balance, unvested shares (in shares)
Balance, unvested shares (in shares)
Common stock, par value (in dollars per share)
Income Tax Disclosure [Text Block]
Granted (in dollars per share)
Stock based compensation
Granted (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Forfeited (in shares)
Current Fiscal Year End Date
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Vested (in shares)
Long-term investments
Document Fiscal Period Focus
Document Fiscal Year Focus
Document Period End Date
Preferred stock, $.01 par value; 500,000 shares; no shares issued or outstanding
us-gaap_FiniteLivedIntangibleAssetUsefulLife
Finite-Lived Intangible Asset, Useful Life
Preferred stock, shares issued (in shares)
Document Type
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term
us-gaap_DepreciationDepletionAndAmortization
Depreciation and amortization
us-gaap_PaymentsToAcquireInvestments
Purchases of investments
Preferred stock, authorized shares (in shares)
Accounts payable
Document Information [Line Items]
Document Information [Table]
Preferred stock, par value (in dollars per share)
us-gaap_AssetsCurrent
Total current assets
Accrued expenses
us-gaap_GoodwillImpairmentLoss
Goodwill, Impairment Loss
Entity Filer Category
Entity Current Reporting Status
Entity Voluntary Filers
Entity Well-known Seasoned Issuer
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Weighted-average exercise price, outstanding (in dollars per share)
Weighted-average exercise price, outstanding (in dollars per share)
Accrued compensation
us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability
us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Exercised (in dollars per share)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Entity Central Index Key
Entity Registrant Name
Entity [Domain]
Legal Entity [Axis]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Options, outstanding (in shares)
Options, outstanding (in shares)
Current Liabilities
Other current assets
Entity Common Stock, Shares Outstanding (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
Cash paid during the year for income taxes
Additional paid-in capital
Goodwill and Intangible Assets Disclosure [Text Block]
us-gaap_Assets
Total Assets
Inventories
Inventories
Shareholders’ Equity
Other Liabilities
Work-in-progress
Trading Symbol
Finished goods
us-gaap_GainLossOnDispositionOfAssets1
Loss on disposal of assets
us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Purchases of property, plant and equipment and intangible assets
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Net income
Net income
us-gaap_StockholdersEquity
Total Shareholders’ Equity
Plan Name [Axis]
Selling, general and administrative
Plan Name [Domain]
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized
Raw materials
Commitments and Contingencies
us-gaap_Liabilities
Total Liabilities
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
Restricted Stock [Member]
Schedules of Concentration of Risk, by Risk Factor [Table Text Block]
Concentration Risk Disclosure [Text Block]
us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Allowance for Doubtful Accounts Receivable, Current
Accounts receivables, net
Statement [Line Items]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Short-term investments
Supplemental disclosures for cash flow information
us-gaap_Goodwill
Goodwill
Current Assets
Property, plant and equipment, net
Customer A [Member]
Disclosure for customer A.
Customer B [Member]
Disclosure for customer B.
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash provided by financing activities
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash used in investing activities
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by (used in) operating activities
us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Increase (decrease) in cash and cash equivalents
us-gaap_TableTextBlock
Notes Tables
Earnings Per Share [Text Block]
Net income per common share: