Customer Concentration Risk [Member]
Document And Entity Information
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized
Note To Financial Statement Details Textual
statementsignificantaccountingpoliciespolicies
Restricted Stock [Member]
statementnote2netincomepersharetables
statementnote3cashcashequivalentsandinvestmentstables
Sales Revenue, Net [Member]
statementnote4stockbasedcompensationtables
statementnote6inventoriestables
statementnote7majorcustomerconcentrationtables
statementnote2netincomepersharenetincomepercommonsharedetails
Concentration Risk Benchmark [Axis]
Amendment Flag
statementnote3cashcashequivalentsandinvestmentscdmaturitydatesdetails
Income Tax Disclosure [Text Block]
Concentration Risk Type [Axis]
statementnote4stockbasedcompensationstockoptionactivitydetails
Concentration Risk Benchmark [Domain]
statementnote4stockbasedcompensationrestrictedstocktransactionsdetails
Plan Name [Domain]
us-gaap_AllocatedShareBasedCompensationExpense
Allocated Share-based Compensation Expense
statementnote6inventoriescomponentsofinventorydetails
us-gaap_PaymentsForRepurchaseOfCommonStock
Repurchase of common stock
statementnote7majorcustomerconcentrationcustomerscomprising10ormoreofnetsalesdetails
Concentration Risk Type [Domain]
Plan Name [Axis]
Notes To Financial Statements
Minimum [Member]
Notes To Financial Statements [Abstract]
Accounts Receivable [Member]
Maximum [Member]
Range [Axis]
Range [Domain]
Customer [Axis]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Document Fiscal Year Focus
Customer [Domain]
Document Fiscal Period Focus
Net income
Net income
Net income
Proceeds from issuance of common stock under employee stock purchase plan
Proceeds from issuance of common stock upon exercise of stock options
Proceeds from Stock Options Exercised
us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities
Accounts payable and accrued expenses
Document Period End Date
Current Fiscal Year End Date
Award Type [Axis]
Entity Current Reporting Status
Entity Voluntary Filers
Entity Filer Category
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.
Document Type
Deferred rent
Equity Award [Domain]
clfd_HeldtomaturitySecuritiesDebtMaturitiesAfterOneThroughThreeYearsNetCarryingAmount
1-3 years
Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the next fiscal year through the third fiscal year following the latest fiscal year.
us-gaap_GoodwillImpairmentLoss
Goodwill, Impairment Loss
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Cash flows from investing activities
Entity Well-known Seasoned Issuer
us-gaap_HeldToMaturitySecurities
Total
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by operating activities
Exercised (in dollars per share)
Other Assets
Cancelled or Forfeited (in dollars per share)
Accounts receivables, net
us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Allowance for Doubtful Accounts Receivable, Current
Statement [Table]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Outstanding at September 30, 2014 (in dollars per share)
Outstanding at June 30, 2015 (in dollars per share)
Cash and cash equivalents
Cash and cash equivalents, beginning of period
Cash and cash equivalents, end of period
Short-term investments
Cash and Cash Equivalents Disclosure [Text Block]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value
Non-cash financing activities
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term
Current Assets
us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
(Decrease) increase in cash and cash equivalents
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value
Income Statement [Abstract]
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash (used in) provided by financing activities
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
Cancelled or Forfeited (in shares)
us-gaap_GainLossOnDispositionOfAssets1
Loss on disposal of assets
Deferred taxes – long term
us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation
Tax withholding related to exercise of stock options
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Outstanding at September 30, 2014 (in shares)
Outstanding at June 30, 2015 (in shares)
us-gaap_StockholdersEquity
Total Shareholders’ Equity
Goodwill and Intangible Assets Disclosure [Text Block]
us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount
Selling, general and administrative
us-gaap_TableTextBlock
Notes Tables
Preferred stock, authorized shares (in shares)
clfd_NumberOfPatentsPending
Number of Patents Pending
Represents the number of patents pending.
clfd_NumberOfPatentsGranted
Number of Patents Granted
Represents the number of patents granted in the United States.
Preferred stock, par value (in dollars per share)
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]
Customer A [Member]
Disclosure for customer A.
Inventories
Preferred stock, shares outstanding (in shares)
Other current assets
Common stock, shares outstanding (in shares)
Operating expenses
Non Employee Directors [Member]
Represents information pertaining to non-employee directors of the Company.
Employees [Member]
Represents information about the Company's employees.
Relationship to Entity [Domain]
Customer D [Member]
Name of major customer.
Title of Individual [Axis]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Forfeited (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Unvested shares at September 30, 2014 (in shares)
Unvested at June 30, 2015 (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Vested (in shares)
Finished goods
Work-in-progress
Customer C [Member]
Disclosure for customer C.
Customer B [Member]
Disclosure for customer B.
Additional paid-in capital
us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Purchases of property, plant and equipment and intangible assets
Raw materials
us-gaap_Assets
Total Assets
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Vested (in dollars per share)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Unvested shares at September 30, 2014 (in dollars per share)
Unvested at June 30, 2015 (in dollars per share)
Current Liabilities
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Forfeited (in dollars per share)
Entity Registrant Name
Property, plant and equipment, net
Entity Central Index Key
Goodwill
Net sales
Other
Entity Common Stock, Shares Outstanding (in shares)
Long-term investments
Commitment and Contingencies
us-gaap_Liabilities
Total Liabilities
Earnings Per Share [Text Block]
Net income per common share:
Deferred taxes
Scenario [Axis]
Scenario, Unspecified [Domain]
Financing Receivables [Text Block]
us-gaap_AssetsCurrent
Total Current Assets
us-gaap_PaymentsToAcquireInvestments
Purchases of investments
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
us-gaap_DeferredIncomeTaxExpenseBenefit
Deferred taxes
us-gaap_LiabilitiesCurrent
Total Current Liabilities
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross
Adjustments to reconcile net income to net cash provided by operating activities:
Changes in operating assets and liabilities:
Supplemental disclosures for cash flow information
us-gaap_DepreciationDepletionAndAmortization
Depreciation and amortization
us-gaap_LiabilitiesAndStockholdersEquity
Total Liabilities and Shareholders’ Equity
Accumulated deficit
us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Stock Issued During Period, Shares, Employee Stock Purchase Plans
Income Tax Authority [Axis]
Proceeds from maturities of investments
Income Tax Authority [Domain]
State and Local Jurisdiction [Member]
Statement of Financial Position [Abstract]
us-gaap_ShareBasedCompensation
Stock-based compensation
us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Exercised (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period
Statement of Cash Flows [Abstract]
Cash flows from operating activities
us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment
Dilutive potential common shares (in shares)
Schedules of Concentration of Risk, by Risk Factor [Table Text Block]
us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits
Concentration Risk Disclosure [Text Block]
Accrued compensation
us-gaap_IncomeTaxesPaid
Cash paid during the year for income taxes
Diluted (in dollars per share)
Diluted (in dollars per share)
us-gaap_OperatingLossCarryforwardsValuationAllowance
Operating Loss Carryforwards, Valuation Allowance
us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Weighted average dilutive common shares outstanding (in shares)
Diluted (in shares)
Accrued expenses
us-gaap_IncreaseDecreaseInInventories
Inventories
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Income before income taxes
Income tax expense
Income Tax Expense (Benefit)
Accounts payable
Cash flows from financing activities
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash used in investing activities
us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Weighted average common shares (in shares)
Basic (in dollars per share)
Basic (in dollars per share)
us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount
Less than one year
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Common stock, authorized 50,000,000, $.01 par value; 13,720,377 and 13,742,964, shares issued and outstanding at June 30, 2015 and September 30, 2014
Class of Stock [Axis]
Common stock, shares issued (in shares)
Common stock, shares authorized (in shares)
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]
Other Liabilities
Common stock, par value (in dollars per share)
us-gaap_IncreaseDecreaseInAccountsReceivable
Accounts receivable, net
us-gaap_EffectiveIncomeTaxRateContinuingOperations
Effective Income Tax Rate Reconciliation, Percent
Schedule of Inventory, Current [Table Text Block]
Preferred stock, $.01 par value; authorized 500 shares; no shares outstanding
Inventory Disclosure [Text Block]
Use of Estimates, Policy [Policy Text Block]
Employee Stock Purchase Plan [Member]
The employee stock purchase plan.
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets
Prepaid expenses and other
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]
Statement [Line Items]
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.
Investments Classified by Contractual Maturity Date [Table Text Block]
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.
us-gaap_GrossProfit
Gross profit
Cost of sales
Basis of Accounting [Text Block]
us-gaap_DeferredTaxLiabilitiesNoncurrent
Deferred taxes
Shareholders’ Equity
us-gaap_LiabilitiesNoncurrent
Total other liabilities
Cashless exercise of stock options
The issuance of common stock funded through shares sold to the company.
us-gaap_FiniteLivedIntangibleAssetUsefulLife
Finite-Lived Intangible Asset, Useful Life
Equity Component [Domain]
Equity Components [Axis]
Patents [Member]
Customer
Concentration Risk, Percentage
Weighted average shares outstanding:
The weighted average shares outstanding.
us-gaap_PolicyTextBlockAbstract
Accounting Policies
us-gaap_OperatingIncomeLoss
Income from operations
Interest income
Finite-Lived Intangible Assets by Major Class [Axis]
Finite-Lived Intangible Assets, Major Class Name [Domain]