Quarterly report pursuant to Section 13 or 15(d)

Note 7 - Share-based Compensation (Details)

v2.4.1.9
Note 7 - Share-based Compensation (Details) (USD $)
3 Months Ended 9 Months Ended 12 Months Ended
Dec. 27, 2014
Jun. 28, 2014
Dec. 28, 2013
Dec. 27, 2014
Dec. 28, 2013
Mar. 29, 2014
Note 7 - Share-based Compensation (Details) [Line Items]            
Percent of Fair Market Value of Common Stock at Date of Grant       100.00%giga_PercentOfFairMarketValueOfCommonStockAtDateOfGrant    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period       187,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod   101,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 475,650us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant     475,650us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross 35,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross   35,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 264,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 430,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 430,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share) $ 1.23us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue   $ 1.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 1.68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 1.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized (in Dollars) $ 765,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized     $ 765,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition       3 years 36 days    
Share-based Compensation Arrangement by Share-based Payment Award Options Vested Number 71,750giga_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedNumber   74,050giga_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedNumber 231,150giga_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedNumber 241,025giga_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedNumber  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value (in Dollars) 97,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1   100,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1 280,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1 303,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised   76,500us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)       $ 2.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue   $ 1.53us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Options Granted to Employees [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-Based Compensation Arrangement by Share-Based Payment Award Expiration       10 years    
Stock Appreciation Rights (SARs) [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period       0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_StockAppreciationRightsSARSMember
   
Outstanding Options [Member] | Minimum [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-Based Compensation Arrangement by Share-Based Payment Award Expiration       5 years    
Outstanding Options [Member] | Maximum [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-Based Compensation Arrangement by Share-Based Payment Award Expiration       10 years    
Performance-based Options [Member] | New Employee [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross           100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= giga_PerformanceBasedOptionsMember
/ us-gaap_TitleOfIndividualAxis
= giga_NewEmployeeMember
Allocated Share-based Compensation Expense (in Dollars) 10,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_PerformanceBasedOptionsMember
/ us-gaap_TitleOfIndividualAxis
= giga_NewEmployeeMember
0us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_PerformanceBasedOptionsMember
/ us-gaap_TitleOfIndividualAxis
= giga_NewEmployeeMember
      0us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_PerformanceBasedOptionsMember
/ us-gaap_TitleOfIndividualAxis
= giga_NewEmployeeMember
Aggregate Share-based Compensation (in Dollars)       39,000giga_AggregateShareBasedCompensation
/ us-gaap_AwardTypeAxis
= giga_PerformanceBasedOptionsMember
/ us-gaap_TitleOfIndividualAxis
= giga_NewEmployeeMember
   
Employee Stock Option [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Allocated Share-based Compensation Expense (in Dollars) 103,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
  36,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
280,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
316,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
 
Accelerated in Connection with Termination Agreement [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Allocated Share-based Compensation Expense (in Dollars)         38,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_AcceleratedInConnectionWithTerminationAgreementMember
 
Share-based Compensation Arrangement by Share-based Payment Award Options Vested Number         40,000giga_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedNumber
/ us-gaap_AwardTypeAxis
= giga_AcceleratedInConnectionWithTerminationAgreementMember
 
Restricted Stock [Member] | Director [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period         71,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember
 
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)         $ 1.53us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember
 
Restricted Stock [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period       187,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
   
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)       $ 2.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
   
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition       6 months    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options (in Dollars) 262,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
    262,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
   
Restricted Stock, Employee Severance [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period         30,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= giga_RestrictedStockEmployeeSeveranceMember
 
Restricted and Unrestricted Stock [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Allocated Share-based Compensation Expense (in Dollars) 131,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_RestrictedAndUnrestrictedStockMember
  31,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_RestrictedAndUnrestrictedStockMember
265,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_RestrictedAndUnrestrictedStockMember
79,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= giga_RestrictedAndUnrestrictedStockMember
 
Performance Shares [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Allocated Share-based Compensation Expense (in Dollars) $ 16,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
    $ 32,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Minimum [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period       4 years    
Maximum [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period       5 years    
Director [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period       25,000us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember
  0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_TitleOfIndividualAxis
= us-gaap_DirectorMember
2000 Stock Option Plan and 2005 Equity Incentive Plan [Member]            
Note 7 - Share-based Compensation (Details) [Line Items]            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 2,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= giga_StockOptionPlan2000And2005EquityIncentivePlanMember
    2,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= giga_StockOptionPlan2000And2005EquityIncentivePlanMember