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Note 7 - Stock-Based Compensation (Details) (USD $)
 3 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended 4 Months Ended 1 Months Ended 3 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 28, 2012
Feb. 28, 2014
Apr. 30, 2014
Apr. 30, 2012
Feb. 28, 2013
Feb. 28, 2012
Feb. 28, 2011
Oct. 31, 2014
Feb. 28, 2015
Jul. 31, 2014
Mar. 31, 2004
Dec. 31, 2012
Nov. 13, 2014
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross                 171,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross   178,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross [1]                          
Allocated Share-based Compensation Expense (in Dollars) $ 14,941,000us-gaap_AllocatedShareBasedCompensationExpense $ 14,679,000us-gaap_AllocatedShareBasedCompensationExpense $ 13,368,000us-gaap_AllocatedShareBasedCompensationExpense $ 15,603,000us-gaap_AllocatedShareBasedCompensationExpense $ 12,487,000us-gaap_AllocatedShareBasedCompensationExpense $ 12,643,000us-gaap_AllocatedShareBasedCompensationExpense $ 12,478,000us-gaap_AllocatedShareBasedCompensationExpense $ 12,123,000us-gaap_AllocatedShareBasedCompensationExpense                                
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options (in Dollars) 100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions               100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions                              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                 1,426,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod [2],[3] 2,974,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod [2] 1,580,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod [2],[4]                          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition                 1 year                              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value (in Dollars)                 17,300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 27,800,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 10,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue                          
Proceeds from Stock Options Exercised (in Dollars)                 11,941,000us-gaap_ProceedsFromStockOptionsExercised 37,877,000us-gaap_ProceedsFromStockOptionsExercised 13,390,000us-gaap_ProceedsFromStockOptionsExercised                          
Proceeds from Stock Plans (in Dollars)                 2,078,000us-gaap_ProceedsFromStockPlans 2,145,000us-gaap_ProceedsFromStockPlans 1,852,000us-gaap_ProceedsFromStockPlans                          
Restricted Stock Units (RSUs) [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Arrangement By Share Based Payment Award Share Increase Modification Ratio                       1.0471mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardShareIncreaseModificationRatio
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                       74,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		                        
Share-based Goods and Nonemployee Services Transaction, Modification of Terms, Incremental Compensation Cost (in Dollars)                       1,500,000us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionModificationOfTermsIncrementalCompensationCost
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		                        
Time-Based RSU's and PSUs [Member] | Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                         336,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		                      
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                         2 years                      
Time-Based RSU's and PSUs [Member] | Non-Executive Employees [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                           139,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		 345,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		                  
Time-Based RSU's and PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Shares Authorized Not Granted                                     674,000mpwr_SharesAuthorizedNotGranted
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested (in Dollars)                 28,900,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		 18,600,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		 10,500,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		                          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding (in Dollars) 201,300,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		               201,300,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		                              
Share Price (in Dollars per share) $ 49.74us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		               $ 49.74us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		                              
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized (in Dollars) 73,600,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		               73,600,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRSUSAndPSUSMember		                              
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition                 6 years                              
Time-Based RSUs [Member] | Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                         84,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		     74,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		 206,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                         2 years     2 years 2 years              
Time-Based RSUs [Member] | Non-Executive Employees [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                           78,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		 220,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		 124,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		                
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                           4 years 4 years 4 years                
Time-Based RSUs [Member] | Chief Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                   153,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefExecutiveOfficerMember		            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                 2 years              
Time-Based RSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                 335,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember		 [2],[3] 299,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember		 [2] 617,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBasedRSUSMember		 [2],[4]                          
PSUs [Member] | Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                         252,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		     220,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		 206,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		   212,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		          
PSUs [Member] | Non-Executive Employees [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                           61,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		 125,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		 91,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		     358,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		          
Share Based Compensation Arrangement By Share Based Payment Award Award Number Of Consecutive Periods                                     5 years          
Share-based Compensation Arrangement by Share-based Payment Award Award, Performance Period                                     2 years          
PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                 1,091,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember		 [2],[3] 875,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember		 [2] 963,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_PSUSMember		 [2],[4]                          
2014 Executive PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                         300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_Executive2014PSUSMember		                      
2014 Non-Executive PSU's [Member] | Minimum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                           200.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutivePSUS2014Member
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                    
2014 Non-Executive PSU's [Member] | Maximum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                           300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutivePSUS2014Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                    
2014 Non-Executive PSU's [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                           2 years                    
Time Base Restricted Unit [Member] | Non-Executive Employees [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                     104,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBaseRestrictedUnitMember
/ us-gaap_TitleOfIndividualAxis
= mpwr_NonExecutiveEmployeesMember		          
2013 MSUs [Member] | Maximum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares, Maximum         1,800,000mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesMaximum
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		         1,800,000mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesMaximum
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                            
2013 MSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate                 38.69%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		                              
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate                 1.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		                              
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		                              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                 720,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		 360,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		                            
Share Price (in Dollars per share) $ 31.73us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		               $ 31.73us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mpwr_MSUS2013Member		                              
2013 Time-Based RSUs and PSUs [Member] | Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                               294,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBased2013RSUSAndPSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		                
2013 Time-Based RSUs and PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                               215,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBased2013RSUSAndPSUSMember		                
2013 Executive PSUs [Member] | Subsequent Event [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                       402,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_Executive2013PSUSMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                       2 years        
2013 Executive PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                               300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_Executive2013PSUSMember		                
2013 Non-Executive PSUs [Member] | Subsequent Event [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                       63,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutive2013PSUSMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                       2 years        
2013 Non-Executive PSUs [Member] | Minimum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                               200.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutive2013PSUSMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                
2013 Non-Executive PSUs [Member] | Maximum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                               300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutive2013PSUSMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                
2012 Time-Based RSUs and PSUs [Member] | Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                 413,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_TimeBased2012RSUSAndPSUSMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ExecutiveOfficerMember		              
2012 Executive PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                 139,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mpwr_Executive2012PSUSMember		              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                 2 years              
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                                 300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_Executive2012PSUSMember		              
2012 Non-Executive PSUs [Member] | Minimum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                             200.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutivePSUSMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		                  
2012 Non-Executive PSUs [Member] | Maximum [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                             300.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutivePSUSMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		                  
2012 Non-Executive PSUs [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                         2 years      
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized                         30,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_AwardTypeAxis
= mpwr_NonExecutivePSUSMember		                      
2012 CEO PSUs [Member] | Chief Executive Officer [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Share Based Payment Other Than Options Percentage Allowed                                 100.00%mpwr_ShareBasedCompensationShareBasedPaymentOtherThanOptionsPercentageAllowed
/ us-gaap_AwardTypeAxis
= mpwr_PSUS2012Member
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefExecutiveOfficerMember		              
2004 Plan [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Arrangement By Share Based Payment Award Other Than Options Percent Increases In Period                                           5.00%mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherThanOptionsPercentIncreasesInPeriod
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		    
Share Based Compensation Arrangement By Share Based Payment Award Automatic Annual Increase Shares                                           2,400,000mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAutomaticAnnualIncreaseShares
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		    
Expired Shares Under Plan                                           2,900,000mpwr_ExpiredSharesUnderPlan
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		    
Share Based Compensation Arrangement By Share Based Payment Award Share Increase Modification Ratio                       1.0471mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardShareIncreaseModificationRatio
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross                       171,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost (in Dollars)                       2,900,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
Allocated Share-based Compensation Expense (in Dollars)                                             2,800,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options (in Dollars)                     100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                       100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term                       1 year 328 days                        
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate                       41.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate                       0.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                       0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_PlanNameAxis
= mpwr_Plan2004Member		                        
2014 Plan [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized                                               5,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= mpwr_Plan2014Member
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 5,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= mpwr_Plan2014Member		               5,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= mpwr_Plan2014Member		                              
2004 Employee Stock Purchase Plan [Member]                                                
Note 7 - Stock-Based Compensation (Details) [Line Items]                                                
Share Based Compensation Arrangement By Share Based Payment Award Other Than Options Percent Increases In Period                 2.00%mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherThanOptionsPercentIncreasesInPeriod
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                              
Share Based Compensation Arrangement By Share Based Payment Award Automatic Annual Increase Shares                 1,000,000mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAutomaticAnnualIncreaseShares
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                              
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 4,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		               4,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                              
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized (in Dollars)                     100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                       100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		  
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee                 2,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                              
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee, Value (in Dollars)                 25,000mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployeeValue
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                              
Stock Issued During Period, Shares, Employee Stock Purchase Plans                 78,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 111,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 152,000us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                          
Stock Issued During Period Shares Employee Stock Purchase Plans Intrinsic Value (in Dollars)                 900,000mpwr_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlansIntrinsicValue
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 800,000mpwr_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlansIntrinsicValue
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 1,000,000mpwr_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlansIntrinsicValue
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                          
Proceeds from Stock Plans (in Dollars)                 $ 2,100,000us-gaap_ProceedsFromStockPlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 $ 2,100,000us-gaap_ProceedsFromStockPlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		 $ 1,900,000us-gaap_ProceedsFromStockPlans
/ us-gaap_PlanNameAxis
= mpwr_EmployeeStockPurchasePlan2004Member		                          
[1] Includes 171,000 options granted as a result of the equity award modification. See "Equity Award Modifications" above for further discussion.
[2] Amount reflects the maximum number of PSUs that can be earned assuming the achievement of the highest level of performance conditions.
[3] Amount does not include 674,000 shares of time-based RSUs and PSUs authorized by the Board of Directors in October 2014, as the grant date of these awards has not been established at the time of approval. See "2014 Time-Based RSUs and PSUs" below for further discussion.
[4] Amount includes 74,000 shares granted as a result of the equity award modification. See "Equity Award Modifications" above for further discussion.