Price target for market-based awards.

No definition available.

Name:	mpwr_MarketAwardsPriceTargets
Namespace Prefix:	mpwr_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum number of equity awards an employee may receive as a percentage.

+ References

No definition available.

+ Details

Name:	mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsMaximumPercentageAllowed
Namespace Prefix:	mpwr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of individual price target.

+ References

No definition available.

+ Details

Name:	mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardIndividualStockPriceTargets
Namespace Prefix:	mpwr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The period of measurement of the reporting entity's revenue growth rate as compared to the industry average used in determination of the vesting status of restricted stock units based on performance conditions.

+ References

No definition available.

+ Details

Name:	mpwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingMeasurementPeriodOfRelativeRevenueGrowthRateToIndustryAverage
Namespace Prefix:	mpwr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of vesting of share-based compensation awards.

+ References

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=mpwr_MSUs2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
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- Details

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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_AwardTypeAxis=mpwr_PSUs2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_VestingAxis=mpwr_AnnualOrQuarterlyVestingOfAwardsNotBasedOnPerformanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Note 16 - Subsequent Event (Details Textual)		1 Months Ended	3 Months Ended	9 Months Ended
Note 16 - Subsequent Event (Details Textual)	Oct. 31, 2018 $ / shares	Oct. 31, 2018 shares	Mar. 31, 2021	Sep. 30, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				688,000
MSUs 2018 [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed		500.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Price Targets	5
MSUs 2018 [Member] \| Subsequent Event [Member] \| Minimum [Member]
Market Awards Price Targets \| $ / shares	$ 140
MSUs 2018 [Member] \| Subsequent Event [Member] \| Maximum [Member]
Market Awards Price Targets \| $ / shares	$ 172
MSUs 2018 [Member] \| Executive Officer [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		60,000
MSUs 2018 [Member] \| Non-Executive Employees [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		60,000
PSUs 2019 [Member] \| Non-Executive Employees [Member] \| Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage			50.00%
PSUs 2019 [Member] \| Non-Executive Employees [Member] \| Scenario, Forecast [Member] \| Annual or Quarterly Vesting of Awards Not Based on Performance [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			2 years
PSUs 2019 [Member] \| Non-Executive Employees [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		53,000
Share-based Compensation Arrangement by Share-based Payment Award, Vesting, Measurement Period of Relative Revenue Growth Rate to Industry Average		2 years
PSUs 2019 [Member] \| Non-Executive Employees [Member] \| Subsequent Event [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed		200.00%
PSUs 2019 [Member] \| Non-Executive Employees [Member] \| Subsequent Event [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Maximum Percentage Allowed		300.00%