Note 4 - Balance Sheet Components (Details) - Other Long-Term Assets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Other Long-Term Assets [Abstract]
Deferred compensation plan assets	$ 8,770	$ 6,084
Prepaid expense	1,277	1,418
Other	1,019	955
Total	$ 11,066	$ 8,457

No definition available.

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Namespace Prefix:	mpwr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount of other miscellaneous assets expected to be realized or consumed after one year or normal operating cycle, if longer.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate carrying amount, as of the balance sheet date, of noncurrent assets not separately disclosed in the balance sheet. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

+ References

+ Details

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Balance Type:	debit
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- Definition

Sum of the carrying amounts as of the balance sheet date of amounts paid in advance for expenses which will be charged against earnings in periods after one year or beyond the operating cycle, if longer.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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