Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 35,495us-gaap_NetIncomeLoss	$ 22,898us-gaap_NetIncomeLoss	$ 15,756us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of tangible and intangible assets	13,130	12,160	9,332
Loss on disposal of property and equipment		31	81
Amortization and realized gains/losses on investments	96mpwr_AmortizationAndLossOnInvestments	443mpwr_AmortizationAndLossOnInvestments	214mpwr_AmortizationAndLossOnInvestments
Deferred taxes, net	17us-gaap_DeferredIncomeTaxExpenseBenefit	(81)us-gaap_DeferredIncomeTaxExpenseBenefit	(8)us-gaap_DeferredIncomeTaxExpenseBenefit
Excess tax benefit from equity awards	(10)		(869)
Stock-based compensation	33,454us-gaap_ShareBasedCompensation	20,701us-gaap_ShareBasedCompensation	18,652us-gaap_ShareBasedCompensation
Changes in operating assets and liabilities, net of effects of an acquisition:
Accounts receivable	(1,870)us-gaap_IncreaseDecreaseInReceivables	(4,347)us-gaap_IncreaseDecreaseInReceivables	(4,286)us-gaap_IncreaseDecreaseInReceivables
Inventories	(1,142)us-gaap_IncreaseDecreaseInInventories	(7,606)us-gaap_IncreaseDecreaseInInventories	(12,004)us-gaap_IncreaseDecreaseInInventories
Prepaid expenses and other assets	(2,029)	121	(456)
Accounts payable	1,632	1,440	754
Accrued liabilities	(3,102)	12,149	(2,097)
Tax liabilities	(248)	86	1,476
Accrued compensation and related benefits	(1,290)	2,691	(1,633)
Net cash provided by operating activities	74,133	60,686	24,912
Cash flows from investing activities:
Property and equipment purchases	(9,511)	(15,764)	(21,059)
Proceeds from sale of property and equipment		88	13
Purchases of short-term investments	(136,872)	(125,756)	(143,094)
Proceeds from sale of short-term investments	149,291	85,700	135,183
Proceeds from sale of long-term investments	4,650	2,025	2,100
Premiums paid on deferred compensation plan	(5,335)	(617)
Change in restricted assets			20
Cash paid for an acquisition, net of cash acquired	(11,590)
Net cash used in investing activities	(9,367)	(54,324)	(26,837)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(400)	(557)
Proceeds from exercise of stock options	11,941	37,877	13,390
Proceeds from shares issued under the employee stock purchase plan	2,078us-gaap_ProceedsFromStockPlans	2,145us-gaap_ProceedsFromStockPlans	1,852us-gaap_ProceedsFromStockPlans
Repurchases of common shares	(41,198)	(20,615)
Dividends and dividend equivalents paid	(11,658)		(35,664)
Excess tax benefits from equity awards	10		869
Net cash provided by (used in) financing activities	(39,227)	18,850	(19,553)
Effect of change in exchange rates	(486)	897	211
Net increase (decrease) in cash and cash equivalents	25,053	26,109	(21,267)
Cash and cash equivalents, beginning of period	101,213	75,104	96,371
Cash and cash equivalents, end of period	126,266	101,213	75,104
Supplemental disclosures for cash flow information:
Cash paid for taxes	1,235us-gaap_IncomeTaxesPaidNet	1,116us-gaap_IncomeTaxesPaidNet	807us-gaap_IncomeTaxesPaidNet
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	1,487	1,941	1,728
Liability accrued for dividends and dividend equivalents	6,660
Sensima [Member]
Supplemental disclosures of non-cash investing and financing activities:
Fair value of contingent consideration related to an acquisition	$ 2,507

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- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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- Definition

The cash outflow for securities or other assets acquired, which qualify for treatment as an investing activity and are to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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- Definition

The cash inflow from sales of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, beyond the current operating cycle.

+ References

No definition available.

+ Details

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- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

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- Definition

The cash inflow from sales of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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- Definition

The cash inflow associated with the amount received from the stock plan during the period.

+ References

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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