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Note 14 - Stock Repurchase Program (Details) - Stock Repurchase Program (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Stock Repurchase Program [Abstract]    
Cumulative balance at January 1, 2015   1,715mpwr_CumulativeSharesRepurchased
Cumulative balance at January 1, 2015 $ 37.66mpwr_RepurchaseStockAveragePricePerShare $ 36.04mpwr_RepurchaseStockAveragePricePerShare
Cumulative balance at January 1, 2015   $ 61,813mpwr_CumulativeSharesRepurchasedValue
Repurchases 203us-gaap_StockRepurchasedAndRetiredDuringPeriodShares  
Repurchases $ 51.33mpwr_RepurchaseStockAveragePricePerShareDuringPeriod  
Repurchases 10,405us-gaap_StockRepurchasedAndRetiredDuringPeriodValue  
Cumulative balance at March 31, 2015 1,918mpwr_CumulativeSharesRepurchased  
Cumulative balance at March 31, 2015 $ 37.66mpwr_RepurchaseStockAveragePricePerShare $ 36.04mpwr_RepurchaseStockAveragePricePerShare
Cumulative balance at March 31, 2015 $ 72,218mpwr_CumulativeSharesRepurchasedValue