v2.4.0.8
Document And Entity Information (USD $)
12 Months Ended
Dec. 31, 2014
Feb. 23, 2015
Jun. 30, 2014
Document and Entity Information [Abstract]      
Entity Registrant Name MONOLITHIC POWER SYSTEMS INC    
Document Type 10-K    
Current Fiscal Year End Date --12-31    
Entity Common Stock, Shares Outstanding   39,290,882  
Entity Public Float     $ 946,000,000
Amendment Flag false    
Entity Central Index Key 0001280452    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Well-known Seasoned Issuer Yes    
Document Period End Date Dec. 31, 2014    
Document Fiscal Year Focus 2014    
Document Fiscal Period Focus FY