v2.4.0.6
Document And Entity Information
3 Months Ended
Mar. 31, 2013
Apr. 25, 2013
Document and Entity Information [Abstract]    
Entity Registrant Name MONOLITHIC POWER SYSTEMS INC  
Document Type 10-Q  
Current Fiscal Year End Date --12-31  
Entity Common Stock, Shares Outstanding   36,775,880
Amendment Flag false  
Entity Central Index Key 0001280452  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Filer Category Accelerated Filer  
Entity Well-known Seasoned Issuer No  
Document Period End Date Mar. 31, 2013  
Document Fiscal Year Focus 2013  
Document Fiscal Period Focus Q1