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Document And Entity Information - shares
 9 Months Ended
Sep. 30, 2018
Oct. 26, 2018
Document Information [Line Items]    
Entity Registrant Name LITHIA MOTORS INC  
Entity Central Index Key 0001023128  
Trading Symbol lad  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Emerging Growth Company false  
Entity Small Business false  
Class A common stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding (in shares)   22,488,323
Class B common stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding (in shares)   1,000,000