v3.10.0.1
Document And Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Feb. 12, 2019
Jun. 29, 2018
Document Information [Line Items]      
Entity Registrant Name RUSH ENTERPRISES INC \TX\    
Entity Central Index Key 0001012019    
Trading Symbol rusha    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer Yes    
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Public Float     $ 1,552,855,317
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Shell Company false    
Common Class A [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding (in shares)   28,236,569  
Common Class B [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding (in shares)   8,267,802