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Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2015
Feb. 23, 2016
Jun. 30, 2015
Common Class B [Member]      
Entity Common Stock, Shares Outstanding (in shares)   10,093,305  
Common Class A [Member]      
Entity Common Stock, Shares Outstanding (in shares)   30,397,361  
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 Public Float     $ 939,968,581
Document Type 10-K    
Document Period End Date Dec. 31, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Amendment Flag false