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Document And Entity Information (USD $)
 12 Months Ended
Dec. 31, 2014
Jun. 30, 2014
Feb. 25, 2015
Document Information [Line Items]      
Entity Registrant Name RUSH ENTERPRISES INC \TX\    
Document Type 10-K    
Current Fiscal Year End Date --12-31    
Entity Public Float   $ 1,232,949,299dei_EntityPublicFloat  
Amendment Flag false    
Entity Central Index Key 0001012019    
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    
Common Class A [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding     29,960,414dei_EntityCommonStockSharesOutstanding
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Common Class B [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding     9,943,045dei_EntityCommonStockSharesOutstanding
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= us-gaap_CommonClassBMember