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Document And Entity Information - shares
 6 Months Ended
Oct. 31, 2015
Dec. 02, 2015
Document And Entity Information    
Entity Registrant Name Caseys General Stores Inc,  
Entity Central Index Key 0000726958  
Current Fiscal Year End Date --04-30  
Entity Filer Category Large Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Well-known Seasoned Issuer No  
Entity Common Stock, Shares Outstanding (in shares)   39,006,613
Document Type 10-Q  
Document Period End Date Oct. 31, 2015  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Amendment Flag false