Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Apr. 30, 2018	Jun. 20, 2018	Oct. 31, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Caseys General Stores Inc,
Document Type	10-K
Current Fiscal Year End Date	--04-30
Entity Common Stock, Shares Outstanding		36,593,575
Entity Public Float			$ 4.3
Amendment Flag	false
Entity Central Index Key	0000726958
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	Apr. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY