Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Apr. 30, 2019	Jun. 20, 2019	Oct. 31, 2018
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		36,763,634
Entity Public Float			$ 4.6
Amendment Flag	false
Entity Central Index Key	0000726958
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Apr. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY