Acquisitions (Details)	9 Months Ended
Jan. 31, 2015 store
Business Combinations [Abstract]
Number of stores acquired	32us-gaap_NumberOfBusinessesAcquired
Period of recognition for tax deductible goodwill	15 years

Goodwill deductible for income tax purposes, period.

No definition available.

Name:	casy_BusinessAcquisitionGoodwillDeductibleForIncomeTaxPurposesPeriod
Namespace Prefix:	casy_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration