Line Of Credit Facility, Facility Fee, Repaid Quarterly, Percentage

No definition available.

Name:	casy_LineOfCreditFacilityFacilityFeeRepaidQuarterlyPercentage
Namespace Prefix:	casy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

+ Details

Name:	us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) of the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Name:	us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=casy_UnsecuredRevolvingCreditFacilityDueJanuary2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=casy_AlternateBaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=casy_UnsecuredRevolvingLineofCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=casy_SeriesGNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=casy_SeriesHNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=casy_FivePointTwoTwoSeniorNotesDueAugust2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-term Debt and Finance Lease Obligations, Lines of Credit, and Fair Value Disclosure - Narrative (Details) - USD ($)		9 Months Ended
	Dec. 23, 2020	Jan. 31, 2021	Dec. 22, 2020	Nov. 08, 2020	Aug. 07, 2020	Apr. 30, 2020
Debt Instrument
Fair value of long-term debt		$ 1,417,000,000				$ 1,341,000,000
Current maturities of long-term debt and finance lease obligations		2,327,000				570,280,000
Senior Notes
Debt Instrument
Debt instrument, face amount					$ 650,000
Revolving Credit Facility \| Federal Funds
Debt Instrument
Effective percentage	0.50%
Unsecured Revolving Credit Facility Due January 2024 \| Revolving Credit Facility
Debt Instrument
Maximum borrowing capacity	$ 450,000,000		$ 300,000,000
Line of credit facility, increase	$ 150,000,000
Fair value of amount outstanding		$ 0				$ 120,000,000
Unsecured Revolving Credit Facility Due January 2024 \| Revolving Credit Facility \| Alternate Base Rate
Debt Instrument
Effective percentage	1.00%
Unsecured Revolving Credit Facility Due January 2024 \| Line of Credit
Debt Instrument
Maximum borrowing capacity	$ 300,000,000
Facility fee percentage repaid quarterly		1.25%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Revolving Credit Facility
Debt Instrument
Facility fee percentage		0.20%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Revolving Credit Facility \| LIBOR
Debt Instrument
Effective percentage	0.75%
Basis spread on variable rate	1.05%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Revolving Credit Facility \| Alternate Base Rate
Debt Instrument
Basis spread on variable rate	0.05%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Line of Credit
Debt Instrument
Facility fee percentage	0.20%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Line of Credit \| LIBOR
Debt Instrument
Basis spread on variable rate	1.55%
Unsecured Revolving Credit Facility Due January 2024 \| Minimum \| Line of Credit \| Alternate Base Rate
Debt Instrument
Basis spread on variable rate	0.20%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Revolving Credit Facility
Debt Instrument
Facility fee percentage		0.40%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Revolving Credit Facility \| LIBOR
Debt Instrument
Basis spread on variable rate	1.85%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Revolving Credit Facility \| Alternate Base Rate
Debt Instrument
Basis spread on variable rate	0.85%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Line of Credit
Debt Instrument
Facility fee percentage	0.40%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Line of Credit \| LIBOR
Debt Instrument
Basis spread on variable rate	2.60%
Unsecured Revolving Credit Facility Due January 2024 \| Maximum \| Line of Credit \| Alternate Base Rate
Debt Instrument
Basis spread on variable rate	1.60%
Unsecured Revolving Line of Credit \| Senior Notes
Debt Instrument
Maximum borrowing capacity				$ 100,000,000
Series G Notes \| Senior Notes
Debt Instrument
Debt instrument, face amount					$ 325,000
Interest rate stated percentage					2.85%
Series H Notes \| Senior Notes
Debt Instrument
Debt instrument, face amount					$ 325,000
Interest rate stated percentage					2.96%
5.22% Senior Notes due August 2020 \| Senior Notes
Debt Instrument
Interest rate stated percentage		5.22%
Current maturities of long-term debt and finance lease obligations		$ 569,000