Employee Retirement Benefit Plans-Level 3 (Details) - Level 3 [Member] $ in Millions	12 Months Ended
Jun. 30, 2021 USD ($)
Employer contributions between measurement date and reporting date
Beginning balance	$ 21
Relating to assets still held at the reporting date	3
Purchases, sales, settlements, contributions and benefits paid	(2)
Transfers in and/or out of Level 3	1
Ending balance	23
Insurance Contracts [Member]
Employer contributions between measurement date and reporting date
Beginning balance	3
Relating to assets still held at the reporting date	0
Purchases, sales, settlements, contributions and benefits paid	0
Transfers in and/or out of Level 3	0
Ending balance	3
Other Unobservable Assets [Member]
Employer contributions between measurement date and reporting date
Beginning balance	18
Relating to assets still held at the reporting date	3
Purchases, sales, settlements, contributions and benefits paid	(2)
Transfers in and/or out of Level 3	1
Ending balance	$ 20

Fair Value Measurement With Unobservable Inputs Reconcilation, Recurring Basis, Assets Held at Reporting Date

No definition available.

Name:	ctlt_FairValueMeasurementWithUnobservableInputsReconcilationRecurringBasisAssetsHeldatReportingDate
Namespace Prefix:	ctlt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=ctlt_InsuranceContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=ctlt_OtherUnobservableAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: