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.

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	duration

- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Balance Type:	credit
Period Type:	duration

- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=crl_CitoxlabMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=crl_MPIResearchMember
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BUSINESS COMBINATIONS - Pro Forma Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
HemaCare Corporation
Business Acquisition [Line Items]
Revenue	$ 2,923,951	$ 2,661,565
Net income attributable to common shareholders	$ 368,800	245,423
Citoxlab
Business Acquisition [Line Items]
Revenue		2,683,610	$ 2,442,283
Net income attributable to common shareholders		$ 268,995	233,288
MPI Research
Business Acquisition [Line Items]
Revenue			2,328,213
Net income attributable to common shareholders			$ 225,550