Additional percent ownership interest obtained in subsidiary

No definition available.

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Namespace Prefix:	cb_
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Period Type:	duration

- Definition

Outstanding additional ownership interest agreed on

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the business acquisition agreement was executed, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionDateOfAcquisitionAgreement1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the acquirer obtains control of the acquiree, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 7
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479405/805-10-25-7

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 6
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479405/805-10-25-6

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-5

+ Details

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

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_OwnershipAxis=cb_HuataiGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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

- Details

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

Acquisitions (Narrative) (Details)	3 Months Ended
Acquisitions (Narrative) (Details)	Jun. 30, 2025	Mar. 31, 2025	Apr. 28, 2025
Huatai Group
Business Acquisition [Line Items]
Subsidiary, Ownership Percentage, Parent		85.50%
Huatai Group \| Subsequent Event
Business Acquisition [Line Items]
Additional percent ownership interest obtained in subsidiary	0.60%
Outstanding additional ownership interest agreed on			1.00%
Liberty Insurance, Vietnam [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement		Mar. 03, 2025
LMG Insurance, Thailand [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement		Mar. 03, 2025
LMG Insurance, Thailand [Member] \| Subsequent Event
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Apr. 01, 2025