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Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2025
Significant Accounting Policies [Line Items]
Premium revenue recognition period	12 months
Vesting period, share-based awards	3 years
Requisite service period, share-based awards	3 years
Minimum
Significant Accounting Policies [Line Items]
Time lag for reporting	1 month
Maximum
Significant Accounting Policies [Line Items]
Time lag for reporting	3 months
Losses occurring
Significant Accounting Policies [Line Items]
Premium revenue recognition period	12 months

X

- Definition

Equity Method Investments Reporting Lag

+ References

No definition available.

+ Details

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Namespace Prefix:	acgl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

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Namespace Prefix:	acgl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

[Line Items] for Significant Accounting Policies [Table]

+ References

No definition available.

+ Details

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Namespace Prefix:	acgl_
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Balance Type:	na
Period Type:	duration

X

- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

X

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

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- Details

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