Equity Method Investments Reporting Lag

No definition available.

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- Definition

Income Loss From Operating Affiliates Equity Method

+ References

No definition available.

+ Details

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- Definition

Investment In Affiliate, Price Per Share

+ References

No definition available.

+ Details

Name:	acgl_InvestmentInAffiliatePricePerShare
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- Definition

Investments in which the Company has significant influence over the operating and financial policies and are accounted for under the equity method.

+ References

No definition available.

+ Details

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- Definition

Operating Affiliate Gain On Acquisition

+ References

No definition available.

+ Details

Name:	acgl_OperatingAffiliateGainOnAcquisition
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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ 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 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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- 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

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- Details

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- Details

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- Details

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Investment Information - Investment in operating affiliates (Details) € / shares in Units, $ / shares in Units, $ in Thousands, € in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€) € / shares	Jul. 01, 2021 $ / shares
Schedule of Equity Method Investments [Line Items]
Time lag for reporting	3 months
Investment in operating affiliates	$ 1,144,255		$ 1,135,655
Income (loss) from operating affiliates	$ 24,518	$ 75,457
Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	29.86%		29.50%	29.50%
Investment in affiliate, price per share \| € / shares				€ 9.95
Operating affiliate, aggregate cost			$ 546,000	€ 453
Investment in operating affiliates	$ 646,000		630,500
Operating affiliate, gain on acquisition			74,500
Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership					40.00%
Investment in affiliate, price per share \| $ / shares					$ 35.00
Operating affiliate, aggregate cost			278,900
Investment in operating affiliates	$ 362,200		375,700
Operating affiliate, gain on acquisition			$ 95,700
Issued Shares Excluding Treasury Stock \| Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	30.09%
Greysbridge Holdings Ltd \| Kelso And Company
Schedule of Equity Method Investments [Line Items]
Percentage ownership					30.00%
Greysbridge Holdings Ltd \| Warburg Pincus LLC
Schedule of Equity Method Investments [Line Items]
Percentage ownership					30.00%