Name:	agii_NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts
Namespace Prefix:	agii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Costs paid to regulatory agencies or industry boards and bureaus primarily based on a percentage of premiums

No definition available.

Name:	agii_PremiumTaxesBoardsAndBureaus
Namespace Prefix:	agii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Costs incurred during the period, such as those relating to general administration and policy maintenance that do not vary with and are not primarily related to the acquisition or renewal of insurance contracts, excluding amortization of deferred acquisition costs.

No definition available.

Name:	agii_UnderwritingAcquisitionAndInsuranceExpenseGross
Namespace Prefix:	agii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Costs incurred during the period related to selling the Company's products and services including the amortization of deferred policy acquisition costs charged to expense in the period, as well as other costs incurred during the period, such as those relating to general administration and policy maintenance.

No definition available.

Name:	agii_UnderwritingAcquisitionAndInsuranceExpenses
Namespace Prefix:	agii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Underwriting acquisition and insurance expenses.

No definition available.

Name:	agii_UnderwritingAcquisitionAndInsuranceExpensesAbstract
Namespace Prefix:	agii_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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

Amount of fees incurred for commissions on mutual funds and insurance products.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882