Name:	gac_FirstLetterOfCreditReceivedAsCollateralUnderReinsuranceArrangement
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents interest rate on withheld funds assets under reinsurance agreement.

No definition available.

Name:	gac_FundsHeldUnderReinsuranceAgreementsAssetInterestRate
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Number of letters of credit obtained by the parent company for the benefit of the entity as collateral under the reinsurance agreement for policy liabilities and capital support.

No definition available.

Name:	gac_NumberOfLettersOfCreditObtainedByParentForBenefitOfRelatedPartyUnderReinsuranceAgreement
Namespace Prefix:	gac_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents guaranteed interest annuity contracts purchases under separate accounts.

No definition available.

Name:	gac_RelatedPartyTransactionPurchasesUnderGuaranteedInterestAnnuityIncludedInSeparateContracts
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Data Type:	xbrli:monetaryItemType
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Represents the reduction in separate account assets and liabilities arising from transactions with related parties so as to eliminate these amounts in the consolidated balance sheets.

No definition available.

Name:	gac_RelatedPartyTransactionReductionInSeparateAccountAssetsAndLiabilitiesOnConsolidation
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Represents the second letter of credit received as collateral under the reinsurance agreement for policy liabilities and capital support.

No definition available.

Name:	gac_SecondLetterOfCreditReceivedAsCollateralUnderReinsuranceArrangement
Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
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Amount of the reinsurer's funds held on its behalf by the ceding insurer, including funds held in trust, under reinsurance treaties or contracts with the assuming insurer as security for the payment of the obligations thereunder.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.2,10)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 2, 10

-Article 7

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Amount of interest income earned from interest-bearing assets owed to the entity by related party.

No definition available.

Name:	us-gaap_InterestIncomeRelatedParty
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Amount of fees earned from providing investment advice and research to customers.

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 210.9-04.13(a),(d))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount borrowed under the credit facility as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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Period Type:	instant

Name:	us-gaap_RelatedPartyTransactionLineItems
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Data Type:	xbrli:stringItemType
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Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gac_CanadaLifeAssuranceCompanyMember
Namespace Prefix:
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