Name:	gac_DebtInstrumentPaymentMinimumMultipleAppliedToAuthorizedControlLevelCapitalAtTimeOfPayment
Namespace Prefix:	gac_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Represents the first letter of credit received as collateral under the reinsurance agreement for policy liabilities and capital support.

No definition available.

Name:	gac_FirstLetterOfCreditReceivedAsCollateralUnderReinsuranceArrangement
Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents interest rate on withheld funds assets under reinsurance agreement.

No definition available.

Name:	gac_FundsHeldUnderReinsuranceAgreementsAssetInterestRate
Namespace Prefix:	gac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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
Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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
Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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
Balance Type:	debit
Period Type:	instant

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

Name:	us-gaap_FundsHeldUnderReinsuranceAgreementsAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of interest expense incurred on a debt or other obligation to related party.

No definition available.

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

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

No definition available.

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

Amount of interest payable on debt, including, but not limited to, trade payables.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_InterestPayableCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: 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(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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.

No definition available.

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

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_LongtermDebtTypeAxis=gac_SurplusNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gac_CanadaLifeAssuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gac_EntitiesAffiliatedToSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CreditFacilityAxis=gac_FirstLetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: