Name:	gac_InitialMaximumLiabilityOfCoveragePerIndividualLifeRetained
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Represents the maximum annual growth in maximum liability of coverage per individual life claim retained by the entity under the insurance arrangement due to automatic increases.

No definition available.

Name:	gac_MaximumAnnualGrowthInMaximumLiabilityOfCoveragePerIndividualLifeRetained
Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the number of insurers and reinsurers from whom risk is assumed by the entity.

No definition available.

Name:	gac_NumberOfInsurersAndReinsurersFromWhomRiskAssumed
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The known and estimated amount recoverable, as of the balance sheet date, from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance, arising from transactions with related parties.

No definition available.

Name:	gac_RelatedPartyTransactionReinsuranceRecoverables
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Balance Type:	debit
Period Type:	instant

Represents the threshold limit of overall growth in maximum liability of coverage per individual life claim retained by the entity under the insurance arrangement due to automatic increases.

No definition available.

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Namespace Prefix:	gac_
Data Type:	xbrli:monetaryItemType
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Amount of earned premiums assumed from other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
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Amount of earned premiums ceded to other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Data Type:	num:percentItemType
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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_DirectPremiumsEarned
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

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

Amount of accrued obligation to policyholders that relates to insured events under long-term life insurance contracts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of life insurance issued and outstanding assumed from other entities. Includes, but not limited to, dividends and adjustments to face value.

Name:	us-gaap_LifeInsuranceInForceAssumed
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of life insurance issued and outstanding ceded to other entities. Includes, but not limited to, dividends and adjustments to face value.

Name:	us-gaap_LifeInsuranceInForceCeded
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount before contracts ceded to other entities and contracts assumed by the entity of life insurance issued and outstanding. Includes, but not limited to, dividends and adjustments to face value.

Name:	us-gaap_LifeInsuranceInForceGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Amount after contracts ceded to other entities and contracts assumed by the entity of life insurance issued and outstanding. Includes, but not limited to, dividends and adjustments to face value.

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

- References

Name:	us-gaap_LifeInsuranceInForceNetAbstract
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Percentage of assumed life insurance issued and outstanding contracts to life insurance issued and outstanding after contracts ceded to other entities and contracts assumed by the entity. Includes, but not limited to, dividends and adjustments to face value.

Name:	us-gaap_LifeInsuranceInForcePercentageAssumedToNet
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_PremiumsEarnedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of recovery (expense) related to provision for policy benefits and costs incurred for policies assumed and ceded.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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Name:	us-gaap_ReinsuranceCostsAndRecoveriesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- References

No definition available.

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

Amount after valuation allowance recoverable including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Paragraph 1
-Subparagraph (SX 210.7-03.(a),6)
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Name:	us-gaap_ReinsuranceRecoverables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis=us-gaap_IndividualPoliciesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis=us-gaap_GroupPoliciesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis=gac_PremiumIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis=us-gaap_LifeInsuranceSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis=us-gaap_VariableAnnuityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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Namespace Prefix:
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Period Type: