Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidated Statements of Comprehensive Income
Non-credit component of impaired losses on fixed maturities available-for-sale	$ 3,726	$ 5,718

Represents the before tax and reclassification adjustments amount of the non-credit component of impairment losses on fixed maturities available-for-sale securities.

No definition available.

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