Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements of Comprehensive Income
Non-credit component of impaired losses on fixed maturities available-for-sale	$ 26,583	$ 13,590	$ 6,346

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