Loans Receivable and Allowance for Loan Losses (Details 3)	9 Months Ended
Sep. 30, 2013
Loans receivable and allowance for loan losses
Historical loss experience analysis period of time, one	12 months
Historical loss experience analysis period of time, two	15 months
Historical loss experience analysis period of time, three	18 months
Historical loss experience analysis period of time, four	24 months
Historical loss experience analysis period of time, five	2 years
Extended prior period over which loss experience factors are evaluated to consider trends for the majority of loan portfolio	2 years
Residential
Loans receivable and allowance for loan losses
Period after which loans are individually evaluated for impairment	180 days

Represents the extended prior period over which loss experience factors are evaluated to consider trends for the majority of loan portfolio.

No definition available.

Name:	af_ExtendedPriorPeriodOverWhichLossExperienceFactorsAreEvaluatedToConsiderTrends
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The past due period of time after which all loans are individually evaluated for impairment.

No definition available.

Name:	af_FinancingReceivableIndividuallyEvaluatedForImpairmentPeriodOfTime
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The historical period over which the entity analyzes its loss experience, period five.

No definition available.

Name:	af_LoanLossHistoricalAnalysisPeriodFive
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The historical period over which the entity analyzes its loss experience, period four.

No definition available.

Name:	af_LoanLossHistoricalAnalysisPeriodFour
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The historical period over which the entity analyzes its loss experience, period one.

No definition available.

Name:	af_LoanLossHistoricalAnalysisPeriodOne
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The historical period over which the entity analyzes its loss experience, period three.

No definition available.

Name:	af_LoanLossHistoricalAnalysisPeriodThree
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The historical period over which the entity analyzes its loss experience, period two.

No definition available.

Name:	af_LoanLossHistoricalAnalysisPeriodTwo
Namespace Prefix:	af_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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