Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014
Basis of Presentation
Increase in net deferred tax asset due to the effects of the New York State tax legislation	$ 11.5
Reduction in income tax expense due to the effects of the New York State tax legislation	$ 11.5

Represents the increase in net deferred tax assets as a result of the effects of state tax legislation.

No definition available.

Name:	af_DeferredTaxAssetsNetIncreaseResultingFromStateTaxLegislation
Namespace Prefix:	af_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration