Mortgage Servicing Rights (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Mortgage Servicing Rights
Unpaid principal balances of loans serviced for others	$ 1,450,000,000	$ 1,500,000,000
Mortgage servicing rights	11,401,000af_MortgageServicingRights	12,800,000af_MortgageServicingRights	6,947,000af_MortgageServicingRights
Estimated fair value
Mortgage Servicing Rights
Mortgage servicing rights	$ 11,400,000	$ 12,800,000

Carrying amount (balance) as of the balance sheet date of an asset representing net future revenues from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements. Such assets are stated at the lower of cost or market (approximates fair value) under the amortization method of measurement. Rights may be obtained via (1) acquisition or assumption of a servicing obligation that does not relate to financial assets of the servicer or its consolidated affiliates; or (2) by originating loans and then transferring the loans in a transaction that meets the requirements for sale accounting.

No definition available.

Name:	af_MortgageServicingRights
Namespace Prefix:	af_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant