Accounting Policies - Real Estate Owned (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Capitalized Costs on Real Estate Owned	$ 0agm_CapitalizedCostsOnRealEstateOwned	$ 0agm_CapitalizedCostsOnRealEstateOwned

Capitalized Costs on Real Estate Owned which include costs related to the production of saleable goods or crops that are realizeable net of any revenues received

No definition available.

Name:	agm_CapitalizedCostsOnRealEstateOwned
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant