Segment Reporting (Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,222,422	$ 3,211,484
Single-Family [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	17,595	11,822
Multifamily [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,182	5,747
Capital Markets [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	723,217	836,700
Consolidated Trusts [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,749,571	2,676,952
Eliminations/Adjustments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (273,143)	$ (319,737)