Financial Guarantees (Narratives) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Guarantor Obligations [Line Items]
Maximum Exposure	$ 48,644	[1]	$ 49,915	[1]
Fair value of guaranty obligation associated with Fannie Mae MBS	$ 943		$ 1,100
Minimum [Member]
Guarantor Obligations [Line Items]
Contractual terms of our guarantees	30 days		30 days
Maximum [Member]
Guarantor Obligations [Line Items]
Contractual terms of our guarantees	40 years		40 years
Loans with higher risk characteristics (current debt service coverage ratio)	1.0		1.0
Single-Family [Member] | Minimum [Member]
Guarantor Obligations [Line Items]
Serious delinquency, days past due	90 days		90 days
Multifamily [Member] | Minimum [Member]
Guarantor Obligations [Line Items]
Serious delinquency, days past due	60 days		60 days
Multifamily [Member] | Maximum [Member]
Guarantor Obligations [Line Items]
Serious delinquency, days past due	89 days

[1] Primarily consists of the unpaid principal balance of the underlying mortgage loans.