Consolidations and Transfers of Financial Assets Managed Loans (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Mortgage Loans on Real Estate [Line Items]
Loans held for sale, unpaid principal balance	$ 486		$ 312
Securitized loans, unpaid principal balance	2,224		2,273
Total loans managed, unpaid principal balance	2,985,336		2,969,200
Fannie Mae [Member]
Mortgage Loans on Real Estate [Line Items]
Loans held for investment, unpaid principal balance	378,110		396,276
Consolidated Trusts [Member]
Mortgage Loans on Real Estate [Line Items]
Loans held for investment, unpaid principal balance	2,604,516		2,570,339
Principal Amount of Delinquent Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Loans held for sale, unpaid principal balance	134	[1]	57	[1]
Securitized loans, unpaid principal balance	1	[1]	71	[1]
Total loans managed, unpaid principal balance	126,633	[1]	147,413	[1]
Principal Amount of Delinquent Loans [Member] | Fannie Mae [Member]
Mortgage Loans on Real Estate [Line Items]
Loans held for investment, unpaid principal balance	107,658	[1]	122,392	[1]
Principal Amount of Delinquent Loans [Member] | Consolidated Trusts [Member]
Mortgage Loans on Real Estate [Line Items]
Loans held for investment, unpaid principal balance	$ 18,840	[1]	$ 24,893	[1]
Single-Family [Member] | Minimum [Member]
Mortgage Loans on Real Estate [Line Items]
Serious delinquency and accruing, days past due	90 days		90 days

[1] Represents the unpaid principal balance of loans held for investment, loans held for sale and securitized loans for which we are no longer accruing interest and loans 90 days or more delinquent which are continuing to accrue interest.