Allowance for Loan Losses Allowance at Recorded Investment (Details) (USD $)	Sep. 30, 2012		Jun. 30, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	$ 48,234,000,000	[1]		$ 46,482,000,000
Allowance for loan losses for collectively reserved loans	14,402,000,000	[1]		25,299,000,000
Allowance for loan losses for acquired credit-impaired loans	376,000,000	[1]		375,000,000		334,000,000
Allowance for loan losses	63,012,000,000	[1],[2]	63,375,000,000	72,156,000,000		71,435,000,000	[2]	69,506,000,000	61,556,000,000
Recorded investment in individually impaired loans	194,038,000,000	[1],[3]		166,521,000,000	[3]
Recorded investment in collectively reserved loans	2,812,275,000,000	[1],[3]		2,809,051,000,000	[3]
Recorded investment in acquired credit-impaired loans	2,661,000,000	[1],[3]		3,319,000,000	[3]
Recorded investment in loans	3,008,974,000,000	[1],[3]		2,978,891,000,000	[3]
Loans Discharged with Bankruptcy Relief [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring recorded investment	22,900,000,000
Troubled debt restructuring, Allowance	1,100,000,000
Single-Family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	47,784,000,000	[1]		45,765,000,000
Allowance for loan losses for collectively reserved loans	13,738,000,000	[1]		24,494,000,000
Allowance for loan losses for acquired credit-impaired loans	375,000,000	[1]		374,000,000
Allowance for loan losses	61,897,000,000	[1]	62,134,000,000	70,633,000,000		69,928,000,000		68,027,000,000	59,980,000,000
Recorded investment in individually impaired loans	190,104,000,000	[1],[3]		161,942,000,000	[3]
Recorded investment in collectively reserved loans	2,629,379,000,000	[1],[3]		2,634,456,000,000	[3]
Recorded investment in acquired credit-impaired loans	2,622,000,000	[1],[3]		3,272,000,000	[3]
Recorded investment in loans	2,822,105,000,000	[1],[3]		2,799,670,000,000	[3]
Troubled debt restructuring recorded investment	190,100,000,000			161,900,000,000
Multifamily [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	450,000,000	[1]		717,000,000
Allowance for loan losses for collectively reserved loans	664,000,000	[1]		805,000,000
Allowance for loan losses for acquired credit-impaired loans	1,000,000	[1]		1,000,000
Allowance for loan losses	1,115,000,000	[1]	1,241,000,000	1,523,000,000		1,507,000,000		1,479,000,000	1,576,000,000
Recorded investment in individually impaired loans	3,934,000,000	[1],[3]		4,579,000,000	[3]
Recorded investment in collectively reserved loans	182,896,000,000	[1],[3]		174,595,000,000	[3]
Recorded investment in acquired credit-impaired loans	39,000,000	[1],[3]		47,000,000	[3]
Recorded investment in loans	186,869,000,000	[1],[3],[4],[5]		179,221,000,000	[3],[4],[5]
Troubled debt restructuring recorded investment	$ 1,000,000,000			$ 956,000,000

[1] As of September 30, 2012, we began classifying as TDRs loans to certain borrowers who have received bankruptcy relief. These loans had a recorded investment of $22.9 billion and a related allowance of $1.1 billion as of September 30, 2012.

[2] Total allowance for loan losses includes $376 million and $334 million as of September 30, 2012 and 2011, respectively, for acquired credit-impaired loans.

[3] Recorded investment consists of unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments, and accrued interest receivable.

[4] Multifamily loans 60-89 days delinquent are included in the seriously delinquent column.

[5] Green (loan with acceptable risk); yellow (loan with signs of potential weakness); orange (loan with a well defined weakness that may jeopardize the timely full repayment); and red (loan with a weakness that makes timely collection or liquidation in full more questionable based on existing conditions and values).