Mortgage Loans Credit Quality Indicators - MF (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 3,053,156,000,000	[1]	$ 3,007,471,000,000	[1]
Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	188,088,000,000	[1],[2],[3]	191,051,000,000	[1],[2],[4]
Multifamily [Member] | Loan with Acceptable Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment			154,235,000,000	[1],[4]
Multifamily [Member] | Loan with Signs of Potential Weakness [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment			21,304,000,000	[1],[4],[5]
Unpaid principal balance of loans with no available current financial information			5,100,000,000
Multifamily [Member] | Loan with a Well Defined Weakness that May Jeopardize the Timely Full Repayment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment			14,199,000,000	[1],[4]
Multifamily [Member] | Loan with a Weakness that Makes Timely Collection or Liquidation in Full More Questionable [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment			1,313,000,000	[1],[4]
Multifamily [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	176,074,000,000	[1],[3]
Multifamily [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	3,390,000,000	[1],[3]
Multifamily [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	7,986,000,000	[1],[3]
Multifamily [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 638,000,000	[1],[3]

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

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

[3] Pass (loan is current and adequately protected by the current financial strength and debt service capacity of the borrower); special mention (loan with signs of potential weakness); substandard (loan with a well defined weakness that jeopardizes the timely full repayment); and doubtful (loan with a weakness that makes collection or liquidation in full highly questionable and improbable based on existing conditions and values).

[4] 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).

[5] Includes approximately $5.1 billion of unpaid principal balance as of December 31, 2012 classified as yellow due to no available current financial information.