Summary of Significant Accounting Policies Narratives(Details) (USD $)	3 Months Ended				9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended							3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Single-Family Individually Impaired Loan Loss Models Update [Member]	Sep. 30, 2013 US Treasury [Member]	Sep. 30, 2013 US Treasury [Member]	Sep. 30, 2012 US Treasury [Member]	Nov. 07, 2013 US Treasury [Member]	Sep. 30, 2013 US Treasury [Member] Temporary Credit and Liquidity Facilities Program [Member]	Dec. 31, 2012 US Treasury [Member] Temporary Credit and Liquidity Facilities Program [Member]	Sep. 30, 2013 US Treasury [Member] New Issue Bond [Member]	Dec. 31, 2012 US Treasury [Member] New Issue Bond [Member]	Sep. 30, 2013 Freddie Mac [Member]	Sep. 30, 2012 Freddie Mac [Member]	Sep. 30, 2013 Freddie Mac [Member]	Sep. 30, 2012 Freddie Mac [Member]	Dec. 31, 2012 Freddie Mac [Member]	Sep. 30, 2013 Single-Family [Member]	Sep. 30, 2012 Single-Family [Member]	Sep. 30, 2013 Single-Family [Member]		Sep. 30, 2012 Single-Family [Member]	Sep. 30, 2013 Single-Family [Member] US Treasury [Member]	Sep. 30, 2012 Single-Family [Member] US Treasury [Member]	Sep. 30, 2013 Single-Family [Member] US Treasury [Member]	Sep. 30, 2012 Single-Family [Member] US Treasury [Member]
Accounting Policies [Abstract]
Deficit of core capital over statutory minimum capital requirement	$ 136,000,000,000				$ 136,000,000,000			$ 141,200,000,000
Expected undeclared dividends payable on senior preferred stock for the next quarter	8,600,000,000
Number of days after which we have not been paying debts or liabilities exceed assets FHFA must place us into receivership	60 days				60 days
Related Parties [Line Items]
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement										116,100,000,000	116,100,000,000
Initial aggregate liquidation preference of senior preferred stock held by US Treasury										1,000,000,000	1,000,000,000
Aggregate liquidation preference of senior preferred stock										117,100,000,000	117,100,000,000
Total available funding from US Treasury pursuant to the senior preferred stock agreement													117,600,000,000
Senior preferred stock dividend rate in effect through December 31, 2012								10.00%
Capital reserve amount for 2013 per the senior preferred stock purchase agreement amendment	3,000,000,000				3,000,000,000
Annual reduction of capital reserve from 2013 to 2018 based on Senior Preferred Stock Purchase Agreement Amendment	600,000,000				600,000,000
Payments of cash dividends on senior preferred stock to Treasury	10,200,000,000				73,835,000,000		8,679,000,000
Percentage of common shares attributable to warrants issued to US Treasury as percentage to total diluted common shares										79.90%	79.90%
Home Affordable Modification Program administrative expense reimbursements from Treasury and Freddie Mac	23,000,000			27,000,000	73,000,000		75,000,000
Income Taxes Paid					1,876,000,000		0			860,000,000	1,876,000,000	0
Principal and interest outstanding														1,000,000,000	1,600,000,000	4,600,000,000	6,100,000,000
Percentage of initial principal loss US Treasury will bear for Temporary Credit and Liquidity Facilities and New Issue Bond Programs										35.00%	35.00%
Loss of principal or interest under Treasury's Temporary Credit and Liquidity Facility and New Issue Bond Programs										0	0
Temporary Payroll Tax Cut related guaranty fee recorded in the Income Statement																												276,000,000	78,000,000	695,000,000	104,000,000
Liability to Treasury Related to Increase in Single-Family Guaranty Fee Resulting from the Temporary Payroll Tax Cut Continuation Act of 2011																												276,000,000		276,000,000
Temporary Payroll Tax Cut related guaranty fee paid to US Treasury																												233,000,000
Fair value of mortgage-backed securities																		9,400,000,000		9,400,000,000		12,200,000,000
Interest receivable	8,696,000,000				8,696,000,000			9,176,000,000										38,000,000		38,000,000		51,000,000
Investment income, interest																		91,000,000	132,000,000	303,000,000	427,000,000
Change in Accounting Estimate [Abstract]
Capital loss carryforwards, valuation allowance	447,000,000				447,000,000
Benefit (Provision) for federal income taxes	(1,355,000,000)		50,600,000,000	0	47,231,000,000	[1]	0																(751,000,000)	(12,000,000)	29,777,000,000	[1]	(12,000,000)
Increase (decrease) to the allowance for loan losses and provision for credit losses									2,200,000,000
Employee Retirement Benefit Plans [Abstract]
Defined benefit plan, curtailments		$ 146,000,000

[1] Primarily represents the release of the valuation allowance for our deferred tax assets that primarily are directly attributable to each segment based on the nature of the item.