Summary of Significant Accounting Policies Related Parties (Details) - USD ($)			2 Months Ended	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 08, 2008	Feb. 29, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2016	Dec. 31, 2012	Sep. 07, 2008
Related Parties [Line Items]
Number of days after which we have not been paying debts or liabilities exceed assets FHFA must place us into receivership													60 days
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement	$ 116,100,000,000				$ 116,100,000,000								$ 116,100,000,000
Annual reduction of capital reserve from 2013 to 2018 based on the Senior Preferred Stock Purchase Agreement, Amendment	600,000,000				600,000,000								600,000,000
Capital reserve amount on January 2018	0				0								0
Payment Of Cash Dividends On Senior Preferred Stock To Treasury	2,200,000,000												10,278,000,000	$ 20,594,000,000	$ 82,452,000,000
Net worth (deficit)	$ 4,059,000,000				$ 4,059,000,000	$ 4,000,000,000			$ 3,720,000,000				$ 4,059,000,000	3,720,000,000	9,591,000,000		$ 7,224,000,000
Percentage of common shares attributable to warrants issued to Treasury as a percentage to total diluted common shares upon exercise of the right	79.90%				79.90%								79.90%
Income taxes paid													$ 1,170,000,000	2,815,000,000	2,350,000,000
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees					$ 429,000,000	413,000,000	$ 397,000,000	$ 382,000,000	367,000,000	$ 351,000,000	$ 335,000,000	$ 322,000,000	$ 1,621,000,000	1,375,000,000	1,001,000,000
Basis Points of Each Dollar of Unpaid Principal Balance	420.00%				420.00%								420.00%
Other expenses													$ 613,000,000	478,000,000	95,000,000
Trading, at fair value	$ 39,908,000,000				$ 39,908,000,000				31,504,000,000				39,908,000,000	31,504,000,000
Accrued interest receivable	7,726,000,000				7,726,000,000				8,193,000,000				7,726,000,000	8,193,000,000
Trading securities					114,000,000	$ 99,000,000	$ 116,000,000	$ 115,000,000	132,000,000	$ 151,000,000	$ 143,000,000	$ 127,000,000	444,000,000	553,000,000	779,000,000
U.S. Treasury Securities [Member]
Related Parties [Line Items]
Trading, at fair value	29,485,000,000				29,485,000,000				19,466,000,000				29,485,000,000	19,466,000,000
Scenario, Forecast [Member]
Related Parties [Line Items]
Undeclared Dividends On Senior Preferred Stock Next Quarter				$ 2,900,000,000
Series 2008-2 Senior Preferred Stock [Member]
Related Parties [Line Items]
Shares of variable liquidation preference senior preferred stock issued		1,000,000
Aggregate liquidation preference of senior preferred stock		$ 1,000,000,000
US Treasury [Member]
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				116,100,000,000				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								1,000,000,000
Aggregate liquidation preference of senior preferred stock	117,100,000,000				117,100,000,000								117,100,000,000
Total remaining funding available from US Treasury pursuant to the senior preferred stock agreement	117,600,000,000				117,600,000,000								117,600,000,000
Capital reserve amount for the fiscal year based on the amended Senior Preferred Stock Purchase agreement	1,800,000,000				1,800,000,000				2,400,000,000				1,800,000,000	2,400,000,000
Annual reduction of capital reserve from 2013 to 2018 based on the Senior Preferred Stock Purchase Agreement, Amendment	$ 600,000,000				$ 600,000,000								$ 600,000,000
Percentage of common shares attributable to warrants issued to Treasury as a percentage to total diluted common shares upon exercise of the right	79.90%				79.90%								79.90%					79.90%
Common stock warrant exercise price per share																		$ 0.00001
Fair value of the warrant at issuance		$ 3,500,000,000
Home Affordable Modification Program administrative expense reimbursements													$ 68,000,000	71,000,000	92,000,000
Income taxes paid													1,200,000,000	2,800,000,000	2,400,000,000
Income tax refund													$ 277,000,000
Percentage of initial principal loss US Treasury will bear for Temporary Credit and Liquidity Facilities and New Issue Bond Programs	35.00%				35.00%								35.00%
Increase of Guarantee Fee Rate Resulting from the Temporary Payroll Tax Cut Continuation Act of 2011.	1000.00%				1000.00%								1000.00%
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees					$ 429,000,000								$ 1,621,000,000	1,375,000,000	1,001,000,000
TCCA guaranty fee remitted													1,600,000,000	1,300,000,000	829,000,000
US Treasury [Member] | U.S. Treasury Securities [Member]
Related Parties [Line Items]
Trading, at fair value	$ 29,500,000,000				29,500,000,000				19,500,000,000				29,500,000,000	19,500,000,000
Accrued interest receivable	15,000,000				15,000,000				16,000,000				15,000,000	16,000,000
Trading securities													35,000,000	18,000,000	28,000,000
US Treasury [Member] | Temporary Credit and Liquidity Facilities Program [Member]
Related Parties [Line Items]
Principal and interest outstanding	0				0				390,000,000				0	390,000,000
US Treasury [Member] | New Issue Bond [Member]
Related Parties [Line Items]
Principal and interest outstanding	3,700,000,000				3,700,000,000				4,200,000,000				3,700,000,000	4,200,000,000
Loss of principal or interest under Treasury's Temporary Credit and Liquid Facilities and New Issue Bond Programs	0				0								0
US Treasury [Member] | Scenario, Forecast [Member]
Related Parties [Line Items]
Capital reserve amount for the fiscal year based on the amended Senior Preferred Stock Purchase agreement																$ 1,200,000,000
US Treasury [Member] | Scenario, Forecast [Member] | Capital Magnet Fund [Member]
Related Parties [Line Items]
Other expenses			$ 57,000,000
US Treasury [Member] | Scenario, Forecast [Member] | HOPE Reserve Fund [Member]
Related Parties [Line Items]
Other expenses			$ 54,000,000
Freddie Mac [Member] | Freddie Mac [Member]
Related Parties [Line Items]
Fair value of mortgage-related securities	5,600,000,000				5,600,000,000				6,900,000,000				5,600,000,000	6,900,000,000
Accrued interest receivable	$ 22,000,000				$ 22,000,000				$ 26,000,000				22,000,000	26,000,000
Investment income, interest													226,000,000	283,000,000	387,000,000
Federal Housing Finance Agency [Member]
Related Parties [Line Items]
FHFA assessment fees/expense													112,000,000	108,000,000	$ 109,000,000
Common Securitization Solutions [Member]
Related Parties [Line Items]
Payments to Acquire Equity Method Investments													$ 66,000,000	$ 43,000,000