Summary of Significant Accounting Policies Narratives(Details) (USD $)	0 Months Ended	3 Months Ended								12 Months Ended			0 Months Ended	3 Months Ended								12 Months Ended										12 Months Ended			0 Months Ended	3 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 08, 2008 US Treasury [Member]	Dec. 31, 2013 US Treasury [Member]	Sep. 30, 2013 US Treasury [Member]	Jun. 30, 2013 US Treasury [Member]	Mar. 31, 2013 US Treasury [Member]	Dec. 31, 2012 US Treasury [Member]	Sep. 30, 2012 US Treasury [Member]	Jun. 30, 2012 US Treasury [Member]	Mar. 31, 2012 US Treasury [Member]	Dec. 31, 2013 US Treasury [Member]		Dec. 31, 2012 US Treasury [Member]		Dec. 31, 2011 US Treasury [Member]	Sep. 07, 2008 US Treasury [Member]	Dec. 31, 2013 US Treasury [Member] Temporary Credit and Liquidity Facilities Program [Member]	Dec. 31, 2012 US Treasury [Member] Temporary Credit and Liquidity Facilities Program [Member]	Dec. 31, 2013 US Treasury [Member] New Issue Bond [Member]	Dec. 31, 2012 US Treasury [Member] New Issue Bond [Member]	Dec. 31, 2013 Freddie Mac [Member]	Dec. 31, 2012 Freddie Mac [Member]	Dec. 31, 2010 Freddie Mac [Member]	Jan. 31, 2013 GMAC Mortgage LLC (a subsidiary of Ally Financial, Inc.) [Member]	Jun. 30, 2013 Single-Family Individually Impaired Loan Loss Models Update [Member]	Sep. 07, 2008 Series 2008-2 Senior Preferred Stock [Member]	Dec. 31, 2013 Series 2008-2 Senior Preferred Stock [Member]	Dec. 31, 2012 Series 2008-2 Senior Preferred Stock [Member]	Dec. 31, 2011 Series 2008-2 Senior Preferred Stock [Member]	Sep. 08, 2008 Series 2008-2 Senior Preferred Stock [Member]
Related Parties [Line Items]
Number of days of that liabilities exceed assets requiring FHFA to place us into receivership	60 days	60 days								60 days
Shares of variable liquidation preference senior preferred stock issued																																					1,000,000
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				$ 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																			1,000,000,000
Total remaining funding available from US Treasury pursuant to the senior preferred stock agreement														117,600,000,000								117,600,000,000
Capital Loss Carryforward, Valuation Allowance	525,000,000	525,000,000								525,000,000
Capital Reserve Amount, current Year, Senior Preferred Stock Purchase Agreement, Amendment	3,000,000,000	3,000,000,000								3,000,000,000				3,000,000,000								3,000,000,000
Capital reserve amount for the next fiscal year based on the amended Senior Preferred Stock Purchase agreement	2,400,000,000	2,400,000,000								2,400,000,000				2,400,000,000								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				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	8,600,000,000	8,600,000,000								82,452,000,000	11,608,000,000	9,613,000,000																										82,500,000,000	11,608,000,000	9,613,000,000
Undeclared Dividends On Senior Preferred Stock Next Quarter		7,200,000,000
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%								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										92,000,000	96,000,000	106,000,000
Income Taxes Paid										2,350,000,000	0	0
Proceeds from income tax refunds												1,100,000,000														1,100,000,000
Income tax benefit recognized from our settlement of 2007 and 2008 tax years with the IRS																										90,000,000
Principal and interest outstanding																												821,000,000	1,600,000,000	4,500,000,000	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 Liquid Facilities and New Issue Bond Programs														0								0
Increase of Guarantee Fee Rate Resulting from the Temporary Payroll Tax Cut Continuation Act of 2011.														0.10%								0.10%
TCCA guaranty fee										1,001,000,000	238,000,000	0		306,000,000	276,000,000	233,000,000	186,000,000	134,000,000	78,000,000	26,000,000	0	1,001,000,000	[1]	238,000,000	[1],[2]
TCCA guaranty fee remitted																						829,000,000		104,000,000
Fair value of mortgage-backed securities																																8,700,000,000	12,200,000,000
Interest receivable	8,319,000,000	8,319,000,000				9,176,000,000				8,319,000,000	9,176,000,000																					35,000,000	51,000,000
Investment income, interest																																387,000,000	551,000,000	700,000,000
Amount received in exchange for our release of specified Ally affiliates from certain potential liability																																			265,000,000
(Benefit) provision for credit losses		0	(2,609,000,000)	(5,383,000,000)	(957,000,000)	(1,890,000,000)	2,079,000,000	(3,041,000,000)	2,000,000,000	(8,949,000,000)	(852,000,000)	26,718,000,000																							(173,000,000)
Change in income tax provision due to valuation allowance changes										58,300,000,000	5,300,000,000	(7,000,000,000)
Change in Accounting Estimate [Abstract]
(Decrease) increase to the allowance for loan losses and provision for credit losses																																				2,200,000,000
Fair value of guaranty obligation	1,100,000,000	1,100,000,000				1,800,000,000				1,100,000,000	1,800,000,000
Reserve for Guaranty Losses	$ 1,400,000,000	$ 1,400,000,000				$ 1,200,000,000				$ 1,400,000,000	$ 1,200,000,000
Maximum term of early lender funding advances										60 days

[1] Pursuant to the TCCA, effective April 1, 2012, we increased the guaranty fee on all single-family residential mortgages delivered to us on or after that date by 10 basis points, and the incremental revenue must be remitted to Treasury. The resulting revenue is included in guaranty fee income and the expense is recognized as “TCCA fees.” This increase in guaranty fee is also included in the single-family average charged guaranty fee.

[2] Certain prior period amounts have been reclassified to conform with the current period presentation.