Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies ResCap Bankruptcy Information (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Aug. 03, 2012	May 14, 2012
ResCap Bankruptcy Information [Line Items]
Stalking Horse Bid	$ 1,600,000,000	$ 1,600,000,000
Cash Contribution to ResCap	750,000,000	750,000,000
Ally Provided Post-Petition Debtor-in-Possession Financing to ResCap	220,000,000	220,000,000
Amount of ResCap Junior Secured Noteholders Supporting Bankruptcy Plan				791,000,000
Total ResCap Junior Secured Notes and Certain Other Notes				2,100,000,000
Threshold for Ownership Significance for Residential Mortgaged-Backed Securities			25.00%	25.00%
Total Number of Residential Mortgage-backed Securitizations for Which There is Support for the Plan			336	290
Amount of Original Principal Balance of Residential Mortgage-backed Securizations for which there is Support for the Plan			189,000,000,000
Total Number of Outstanding Residential Mortgage-Backed Securitizations			392
Total Outstanding Residential Mortgage-backed Securitizations Principal Balance			221,000,000,000
Total Charge Recorded Related to ResCap Bankruptcy	1,200,000,000
Impairment of Investment in ResCap		$ 442,000,000