Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies ResCap Bankruptcy Information (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Nov. 02, 2012	May 14, 2012
ResCap Bankruptcy Information [Line Items]
Stalking Horse Bid	$ 1,600,000,000
Cash Contribution to ResCap	750,000,000
Ally Provided Post-Petition Debtor-in-Possession Financing to ResCap	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
Finance Receivable Due from ResCap	$ 1,200,000,000