Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Maximum [Member]	Dec. 31, 2013 Gmac Saic [Member] Rate	Dec. 31, 2013 Ally Financial International Operations [Member]
Summary of Significant Accounting Policies [Line Items]
Payments to Acquire Businesses, Gross					$ 3,300,000,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners				40.00%
Number of Operating Segments	2
Intercompany Subvention Receivable	149,000,000	129,000,000
Intercompany Receivable - Commercial Lending	64,000,000	62,000,000
Intercompany Receivables - Wholesale financing	561,000,000	588,000,000
Intercompany Receivable - Commercial Receivables	468,000,000	368,000,000
Deferred income taxes	8,000,000	87,000,000	1,000,000,000
Related party taxes payable	838,000,000	643,000,000
Line of Credit Facilities - GM Related Party Facility	$ 600,000,000