Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Summary of Significant Accounting Policies [Line Items]
Number of Operating Segments	2
Intercompany Subvention Receivable	$ 185	$ 129
Intercompany Receivable - Commercial Lending	90	62
Intercompany Receivables - Wholesale financing	228	588
Intercompany Receivable - Commercial Receivables	432	368
Deferred income taxes	12	87
Related party taxes payable	891	643
Line of Credit Facilities - GM Related Party Facility	600
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Deferred income taxes	$ 1,000
Gmac Saic [Member]
Summary of Significant Accounting Policies [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		40.00%