Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	9 Months Ended								1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Maximum [Member]	Sep. 30, 2014 Gmac Saic [Member] Rate	Sep. 30, 2014 Junior Subordinated Revolving Credit Facility [Member]	Sep. 30, 2014 General Motors [Member]	Oct. 23, 2014 Subsequent Event [Member] General Motors [Member] Amended Credit Facility [Member]	Oct. 23, 2014 Subsequent Event [Member] General Motors [Member] Three Year Credit Facility [Member]	Oct. 23, 2014 Subsequent Event [Member] General Motors [Member] Five Year Credit Facility [Member]
Summary of Significant Accounting Policies [Line Items]
Adjustment to Net cash Provided by Operating Activities		$ 100,000,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					40.00%
Number of Operating Segments	2
Due from Related Parties	195,000,000		129,000,000
Intercompany Receivable - Commercial Lending	116,000,000		62,000,000
Intercompany Receivables - Wholesale financing	342,000,000		588,000,000
Related party payable	603,000,000		368,000,000
Deferred income taxes	21,000,000		87,000,000	1,000,000,000
Related party taxes payable	877,000,000		643,000,000
Line of Credit Facility, Maximum Borrowing Capacity							4,000,000,000	4,000,000,000	2,000,000,000
Line of Credit Facilities - GM Related Party Facility	600,000,000					1,000,000,000
Line of Credit Facility, Current Borrowing Capacity							11,000,000,000	12,500,000,000	5,000,000,000	7,500,000,000
Line of Credit Facility, Expiration Period									3 years	5 years
Adjustment to Net cash Used by Investing Activities		$ 100,000,000