Servicing Activities (Schedule Of Total Serviced Automobile Loans Outstanding) (Details) (Automobile Member, USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	$ 132,817	$ 134,122
On-Balance Sheet Loans [Member] | Consumer Loans Auto Financing Receivable [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	55,014	53,715
On-Balance Sheet Loans [Member] | Commercial Automobile [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	31,875	32,822
On-Balance Sheet Loans [Member] | Operating Leases [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	14,828	13,550
On-Balance Sheet Loans [Member] | Operations Held-For-Sale [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	15,304	25,979
On-Balance Sheet Loans [Member] | Other Assets [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	45	41
Off-Balance Sheet Loans [Member] | Other Assets [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	9,060	0
Off-Balance Sheet Loans [Member] | Securitizations [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	1,317	1,474
Off-Balance Sheet Loans [Member] | Whole-Loan Transactions [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	$ 5,374	$ 6,541