Commitments And Contingencies Guarantees (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Third party commercial loans and other obligations [Member]
Guarantees [Abstract]
Liability Recorded	$ 87	$ 168
Maximum Liability	14,858	22,496
Guarantees of Product Related Claims [Member]
Guarantees [Abstract]
Liability Recorded	53	51
Maximum Liability	1,160	1,040
Ally Financial [Member] | Third party commercial loans and other obligations [Member]
Guarantees [Abstract]
Liability Recorded	10	15
Maximum Liability	$ 14,600	$ 22,100