Goodwill (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Goodwill [Roll Forward]
Balance at beginning of period	$ 1,240		$ 1,108
Acquisition	6	[1]	132
Foreign currency translation	(2)		0
Balance at end of period	1,244		1,240
Ally Financial International Operations [Member]
Goodwill [Roll Forward]
Balance at beginning of period	138
Acquisition	6	[1]
Balance at end of period	138
North America Segment [Member]
Goodwill [Roll Forward]
Balance at beginning of period	1,108		1,108		1,108
Acquisition	0		0		0
Foreign currency translation	(2)		0		0
Balance at end of period	1,106		1,108		1,108
International Segment [Member]
Goodwill [Roll Forward]
Balance at beginning of period	132	[1]	0	[1]
Acquisition	6	[1]	132	[1]
Foreign currency translation	0	[1]	0	[1]
Balance at end of period	$ 138	[1]	$ 132	[1]

[1] See Note 2 - "Acquisition of Ally Financial International Operations" for further discussion. Goodwill increased $6 million during 2014 due to certain post-closing adjustments to the purchase price.