Fair Value Measurements Nonrecurring Fair Value Changes (Details) (Financial Services [Member], Fair Value, Measurements, Nonrecurring [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Items measured at fair value [Line Items]
Total Gains / (Losses)	$ (25)	$ (37)	$ (57)
North America [Member]
Items measured at fair value [Line Items]
Total Gains / (Losses)	(14)	(23)	(32)
International [Member]
Items measured at fair value [Line Items]
Total Gains / (Losses)	(11)	(14)	(25)
Retail [Member] | North America [Member]
Items measured at fair value [Line Items]
Total Gains / (Losses)	(13)	(23)	(29)
Retail [Member] | International [Member]
Items measured at fair value [Line Items]
Total Gains / (Losses)	(11)	(14)	(25)
Dealer loans [Member] | North America [Member]
Items measured at fair value [Line Items]
Total Gains / (Losses)	$ (1)	$ 0	$ (3)