Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts	$ 314	$ 306
Other intangible assets, accumulated amortization	193	276
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,200,000,000	1,200,000,000
Common stock, shares issued	812,021,363	810,679,839
Common stock, shares outstanding	746,474,449	744,263,855
Treasury stock, shares	65,546,914	66,415,984
Variable Interest Entity [Line Items]
Non-recourse debt - current, balance at variable interest entities	3,108	2,829
Non-recourse debt - noncurrent, balance at variable interest entities	12,815	12,554
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current, balance at variable interest entities	424	282
Non-recourse debt - noncurrent, balance at variable interest entities	$ 1,118	$ 1,076