Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts	$ 287	$ 306
Other intangible assets, accumulated amortization	200	276
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,200,000,000	1,200,000,000
Common stock, shares issued (in shares)	812,248,090	810,679,839
Common stock, shares outstanding (in shares)	745,144,098	744,263,855
Treasury stock, shares (in shares)	67,103,992	66,415,984
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	2,923	2,829
Non-recourse debt - noncurrent, balance at variable interest entities	12,476	12,554
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	287	282
Non-recourse debt - noncurrent, balance at variable interest entities	$ 1,172	$ 1,076