Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts	$ 140	$ 195
Other intangible assets, accumulated amortization	151	222
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)	813,077,875	810,679,839
Common stock, shares outstanding (in shares)	742,245,268	744,263,855
Treasury stock, shares (in shares)	70,832,607	66,415,984
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	2,385	2,495
Non-recourse debt - noncurrent, balance at variable interest entities	12,981	12,286
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	267	275
Non-recourse debt - noncurrent, balance at variable interest entities	$ 939	$ 858