Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 85	$ 96
Other intangible assets, accumulated amortization	$ 131	$ 158
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)	815,846,624	814,539,146
Common stock, shares outstanding (in shares)	674,461,074	703,851,297
Treasury stock, shares (in shares)	141,385,550	110,687,849
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	$ 2,300	$ 1,982
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	217	240
Non-recourse debt - current balance at variable interest entities	$ 1,050	$ 1,030