Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 96	$ 134
Other intangible assets, accumulated amortization	158	153
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)	814,539,146	813,316,510
Common stock, shares outstanding (in shares)	703,851,297	722,508,342
Treasury stock, shares (in shares)	110,687,849	90,808,168
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	1,982	2,062
Non-recourse debt - noncurrent, balance at variable interest entities	13,618	13,318
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	240	267
Non-recourse debt - noncurrent, balance at variable interest entities	$ 1,030	$ 979