CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 440	$ 401
Property and equipment, accumulated depreciation and amortization (in dollars)	3,756	3,494
Other intangible assets, accumulated amortization (in dollars)	$ 490	$ 426
Common stock, par value (in dollars per share)	$ 0.05	$ 0.05
Common stock, authorized shares	262,500,000	262,500,000
Common stock, shares issued	143,973,854	142,363,915
Common stock in treasury, shares	44,807,632	37,730,431