CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 407	$ 401
Property and equipment, accumulated depreciation and amortization (in dollars)	3,580	3,494
Other intangible assets, accumulated amortization (in dollars)	$ 447	$ 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	143,597,960	142,363,915
Common stock in treasury, shares	40,172,225	37,730,431