CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 401	$ 397
Property and equipment, accumulated depreciation and amortization (in dollars)	3,494	3,386
Other intangible assets, accumulated amortization (in dollars)	$ 426	$ 360
Preferred stock, par value (in dollars per share)	$ 0.15	$ 0.15
Preferred stock, authorized shares	2,500,000	2,500,000
Preferred stock, percent of mandatory convertible shares	7.00%	7.00%
Preferred stock, 7% mandatory convertible shares issued	0	345,000
Preferred stock, liquidation preference per share (in dollars per share)	$ 1,000	$ 1,000
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	142,363,915	137,867,138
Common stock in treasury, shares	37,730,431	34,110,674