CONSOLIDATED BALANCE SHEETS (Parenthetical)-K - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED BALANCE SHEETS
Trade receivables allowance	$ 29	$ 34
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	184,480,646	183,915,370
Treasury stock, shares	23,519,049	19,718,055