CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED BALANCE SHEETS
Trade receivables allowance	$ 32	$ 29
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	185,354,796	184,480,646
Treasury stock, shares	23,017,367	23,519,049