CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Allowance for doubtful accounts	$ 114	$ 103
LIABILITIES AND STOCKHOLDERS’ EQUITY
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	114,145,755	113,825,667
Common stock, shares outstanding (in shares)	72,132,246	74,362,195
Treasury stock, shares (in shares)	42,013,509	39,463,472