Consolidated Balance Sheet (Parenthetical) (Unaudited) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Trade, allowance for doubtful accounts	$ 8	$ 9
Deferred debt issuance costs	$ 27	$ 18
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	450,000,000	450,000,000
Common stock, outstanding	143,923,921	144,663,403
Treasury stock, shares	10,103,374	8,342,185