Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Trade, allowance for doubtful accounts	$ 9	$ 9
Debt issuance costs	$ 28	$ 18
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	450,000,000	450,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares outstanding	143,942,539	144,663,403
Treasury stock, shares	10,111,191	8,342,185