Consolidated Balance Sheet (Parenthetical) (Unaudited) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Trade, allowance for doubtful accounts	$ 7	$ 6
Deferred debt issuance costs	$ 20	$ 21
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, outstanding	144,541,593	143,938,280
Treasury stock, shares	6,957,065	6,812,784