Consolidated Balance Sheet (Parenthetical) (Unaudited) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Trade, allowance for doubtful accounts	$ 5	$ 6
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	153,989,973	166,070,057
Treasury stock, shares	14,192,554	1,588,990