Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Trade, allowance for doubtful accounts	$ 6	$ 7
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	450,000,000	450,000,000
Common stock, outstanding	157,148,833	145,338,342
Treasury stock, shares	21,914,062	18,742,288
Series B Preferred Stock [Member]
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	2,101,384	3,803,774