Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data	Jun. 30, 2011	Dec. 31, 2010
Trade, allowance for doubtful accounts	$ 11	$ 11
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	146,866,944	144,126,032
Treasury stock, shares	512,004	379,631
Series A Preferred stock
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	2,500,000	2,500,000
Series B Preferred stock
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	5,221,199	5,311,298