Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Trade, allowance for doubtful accounts	$ 8	$ 8
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	147,896,999	147,319,438
Treasury stock, shares	712,779	645,734
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	5,221,199