Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Common Stock, Shares, Outstanding beginning of period	75,362,956
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,666
Net Income (Loss) Attributable to Parent	49	69
Common Stock, Shares, Outstanding end of period	75,504,580
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,695
Common Stock [Member]
Common Stock, Shares, Outstanding beginning of period	75,362,956	75,316,419
Vesting of Restricted and Performance Stock Units, Shares	140,714	9,184
Shares Issued During Period, Dividend Reinvestment and Direct Stock Purchase Plan	910
Common Stock, Shares, Outstanding end of period	75,504,580	75,325,603
Common Stock Including Additional Paid in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	836	831
Vesting of Restricted and Performance Stock Units, Value	0	0
Stock Issued During Peirod, Value, Dividend Reinvestment and Direct Stock Purchase Plan	0
Stock-based Compensation	0	1
Dividends, Common Stock	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	836	832
Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6)	(5)
Vesting of Restricted and Performance Stock Units, Value	0	0
Stock-based Compensation	0	0
Dividends, Common Stock	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6)	(5)
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	833	766
Vesting of Restricted and Performance Stock Units, Value	0	0
Stock-based Compensation	0	0
Dividends, Common Stock	(20)	(20)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Net Income (Loss) Attributable to Parent	49	69
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	862	815
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3	7
Vesting of Restricted and Performance Stock Units, Value	0	0
Stock-based Compensation	0	0
Dividends, Common Stock	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0	(4)
Net Income (Loss) Attributable to Noncontrolling Interest	0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 3	$ 3