Basis of Presentation (Details 3) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Restatement Adjustment	Jun. 30, 2012 Restatement Adjustment	Sep. 30, 2012 Restatement Adjustment	Dec. 31, 2011 Restatement Adjustment
Depreciation expense					$ (45)	$ (15)		$ (30)
Net income	$ 270	$ 138	$ 544	$ 464	$ 28		$ 18
Net income per share	$ 0.43	$ 0.22	$ 0.88	$ 0.91	$ 0.05		$ 0.03