Acquisitions and Divestitures - Pro- Forma Information for Company as if Acquisition of Properties (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2010
Business Acquisition Pro Forma Information [Line Items]
Revenues and Other	$ 13,780
Net Income (Loss)	3,364
Preferred Stock Dividends	76
Income (Loss) Attributable to Common Stock	$ 3,288
Net Income (Loss) per Common Share - Basic	$ 8.62
Net Income (Loss) per Common Share - Diluted	$ 8.52