Supplemental Data (Other Cash Flow Data and Interest Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Supplemental Data
Interest paid	$ 273	$ 248	$ 290
Income Taxes Paid	463	582	764
Gross interest cost	285	255	288
Capitalized interest on major construction projects	(8)	(12)	(13)
Interest expense	$ 277	$ 243	$ 275