Supplemental Data (Other Cash Flow Data and Interest Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Data
Interest paid	$ 299	$ 273	$ 248
Income Taxes Paid	451	463	582
Gross interest cost	293	285	255
Capitalized interest on major construction projects	(9)	(8)	(12)
Interest expense	$ 284	$ 277	$ 243