Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Noncash Investing and Financing Activities
Increase in PP&E related to increase in asset retirement obligations	$ 1,010	[1]	$ 182	$ 808
Cash payments
Interest	724		919	1,120
Income taxes	8,568		10,285	8,262
Net Sales (Purchases) of Short-Term Investments
Short-term investments purchased	(497)		(6,744)	(982)
Short-term investments sold	1,094		7,144
Net Sales (Purchases) of Short-Term Investments	597		400	(982)
ARO increase related to UK tax law changes	$ 152

[1] *Includes $152 million primarily related to U.K. tax law changes on the deductibility of decommissioning costs.