Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation Beginning Balance	$ 2,096	[1]	$ 1,783
Incurred, including acquisitions	89		84
Settled, including dispositions	(426)	[2]	(78)	[2]
Accretion expense (included in depreciation, depletion and amortization)	104		106
Revisions to previous estimates	95		244
Held for sale	0		(43)
Asset Retirement Obligation Ending Balance	1,958	[1]	2,096	[1]
Asset Retirement Obligation, Current	$ 41		$ 87

[1] Includes asset retirement obligations of $41 million and $87 million classified as short-term at December 31, 2014 and 2013.

[2] Includes the sale of our Norway business in the fourth quarter of 2014.