Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations, Beginning Balance	$ 402		$ 377
Liabilities Incurred	2		23
Liabilities Settled	(10)		(2)
Revision of Estimate	7		20
Accretion Expense	14	[1]	14	[1]
Other	0		(89)
Asset Retirement Obligations, Ending Balance	$ 415		$ 343

[1] Accretion expense is included in DD&A expense in the consolidated statements of operations.