Non-Mineral Leases - Operating lease rental (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011
Operating lease rental expense
Total rentals	$ 317	$ 282	[1]	$ 304	[1]
Less sublease rentals	(12)	(15)		(14)
Operating Leases, Rent Expense, Total	305	267		290
Non Mineral Leases (Textual) [Abstract]
Contingent Rentals		$ 3		$ 29

[1] *Includes $3 million and $29 million of contingent rentals in 2012 and 2011, respectively. Contingent rentals are primarily related to drilling equipment and are based on usage or volume of product sold.