Oil and Gas Exploration and Production Industries Disclosures (Details 1) (Oil) (Oil [Member])	12 Months Ended
	Dec. 31, 2012 MMBbls	Dec. 31, 2011 MMBbls	Dec. 31, 2010 MMBbls
Oil [Member]
Proved developed and undeveloped reserves, Beginning of year	546	538	506
Revisions of Previous Estimates	(19)	63	92
Extensions, discoveries and other additions	0	0	0
Production	(45)	(55)	(60)
Proved developed and undeveloped reserves, End of year	482	546	538
Proved developed reserves, Beginning of the year	474	433	383
Proved developed reserves, End of year	482	474	433
Proved undeveloped reserves, Beginning of year	71	105	123
Proved undeveloped reserves, End of year	0	71	105