Financial Instruments (Details 2)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 bbl	Sep. 30, 2012 bbl	Sep. 30, 2013 bbl	Sep. 30, 2012 bbl
Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	695,000	470,000	2,025,000	1,153,000
Purchases [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	805,000	380,000	2,095,000	1,066,000