Financial Instruments and Risk Management (Recognized Gains and Losses for Derivative Instruments Not Designated as Hedging Instruments) (Details) - Nondesignated [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ 39,425	$ 36,467	$ 46,858	$ (13,088)
Commodity Derivative Contracts [Member] | Sales and other operating revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	39,392	37,305	46,811	(17,150)
Foreign Exchange Derivative Contracts [Member] | Interest and other income (loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ 33	$ (838)	$ 47	$ 4,062