Financial Instruments (Changes in Level 3 Inputs) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Hypothetical change to estimated future cash flows attributable to commodity price swaps, percent			10.00%
Estimated change in fair value resulting from hypothetical percentage change in future cash flows attributable to commodity price swaps			$ 1,200,000
Commodity Contract [Member] | Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset (liability) balance at beginning of period	37,126,000	119,461,000	(33,658,000)	31,616,000
Unrealized (gains) losses included in other comprehensive income	(9,956,000)	(192,446,000)	(8,542,000)	(158,893,000)
Change in Fair Value Recognized in Cost of Product Sold	(17,194,000)	0	30,027,000	0
Settlements Recognized in Sales and Other Revenues	10,138,000	44,937,000	25,454,000	99,229,000
Settlements Recognized in Cost of Product Sold	(8,460,000)		(1,627,000)
Asset balance at end of period	$ 11,654,000	$ (28,048,000)	$ 11,654,000	$ (28,048,000)