Financial Instruments (Changes in Level 3 Inputs) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
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			$ 11,600,000
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	(75,637,000)	37,126,000	(35,318,000)	(33,658,000)
Change in fair value recognized in other comprehensive income	178,511,000	(9,956,000)	65,816,000	(8,542,000)
Change in Fair Value Recognized in Cost of Product Sold	11,085,000	(17,194,000)	12,970,000	30,027,000
Settlements Recognized in Sales and Other Revenues	6,202,000	10,138,000	80,476,000	25,454,000
Settlements Recognized in Cost of Product Sold	(4,251,000)	(8,460,000)	(8,034,000)	(1,627,000)
Asset (liability) balance at end of period	$ 115,910,000	$ 11,654,000	$ 115,910,000	$ 11,654,000