Financial Instruments (Changes in Level 3 Inputs) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 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			$ 7,500,000
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	(22,473,000)	(6,249,000)	(35,318,000)	(33,658,000)	37,126,000
Change in fair value recognized in other comprehensive income	(90,559,000)	50,615,000	(112,695,000)	1,413,000
Change in Fair Value Recognized in Cost of Product Sold	(7,084,000)	3,662,000	1,885,000	47,222,000
Settlements Recognized in Sales and Other Revenues	48,942,000	(3,868,000)	74,273,000	15,316,000
Settlements Recognized in Cost of Product Sold	(4,463,000)	(7,034,000)	(3,782,000)	6,833,000
Asset (liability) balance at end of period	$ (75,637,000)	$ 37,126,000	$ (75,637,000)	$ 37,126,000	$ 37,126,000