Financial Instruments (Changes in Level 3 Inputs) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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	$ 2,500,000
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	(35,318,000)	(33,658,000)
Change in fair value recognized in other comprehensive income	(22,137,000)	(49,202,000)
Change in Fair Value Recognized in Cost of Product Sold	8,970,000	43,559,000
Settlements Recognized in Sales and Other Revenues	25,331,000	19,185,000
Settlements Recognized in Cost of Product Sold	681,000	13,867,000
Asset (liability) balance at end of period	$ (22,473,000)	$ (6,249,000)