Derivative Accounting (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Commodity Contracts
Assets
Amount Reported on Balance Sheet	$ 39,000
Assets and Liabilities
Gross Recognized Derivatives	(51,289)	(72,712)
Amounts Offset	49,199	19,000
Net Recognized Derivatives	(2,090)	(53,712)
Other	(8,346)	(7,511)
Amount Reported on Balance Sheet	(10,436)	(61,223)
Commodity Contracts | Current Assets
Assets
Gross Recognized Derivatives	32,470	24,587
Amounts Offset	(15,816)	(7,425)
Net Recognized Derivatives	16,654	17,162
Other	297	7
Amount Reported on Balance Sheet	16,951	17,169
Commodity Contracts | Investments and Other Assets
Assets
Gross Recognized Derivatives	23,913	25,364
Amounts Offset	(2,287)	(1,549)
Net Recognized Derivatives	21,626	23,815
Amount Reported on Balance Sheet	21,626	23,815
Commodity Contracts | Total Assets
Assets
Gross Recognized Derivatives	56,383	49,951
Amounts Offset	(18,103)	(8,974)
Net Recognized Derivatives	38,280	40,977
Other	297	7
Amount Reported on Balance Sheet	38,577	40,984
Commodity Contracts | Current Liabilities
Liabilities
Gross Recognized Derivatives	(42,161)	(50,540)
Amounts Offset	30,897	26,166
Net Recognized Derivatives	(11,264)	(24,374)
Other	(8,643)	(7,518)
Amount Reported on Balance Sheet	(19,907)	(31,892)
Commodity Contracts | Deferred Credits and Other
Liabilities
Gross Recognized Derivatives	(65,511)	(72,123)
Amounts Offset	36,405	1,808
Net Recognized Derivatives	(29,106)	(70,315)
Amount Reported on Balance Sheet	(29,106)	(70,315)
Commodity Contracts | Total Liabilities
Liabilities
Gross Recognized Derivatives	(107,672)	(122,663)
Amounts Offset	67,302	27,974
Net Recognized Derivatives	(40,370)	(94,689)
Other	(8,643)	(7,518)
Amount Reported on Balance Sheet	(49,013)	(102,207)
Designated as Hedging Instruments
Liabilities
Amount Reported on Balance Sheet	$ 4,000	$ 5,000