Derivative Accounting (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Commodity Contracts
Assets
Amount Reported on Balance Sheet	$ 37,000
Assets and Liabilities
Gross Recognized Derivatives	(43,889)	(72,712)
Amounts Offset	41,400	19,000
Net Recognized Derivatives	(2,489)	(53,712)
Other	(5,379)	(7,511)
Amount Reported on Balance Sheet	(7,868)	(61,223)
Commodity Contracts | Current Assets
Assets
Gross Recognized Derivatives	26,941	24,587
Amounts Offset	(12,125)	(7,425)
Net Recognized Derivatives	14,816	17,162
Other	604	7
Amount Reported on Balance Sheet	15,420	17,169
Commodity Contracts | Investments and Other Assets
Assets
Gross Recognized Derivatives	23,824	25,364
Amounts Offset	(3,753)	(1,549)
Net Recognized Derivatives	20,071	23,815
Other	1,510
Amount Reported on Balance Sheet	21,581	23,815
Commodity Contracts | Total Assets
Assets
Gross Recognized Derivatives	50,765	49,951
Amounts Offset	(15,878)	(8,974)
Net Recognized Derivatives	34,887	40,977
Other	2,114	7
Amount Reported on Balance Sheet	37,001	40,984
Commodity Contracts | Current Liabilities
Liabilities
Gross Recognized Derivatives	(40,376)	(50,540)
Amounts Offset	26,367	26,166
Net Recognized Derivatives	(14,009)	(24,374)
Other	(7,493)	(7,518)
Amount Reported on Balance Sheet	(21,502)	(31,892)
Commodity Contracts | Deferred Credits and Other
Liabilities
Gross Recognized Derivatives	(54,278)	(72,123)
Amounts Offset	30,911	1,808
Net Recognized Derivatives	(23,367)	(70,315)
Amount Reported on Balance Sheet	(23,367)	(70,315)
Commodity Contracts | Total Liabilities
Liabilities
Gross Recognized Derivatives	(94,654)	(122,663)
Amounts Offset	57,278	27,974
Net Recognized Derivatives	(37,376)	(94,689)
Other	(7,493)	(7,518)
Amount Reported on Balance Sheet	(44,869)	(102,207)
Designated as Hedging Instruments
Liabilities
Amount Reported on Balance Sheet	$ 4,000	$ 5,000