Risk Management Activities (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net (Gains) Losses on Mark-to-Market Commodity Derivative Contracts		$ (61,924,000)	$ (834,273,000)	$ 166,349,000
Net Cash Received from Settlements of Crude Oil and Natural Gas Derivative Contracts		$ 730,114,000	$ 34,007,000	$ 116,361,000
Derivatives, Fair Value [Line Items]
Receivable Major Customer Percentage		10.00%	10.00%
Derivatives assets, current		$ 0	$ 465,128,000
Derivative Collateral [Abstract]
Collateral Held on Derivative		0	278,000,000
Collateral Had on Derivaitve		0	0
Crude Oil and Natural Gas Derivative Contracts [Member] | Assets From Price Risk Management Activities [Member]
Derivatives, Fair Value [Line Items]
Derivatives assets, current	[1]	0	465,000,000
Derivative asset, gross assets			477,000,000
Derivative asset, gross liabilities			12,000,000
Crude Oil and Natural Gas Derivative Contracts [Member] | Liabilities From Price Risk Management Activities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities, current	[2]	$ 0	0
Derivative liabilities, gross liabilities			12,000,000
Derivative liabilities, gross assets			$ 12,000,000

[1] The current portion of Assets from Price Risk Management Activities consists of gross assets of $477 million, partially offset by gross liabilities of $12 million, at December 31, 2014.

[2] The current portion of Liabilities from Price Risk Management Activities consists of gross liabilities of $12 million, offset by gross assets of $12 million, at December 31, 2014.