Fair Value of Derivative and Balance Sheet Location (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	$ 15,582		$ 58,925
Derivative Liability, Fair Value, Gross Liability	21,196		28,576
Current Assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	9,660		52,042
Non Current Assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	5,922		6,883
Current Liabilities
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Liability	14,623		18,439
Non Current Liabilities
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Liability	6,573		10,137
Commodity Contracts Related to Natural Gas and Crude Oil Sales | Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	9,067		47,016
Commodity Contracts Related to Natural Gas and Crude Oil Sales | Non Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	5,792		6,671
Commodity Contracts Related to Natural Gas and Crude Oil Sales | Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	12,880		1,744
Commodity Contracts Related to Natural Gas and Crude Oil Sales | Non Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	6,403		9,969
Commodity Contracts Related to Affiliated Partnership | Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	0	[1]	4,707	[1]
Commodity Contracts Related to Natural Gas Marketing | Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	444		302
Commodity Contracts Related to Natural Gas Marketing | Non Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	85		203
Commodity Contracts Related to Natural Gas Marketing | Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	310		226
Commodity Contracts Related to Natural Gas Marketing | Non Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	40		168
Basis Protection Contracts Related to Natural Gas and Crude Oil Sales | Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	133		0
Basis Protection Contracts Related to Natural Gas and Crude Oil Sales | Non Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	44		0
Basis Protection Contracts Related to Natural Gas and Crude Oil Sales | Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	1,433		14,329
Basis Protection Contracts Related to Natural Gas and Crude Oil Sales | Non Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	130		0
Basis Protection Contracts Related to Natural Gas Marketing | Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	16		17
Basis Protection Contracts Related to Natural Gas Marketing | Non Current Assets
Derivatives, Fair Value
Fair Value of Derivatives	1		9
Basis Protection Contracts Related to Affiliated Partnerships | Current Liabilities
Derivatives, Fair Value
Fair Value of Derivatives	$ 0	[2]	$ 2,140	[2]

[1] Represents derivative positions designated to our affiliated partnerships. Accordingly, our accompanying December 31, 2012 condensed consolidated balance sheet includes a corresponding payable to our affiliated partnerships representing their proportionate share of the derivative assets.

[2] Represents derivative positions designated to our affiliated partnerships. Accordingly, our accompanying December 31, 2012 condensed consolidated balance sheet includes a corresponding receivable from our affiliated partnerships representing their proportionate share of the derivative liabilities