Derivatives (Derivatives Outstanding) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Derivative [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ 3,312
Cash Flow Liquid Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(8,000.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	902
Swing swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(620.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(3)
Swing swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	186.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(1)
Physical offset to swing swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(186.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	0
Physical offset to swing swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	620.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	0
Basis Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(775.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	23
Basis Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(4,393.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	1,126
Basis Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	775.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(28)
Physical Offset To Basis Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(775.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	2,071
Physical Offset To Basis Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	775.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(2,233)
Processing Margin Hedges [Member] | Short Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(161.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	147
Processing Margin Hedges [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(8,791.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	2,453
Processing Margin Hedges [Member] | Long Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	1,167.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(285)
Storage Swap [Member] | Short Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(300.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	(77)
Storage Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	(1,470.0)
Cash Flow Hedges Derivative Instruments at Fair Value, Net	102
Storage Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	630.0
Cash Flow Hedges Derivative Instruments at Fair Value, Net	$ 17