Derivatives (Derivatives Outstanding) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(4,393.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	$ 1,035
Long Contracts [Member] | Third Party On System [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	465.0
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	(19)
Cash Flow Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(5,496.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	619
Swing Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	890.0
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	(2)
Physical Offset To Swing Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(890.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	0
Physical Offset To Swing Swap [Member] | Short Contracts [Member] | Third Party On System [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(465.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	33
Basis Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(2,450.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	5
Basis Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	2,450.0
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	13
Physical Offset To Basis Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(2,450.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	7,179
Physical Offset To Basis Swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	2,450.0
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	(8,029)
Processing Margin Hedges [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(6,423.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	1,212
Processing Margin Hedges [Member] | Long Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	750.0
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	(21)
Storage Swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	(2,400.0)
Derivative Non Designated Assets (Liabilities), at Fair Value, Net	$ (101)