Derivatives (Derivatives Outstanding) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Derivative [Line Items]
Mark to Market Derivatives, Fair Value	$ 491		$ 1,924
Cash Flow Liquid Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(9,322,000)
Cash Flow Hedges, Fair Value	(45)
Swing swap [Member] | Long Contracts [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	1,659,000	[1]
Mark to Market Derivatives, Fair Value	4	[1]
Physical offset to swing swap [Member] | Short Contracts [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(1,659,000)	[1]
Mark to Market Derivatives, Fair Value	(1)	[1]
Basis Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(1,369,000)
Mark to Market Derivatives, Fair Value	308
Processing Margin Hedges [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(3,926,000)
Mark to Market Derivatives, Fair Value	256
Processing Margin Hedges [Member] | Long Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	422,000
Mark to Market Derivatives, Fair Value	(125)
Storage Swap [Member] | Short Contracts [Member] | Gas [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(100,000)
Mark to Market Derivatives, Fair Value	21
Storage Swap [Member] | Short Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	(1,680,000)
Mark to Market Derivatives, Fair Value	70
Storage Swap [Member] | Long Contracts [Member] | Liquids [Member]
Derivative [Line Items]
Derivative nonmonetary notional amount (volume)	420,000
Mark to Market Derivatives, Fair Value	3
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark to Market Derivatives, Fair Value	$ 536

[1] All are gas contracts except