Derivative Instruments and Hedging Activities, Quantitative Disclosures Related to Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 0
Derivative Instruments With Credit Risk Related Contingent Features	0
Enogex [Member] | Natural Gas [Member]
Derivative [Line Items]
Percent of Contract with Durations of One Year or Less		95.10%
Percent of Contracts With Durations of More Than One Year and Less Than Two Years		2.90%
Percent of Contracts Having a Duration of More Than Two Years		2.00%
Enogex [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 0
Derivative Purchases [Member] | Fixed Swaps/Futures [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		16,200,000	[1],[2]
Derivative Purchases [Member] | Basis Swaps [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		7,300,000	[1],[2]
Derivative Purchases [Member] | Physical [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		7,000,000	[1],[2],[3],[4]
Derivative Sales [Member] | Enogex [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	0	3,700,000	[1]
Derivative Sales [Member] | Fixed Swaps/Futures [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		17,900,000	[1],[2]
Derivative Sales [Member] | Basis Swaps [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		6,700,000	[1],[2]
Derivative Sales [Member] | Physical [Member] | Enogex [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		30,100,000	[1],[2],[3],[4]

[1] Natural gas in MMBtu's.

[2] 95.1 percent of the natural gas contracts have durations of one year or less, 2.9 percent have durations of more than one year and less than two years and 2.0 percent have durations of more than two years.

[3] Of the natural gas physical purchases and sales volumes not designated as hedges, the majority are priced based on a monthly or daily index and the fair value is subject to little or no market price risk.

[4] Natural gas physical sales volumes exceed natural gas physical purchase volumes due to the marketing of natural gas volumes purchased via Enogex's processing contracts, which are not derivative instruments and are excluded from the table above.