Derivatives And Risk Management (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Derivative [Line Items]
Accumulated other comprehensive income, net gain related to hedging activities	$ 36.0
Deferred income tax liability, accumulated other comprehensive income	24.0
Cash flow hedge after-tax net gain to be transferred from accumulated other comprehensive income to earnings during the next twelve months	30.0
Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	117,000,000,000
Year 2015 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	240,000,000,000
Designated as Hedging Instrument [Member] | Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	71,000,000,000
Designated as Hedging Instrument [Member] | Year 2015 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	120,000,000,000
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount	$ 170
Not Designated as Hedging Instrument [Member] | Year 2014 [Member] | Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	10,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	46,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	15,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	200,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	120,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2016 [Member] | Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	4,000,000,000
Not Designated as Hedging Instrument [Member] | Year 2016 [Member] | Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	120,000,000,000