Derivatives And Risk Management (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Derivative [Line Items]
Accumulated other comprehensive income, net loss related to hedging activities	$ (18.6)
Deferred income tax benefit, accumulated other comprehensive income	(12.4)
Cash flow hedge after-tax net loss to be transferred from accumulated other comprehensive income to earnings during the next twelve months	(18.6)
Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	348,600,000,000
Year 2015 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	119,500,000,000
Designated as Hedging Instrument [Member] | Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	211,800,000,000
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	21,100,000,000
Not Designated as Hedging Instrument [Member] | Year 2014 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	136,800,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	8,700,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	199,800,000,000
Not Designated as Hedging Instrument [Member] | Year 2015 [Member] | Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	119,500,000,000
Not Designated as Hedging Instrument [Member] | Year 2016 [Member] | Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	900,000,000
Not Designated as Hedging Instrument [Member] | Year 2016 [Member] | Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	119,900,000,000