Derivatives And Risk Management (Narrative) (Details) ft³ in Billions	12 Months Ended
	Dec. 31, 2015 USD ($) ft³
2015 Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	0
Accumulated other comprehensive income | $	$ 0
Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount | $	$ 170,000,000
Derivative, expiration	Jun. 30, 2020
Not Designated as Hedging Instrument [Member] | 2016 Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	5
Not Designated as Hedging Instrument [Member] | 2016 Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of Natural Gas Production (in Bcf), Fixed Price Swaps Not Qualifying for Hedge Accounting Treatment	120