Derivative Instruments (Schedule Of U.S. Natural Gas Derivative Positions) (Details) (Natural Gas Derivative Positions [Member])	Sep. 30, 2013 MMBTU
Swaps [Member] | 2013 [Member]
Derivative [Line Items]
Volume (in MMBtu/d)	55,000
Weighted Average Floor Price ($/MMBtu)	4.58
Weighted Average Ceiling Price ($/MMBtu)
Swaps [Member] | 2014 [Member]
Derivative [Line Items]
Volume (in MMBtu/d)	40,000
Weighted Average Floor Price ($/MMBtu)	4.07
Weighted Average Ceiling Price ($/MMBtu)
Swaps [Member] | 2015 [Member]
Derivative [Line Items]
Volume (in MMBtu/d)	10,000
Weighted Average Floor Price ($/MMBtu)	4.33
Weighted Average Ceiling Price ($/MMBtu)
Calls [Member] | 2014 [Member]
Derivative [Line Items]
Volume (in MMBtu/d)	10,000
Weighted Average Ceiling Price ($/MMBtu)	5.50