Natural Gas And Oil Producing Activities (Unaudited) (Composition of Net Unevaluated Costs Excluded from Amortization (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			84 Months Ended	120 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013
Property aquisition costs	$ 147,791	$ 81,889	$ 221,451	$ 109,994	$ 561,125
Exploration and Development Costs	166,725	48,428	47,784	38,858	301,795	[1]
Capitalized interest	7,792	11,067	38,145	36,545	93,549	[1]
Capitalized Costs of Unproved Properties Excluded from Amortization, Period Cost, Total	322,308	141,384	307,380	185,397	956,469	[1]
Exploration Program in Canada [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization, Period Cost, Total	72,300
Composition of Net Unevaluated Costs [Member] | Exploration Program in Canada [Member]
Property aquisition costs					35,000
Exploration and Development Costs					31,800
Capitalized interest					$ 5,500

[1] Property acquisition costs include $35.0 million, exploration costs include $31.8 million and capitalized interest includes $5.5 million related to our exploration program in Canada.