Natural Gas And Oil Producing Activities (Unaudited) (Standardized Measures of Discounted Future Net Cash Flows Relating to Proved Natural Gas and Oil Reserves) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Natural Gas And Oil Properties [Abstract]
Future cash inflows	$ 22,624,562	$ 9,570,652	$ 22,012,205
Future production costs	(8,895,956)	(4,737,297)	(8,080,207)
Future development costs	(3,626,496)	(711,050)	(3,425,185)
Future income tax expense	(3,223,271)	(745,251)	(3,366,175)
Future net cash flows	6,878,839	3,377,054	7,140,638
10% annual discount for estimated timing of cash flows	(3,142,795)	(1,326,389)	(3,689,838)
Standardized measure of discounted future net cash flows	$ 3,736,044	$ 2,050,665	$ 3,450,800
Annual discount for estimated timing of cash flows percent	10.00%	10.00%	10.00%