Natural Gas And Oil Producing Activities (Unaudited) (Standardized Measure Of Discounted Future Cash Flows Relating To Proved Reserves Disclosure) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Natural Gas And Oil Producing Activities (Unaudited) [Abstract]
Future cash inflows	$ 41,812	$ 22,624	$ 9,570
Future production costs	(16,477)	(8,896)	(4,737)
Future development costs	(5,750)	(3,626)	(711)
Future income tax expense	(4,743)	(3,223)	(745)
Future net cash flows	14,842	6,879	3,377
10% annual discount for estimated timing of cash flows	(7,299)	(3,143)	(1,326)
Standardized measure of discounted future net cash flows	$ 7,543	$ 3,736	$ 2,051
Annual discount for estimated timing of cash flows percent	10.00%	10.00%	10.00%