Supplemental Oil And Gas Disclosures (Standardized Measure Of Discounted Future Cash Flows Relating To Proved Reserves Disclosure) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental Oil and Gas Disclosures [Abstract]
Future cash flows	$ 6,398,236	$ 5,573,119	$ 4,522,351
Future production costs	(2,069,636)	(1,734,985)	(1,405,773)
Future development costs	(560,102)	(571,170)	(431,673)
Future income tax expenses	(1,228,533)	(1,044,608)	(762,519)
Future net cash flows	2,539,965	2,222,356	1,922,386
10% annual discount for estimated timing of cash flows	(1,104,221)	(996,380)	(842,430)
Standardized measure of discounted future net cash flows relating to proved oil, NGLs and natural gas reserves	$ 1,435,744	$ 1,225,976	$ 1,079,956	$ 1,087,909
Percentage of annual discount for estimated timing of cash flows	10.00%	10.00%	10.00%