Fixed Assets And Asset Retirement Obligations (Schedule Of Reconciliation Of Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations, beginning balance	$ 14,790	$ 14,332
Asset Retirement Obligation, Liabilities Incurred	158,230	0
Asset Retirement Obligation, Liabilities Incurred From Historical Interests	1,988
Accretion expense	4,941	458
Asset retirement obligations, ending balance	188,662	$ 14,790
Asset Retirement Obligation, Revisions in Timing of Expected Settlement	9,986
Asset Retirement Obligation, Liabilities Settled	$ 1,273