Summary Of Significant Accounting Policies (Intangible And Other Long-Term Assets) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Escrow Deposit Required by Seller of Oil and Gas Properties	$ 58,500				$ 58,400			$ 58,500	$ 58,400
Reduction in value of assets	35,961	$ 1,963	$ 460,283	$ 2,198	$ 175,618	$ 755,632	$ 807,637	500,405	1,738,887
Amortization expense exclusive of debt acquisition costs								16,200	$ 23,000	$ 25,900
Amortization of intangible assets exclusive of debt acquisitions costs for 2017	12,700							12,700
Amortization of intangible assets exclusive of debt acquisitions costs for 2018	12,700							12,700
Amortization of intangible assets exclusive of debt acquisitions costs for 2019	12,700							12,700
Amortization of intangible assets exclusive of debt acquisitions costs for 2020	12,700							12,700
Amortization of intangible assets exclusive of debt acquisitions costs for 2021	$ 12,700							$ 12,700
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life								17 years
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life								10 years
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life								3 years