Derivative And Financial Instruments (Changes In Fair Value) (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) item	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	$ 1,071	$ 17,322	$ (2,664)	$ 16,258
Net settlements on derivative contracts			(3,197)
Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Beginning fair value of commodity derivatives			31,018	22,829	$ 22,829
Net premiums on derivative contracts			3,197
Ending fair value of commodity derivatives	11,364		$ 11,364		31,018
Number of counterparties | item			3
Oil | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives			$ (4,601)		22,410
Net settlements on derivative contracts			(13,673)		(13,191)
Oil | Oil And Liquids Sales | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	(1,033)	14,970	(4,600)	12,058
Natural Gas | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives			1,937		6,148
Net settlements on derivative contracts			(6,514)		$ (7,178)
Natural Gas | Natural Gas Sales | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	$ 2,104	$ 2,352	$ 1,936	$ 4,200