Derivative And Financial Instruments (Changes In Fair Value) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	$ (7,239)	$ 25,149
Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Beginning fair value of commodity derivatives	31,018	22,829
Net premiums on derivative contracts	3,197
Ending fair value of commodity derivatives	$ 6,435	31,018
Number of counterparties | item	4
Oil | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	$ (8,355)	22,410
Net settlements on derivative contracts	(13,622)	(13,191)
Oil | Oil And Liquids Sales
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	(8,355)	19,146
Natural Gas | Commodity Contract
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	1,116	6,148
Net settlements on derivative contracts	(6,919)	(7,178)
Natural Gas | Natural Gas Sales
Derivative Instruments Gain Loss [Line Items]
Net gains (losses) on derivatives	$ 1,116	$ 6,003