Derivative And Financial Instruments (Change In Fair Value) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) item	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Derivative Instruments Gain Loss [Line Items]
Net gains on derivatives	$ 3,990	$ 4,832
Commodity Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Beginning fair value of commodity derivatives	31,018	22,829	$ 22,829
Ending fair value of commodity derivatives	$ 27,913		31,018
Number of counterparties | item	3
Oil [Member] | Commodity Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Net gains on derivatives	$ 2,692		22,410
Net settlements on derivative contracts	(4,856)		(13,191)
Oil [Member] | Oil And Liquids Sales [Member] | Commodity Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Net gains on derivatives	2,692	2,643
Natural Gas [Member] | Commodity Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Net gains on derivatives	1,298		6,148
Net settlements on derivative contracts	(2,239)		$ (7,178)
Natural Gas [Member] | Natural Gas Sales [Member] | Commodity Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Net gains on derivatives	$ 1,298	$ 2,189