Derivative Financial Instruments (Schedule Of Open Oil Derivative Positions) (Details)	6 Months Ended
	Jun. 30, 2018 $ / bbl bbl
NYMEX West Texas Intermediate Price Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	89,300
Weighted Average Price Swap	57.96
NYMEX West Texas Intermediate Price Swaps Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	50,130
Weighted Average Price Swap	58.95
NYMEX West Texas Intermediate Price Collars Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	100,200
Weighted Average Floor Price	52.23
Weighted Average Ceiling Price	62.83
NYMEX West Texas Intermediate Price Collars Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	65,790
Weighted Average Floor Price	52.60
Weighted Average Ceiling Price	62.60
Midland Sweet Basis Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	23,000
Weighted Average Differential To WTI	(1.02)
Argus LLS Basis Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	12,000
Weighted Average Differential To WTI	3.95
Argus MEH Basis Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	15,832
Weighted Average Differential To WTI	2.82
NYMEX Roll Basis Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	19,989
Weighted Average Differential To WTI	0.60
Western Canadian Select Basis Swaps Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	64,859
Weighted Average Differential To WTI	(14.91)
Midland Sweet Basis Swaps Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	28,000
Weighted Average Differential To WTI	(0.46)
Argus LLS Basis Swaps Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	1,000
Weighted Average Differential To WTI	4.60
Argus MEH Basis Swaps Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	16,000
Weighted Average Differential To WTI	2.84
NYMEX Roll Basis Swaps Oil Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	22,000
Weighted Average Differential To WTI	0.53
NYMEX Roll Basis Swaps Oil Q1-Q4 2020 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	22,000
Weighted Average Differential To WTI	0.32
Western Canadian Select Basis Collars Oil Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	1,663
Weighted Average Floor Differential to WTI	(15.50)
Weighted Average Ceiling Differential to WTI	(13.93)