Derivative Financial Instruments (Schedule Of Open NGL Derivative Positions) (Details)	6 Months Ended
	Jun. 30, 2018 $ / bbl bbl
OPIS Mont Belvieu Texas Ethane Price Swaps NGL Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	6,000
Weighted Average Price Swap | $ / bbl	11.73
OPIS Mont Belvieu Texas Natural Gasoline Price Swaps NGL Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	6,500
Weighted Average Price Swap | $ / bbl	56.13
OPIS Mont Belvieu Texas Normal Butane Price Swaps NGL Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	7,000
Weighted Average Price Swap | $ / bbl	38.69
OPIS Mont Belvieu Texas Propane Price Swaps NGL Q3-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	12,000
Weighted Average Price Swap | $ / bbl	33.72
OPIS Mont Belvieu Texas Ethane Price Swaps NGL Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	1,000
Weighted Average Price Swap | $ / bbl	11.55
OPIS Mont Belvieu Texas Natural Gasoline Price Swaps NGL Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	4,500
Weighted Average Price Swap | $ / bbl	55.93
OPIS Mont Belvieu Texas Normal Butane Price Swaps NGL Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	4,000
Weighted Average Price Swap | $ / bbl	33.69
OPIS Mont Belvieu Texas Propane Price Swaps NGL Q1-Q4 2019 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	8,500
Weighted Average Price Swap | $ / bbl	30.01