Derivative Financial Instruments (Schedule Of Open NGL Derivative Positions) (Details)	12 Months Ended
	Dec. 31, 2017 $ / bbl bbl
OPIS Mont Belvieu Texas Ethane Price Swaps NGL Q1-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	6,747
Weighted Average Price Swap | $ / bbl	11.89
OPIS Mont Belvieu Texas Natural Gasoline Price Swaps NGL Q1-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	5,500
Weighted Average Price Swap | $ / bbl	54.24
OPIS Mont Belvieu Texas Normal Butane Price Swaps NGL Q1-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	6,750
Weighted Average Price Swap | $ / bbl	38.46
OPIS Mont Belvieu Texas Propane Price Swaps NGL Q1-Q4 2018 [Member]
Derivative [Line Items]
Volume Per Day (Bbls/d) | bbl	9,500
Weighted Average Price Swap | $ / bbl	33.19