Summary Of Significant Accounting Policies (Schedule Of Segment's Revenues) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sunoco Logistics Partners L.P. | Oil and Natural Gas
Revenue, Major Customer [Line Items]
Segment's revenues	10.00%	24.00%	19.00%
Valero Energy Corporation | Oil and Natural Gas
Revenue, Major Customer [Line Items]
Segment's revenues	9.00%	11.00%	15.00%
QEP Resources, Inc. | Drilling
Revenue, Major Customer [Line Items]
Segment's revenues	26.00%	28.00%	25.00%
Whiting Petroleum Corp. (formerly Kodiak Oil and Gas Corp.) | Drilling
Revenue, Major Customer [Line Items]
Segment's revenues	7.00%	18.00%	7.00%
ONEOK, Inc. | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	36.00%	30.00%	29.00%
Range Resources Corporation | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	9.00%	10.00%	5.00%
Koch Energy Services, LLC | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	8.00%	11.00%	9.00%
Tenaska Resources, LLC | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	6.00%	10.00%	18.00%
Laclede Group, Inc. | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	1.00%	9.00%	12.00%