Summary Of Significant Accounting Policies (Schedule Of Segment's Revenues) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CVR Refining, LP | Oil and Natural Gas
Revenue, Major Customer [Line Items]
Segment's revenues	14.00%	2.00%	0.00%
Valero Energy Corporation | Oil and Natural Gas
Revenue, Major Customer [Line Items]
Segment's revenues	10.00%	9.00%	11.00%
Energy Transfer Partners (formerly Sunoco Logistics Partners) | Oil and Natural Gas
Revenue, Major Customer [Line Items]
Segment's revenues	3.00%	10.00%	24.00%
QEP Resources, Inc. | Drilling
Revenue, Major Customer [Line Items]
Segment's revenues	16.00%	26.00%	28.00%
Slawson Exploration Company, Inc | Drilling
Revenue, Major Customer [Line Items]
Segment's revenues	10.00%	6.00%	3.00%
Whiting Petroleum Corp. (formerly Kodiak Oil and Gas Corp.) | Drilling
Revenue, Major Customer [Line Items]
Segment's revenues	3.00%	7.00%	18.00%
ONEOK, Inc. | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	45.00%	36.00%	30.00%
Range Resources Corporation | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	7.00%	9.00%	10.00%
Koch Energy Services, LLC | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	6.00%	8.00%	11.00%
Tenaska Resources, LLC | Mid-Stream
Revenue, Major Customer [Line Items]
Segment's revenues	4.00%	6.00%	10.00%