Summary Of Significant Accounting Policies (Schedule Of Segment's Revenues) (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
QEP Resources, Inc.[Member] | Drilling [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	15.00%	22.00%	28.00%
Kodiak Oil and Gas Corp. [Member] | Drilling [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	10.00%	6.00%	5.00%
Valero Energy Corporation [Member] | Oil and Natural Gas [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	26.00%	18.00%	7.00%
Sunoco Partners Marketing [Member] | Oil and Natural Gas [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	8.00%	10.00%	8.00%
ONEOK [Member] | Mid-Stream [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	54.00%	54.00%	53.00%
Gavilon LLC [Member] | Mid-Stream [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	10.00%	19.00%	12.00%
ConocoPhillips [Member] | Mid-Stream [Member]
Revenue, Major Customer [Line Items]
Segment's revenues	4.00%	7.00%	12.00%