For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13537-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13531-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

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Commitments and Contingencies (Details 2) (USD $) In Millions, unless otherwise specified		6 Months Ended		0 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Multi-year contracts Revenues	Jun. 30, 2012 Multi-year contracts Revenues	Aug. 23, 2012 Western Minerals LLC item	Aug. 23, 2012 CPE Inc item	Jun. 30, 2013 Performance bonds	Jul. 09, 2012 Decker Litigation
Concentrations of Risk and Major Customer
Joint venture ownership percentage							50.00%
Number of counterclaims asserted				6	2
Percentage of revenue		91.00%	88.00%
Standby letters of credit	$ 0
Outstanding amount of surety bonds						$ 647.5