Represents the total amount of the contingent obligation as performance bonds outstanding as of the reporting date.

No definition available.

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- Definition

Represents the total amount of self bond granted to meet the contingent obligation.

+ References

No definition available.

+ Details

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- Definition

Represents the total amount of the contingent obligation as self-funded bond outstanding, as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

Description of risks that arise due to the volume of business transacted with a particular customer. At a minimum, the description informs financial statement users of the general nature of the risk, but excludes "Information about Major Customers" that may be disclosed elsewhere (for instance, segment disclosures).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-Subparagraph (a)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6327-108592

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

Reference 1: 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

Reference 2: 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=35750535&loc=d3e13531-108611

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

-Publisher FASB

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-Topic 275

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-Section 50

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- Details

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- Details

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Commitments and Contingencies (Details 2) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	May. 07, 2014
Concentration Risk [Line Items]
Outstanding amount of self-funded bonds	$ 200.0
Outstanding amount of surety bonds	$ 441.2
Wyoming
Concentration Risk [Line Items]
Self bond granted amount			$ 200.0
Revenues
Concentration Risk [Line Items]
Percentage of revenue	10.00%	10.00%
Customers that represent a concentration risk	no single customer
Multi-year contracts \| Revenues
Concentration Risk [Line Items]
Percentage of revenue	10.00%	10.00%
Customers that represent a concentration risk	0