Contingencies, Commitments and Leases Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Loss Contingencies [Line Items]
Environmental expense for previously-owned chemical company	$ 5.0us-gaap_EnvironmentalRemediationExpense
Accrual for environmental loss contingency on previously-owned chemical company	5.4
Wexpro [Member]
Loss Contingencies [Line Items]
Overriding royalty interest demanded in Rocky Mountain Resources litigation (in hundredths)	4.00%
Maximum expected loss on Rocky Mountain Resources litigation	14.1
Unaffiliated Entity [Member]
Loss Contingencies [Line Items]
Maximum expected loss on Rocky Mountain Resources litigation	$ 16.2

Overriding royalty interest stipulated in original oil & gas lease assigned to Wexpro and QEP Energy Company.

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- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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- Definition

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

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