Discontinued Operations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Value of midstream business sold			$ 2,500.0qep_ValueOfBusinessSold
Debt Refinanced In Business Sale			230.0qep_DebtRefinancedInBusinessSale
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax			1,800.0
Discontinued Operation, Amount of Continuing Cash Flows after Disposal	22.7	34.9
Depreciation, depletion and amortization	195.4	225.9
Employee Retention Bonus Cost			10.4qep_EmployeeRetentionBonusCost
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation, depletion and amortization		14.3
Payments to Acquire Oil and Gas Property and Equipment		12.7
Employee Retention Bonus Cost		$ 2.3

Debt Refinanced In Business Sale

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- Definition

Employee Retention Bonus Cost

+ References

No definition available.

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- Definition

Value Of Business Sold

+ References

No definition available.

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- Definition

Amount of cash flows that are expected to continue with the disposal group that is a component of the entity (discontinued operation) after it has been sold or otherwise disposed of.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Continuation of Activities

-URI http://asc.fasb.org/extlink&oid=6508610

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Continuing Cash Flows

-URI http://asc.fasb.org/extlink&oid=6508624

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1482-107760

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- Definition

Amount of gain (loss), before tax expense or benefit and not previously recognized, resulting from the sale of a business component.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

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-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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- Definition

The cash outflow to purchase long lived physical asset for use in the normal oil and gas operations and to purchase mineral interests in oil and gas properties not intended for resale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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- Definition

Depreciation, depletion, amortization, and accretion related to oil and gas producing activities.

+ References

No definition available.

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