COMMONLY OWNED FACILITIES (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Commonly Owned Facilities
Proportionate ownership interest (as a percent)	12.00%
Distance of Iatan Generating Facility from Kansas city (in miles)	35
Ownership interest in the site (as a percent)	3.00%
EDE
Commonly Owned Facilities
Ownership interest in certain common facilities (as a percent)	12.00%
Iatan
Commonly Owned Facilities
Proportionate ownership interest (as a percent)	12.00%
Amounts included in property, plant and equipment
Cost of ownership in plant in service	$ 373.3	$ 367.1
Accumulated Depreciation	99.1	91.1
Expenditures	27.8	31.6
Iatan1 \| KCP&L
Commonly Owned Facilities
Ownership interest in the site (as a percent)	70.00%
Iatan1 \| KCP&L Greater Missouri Operations Co.
Commonly Owned Facilities
Ownership interest in the site (as a percent)	18.00%
Iatan2 \| KCP&L
Commonly Owned Facilities
Ownership interest in the site (as a percent)	54.00%
Iatan2 \| KCP&L Greater Missouri Operations Co.
Commonly Owned Facilities
Ownership interest in the site (as a percent)	18.00%
State Line Combined Cycle Unit
Amounts included in property, plant and equipment
Cost of ownership in plant in service	161.5	163.3
Accumulated Depreciation	40.0	37.0
Expenditures	47.1	52.6
Power capacity (in megawatts)	500
State Line Combined Cycle Unit \| EDE
Commonly Owned Facilities
Percentage share in available capacity	60.00%
Plum point
Amounts included in property, plant and equipment
Cost of ownership in plant in service	108.3	108.2
Accumulated Depreciation	9.4	7.3
Expenditures	$ 8.1	$ 11.3
Plum point \| EDE
Commonly Owned Facilities
Proportionate ownership interest (as a percent)	7.52%

Represents the total power capacity of a jointly owned utility plant.

No definition available.

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- Definition

Represents the distance of Iatan Generating Facility from Kansas city.

+ References

No definition available.

+ Details

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- Definition

The share of the available capacity of which the reporting entity is entitled.

+ References

No definition available.

+ Details

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- Definition

The expenditure incurred by the reporting entity of a jointly owned utility.

+ References

No definition available.

+ Details

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- Definition

The proportionate ownership interest in common facilities of a jointly owned utility plant.

+ References

No definition available.

+ Details

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- Definition

The proportionate share of interest (percent) in the site at jointly owned facility.

+ References

No definition available.

+ Details

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- Definition

The period end amount owned by the reporting utility of a jointly owned utility plant in service.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 10.C)

-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section C

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- Definition

The period end amount of accumulated depreciation in a jointly owned electricity generation plant.

+ References

+ Details

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- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

+ References

+ Details

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