COMMONLY OWNED FACILITIES (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) mi MW	Dec. 31, 2014 USD ($)
COMMONLY OWNED FACILITIES
Proportionate ownership interest (as a percent)	12.00%
Distance of Iatan Generating Facility from Kansas city (in miles) | mi	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	$ 380.2	$ 373.3
Accumulated Depreciation	105.3	99.1
Expenditures	$ 26.9	27.8
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	$ 163.0	161.5
Accumulated Depreciation	43.5	40.0
Expenditures	$ 40.7	47.1
Power capacity (in megawatts) | MW	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	$ 109.1	108.3
Accumulated Depreciation	11.9	9.4
Expenditures	$ 9.6	$ 8.1
Plum point | EDE
COMMONLY OWNED FACILITIES
Proportionate ownership interest (as a percent)	7.52%