REGULATORY MATTERS (Details 2)									12 Months Ended
	Jan. 22, 2016 USD ($)	Jul. 26, 2015 USD ($) $ / MWh	Jun. 08, 2015	Jun. 01, 2015 USD ($)	Jan. 22, 2015 USD ($)	Dec. 05, 2014 USD ($)	Oct. 29, 2013 item	Jun. 13, 2012	Dec. 31, 2015	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 16, 2015 USD ($)	Feb. 23, 2015 USD ($)	Sep. 26, 2014 USD ($)	Aug. 29, 2014 USD ($)	May. 20, 2014 USD ($)	Dec. 03, 2013 USD ($)	Apr. 01, 2013 USD ($)
RATE MATTERS
Plant Disallowance										$ 86,000	$ 2,409,000
Utilities Operating Expense Reverse Gain on Sale of Assets										$ 44,000	$ 1,236,000
Number of new Missouri demand-side management programs | item							4
Missouri Public Service Commission (MPSC) | Missouri 2015 Rate Case
RATE MATTERS
Net reduction in base fuel and purchased power | $ / MWh		1.60
Fuel Adjustment Charge (in percent)									34
Missouri Public Service Commission (MPSC) | Electric
RATE MATTERS
Approved amount of annual increase in base rate		$ 17,125,000																$ 27,500,000
Approved percentage of annual increase in base rate		3.90%																6.78%
Missouri Public Service Commission (MPSC) | Electric | Missouri 2015 Rate Case
RATE MATTERS
Requested amount of annual increase in base rate												$ 33,400,000
Requested percentage of annual increase in base rate												7.30%
Missouri Public Service Commission (MPSC) | Electric | Missouri 2014 Rate Case
RATE MATTERS
Requested amount of annual increase in electric base rate															$ 24,300,000
Percentage of annual base rate increase requested															5.50%
Kansas Corporation Commission (KCC) | 2014 Environmental Cost Recovery Rider Member
RATE MATTERS
Proposed recover costs						$ 860,000
Approved recover costs				$ 780,000
Kansas Corporation Commission (KCC) | Ad Valorem Tax Surcharge
RATE MATTERS
Annual increase related to Ad Valorem taxes					$ 270,000,000
Additional Annual Increase Related To AdValorem Taxes	$ 200,000
Kansas Corporation Commission (KCC) | Electric
RATE MATTERS
Approved amount of annual increase in base rate				$ 782,479									$ 273,455
Approved percentage of annual increase in base rate				4.71%									1.08%
Oklahoma Corporation Commission (OCC) | Electric | High end of range
RATE MATTERS
Customer rate reciprocity who serve less of total customers (in percent)			10
Arkansas Public Service Commission (APSC) | Electric
RATE MATTERS
Approved amount of annual increase in base rate													$ 457,000	$ 1,366,809
Approved percentage of annual increase in base rate													3.35%	11.34%
Arkansas Public Service Commission (APSC) | Electric | Missouri 2014 Rate Case
RATE MATTERS
Requested amount of annual increase in electric base rate																$ 1,375,000
Percentage of annual base rate increase requested																11.00%
Arkansas Public Service Commission (APSC) | Electric | Arkansas 2013 Rate Case
RATE MATTERS
Requested amount of annual increase in electric base rate																	$ 2,200,000
Percentage of annual base rate increase requested																	18.00%
Federal Energy Regulatory Commission (FERC) | TFR rate case
RATE MATTERS
Percentage of ROE								10.00%