REGULATORY MATTERS (Details 3) (USD $)	1 Months Ended			12 Months Ended		1 Months Ended	12 Months Ended		1 Months Ended	3 Months Ended	12 Months Ended				12 Months Ended	1 Months Ended							0 Months Ended				1 Months Ended			1 Months Ended										0 Months Ended
	May 31, 2011	Aug. 31, 2010 phase	Dec. 31, 2012	Dec. 31, 2012 Missouri Public Service Commission (MPSC) Electric Missouri 2012 Rate Case	Jul. 06, 2012 Missouri Public Service Commission (MPSC) Electric Missouri 2012 Rate Case	Jun. 30, 2011 Missouri Public Service Commission (MPSC) Electric Missouri 2010 Rate Case	Jun. 15, 2011 Missouri Public Service Commission (MPSC) Electric Missouri 2010 Rate Case	Sep. 28, 2010 Missouri Public Service Commission (MPSC) Electric Missouri 2010 Rate Case	Sep. 30, 2010 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	Mar. 31, 2010 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	Dec. 31, 2012 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	Sep. 10, 2010 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	May 12, 2010 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	Oct. 29, 2009 Missouri Public Service Commission (MPSC) Electric Missouri 2009 Rate Case	Dec. 31, 2012 Missouri Public Service Commission (MPSC) Electric Tornado Recovery	Jun. 30, 2009 Missouri Public Service Commission (MPSC) Gas Gas rate case	Apr. 02, 2010 Missouri Public Service Commission (MPSC) Gas Gas rate case	Jun. 05, 2009 Missouri Public Service Commission (MPSC) Gas Gas rate case mi	Nov. 23, 2012 Missouri Public Service Commission (MPSC) Water Missouri 2012 Rate Case	Oct. 18, 2012 Missouri Public Service Commission (MPSC) Water Missouri 2012 Rate Case	Jul. 02, 2010 Kansas Corporation Commission (KCC) Electric Kansas 2009 Rate Case	Nov. 04, 2009 Kansas Corporation Commission (KCC) Electric Kansas 2009 Rate Case	Jun. 17, 2011 Kansas Corporation Commission (KCC) Electric Kansas 2011 Rate Case	Jan. 31, 2012 Kansas Corporation Commission (KCC) Electric Kansas 2011 Rate Case	Jan. 02, 2012 Kansas Corporation Commission (KCC) Electric Kansas 2011 Rate Case	Sep. 01, 2011 Oklahoma Corporation Commission (OCC) First Phase Capital Reliability Rider (CRR)	Mar. 31, 2010 Oklahoma Corporation Commission (OCC) Electric Capital cost recovery rider (CCRR) step	Mar. 25, 2010 Oklahoma Corporation Commission (OCC) Electric Capital cost recovery rider (CCRR)	Jan. 04, 2012 Oklahoma Corporation Commission (OCC) Electric Oklahoma 2011 Rate Case	Jan. 31, 2012 Oklahoma Corporation Commission (OCC) Electric Capital Reliability Rider (CRR)	Mar. 31, 2011 Oklahoma Corporation Commission (OCC) Electric Capital Reliability Rider (CRR)	Aug. 31, 2010 Oklahoma Corporation Commission (OCC) Electric Capital Reliability Rider (CRR) phase	Jun. 30, 2011 Oklahoma Corporation Commission (OCC) Electric Capital Reliability Rider (CRR)	Sep. 01, 2011 Oklahoma Corporation Commission (OCC) Electric First Phase Capital Reliability Rider (CRR)	Mar. 02, 2011 Oklahoma Corporation Commission (OCC) Electric Phase 2 Capital Reliability Rider (CRR)	Jan. 28, 2011 Oklahoma Corporation Commission (OCC) Electric Phase 2 Capital Reliability Rider (CRR)	Apr. 13, 2011 Arkansas Public Service Commission (APSC) Electric Arkansas 2010 Rate Case	Feb. 02, 2011 Arkansas Public Service Commission (APSC) Electric Arkansas 2010 Rate Case	Aug. 19, 2010 Arkansas Public Service Commission (APSC) Electric Arkansas 2010 Rate Case	Jul. 31, 2012 Federal Energy Regulatory Commission (FERC)	May 18, 2012 Federal Energy Regulatory Commission (FERC)	Dec. 31, 2012 Federal Energy Regulatory Commission (FERC) GFR rate case.
REGULATORY MATTERS
Test period for operating expense taken as a basis for increase in base rate	12 months
RATE MATTERS
Approved amount of annual increase in base rate							$ 18,700,000					$ 46,800,000					$ 2,600,000		$ 450,000		$ 2,800,000			$ 1,250,000		$ 1,456,979			$ 240,722					$ 2,600,000	$ 1,063,100		$ 2,104,321
Approved percentage of annual increase in base rate							4.70%					13.40%					4.37%		25.50%		12.40%				5.20%	15.70%			1.66%					27.67%	9.32%		19.00%
Requested amount of annual increase in electric base rate					30,700,000			36,500,000						68,200,000				2,900,000	516,400			5,200,000	1,500,000					3,000,000					600,000			1,100,000			3,200,000
Period to recover costs in Missouri, Kansas and Oklahoma rates																							3 years
Percentage of annual base rate increase requested					7.56%			9.20%						19.60%				4.90%	29.60%			24.60%	6.39%					33.00%					4.10%						27.30%
Revenue paid by customers after factoring in fuel cost adjustment					8,600,000
Portion of the case related to the tornado recovery costs and cost of service					6,200,000
Impact of the requested amount of annual increase in base rates					22,100,000
Impact of the requested amount of annual increase in base rates (as a percent)					5.30%
Tax benefits of cost of removal to be flowed through to customers				9,600,000
Amount of increase in base rate for which unanimous agreement filed																				450,000
Annual regulatory amortization expense terminated as a result of rate case settlement							14,500,000
Stipulated annual base rate increase if in-service criteria met													46,800,000
Stipulated annual base rate increase if in-service criteria were not met													33,100,000
Base rate revenue included in authorized amount of increase in annual revenues									36,800,000																					200,000
Deferred depreciation, operations and maintenance, and carrying costs related to capital expenditure															3,300,000
Regulatory amortization included in authorized amount of increase in annual revenues									10,000,000
Amortization period for deferred asset related to the tax benefits of cost of removal											18 years				10 years
Deferred expenses related to rate cases			1,800,000
Approximate tax benefits flowed through to customers											11,100,000
Regulatory assets recorded to recover tax benefits written off										1,200,000
Return on equity (as a percent)																11.30%
Number of steps requested under the capital cost recovery rider preceding a general rate case																											3
Number of phases approved under the capital reliability rider preceding a general rate case		2																														2
Approximate total revenue requested under rate increase requests																															2,500,000
Percentage of general rate increase in electric base rate																																						19.00%
Period for which effective date of the filing requested to suspend																																									5 months
Period for which rate suspended																																								5 months
Accumulated provision - rate refunds																																										1,300,000
Area covered by gas distribution system (in miles)																		1,200
Period within which SWPA payment will be made to customers						10 years
Base rate increase request annual decrease to expenses							$ 1,400,000