SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) (USD $)	12 Months Ended						12 Months Ended						12 Months Ended
	Dec. 31, 2012 assumption approach	Dec. 31, 2011	Dec. 31, 2012 Electric Missouri Public Service Commission (MPSC)	Dec. 31, 2012 Gas count	Dec. 31, 2012 High end of range	Oct. 31, 2012 High end of range Gas	Dec. 31, 2012 Low end of range	Oct. 31, 2012 Low end of range Gas	Dec. 31, 2012 Asset retirement obligation	Dec. 31, 2011 Asset retirement obligation	Dec. 31, 2012 Under recovered electric fuel and purchased power costs Electric Missouri and Kansas	Dec. 31, 2012 Iatan	Dec. 31, 2012 Iatan2	Dec. 31, 2012 All projects except Iatan 2	Dec. 31, 2011 All projects except Iatan 2	Dec. 31, 2010 All projects except Iatan 2
Asset Retirement Obligation.
Proportionate ownership interest (as a percent)	12.00%											12.00%
Credit adjusted risk-free rate (as a percent)					5.52%		4.50%
Change in asset retirement obligation
Opening balance of asset retirement obligation	$ 3,944,000	$ 3,757,000
Accretion	252,000	187,000
Cash flow revisions	515,000
Closing balance of asset retirement obligation	4,711,000	3,944,000
Regulatory assets	250,335,000	239,646,000							4,400,000	3,600,000
Allowance for Funds Used During Construction
Aggregate rates (on a before-tax basis) utilized in determining AFUDC (as a percent)														5.60%	5.20%	7.50%
Reduction in equity portion of AFUDC rate (as a percent)													2.50%
Goodwill
Goodwill	39,492,000	39,492,000
Number of assumptions whose negative charge will affect impairment	1
Number of approaches used to estimate the fair value	2
Excess fair value of the reporting unit over carrying value						8,000,000		5,000,000
Fuel and Purchased Power
Percentage of changes in fuel and purchased power costs from the base cost permitted for distribution to customers under fuel adjustment clause			95.00%
Regulatory liability	137,358,000	128,440,000									4,000,000
Maximum number of rate changes allowed by PGA clause throughout the year				4
Pension and Other Postretirement Benefits
Percentage that unrecognized gains or losses must exceed postretirement benefit obligation or fair value of plan assets for recognition of additional income or expense	10.00%
Amortization period of unrecognized gains or losses into actuarial expense	10 years
Period of recovery for difference between regulatory costs and the costs being recovered fro customers	5 years
Federal subsidy as percentage of prescription drug costs	28.00%
Prescription drug costs for which the basis of the federal subsidy is calculated					5,000		250
Cash & Cash Equivalents
Checks and electronic fund transfers that have been issued but not cleared through bank	19,700,000	16,600,000
Restricted Cash
Amounts restricted for construction costs	2,500,000	2,500,000
Amounts restricted for operating costs	$ 1,800,000	$ 1,800,000