SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) (USD $)	12 Months Ended													12 Months Ended						12 Months Ended
	Dec. 31, 2011 approach assumption Y M	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Electric Missouri Public Service Commission (MPSC)	Dec. 31, 2011 Gas count	Dec. 31, 2011 Regulated	Dec. 31, 2010 Regulated	Dec. 31, 2009 Regulated	Dec. 31, 2011 Regulated General	Dec. 31, 2010 Regulated General	Dec. 31, 2009 Regulated General	Dec. 31, 2011 High end of range	Oct. 31, 2011 High end of range Gas	Dec. 31, 2011 Low end of range	Oct. 31, 2011 Low end of range Gas	Dec. 31, 2011 Asset retirement obligation:	Dec. 31, 2010 Asset retirement obligation:	Dec. 31, 2011 Under recovered electric fuel and purchased power costs Electric Missouri and Kansas	Dec. 31, 2011 Iatan	Dec. 31, 2011 Iatan2	Dec. 31, 2011 All projects except Iatan 2	Dec. 31, 2010 All projects except Iatan 2	Dec. 31, 2009 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	$ 3,757,000	$ 3,607,000
Accretion	187,000	150,000
Closing balance of asset retirement obligation	3,944,000	3,757,000	3,607,000
Regulatory assets	239,646,000	194,378,000														3,600,000	3,400,000	6,000,000
Depreciation
Amortization	7,445,000	8,347,000	5,159,000			6,600,000	7,500,000	4,500,000	6,600,000	7,500,000	4,500,000
Allowance for Funds Used During Construction
Aggregate rates (on a before-tax basis) utilized in determining AFUDC (as a percent)																					5.20%	7.50%	7.00%
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 assets	239,646,000	194,378,000														3,600,000	3,400,000	6,000,000
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 (in years)	10
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
Initial maturity period of investments to be classified as cash equivalents (in months)	3
Checks and electronic fund transfers that have been issued but not cleared through bank	16,600,000	14,500,000
Restricted Cash
Restricted Cash and Cash Equivalents Related to Construction Costs	2,500,000	0
Restricted Cash and Cash Equivalents Related to Operating Costs	$ 1,800,000	$ 1,800,000