REGULATORY MATTERS (Details) (USD $)																		12 Months Ended						12 Months Ended					12 Months Ended				12 Months Ended						12 Months Ended												12 Months Ended					1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Missouri jurisdictional portion of the payment, net of tax	Dec. 31, 2012 Over recovered electric fuel and purchased power costs	Dec. 31, 2011 Over recovered electric fuel and purchased power costs	Dec. 31, 2012 Cost of removal	Dec. 31, 2011 Cost of removal	Dec. 31, 2012 Income taxes	Dec. 31, 2011 Income taxes	Dec. 31, 2012 Unamortized gain on interest rate derivative	Dec. 31, 2011 Unamortized gain on interest rate derivative	Dec. 31, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Dec. 31, 2012 Deferred construction accounting costs - fuel	Dec. 31, 2011 Deferred construction accounting costs - fuel	Dec. 31, 2012 SWPA payment for Ozark Beach lost generation	Dec. 31, 2011 SWPA payment for Ozark Beach lost generation	Dec. 31, 2012 SWPA payment for Ozark Beach lost generation Missouri, Kansas and Oklahoma	Dec. 31, 2012 SWPA payment for Ozark Beach lost generation Arkansas	Dec. 31, 2012 Other	Dec. 31, 2011 Other	Dec. 31, 2012 Under recovered electric fuel and purchased power costs	Dec. 31, 2011 Under recovered electric fuel and purchased power costs	Dec. 31, 2012 Under recovered electric fuel and purchased power costs Missouri	Dec. 31, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Dec. 31, 2012 Income taxes	Dec. 31, 2011 Income taxes	Dec. 31, 2012 Storm costs	Dec. 31, 2011 Storm costs	Dec. 31, 2012 Unamortized loss on reacquired debt	Dec. 31, 2011 Unamortized loss on reacquired debt	Dec. 31, 2012 Unamortized loss on reacquired debt Minimum	Dec. 31, 2012 Unamortized loss on reacquired debt Maximum	Dec. 31, 2012 Deferred operating and maintenance expenses	Dec. 31, 2011 Deferred operating and maintenance expenses	Dec. 31, 2012 Unamortized loss on interest rate derivative	Dec. 31, 2011 Unamortized loss on interest rate derivative	Dec. 31, 2012 Unamortized loss on interest rate derivative Minimum	Dec. 31, 2012 Unamortized loss on interest rate derivative Maximum	Dec. 31, 2012 Deferred construction accounting costs.	Dec. 31, 2011 Deferred construction accounting costs.	Dec. 31, 2012 Asset retirement obligation	Dec. 31, 2011 Asset retirement obligation	Dec. 31, 2012 Customer programs	Dec. 31, 2011 Customer programs	Dec. 31, 2012 System reliability - vegetation management	Dec. 31, 2011 System reliability - vegetation management	Dec. 31, 2012 Other	Dec. 31, 2011 Other	Dec. 31, 2012 Asbury five-year maintenance	Dec. 31, 2012 Gas Cost of removal	Dec. 31, 2011 Gas Cost of removal	Dec. 31, 2012 Gas Under recovered purchased gas costs	Dec. 31, 2011 Gas Under recovered purchased gas costs	Jan. 31, 2012 Electric Kansas 2009 Rate Case Kansas Corporation Commission (KCC)	Dec. 31, 2012 Electric Cost of removal	Dec. 31, 2011 Electric Cost of removal	Dec. 31, 2012 Electric Unsettled derivative losses	Dec. 31, 2011 Electric Unsettled derivative losses	Dec. 31, 2012 Iatan2	Dec. 31, 2011 Iatan2
Regulatory Assets and Liabilities
Deferred depreciation, operations and maintenance, and carrying costs related to capital expenditure			$ 3,300,000
Period over which deferred depreciation, operating and maintenance expenses will be recovered																																																								4 years
Deferred construction accounting costs	16,717,000	17,095,000																																																											10,661,000	10,890,000
Deferred fuel and purchased power expense																																																													8,200,000
Regulatory Assets:
Regulatory assets, current	6,377,000	11,839,000																				1,196,000	7,513,000																										3,492,000	4,115,000				1,689,000	211,000
Regulatory assets, long-term	243,958,000	227,807,000																				314,000	231,000		136,480,000	121,058,000	48,759,000	49,631,000	4,223,000	4,990,000	11,078,000	10,138,000			2,011,000	990,000	989,000	1,147,000			16,277,000	16,717,000	4,430,000	3,571,000	3,916,000	2,968,000	8,340,000	5,908,000	584,000	1,338,000					1,281,000				6,557,000	7,839,000
Regulatory assets, total	250,335,000	239,646,000																																									4,400,000	3,600,000
Regulatory Asset Noncurrent, Amortization Period																									5 years				5 years				1 year	28 years					1 year	28 years											5 years
Amortization period																		10 years	50 years
Period to recover costs in Missouri, Kansas and Oklahoma rates																								12 months
Pension and other postretirement benefit costs recognized																									500,000
Portion of regulatory assets expected to be recoverable in future periods																									130,300,000
Regulatory Liabilities:
Regulatory liabilities, current	3,089,000	3,150,000														2,774,000	2,833,000			315,000	317,000
Regulatory liabilities, long-term	134,269,000	125,290,000		5,826,000	2,513,000	83,368,000	73,562,000	11,972,000	12,337,000	3,371,000	3,541,000	2,007,000	2,939,000	8,011,000	8,156,000	19,467,000	22,242,000			247,000
Regulatory liabilities, total	137,358,000	128,440,000		4,000,000																																																6,100,000	5,000,000				77,300,000	68,600,000
Pension and other postretirement benefit costs reduction recognized																									$ 900,000