Regulatory Matters (Details) (USD $)																				3 Months Ended																									1 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Missouri jurisdictional portion of the payment, net of tax	Mar. 31, 2012 Over recovered electric fuel and purchased power costs	Dec. 31, 2011 Over recovered electric fuel and purchased power costs	Mar. 31, 2012 Cost of removal	Dec. 31, 2011 Cost of removal	Mar. 31, 2012 Income taxes	Dec. 31, 2011 Income taxes	Mar. 31, 2012 Unamortized gain on interest rate derivative	Dec. 31, 2011 Unamortized gain on interest rate derivative	Mar. 31, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Mar. 31, 2012 Deferred construction accounting costs - fuel	Dec. 31, 2011 Deferred construction accounting costs - fuel	Mar. 31, 2012 SWPA payment for Ozark Beach lost generation	Dec. 31, 2011 SWPA payment for Ozark Beach lost generation	Mar. 31, 2012 Under recovered electric fuel and purchased power costs	Dec. 31, 2011 Under recovered electric fuel and purchased power costs	Mar. 31, 2012 Under recovered electric fuel and purchased power costs Missouri, Kansas and Oklahoma M	Mar. 31, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Mar. 31, 2012 Income taxes	Dec. 31, 2011 Income taxes	Mar. 31, 2012 Storm costs	Dec. 31, 2011 Storm costs	Mar. 31, 2012 Unamortized loss on reacquired debt	Dec. 31, 2011 Unamortized loss on reacquired debt	Mar. 31, 2012 Deferred operating and maintenance expenses	Dec. 31, 2011 Deferred operating and maintenance expenses	Mar. 31, 2012 Unamortized loss on interest rate derivative	Dec. 31, 2011 Unamortized loss on interest rate derivative	Mar. 31, 2012 Asset retirement obligation:	Dec. 31, 2011 Asset retirement obligation:	Mar. 31, 2012 Customer programs	Dec. 31, 2011 Customer programs	Mar. 31, 2012 System reliability - vegetation management	Dec. 31, 2011 System reliability - vegetation management	Mar. 31, 2012 Other:	Dec. 31, 2011 Other:	Mar. 31, 2012 Deferred construction accounting costs.	Dec. 31, 2011 Deferred construction accounting costs.	Mar. 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) Y	Mar. 31, 2012 Electric Unsettled derivative losses	Dec. 31, 2011 Electric Unsettled derivative losses
Regulatory Assets and Liabilities
Deferred depreciation, operations and maintenance, and carrying costs related to capital expenditure			$ 2,000,000
Period over which deferred depreciation, operating and maintenance expenses will be recovered (in years)																																													4
Regulatory Assets:
Regulatory assets, current	3,885,000	7,724,000																3,661,000	7,513,000																								224,000	211,000
Regulatory assets, long-term	231,428,000	231,922,000																233,000	231,000		118,417,000	121,058,000	49,330,000	49,631,000	5,025,000	5,303,000	11,333,000	11,610,000	1,676,000	1,444,000	1,383,000	1,462,000	4,568,000	3,571,000	3,718,000	3,408,000	7,218,000	6,569,000	696,000	1,420,000	17,087,000	17,095,000	627,000	1,281,000		10,117,000	7,839,000
Regulatory assets, total	235,313,000	239,646,000
Period to recover costs in Missouri rates (in months)																				12
Pension and other postretirement benefit costs recognized																					100,000
Regulatory Liabilities:
Regulatory liabilities, long-term	131,667,000	128,440,000		4,446,000	2,513,000	75,923,000	73,562,000	12,270,000	12,337,000	3,669,000	3,711,000	2,675,000	2,939,000	8,266,000	8,304,000	24,418,000	25,074,000
Regulatory liabilities, total	131,667,000	128,440,000
Pension and other postretirement benefit costs reduction recognized																					$ 100,000