Regulatory Matters (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Regulatory Assets:
Regulatory assets, current	$ 7,685,000	$ 6,377,000
Regulatory assets, long-term	237,942,000	243,958,000
Regulatory assets, total	245,627,000	250,335,000
Regulatory Liabilities:
Regulatory liabilities, current	3,542,000	3,089,000
Regulatory liabilities, long-term	136,528,000	134,269,000
Regulatory liabilities, total	140,070,000	137,358,000
Missouri, Kansas and Oklahoma
Regulatory Assets:
Period to recover costs in Missouri, Kansas and Oklahoma rates	12 months
SWPA payment for Ozark Beach lost generation
Regulatory Liabilities:
Regulatory liabilities, current	2,927,000	2,774,000
Regulatory liabilities, long-term	18,583,000	19,467,000
Other
Regulatory Liabilities:
Regulatory liabilities, current	615,000	315,000
Cost of removal
Regulatory Liabilities:
Regulatory liabilities, long-term	85,528,000	83,368,000
Deferred construction accounting costs - fuel
Regulatory Liabilities:
Regulatory liabilities, long-term	7,975,000	8,011,000
Unamortized gain on interest rate derivative
Regulatory Liabilities:
Regulatory liabilities, long-term	3,328,000	3,371,000
Over recovered electric fuel and purchased power costs
Regulatory Liabilities:
Regulatory liabilities, long-term	5,954,000	5,826,000
Over recovered purchased gas costs
Regulatory Liabilities:
Regulatory liabilities, long-term	1,908,000	247,000
Under recovered electric fuel and purchased power costs
Regulatory Assets:
Regulatory assets, current	927,000	1,196,000
Regulatory assets, long-term	1,415,000	314,000
Pension and other postretirement benefits
Regulatory Assets:
Regulatory assets, long-term	133,539,000	136,480,000
Pension and other postretirement benefit costs recognized	100,000
Regulatory Liabilities:
Regulatory liabilities, long-term	1,635,000	2,007,000
Pension and other postretirement benefit costs reduction recognized	200,000
Income taxes
Regulatory Assets:
Regulatory assets, long-term	47,297,000	48,759,000
Regulatory Liabilities:
Regulatory liabilities, long-term	11,617,000	11,972,000
Deferred construction accounting costs.
Regulatory Assets:
Regulatory assets, long-term	16,167,000	16,277,000
Unamortized loss on reacquired debt
Regulatory Assets:
Regulatory assets, long-term	10,910,000	11,078,000
System reliability - vegetation management
Regulatory Assets:
Regulatory assets, long-term	7,460,000	8,340,000
Storm costs
Regulatory Assets:
Regulatory assets, long-term	4,437,000	4,223,000
Asset retirement obligation
Regulatory Assets:
Regulatory assets, long-term	4,492,000	4,430,000
Customer programs
Regulatory Assets:
Regulatory assets, long-term	3,756,000	3,916,000
Unamortized loss on interest rate derivative
Regulatory Assets:
Regulatory assets, long-term	978,000	989,000
Other
Regulatory Assets:
Regulatory assets, current	5,994,000	3,492,000
Regulatory assets, long-term	589,000	584,000
Deferred operating and maintenance expenses
Regulatory Assets:
Regulatory assets, long-term	2,154,000	2,011,000
Gas | Under recovered purchased gas costs
Regulatory Assets:
Regulatory assets, current	764,000	1,689,000
Electric | Unsettled derivative losses
Regulatory Assets:
Regulatory assets, long-term	$ 4,748,000	$ 6,557,000