Regulatory Matters (Details) (USD $)				9 Months Ended																	9 Months Ended																						9 Months Ended			1 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Missouri jurisdictional portion of the payment, net of tax	Sep. 30, 2012 Missouri, Kansas and Oklahoma	Sep. 30, 2012 Cost of removal	Dec. 31, 2011 Cost of removal	Sep. 30, 2012 SWPA payment for Ozark Beach lost generation	Dec. 31, 2011 SWPA payment for Ozark Beach lost generation	Sep. 30, 2012 Income taxes	Dec. 31, 2011 Income taxes	Sep. 30, 2012 Deferred construction accounting costs - fuel	Dec. 31, 2011 Deferred construction accounting costs - fuel	Sep. 30, 2012 Unamortized gain on interest rate derivative	Dec. 31, 2011 Unamortized gain on interest rate derivative	Sep. 30, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Sep. 30, 2012 Over recovered electric fuel and purchased power costs	Dec. 31, 2011 Over recovered electric fuel and purchased power costs	Sep. 30, 2012 Under recovered electric fuel and purchased power costs	Dec. 31, 2011 Under recovered electric fuel and purchased power costs	Sep. 30, 2012 Pension and other postretirement benefits	Dec. 31, 2011 Pension and other postretirement benefits	Sep. 30, 2012 Income taxes	Dec. 31, 2011 Income taxes	Sep. 30, 2012 Deferred construction accounting costs.	Dec. 31, 2011 Deferred construction accounting costs.	Sep. 30, 2012 Unamortized loss on reacquired debt	Dec. 31, 2011 Unamortized loss on reacquired debt	Sep. 30, 2012 System reliability - vegetation management	Dec. 31, 2011 System reliability - vegetation management	Sep. 30, 2012 Storm costs	Dec. 31, 2011 Storm costs	Sep. 30, 2012 Asset retirement obligation	Dec. 31, 2011 Asset retirement obligation	Sep. 30, 2012 Customer programs	Dec. 31, 2011 Customer programs	Sep. 30, 2012 Unamortized loss on interest rate derivative	Dec. 31, 2011 Unamortized loss on interest rate derivative	Sep. 30, 2012 Other	Dec. 31, 2011 Other	Sep. 30, 2012 Deferred operating and maintenance expenses	Dec. 31, 2011 Deferred operating and maintenance expenses	Sep. 30, 2012 Arkansas jurisdictional portion of the 2010 SWPA payment	Sep. 30, 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)	Sep. 30, 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			$ 2,700,000
Period over which deferred depreciation, operating and maintenance expenses will be recovered																																														4 years
Regulatory Assets:
Regulatory assets, current	1,146,000	7,724,000																	921,000	7,513,000																								225,000	211,000
Regulatory assets, long-term	225,196,000	231,922,000																	0	231,000	113,111,000	121,058,000	48,851,000	49,631,000	16,811,000	17,095,000	12,544,000	11,610,000	8,012,000	6,569,000	4,700,000	5,303,000	4,744,000	3,571,000	4,173,000	3,408,000	1,226,000	1,462,000	776,000	1,420,000	2,220,000	1,444,000		1,983,000	1,281,000		6,045,000	7,839,000
Regulatory assets, total	226,342,000	239,646,000
Period to recover costs in Missouri, Kansas and Oklahoma rates				12 months
Pension and other postretirement benefit costs recognized																					400,000
Regulatory Liabilities:
Regulatory liabilities, long-term	136,903,000	128,440,000			81,201,000	73,562,000	22,911,000	25,074,000	12,022,000	12,337,000	8,192,000	8,304,000	3,584,000	3,711,000	2,240,000	2,939,000	6,753,000	2,513,000
Regulatory liabilities, total	136,903,000	128,440,000
Pension and other postretirement benefit costs reduction recognized																					$ 100,000
Amortization period				10 years																																							50 years