Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Current Assets
Cash and cash equivalents	$ 13.6		$ 10.6
Funds on deposit	5.5		0.8
Receivables, net	151.4		162.2
Accounts receivable pledged as collateral	175.0		175.0
Fuel inventories, at average cost	71.6		76.4
Materials and supplies, at average cost	151.4		152.3
Deferred refueling outage costs	25.4		29.5
Refundable income taxes	10.5		10.5
Deferred income taxes	92.1		80.3
Assets held for sale	0		36.2
Prepaid expenses and other assets	39.9		33.2
Assets, Current, Total	736.4		767.0
Utility Plant, at Original Cost
Electric	11,659.2		11,575.3
Less-accumulated depreciation	4,684.3		4,628.4
Net utility plant in service	6,974.9		6,946.9
Construction work in progress	818.9		736.7
Nuclear Fuel, Net of Amortization	65.9		62.8
Public Utilities, Property, Plant and Equipment, Net	7,859.7		7,746.4
Investments and Other Assets
Nuclear decommissioning trust fund	187.4		183.9
Regulatory Assets	849.6		849.7
Goodwill	169.0		169.0
Other Assets, Noncurrent	82.8		79.4
Investments and Other Assets, Total	1,288.8		1,282.0
Assets, Total	9,884.9		9,795.4
Current Liabilities
Notes payable	5.0		9.0
Collateralized note payable	175.0		175.0
Commercial paper	217.8		108.2
Current maturities of long-term debt	15.1		1.1
Accounts payable	240.3		327.4
Accrued taxes	63.9		29.7
Accrued interest	61.8		45.4
Accrued compensation and benefits	39.0		47.3
Pension and post-retirement liability	3.2		3.2
Other Liabilities, Current	23.0		23.5
Liabilities, Current, Total	844.1		769.8
Deferred Credits and Other Liabilities
Deferred income taxes	985.5		964.8
Deferred tax credits	127.0		127.4
Asset retirement obligations	161.1		158.8
Pension and post-retirement liability	367.5		360.5
Regulatory Liabilities	279.3		264.0
Other Liabilities, Noncurrent	124.7		121.0
Liabilities, Noncurrent, Total	2,045.1		1,996.5
Common shareholders' equity
Common Stock, Value, Issued	2,633.9		2,631.1
Retained earnings	859.1		871.4
Treasury Stock, Value	(2.2)		(2.8)
Accumulated other comprehensive loss	(22.3)	[1]	(25.3)	[1]
Common Shareholders' Equity, Total	3,468.5		3,474.4
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued	39.0		39.0
Long-term debt	3,488.2		3,515.7
Total Capitalization	6,995.7		7,029.1
Commitments and Contingencies
Liabilities and Equity, Total	9,884.9		9,795.4
Preferred Stock 3 Point 80 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued	10.0		10.0
Preferred Stock 4 Point 50 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued	10.0		10.0
Preferred Stock 4 Point 20 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued	7.0		7.0
Preferred Stock 4 Point 35 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued	12.0		12.0
Kansas City Power and Light Company [Member]
Current Assets
Cash and cash equivalents	5.8		4.0
Funds on deposit	3.5		0.7
Receivables, net	127.3		129.2
Accounts Receivable, Related Parties, Current	38.6		50.4
Accounts receivable pledged as collateral	110.0		110.0
Fuel inventories, at average cost	48.5		50.3
Materials and supplies, at average cost	108.5		109.0
Deferred refueling outage costs	25.4		29.5
Refundable income taxes	0.7		15.1
Deferred income taxes	1.8		0
Assets held for sale	0		4.7
Prepaid expenses and other assets	34.0		27.5
Assets, Current, Total	504.1		530.4
Utility Plant, at Original Cost
Electric	8,342.7		8,274.9
Less-accumulated depreciation	3,557.5		3,518.3
Net utility plant in service	4,785.2		4,756.6
Construction work in progress	732.4		660.4
Nuclear Fuel, Net of Amortization	65.9		62.8
Public Utilities, Property, Plant and Equipment, Net	5,583.5		5,479.8
Investments and Other Assets
Nuclear decommissioning trust fund	187.4		183.9
Regulatory Assets	595.6		614.1
Other Assets, Noncurrent	32.6		31.0
Investments and Other Assets, Total	815.6		829.0
Assets, Total	6,903.2		6,839.2
Current Liabilities
Collateralized note payable	110.0		110.0
Commercial paper	166.7		93.2
Current maturities of long-term debt	14.0		0
Accounts payable	183.9		239.8
Accounts Payable, Related Parties, Current	0		0.2
Accrued taxes	47.5		23.8
Accrued interest	41.2		29.1
Accrued compensation and benefits	39.0		47.3
Pension and post-retirement liability	1.9		1.9
Deferred income taxes	0		1.7
Other Liabilities, Current	13.2		13.0
Liabilities, Current, Total	617.4		560.0
Deferred Credits and Other Liabilities
Deferred income taxes	926.5		922.1
Deferred tax credits	125.1		125.3
Asset retirement obligations	143.7		141.7
Pension and post-retirement liability	347.0		339.9
Regulatory Liabilities	172.3		168.3
Other Liabilities, Noncurrent	93.1		90.4
Liabilities, Noncurrent, Total	1,807.7		1,787.7
Common shareholders' equity
Common Stock, Value, Issued	1,563.1		1,563.1
Retained earnings	635.6		636.4
Accumulated other comprehensive loss	(18.9)		(20.2)
Common Shareholders' Equity, Total	2,179.8		2,179.3
Cumulative preferred stock $100 par value
Long-term debt	2,298.3		2,312.2
Total Capitalization	4,478.1		4,491.5
Commitments and Contingencies
Liabilities and Equity, Total	$ 6,903.2		$ 6,839.2

[1] Net of tax