Short-term Borrowings and Short-term Bank Lines of Credit (Details) - USD ($)	1 Months Ended	6 Months Ended
	May. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Amount of outstanding cash borrowings		$ 11,000,000	$ 4,000,000
Commercial paper outstanding		629,300,000	358,300,000
Parent Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 200,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum borrowing capacity with transfer of unused commitments		$ 400,000,000
Line of Credit Facility, Covenant Terms		A default by Great Plains Energy or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, Great Plains Energy is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 11,000,000	$ 4,000,000
Weighted-average interest rate from outstanding borrowings		1.69%	1.69%
Amount of letters of credit outstanding		$ 200,000	$ 0
Kansas City Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial paper outstanding		$ 484,000,000	$ 358,300,000
Weighted-average interest rate from outstanding borrowings		0.49%	0.48%
Kansas City Power and Light Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 600,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum transfer of unused commitments		$ 200,000,000
Line Of Credit Facility Transfer Unused Commitments	$ 200,000,000
Line of Credit Facility, Covenant Terms		A default by KCP&L on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, KCP&L is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 0	$ 0
Amount of letters of credit outstanding		2,700,000	2,700,000
KCPL Greater Missouri Operations [Member]
Short-term Debt [Line Items]
Commercial paper outstanding		$ 145,300,000	0
Weighted-average interest rate from outstanding borrowings		0.45%
KCPL Greater Missouri Operations [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 450,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum transfer of unused commitments		$ 200,000,000
Line Of Credit Facility Transfer Unused Commitments	$ (50,000,000)
Line of Credit Facility, Covenant Terms		A default by GMO or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 0	0
Amount of letters of credit outstanding		$ 3,000,000	$ 3,200,000