Regulatory Matters (Details) (USD $) In Millions, unless otherwise specified	Jan. 26, 2013
Kansas City Power and Light Company [Member] | Rate jurisdiction - Missouri [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase authorized	$ 67.4
KCPL Greater Missouri Operations [Member] | Rate jurisdiction - St. Joseph Light and Power division [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase authorized	21.7
KCPL Greater Missouri Operations [Member] | Rate jurisdiction - Missouri Public Service division [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase authorized	$ 26.2