Receivables (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	$ 0		$ 0
Gain (Loss) on Sale of Accounts Receivable	0.1	[1]	0	[1]
Servicing fees received (paid)	0		0
Fees paid to outside investor	(0.5)		(0.5)
Cash from customers (transferred) received	0		0
Cash received from (paid for) receivables purchased	0		0
Intercompany interest income (expense) on notes			0
Kansas City Power and Light Company [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	0		0
Gain (Loss) on Sale of Accounts Receivable	0.1	[1]	0	[1]
Servicing fees received (paid)	0		0
Fees paid to outside investor	(0.3)		(0.3)
Cash from customers (transferred) received	0		0
Cash received from (paid for) receivables purchased	0		0
Intercompany interest income (expense) on notes			0
Kansas City Power And Light Company Unconsolidated [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	(353.1)		(334.7)
Gain (Loss) on Sale of Accounts Receivable	(4.5)	[1]	(4.2)	[1]
Servicing fees received (paid)	0.6		0.6
Fees paid to outside investor	0		0
Cash from customers (transferred) received	(367.6)		(336.7)
Cash received from (paid for) receivables purchased	363.0		332.5
Intercompany interest income (expense) on notes			0.1
KCPL Receivables Company [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	353.1		334.7
Gain (Loss) on Sale of Accounts Receivable	4.6	[1]	4.2	[1]
Servicing fees received (paid)	(0.6)		(0.6)
Fees paid to outside investor	(0.3)		(0.3)
Cash from customers (transferred) received	367.6		336.7
Cash received from (paid for) receivables purchased	(363.0)		(332.5)
Intercompany interest income (expense) on notes			(0.1)
KCPL Greater Missouri Operations [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	(193.8)		(185.4)
Gain (Loss) on Sale of Accounts Receivable	(2.5)	[1]	(2.3)	[1]
Servicing fees received (paid)	0.3		0.3
Fees paid to outside investor	0		0
Cash from customers (transferred) received	(200.8)		(184.9)
Cash received from (paid for) receivables purchased	198.3		182.6
Intercompany interest income (expense) on notes			0
GMO Receivables Company Member
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased	193.8		185.4
Gain (Loss) on Sale of Accounts Receivable	2.5	[1]	2.3	[1]
Servicing fees received (paid)	(0.3)		(0.3)
Fees paid to outside investor	(0.2)		(0.2)
Cash from customers (transferred) received	200.8		184.9
Cash received from (paid for) receivables purchased	(198.3)		(182.6)
Intercompany interest income (expense) on notes			$ 0

[1] Any net gain (loss) is the result of the timing difference inherent in collecting receivables and over the life of the agreement will net to zero.