Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
OPERATING REVENUES	$ 4,913.4	$ 5,147.8	$ 4,275.9
OPERATING EXPENSES:
Fuel and purchased power	1,099.0	1,265.0	1,078.7
SPP network transmission costs	263.2	251.3	259.9
Operating and maintenance	1,163.0	1,218.5	1,115.8
Depreciation and amortization	880.1	861.7	618.8
Taxes other than income tax	364.2	365.5	269.1
Total Operating Expenses	3,769.5	3,962.0	3,342.3
INCOME FROM OPERATIONS	1,143.9	1,185.8	933.6
OTHER INCOME (EXPENSE):
Investment earnings	10.8	11.0	8.8
Other income	31.3	26.9	15.5
Other expense	(78.2)	(76.9)	(78.7)
Total Other Expense, Net	(36.1)	(39.0)	(54.4)
Interest expense	383.9	374.0	279.6
INCOME BEFORE INCOME TAXES	723.9	772.8	599.6
Interest expense	102.2	97.0	59.0
Equity in earnings of equity method investees, net of income taxes	8.3	9.8	5.4
NET INCOME	630.0	685.6	546.0
Less: Net income attributable to noncontrolling interests	11.7	15.7	10.2
Net income attributable to Evergy, Inc.	$ 618.3	$ 669.9	$ 535.8
BASIC AND DILUTED EARNINGS PER AVERAGE COMMON SHARE OUTSTANDING ATTRIBUTABLE TO EVERGY, INC. (see Note 1)
Basic earnings per common share (in dollars per share)	$ 2.72	$ 2.80	$ 2.50
Diluted earnings per common share (in dollars per share)	$ 2.72	$ 2.79	$ 2.50
AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)	227.2	239.5	213.9
Diluted (in shares)	227.5	239.9	214.1
COMPREHENSIVE INCOME
Net income	$ 630.0	$ 685.6	$ 546.0
Derivative hedging activity
Loss on derivative hedging instruments	0.0	(64.4)	(5.4)
Income tax benefit	0.0	16.5	1.4
Net loss on derivative hedging instruments	0.0	(47.9)	(4.0)
Reclassification to expenses, net of tax	3.0	1.5	0.0
Derivative hedging activity, net of tax	3.0	(46.4)	(4.0)
Defined benefit pension plans
Net gain (loss) arising during period	(3.0)	(0.8)	1.4
Income tax expense (benefit)	0.7	0.2	(0.4)
Net gain (loss) arising during period, net of tax	(2.3)	(0.6)	1.0
Amortization of net losses included in net periodic benefit costs, net of tax	(0.1)	0.0	0.0
Change in unrecognized pension expense, net of tax	(2.4)	(0.6)	1.0
Total other comprehensive income (loss)	0.6	(47.0)	(3.0)
COMPREHENSIVE INCOME	630.6	638.6	543.0
Less:  comprehensive income attributable to noncontrolling interest	11.7	15.7	10.2
COMPREHENSIVE INCOME	$ 618.9	$ 622.9	$ 532.8